Semiconductor photocatalysis has become an interdisciplinary research area that covers applications such as water purification and air cleaning, solar fuel generation, and/or development of photovoltaic cells. Due to its high efficiency, innocuous nature, and affordable price, anatase (TiO2) is considered the most promising semiconductor photocatalyst today. The photocatalytic activity of anatase nanomaterials is conventionally aimed at the photodegradation of organic pollutants, with recent extrapolations to bacteria and tumor cells. Here, we present a novel approach for anatase nanoparticle photocatalysis applied to the field of low-temperature solution processing of multifunctional oxide layers. The method is based on the phototocatalytic-assisted decomposition of organic species from a solution-derived oxide precursor containing anatase nanoparticles after irradiation with UV light. Removal of organic species from the system at an early stage results in an advanced crystallization of the crystalline phase at low temperatures. The applicability of this technique for the low-temperature processing of functional oxide films is demonstrated for the first time on the Pb(ZrxTi1-x)O3 (PZT) ferro-piezoelectric system. Several nanoparticle suspensions of anatase with different physicochemical properties were studied for the preparation of the resulting TiO2-seeded precursor solutions of PZT. The effectiveness of anatase photocatalysis on the decomposition of organic species from the system upon UV illumination was evaluated in both dynamic (solution) and quasi-static (gel layer) media. The electronic excitation of certain photosensitive compounds (e.g., acetylacetone) in the wet films was also considered at this step. After complete pyrolysis of the films, the presence of TiO2 nanoparticles within the microstructure of the amorphous PZT layer was observed to influence the mechanisms for nucleation and growth of the resulting perovskite phase (seeding effect). Single-phase, ferroelectric PZT thin films could be achieved at processing temperatures le; 400 °C by this solution method. The low temperatures attained would allow not only the reliable integration of multifunctional oxide layers with latest CMOS devices, but also their direct preparation on large-area, light-weight, plastic substrates with multiple (ferro, pyro, piezo) applications in the emerging field of flexible electronics.
Work financed by the Spanish project MAT2010-15369. I.B. acknowledges the financial support of the Juan de la Cierva Spanish programme.

The development of nanometer-sized particles has brought about a new generation of multifunctional and innovative materials. In comparison to their bulk counterparts, nanomaterials often exhibit novel size- and shape-dependent optical, electrical, chemical, and magnetic properties. Furthermore, bottom-up manipulation while controlling spatial position and inter-particle distances has made possible the construction of 2- and 3-D assemblies of nanoparticles with properties tailored at the nanometer level. In fact, properties of such an assembly are neither due to the isolated nano element exclusively nor to the corresponding bulky phase but instead they arise in a synergistic contribution from both. In particular, superparamagnetic iron oxide (SPIO) particles play an important role since their high magnetization and biocompatibility make them potential nanomaterials for use in biomedicine or new industrial technologies, as for instance in drug delivery systems, biolabeling, magnetic hyperthermia, contrast enhancers for magnetic resonance imaging, just to cite a few. Furthermore, their electron-spintronic properties pose them as potential candidates for the development of spintronic and energy conversion devices, chemical and biological sensors, and nanocatalysts. SPIO-based nanocomposites can exhibit collective magnetic properties arising from inter-particle interactions. These interactions may be tuned by a fine control of particle characteristics, as well as their spatial distribution inside the matrix. The layer-by-layer (LbL) technique for film deposition which bases on the sequential adsorption of polyelectrolytes and colloidal particles onto solid surfaces can provide the required control of film thickness [1] and average interparticle distances within nanocomposites made with SPIO materials [2]. In fact, the LbL has become an effective way of studying interparticle magnetic interactions in solid assemblies [2]. For example, the strength of dipolar interactions in nanocomposites with maghemite nanoparticles could be modulated by setting-up deposition parameters of the LbL assembly at pre-defined conditions. The barrier energy for the magnetic moment reversal in these assemblies could be increased by adding more iron oxide/polyelectrolyte bilayers to the nanocomposites as well as by changing the concentration of iron oxide nanoparticles in the deposition dispersion. Cross-sectional transmission electron microscopy and magnetization measurements (ZFC/FC and ac susceptibility) give further evidence of the potential use of LbL technique to modulate dipolar interactions in nanocomposites.
[1] G.B. Alcantara, A. S. Afonso, R.C. Faria, M.A. Pereira-da-Silva, P. C. Morais, M.A. G. Soler. Phys. Chem. Chem. Phys. 13 (2011) 21233-21242.
[2] M.A.G. Soler, LG. Paterno, J.P Sinnecker, J.G. Wen, E.H.C.P. Sinnecker, R. F. Newman, M. Bahia, M.A. Novak, P.C. Morais. J. Nanopart. Res. 14(2012) 653.

Magnetoelectric (ME) mulitferroic materials can essentially be divided into two types: (i) single phase and (ii) composite. The direct ME coupling is present in a single-phase materials, such as Cr2O3, BiFeO3, TbMnO3, etc. whereas an indirect coupling is observed via strain in composite materials, where the magnetic (magnetostrictive materials, such as CoFe2O4) and electrical (piezoelectric materials, such as PbZrxTi1-xO3) order parameters arise in separate but intimately connected phases. The value of ME coefficient in single phase materials is usually an order of magnitude lower that that observed in composite materials, however these show interesting and complex magnetic behavior. In case of composites, the connectivity and distribution of the piezoelectric and magnetostrictive strongly affects its ME performance. In this talk, the results of magnetic measurements on single phase TbMnO3 bulk powders and multiferroic properties of PbZrxTi1-xO3:CoFe2O4 composite thin films will be presented.

Generation of large area arrays of self-organized oxide nanostructures (nanodots, nanowires) and thin films or nanocomposites provides unique opportunities for the development of novel functionalities with a wide range of potential applications (magnetic, superconducting, electronic, etc.). Bottom-up approach allows the fabrication of complex oxide nanostructures by self-organization, where spontaneously ordered, large-area patterns of nanometric objects appear. In this context, and although much less studied, chemical solution deposition (CSD) offers a high throughput and cost-efficient route for the generation of complex oxides.
In recent years we have widely investigated the unique microstructural and physical properties of different sorts of CSD-grown functional oxide nanostructures and thin films, including CeO2, ferromagnetic La1-xSrxMnO3 and YBa2Cu3O7 - derived nanocomposite superconductors [1-10]. Here I will review a few outstanding properties of these complex oxides where interfacial and internal strain is controlled at the nanoscale.
I will show first how the choice of the substrate and the interfacial strain anisotropy can be used to determine the shape and dimension of self-assembled CeO2 oxide nanostructures which are used as model systems. This methodology is used then to obtain ultrathin films, self-assembled islands and nanowires of La1-xSrxMnO3. We show first that metal-insulating transitions may be induced through strain control in ultrathin films, second we show that the size and shape of islands control the ferromagnetic domain structure (single, multiple domain and vortex) and finally, a novel monoclinic high Tc ferromagnetic material has been discovered when polymeric templates are used to generate the nanostructures. Also, I will show that Conductive-Scanning Force Microscopy allows nanoscale manipulation of the electronic properties leading to reversible resistive switching transitions which can carefully controlled.
I will finally report on the remarkable performance of CSD epitaxial superconducting YBa2Cu3O7 nanostructured films with second phase insulating nanoparticles where the nanostrain induced at the interfaces controls the local superconducting properties. These novel oxide materials have allowed to demonstrate that a complex vortex pinning landscape can be engineered and also that strain leads to local suppression of Cooper pair formation, accordingly with the predictions of the Bond Contraction Pairing model.
Ref: M Gibert et al; Adv Mater 19, 3937 (2007); C Moreno et al; Adv Funct Mater 19, 2139 (2009); M Gibert et al; Small 23, 2716 (2010); A Carretero-Genevrier et al; J Am Chem Soc 133, 4053 (2011); P. Abellán et al; Appl Phys Lett 98, 041903 (2011); J Zabaleta et al; J Appl Phys 111, 024307 (2012); C Moreno et al; Nano Lett 10, 3828 (2010); J. Gutierrez et al; Nature Mater 6, 367 (2007); A Llordés et al; Nature Mater 11, 329 (2012); A Carretero-Genevrier et al; Chem Comm 48, 6223 (2012)

Ceria-based oxide thin films have received notable attention as they reveal exceptional physical and chemical properties which make them suitable for numerous applications such as oxygen gas sensors, integrated solid-oxide fuel cells, and dynamic random access memories. Additionally, Ce-based oxide films are also used as buffer layers in complex architectures such as high-temperature superconducting tapes. In most of these applications, the growth of epitaxial oxide layers is required. Chemical solution deposition (CSD) routes represent a versatile low-cost way for the synthesis of functional epitaxial oxide thin films and multilayers with good chemical purity, and control of nucleation and growth characteristics. In essence, CSD methods consist on the deposition of a thin film metal organic precursor solution on the desired substrate, followed by thermal annealing in controlled environment which leads to precursor pyrolysis. In a subsequent thermal treatment, crystallization of the whole oxide films is normally made through conventional electrically heated furnaces. An appealing technological challenge would be the achievement of spatially-resolved precursor pyrolysis in the micrometric scale in order to facilitate the manufacture of functional devices. It also appears attractive to explore methods which can genuinely modify the kinetics of the metal-organic precursor pyrolysis processes which could lead to the formation of novel materials and nanostructures. To achieve these goals a thermal source with high spatial resolution and fast pulsed structure, as laser radiation, is required.
In this work, pulsed laser radiation was used for inducing the pyrolysis of cerium-zirconium propionates precursor layers with the aim to further obtain the growth of epitaxial Ce_0.9Zr_0.1O₂ (CZO) thin-films on yttria-stabilized zirconia (YSZ) (001) single crystal substrates. The laser irradiations, performed by means of a Nd:YAG laser system (lambda; = 266 nm, tau; = 3 ns, nu; = 10 Hz), provoked a fast partial decomposition of the precursors with every laser pulse in addition to a number of physical mechanisms usually not present during conventional pyrolysis treatments. The influence of processing parameters such as the laser fluence, number of accumulated pulses and substrate temperature on the morphology, surface roughness and composition of the pyrolyzed material was studied and related to the optical and thermophysical properties of the precursors. Subsequently, the thin films were crystallized by means of conventional annealing. The obtained results reveal that through laser pyrolysis it is possible to obtain epitaxial 20 nm-thick CZO films, with similar nanostructure than in conventional thermal treatments but with an important saving of processing time. In addition, it is demonstrated the capability of laser processing to create CZO micrometric patterns with enhanced versatility.

Keeping long-range structural order along the three dimensions (3D) is essential for the development of composite systems for different emerging areas, including metamaterials, magnonics, phononics and photonics. One conspicuous example is that of photonic crystals in which structures of sub-micronic spheres ordered in space give rise to an electromagnetic bandgap within which the propagation of radiation is forbidden. The fine tailoring of the photonic band gap and/or providing new functionalities to the photonic crystals requires an appropriate coating of the 3D-opal structure by a given functional material while keeping the high quality 3D structures. Conventional methods such as atomic layer deposition, thermal chemical vapor deposition, electrodeposition or deposition in aqueous solutions are limited by either the amount of available reagents or the required long unpractical processing times [1]. Instead, we show that sol-gel microwave-assisted chemistry is a very efficient method to achieve fast conformal ultrathin coating of opals with multivalent complex oxides, adding new functionalities to these photonic structures [2]. Using this methodology, we have achieved a conformal coverage of large areas of three-dimensional opals with a superparamagnetic manganese ferrite layer, yielding magneto-photonic crystals with excellent quality. Results from optical and magneto-optical characterization are consistent with a homogeneous magnetic infiltration of the opal structures that gives rise to both a red-shift of the optical bandgap and a deep modification of the magneto-optical spectral response due to photonic bandgap effects [2, 3]. In particular, these crystals exhibit a conspicuous enhancement of the magneto-optical signal at frequencies around the stop-band edges of the photonic crystals, as expected from theoretical predictions. We emphasize that the use of a ternary oxide for the ultrathin coating of three-dimensional intricate structures demonstrates the potential of microwave chemistry to realize three-dimensional structures with complex materials that may find applications beyond photonics, such as energy, sensing or catalysis.
[1] O. Pascu et al., J. Phys. Chem. C (2012), 116, 15108
[2] O. Pascu et al., Nanoscale, 3 (2011) 4811.
[3] J.M. Caicedo et al., ACS Nano, 5 (2011) 2957.

Functional complex oxide nanoparticles and thin films are required for innovations in communication, electronics, energy technology and catalysis. The enormous potential of these ceramics is based on their manifold functionalities. Especially in the form of nanostructures (particles or coatings) these material properties can be tailored for use in innovative applications and give added value to existing products. For this purpose the nanoparticles and layers have to be processed and deposited in an orientated and pure manner on appropriate substrates.
In today's processes, large-scale exploitation of the established physical processes is hampered by their complex process technology and the low yield and deposition speed.
This research proposes alternative processing methods for ceramic nanoparticles based on microwave heating from aqueous solutions or on hot injection methods. Afterwards, deposition of nanoparticles containing inks using ink-jet printing at ambient pressure is performed. With that, we aim at developing smart and environmentally friendly processes that require lower energy input. The main advantages of this approach are the lower investment cost, the faster deposition with higher yield and the processing under ambient pressure enabling a complete continuous processing. This method holds the promise of improved scalability due to lower ink losses, continuous processing and a drastically increased precursor lifetime due to the prevention of solvent evaporation and dust incorporation. Moreover, ink-jet printing has the potential to switch quite easily from continuous coatings to a multi-filamentary pattern, which is particularly important for specific applications. The fluid properties, often expressed with dimensionless constants, like the Reynolds and Weber numbers, for printable liquids were determined. The technique was employed to deposit superconducting layers in coated conductors, containing pinning centers of multi-oxide nanoparticles, YSZ as electrolyte in solid oxide fuel cells and in thermal barrier coatings and TiO2 as photocatalytic coatings.

Thin films find a variety of technological applications. Assembling thin films from atoms in the liquid phase is intrinsically a non-equilibrium phenomenon, controlled by the competition between thermodynamics and kinetics. We demonstrate here that microwave energy can assist in assembling atoms into thin films directly on a substrate at significantly lower temperatures than conventional processes, potentially enabling plastic-based electronics.
As an example, Titanium dioxide (TiO2) thin films were grown on indium tin oxide (ITO)-coated glass substrates that were immersed in a growth solution and heated in a microwave reactor. We show that the ITO layer strongly absorbs microwave energy, causing localized heating that catalyzes growth of anatase TiO2 thin films, while the solution temperature remains at 150 oC. In contrast, classical synthesis routes for anatase films comprise of chemical deposition techniques (sol-gel) and vacuum deposition techniques (sputtering, atomic layer deposition), followed by a high-temperature sintering step at ge; 450 oC to crystallize the films. Such high temperatures limit the choice of thin film growth substrates as flexible polymeric/plastic substrates typically decompose between 200 - 250 oC.
To better understand the microwave-assisted selective heating of the ITO layer and the resulting film growth, an electromagnetic model of the experimental setup was constructed. Both experimental and electromagnetic simulation results show microwave fields can selectively interact with a conducting layer on the substrate despite the discrepancy between the substrate size and the microwave wavelength. The microwave interaction leads to localized energy absorption, heating, and subsequent nucleation and growth of the desired films. Electromagnetic simulations show remarkable agreement with experiments and are employed to identify conditions to improve uniformity of the films. The films can be patterned and grown on various substrates, enabling their use in widespread applications. Specifically, we have successfully employed these microwave-grown TiO2 films as electron transporters in solid state dye sensitized solar cells, and as anodes in thin film lithium-ion batteries.

Epitaxial growth of complex functional oxides has generated a lot of interest for their outstanding physical properties such as high Tc superconductivity, colossal magnetoresistance, ferroelectricity, or more recently resistive switching phenomena. In recent years, these materials have become more appealing since novel or improved functionalities are reached by artificially engineering the interfaces between two combined oxides. Chemical Solution Deposition (CSD) and Atomic Layer Deposition (ALD), individually, are foreseen as innovative and powerful chemical methods for growth of complex functional oxides. However their combined potentiality in interface engineering and nanoscale control has yet not been exploited. In this contribution we study the benefit of combining both methodologies to reach bilayers where one oxide layer is grown by CSD whereas the subsequent layer is grown by ALD, with special interest in oxide electronics for superconductivity and resistive switching phenomena. Whereas CSD appears as a very competitive method for the epitaxial growth of YBa2Cu3O7-x (YBCO) and La0.7Sr0.3MnO3 (LSMO) oxide films of various thickness with fine control of stoichiometry and homogeneity, ALD, as a unique chemical gas-phase thin-film deposition method with self-limiting surface reaction, arises as a unique method to grow epitaxial CeO2 ultrathin films at the very low temperatures of 275 ° on top of the mentioned CSD layers without degradation of functional properties. Bilayers with thickness ranges for CeO2 (2- 10 nm), LSMO (3-30 nm) and YBCO (50-200 nm) have been grown and XRD, XPS, AFM, STEM, and EELS analysis have confirmed the epitaxial quality of all oxide layers and their interfaces, identified the strains states and cation stoichiometries. The functional properties of CeO2/YBCO and CeO2/LSMO bilayers have been evaluated in view of their potentiality for area resistive switching elements and reconfigurable superconducting devices. Switching characteristics have been evaluated by C-AFM and I(V) curves at room temperature as well as low temperatures.

Lead-free (K,Na)NbO3-based (NKN) solid solutions can exhibit piezoelectric properties comparable to that of actuator grade lead zirconate titanate piezoelectrics in the vicinity of the morphotrophic phase boundary (MPB). Unfortunately current techniques available to deposit NKN based solid solutions require high temperatures, sometimes above 1000°C, that are detrimental to the stoichiometry and also create unwanted thermal-related defects such as twins and cracking upon cooling through the Curie temperature. Besides being the first report of the successful growth of epitaxial (Na,K)NbO3-LiTaO3 films deposited hydrothermally at 130oC [1], the difficulty of synthesizing single phase (Na,K)NbO3 solid solutions with compositions around the MPB will also be discussed [2].
(Na,K)NbO3 powders were synthesized from aqueous mixtures of NaOH and KOH at 200oC. It was observed that above a critical NaOH to KOH ratio, a secondary NaNbO3 perovskite phase always formed together with the NKN powders, preventing the formation of single phase NKN. Despite this, a short 2 hour heat treatment at 800oC was successfully used to convert the mixtures of NKN and NaNbO3 powders to a single solid solution phase powder with compositions spanning the morphotropic phase boundary. In addition, Rietveld refinement of the as-synthesized powders also showed that the NKN powder in the mixed powders could reach compositions close to the MPB. It is believed that increasing NaOH fraction was responsible for the development of large supersaturations that could only be relieved by the precipitation of the second NaNbO3 phase.
Ferroelectrically active epitaxial films of KNbO3, (Na,K)NbO3 and (Na,K)NbO3-LiTaO3 were grown at 200oC and 130oC on single crystal SrTiO3 substrates. Post deposition treatments designed to remove protons incorporated during synthesis were important in lowering the leakage currents and improve the polarisability of the films [3]. Accurate values of d33 were determined by scanning laser vibrometry so that both film and substrate displacements were taken into account during measurement. As observed during the synthesis of powders, the formation of secondary phases places a limit on the fraction of sodium that can be incorporated into the films. As such, the films do not have the ideal compositions near the MPB and do not display the maximum d33 values expected, although a d33 of 25 pmV-1 represents a good starting point for further improvements.
References
[1] A. D. Handoko, G. K. L. Goh, ‘Hydrothermal Growth of Piezoelectrically Active Lead Free (Na,K)NbO3-LiTaO3 Thin Films&’, CrystEngComm, (2012) DOI: 0.1039/c2ce26311d.
[2] A. D. Handoko, G. K. L. Goh, ‘Hydrothermal Synthesis of Sodium Potassium Niobate Solid Solutions at 200°C&’, Green Chem. 12 (2010) 680.
[3] A. D. Handoko, G. K. L. Goh, R. X. Chew, ‘Piezoelectrically active hydrothermal KNbO3 thin films&’, CrystEngComm 14[2] (2012) 421.

The fast and accurate identification of unknown liquids is important for the safety and security of human beings. Recently, sensors based on the localized surface plasmon resonance (LSPR) effect demonstrated an outstanding sensitivity in detecting chemical and biological species. In the present study, we suggest that a dual-responsive hybrid nanocomposite composed of two polymer brushes and two noble metal nanoparticles provide a significantly improved selectivity for distinguishing diverse liquids, compared to a single-responsive LSPR sensor. The dual-responsive LSPR sensor platform was realized by the synergic combinations of two hydrophobic and hydrophilic polymer brushes, which respond differently depending on the degree of interaction between the polymer brushes and the surrounding liquids. Moreover, the mixing ratio of two known solvents can also be estimated with high accuracy using the dual-nanocomposite LSPR sensor, suggesting that this approach would be highly practical for in-situ process monitoring system that can instantly detect the change of solvent composition.

Graphene is a two dimensional nanostructure, composed of sp2 hybridized carbon. Graphene with its unique features such as high mobility, high transparency and flexibility among many other interesting features has attracted interest of researchers in various fields. With high theoretical value of specific surface area which reaches to 2630 m2/g, and high transparency (88.8%) over whole solar spectrum Graphene can be a very promising material in Dye Sensitized Solar cells (DSSC). However direct growth of nanostructures on Graphene has been a challenge owing to its chemical inertness. Here we report on a direct growth method of ZnO nanostructures on untreated Graphene over Fluorine-doped tin oxide (FTO) glass.
Graphene was grown by thermal chemical vapor deposition (CVD) and transferred on to FTO via chemical process. We employed a novel seed layer-free sonochemical technique to synthesize ZnO nanostructures on Graphene. Sonochemistry is a low temperature, catalyst free process which is done at atmospheric conditions, making it environmental friendly. ZnO nanostructures are synthesized by reacting Zinc acetate dehydrate (Zn (O2CCH3)2 .2H2O), zinc nitrate hexahydrate (Zn (NO3)2. 6H2O) and hexamethylenetetramine (HMT, (CH2). 6N4) in aqueous solutions. The presence of Graphene and ZnO over FTO is confirmed by Raman spectroscopy. Comparative study of structural and electrical characteristics by SEM, XRD, TEM, transparency and conductivity measurements for ZnO nanorods and ZnO nanowalls grown directly on Graphene as photoanode is presented. The effect of Graphene on dye loading and on efficiency of DSSC is quantitatively investigated. The results prove the feasibility of our method to synthesize various nanostructures on graphene at room temperature in an environmentally benign manner as well as the promising characteristics of ZnO nanostructure photoanodes for high efficiency DSSCs.

Nanostructured titanium dioxide is a potential energy material with applications in energy conversion and accumulation by photovoltaic solar cells and batteries, respectively and in energy conservation by electrochromic devices. Electrochemical processes governing the interface charge transfer when modified by encapsulating the TiO₂ nanostructure by a conformal thin layer of conducting polymer offers a unique opportunity for electrochemical energy storage through anionic charge trapping for performance as an electrode in supercapacitor devices. Although macroporous two-dimensional (2D) structures of conducting polymers have been widely studied for supercapacitors, but in the one-dimensional (1D) form commensurate enhancement in capacitive storage and charge stability has not been realized. In this work, synthesis of a novel composite electrode comprising of TiO₂ nanotube arrays with its inner and outer interface regions topotaxially coated with ~10-50 nm thin doped-polypyrrole conducting polymer and its electrochemical properties relevant to the energy storage are discussed.
Self ordered vertical 1D TiO₂ nanotube arrays were synthesized over Ti foil by electrochemical anodization in ethylene glycol containing 0.50 wt% NH₄F. Specific for use in energy storage, controlled ripple like TiO₂ nanotube wall geometry was created by addition of 10-30 vol% water in the anodizing medium. Conformal doped-polypyrrole- TiO₂ composite supercapacitor electrode (PPy/ TiO₂) in 1D nanostructure was obtained by coating inner and outer walls of TiO₂
nanotubes. Electrochemical functionalities were evaluated using cyclic voltammetry , impedance spectroscopy and galvanostatic charge-discharge techniques. CV plots scanned at different rates 10-100 mV/s in the -0.25 to +0.5V range exhibit near rectangular shape indicating highly capacitive nature of the PPy/ TiO₂ electrodes. Higher current obtained with increasing scan rates shows fast diffusion path for ions is realized from an open 1D nanostructure of PPy/ TiO₂. Electron transport and charge transfer resistances as well as ion accumulation capacitance of PPy/ TiO₂ electrode-electrolyte interface were evaluated. The impedance curve at low frequencies indicates highly capacitive properties of the PPy/ TiO₂ electrodes with overall capacitance rising from 50 mF to 64 mF with more open TiO₂ nanotubes network consistent with decrease in charge transfer resistance from 13 Omega; cm² to 4.5 Omega; cm² . Sequential charge-discharge studies show full reversibility with insignificant resistive component. Reasonable conductivity of TiO₂/PPy and low loss charge transfer with electrolyte enables deep discharge with high Coulomb efficiency.
This paper will report on the results of microstructure and electrochemical studies and discuss the mechanistic aspects of charge storage in 1D TiO₂ core-shell nanostructures with polypyrrole.

In this work, we present the sol-gel synthesis and characterization of highly porous nanocomposites constituted of NiFe2O4 nanoparticles dispersed into a highly porous amorphous silica aerogel matrix. The nanocomposite composition, morphology and structure have been optimized in view of their use as catalysts for multiwalled carbon nanotubes (MWCNTs) production.
The aerogels were synthesized using an acid-base catalyzed two-step sol-gel method,1-2 by co-gelation of the precursors of the dispersed and of the matrix phases. Urea is used in the second step to achieve gelation, which is followed by supercritical drying. Different thermal treatments were performed in order to obtain nanocrystalline nickel spinel ferrite as the catalytically active dispersed phase.
Characterization of the aerogels was performed by X-ray powder diffraction, transmission electron microscopy and N2 physisorption at 77 K. The aerogel matrix shows high surface area and very large mesopores. XRD and TEM analysis indicate that the formation of nanocrystalline NiFe2O4 in the aerogel matrix is complete at 900°C and the nanoparticles are well dispersed within the matrix with an average size of about 8 nm. The results are referred to a nanocomposite aerogel having a nominal ratio of 10 wt% of metals in the final nanocomposite.
These nanocomposites were tested as catalysts for MWCNTs production by CCVD (Catalytic Chemical Vapour Deposition) at different synthesis temperatures and using CH4 as carbon source. The results of the quantitative (yield) and qualitative (shape and dimension) analysis of the MWCNTs show that nanocomposites are very effective in producing high purity MWCNTs with very high yield (up to 600% in carbon deposit %) and homogenous diameters, that mainly depend on CCVD temperature.
This work has been funded by the Italian Institute of Technology (IIT), project SEED “NANOCAT”, the project “Porous catalyst for the production of carbon nanotubes with tailored features”, funded by the Italian Ministry for Education, University and Research (MIUR) through the PRIN 2009 call, with the contribution of “Ministero degli Affari Esteri, Direzione Generale per la Promozione del Sistema Paese”.
[1] M.F. Casula, D. Loche, S. Marras, G. Paschina, A. Corrias, Langmuir, Vol. 23 (2007) 3509-3512.
[2] D. Loche, M.F. Casula, A. Falqui, S. Marras, A. Corrias, Journal of Nanoscience and Nanotechnology., Vol. 10 (2010) 1-9.

Phosphors based on oxide hosts are of great interest due to their stability and ease of fabrication. Currently very few oxide phosphors that emit in blue are available. The nanophosphor La2O3:Bi has gained interest as a blue emitting phosphor around 450 nm wavelength with a broad bandwidth. Currently solution based techniques are used to form La2O3:Bi nanoparticles. As grown nanoparticles are not luminescent and have to be annealed at high temperature to maximize emission. We have developed a near-atmospheric pressure microwave plasma process to deposit stoichiometric nanoparticle coatings of La2O3:Bi that show high luminescence as-grown. This process enables direct incorporation of the nanophosphors into device structures. In this method a dilute stoichimetric aqueous mixture of La(NO3)3 and Bi(NO3)3 is atomized using an ultrasonic nebulizer and injected into a high temperature zone of an oxygen plasma. The microwave plasma system for nanoparticle growth consists of three main regions; (1) nebulizer to forms 1-1.5 micrometer aerosol droplets of the precursor, (2) plasma reaction zone where microwave energy generates a high temperature reaction zone for evaporation of the solvents and reaction of the chemicals in droplets and plasma gas to form the nanophosphors, (3) substrate placed above the plasma zone for the deposition of the nanophosphors. This process allows control of nanophosphor particle sizes by controlling the precursor concentration. We have demonstrated the ability to deposit La2O3:Bi nanophosphors as single crystals with sizes from 5nm to 100 nm. Structural characteristics of the as-grown particles and the dependence of the emission characteristics of the phosphors on particle size will be presented.

The mechanism of the gelation reaction of colloidal silica Si(OH)4(aq)+ Si(OH)3O^-(aq) -> Si2(O)8(H)5^-(aq) +H2O
by an anionic pathway was investigated using density functional theory (DFT). Using transition state theory, the rate constants were obtained by analyzing the potential energy surface at the reactants, saddle point, and the products. In addition, reaction rates were investigated in the presence of ammonium chloride (NH4Cl), sodium chloride (NaCl), and potassium chloride (KCl). These salts act as catalysis to induce gelation due to their ability to destabilize the double layer of colloid. Furthermore, it was observed that ammonium chloride plays an important roll by initiating a hydride transfer allowing the reaction to proceed from the second transition state to the final product.

Recently, there is growing interest in using dialkyl dichalcogenide precursors to synthesize metal chalcogenide nanocrystals in solution phase. Two distinctively reactive C-E and E-E bonds make the chemistry and photochemistry of these precursors much richer and more interesting than that of phosphine chalcogenides. Here we adopt cheap and commercially available di-chalcogenide precursors for synthesizing II-VI semiconductor nanocrystals. Specific di-chalcogenide precursors discussed were sulfides and selenides of diallyl, dibenzyl, di-tert-butyl, di-iso-propyl, diethyl, dimethyl and diphenyl. Computational studies (DFT) reveal that the dissociation energy of carbon-chalcogen bond increase in the order: Diallyl

We demonstrate molecular control of nanoscale composition, alloying, and morphology in II-VI semiconductor nanocrystal dots and rods by modulating the chemical reactivity of phosphine-chalcogenide precursors. Specific molecular precursors studied were sulfides and selenides of triphenylphosphite (TPP), diphenylpropylphosphine (DPP), tributylphosphine (TBP), trioctylphosphine (TOP), and hexaethylphosphorustriamide (HPT). Computational (DFT), NMR (31P and 77Se), and high-temperature crossover studies unambiguously confirm a chemical bonding interaction between phosphorus and chalcogen atoms in all precursors. Phosphine-chalcogenide precursor reactivity increases in the order: HPT < TOPE < TBPE < DPPE < TPPE (E = S, Se). For a given phosphine, the selenide is always more reactive than the sulfide. CdS1-xSex quantum dots were synthesized via single injection of a R3PS-R3PSe mixture to cadmium oleate at 250 °C. X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV/Vis and PL optical spectroscopy reveal that relative R3PS and R3PSe reactivity dictates CdS1-xSex dot chalcogen content and the extent of radial alloying (alloys vs. core/shells). CdS, CdSe, and CdS1-xSex quantum rods were synthesized by injection of a single R3PE (E = S or Se) precursor or a R3PS-R3PSe mixture to cadmium-phosphonate at 320 or 250 °C. XRD and TEM reveal that the length-to-diameter aspect ratio of CdS and CdSe nanorods is inversely proportional to R3PE precursor reactivity. Purposely matching or mismatching R3PS-R3PSe precursor reactivity leads to CdS1-xSex nanorods without or with axial composition gradients, respectively. We expect these observations will lead to scalable and highly predictable “bottom-up” programmed syntheses of finely heterostructured nanomaterials with well-defined architectures and properties that are tailored for precise applications.
We used as-synthesized semiconductor nanorods in photochemical fabrication of CdS-M and CdS1-xSex-M (M= Pt, Pd) hybrid nanostructures. Here, we have successfully used these hybrid nanostructures for sunlight-driven dehydrogenation and hydrogenolysis of benzyl alcohol. The heterostructure composition dictates activity, product distribution and turnovers. A few metal islands on the semiconductor surface significantly enhance activity and selectivity, and also greatly stabilize the semiconductor against photo-induced etching and degradation. Under selected conditions, CdS-Pt favors dehydrogenation (H2) over hydrogenolysis (toluene) 8:1, whereas CdS0.4Se0.6-Pd favors hydrogenolysis over dehydrogenation 3:1. Photochemically generated, surface-adsorbed hydrogen is useful in tandem catalysis, for example via transfer hydrogenation. We expect this work will lead to new paradigms for sunlight-driven conversions of biomass-relevant substrates.

The discovery of iron- based pnictide (AFeAs, where A= Na, Li) and oxypnictide (LnFeAsO, where Ln= La, Sm, Gd) superconductors have brought the transition metal pnictides especially FeAs under limelight. The iron pnictide layer is responsible for superconductivity in these compounds. Intercalation of the anionic FeAs layers with cationic Li+ or Na+ generate the 111 family of superconductors. We are attempting to synthesize these 111 nanostructured superconductors using the sacrificial template method where nanostructured FeAs can act as a morphology directing agent. As a part of these efforts we have developed a method for the synthesis of FeAs nanoparticles and nanowires. This method can effectively be applied to the formation of other transition metal arsenides like CoAs and MnAs. The synthesis involved usage of transition metal carbonyls as a source of Fe, Co and Mn , a novel arsenic precursor , Triphenylarsine (TPA) and Hexadecylamine (HDA) as a surfactant. Reaction proceeds by displacement of a carbonyl (CO) by the triphenylarsine in transition metal carbonyls at low temperatures (300°C). The close proximity of Tm ( Fe, Co, Mn) and As in the formed intermediate is believed to aid in the internal redox therefore a reducing agent is not needed in this method. Hexadecylamine (HDA) due to its coordinating ability and melting point in the temperature range of the reaction makes this synthesis a solvent-less method. For FeAs the as-synthesized nanoparticles are superparamagnetic with blocking temperature, TB as high as 240 K. The nanoparticles have a core and a carbonaceous shell. STEM, TEM, Mossbauer and XPS studies will be discussed along with details of this simple, one pot synthesis of arsenide nanostructures using this novel method.

To meet the need of function-structure integration design in BFPT-based multiferroic ceramics, specimens formed by tape casting method were studied in this letter. Firstly, Phase-pure powders 0.6(Bi_0.85La_0.15)FeO₃-0.4PbTiO₃ were obtained by solid state reaction calcined at 750^oC. The prepared powders were mixed with ethanol as solvent, polyvinylbutyral(PVB) as binder, dibutyl phthalate(DBP)-polyethylene glycol(PEG) as plasticizers and Triethylolamine(TEA) as dispersant to form tape casting slurry with viscosity range from 650 to 2700 mPa.s. Filming and rheological properties of slurry was studied by adjusting the components content. High quality casting films were obtained when the ratio of DBP-PEG/PVB was 1.5~2 with 1%~2% TEA in slurry. Casting films were dried, cut, laminated and sintered into ceramic disks. The effects of forming and sintering process on densification and dielectric properties were studied via controlling forming pressure and sintering temperature. Ceramics formed by 100-200MPa sintered from 1030 to 1070^oC with Tc=410^oC, tanδ=2.2%, εr=480 at 1kHz while Pr=5.5mu;C/cm² at 20kV/cm were obtained.

We discuss the main mechanisms of leakage current in thin PZT ferroelectric films prepared by the sol-gel method. The samples were prepared by the sol-gel method. Preparation of film-forming solutions of Pb_(1+x)(Zr_yTi_1-y)O₃) is performed by dissolving estimated amounts of the components in 2-methoxyethanol with x = 0.15 and y = 0.48. Lead acetate Pb(CH₃COO)₂ is used as Pb - containing component. Zr is introduced as solution of crystalline zirconium isopropoxide monosolvate Zr(OiPr)₄HOiPr in 2-methoxyethanol. Ti is introduced as titanium tetraisopropoxide Ti(OiPr)₄. Film-forming solution is deposited by layer-by-layer procedure on Pt - TiO₂ - SiO₂ - Si substrates . After deposition the samples are subjected to annealing (crystallization) at the temperatures of 550 - 700 °C during 20 min. Four specific regions are determined in I-V dependencies:
1) The region of very low fields (< 10 kV/cm) is characterized by the fact that the current having some finite value in the absence of the external electric field, first decreases to zero, and only after that increases with further increase of the external bias. This part of the I-V dependence characteristic may be represented as the sum of two components directed to meet each other, namely, the current due to external voltage and the depolarization current.
2) In the low fields region (from 10 to 70-90 kV/cm) I-V demonstrates a close-to-linear dependence. Leakage current in this region decreases with increasing delay time. The main leakage current components in this region are ohmic and displacement currents. Sometimes the space charge limited current which has quadratic voltage dependence is observed.
3) Next region (from 80 up to ~ 130 kV/cm) presents a transition between the low and high field regions. A relaxing jump current increase is observed, which is caused by the breakdown of the reverse bias Schottky barrier.
4) The next region is the high field one (ge; 110-130 kV/cm), where the current has more pronounced dependence on the electric field. In this region leakage current increases with the rise of the delay time in contrast to the low field region. Approximation of experimental data in the high field region gives the best results for the Pool-Frenkel model.
The experimental study of long-term (tens of minutes) depolarization process of sol-gel PZT thin films is performed. Short-circuit I-t dependences have a decaying exponential form and can be approximated by the sum of exponents with different relaxation times. Analysis of the experimental data leads to a conclusion that two different relaxation mechanisms exist. One of them has 5 - 6 times shorter relaxation times and 2 - 3 times smaller depolarization values than the second one. Comparison of sol-gel films prepared at different crystallization temperatures shows that both absolute and relative values of the depolarization increase with the increase of annealing temperature as a result of film-substrate interface distortion.

In this work we have tried to establish main regular trends in formation of crystalline structure during crystallization of thin sol-gel ferroelectric films and its effect on electrical properties of the films. For this purpose we studied microstructural and electrical properties of PbZr_0.48Ti_0.52O₃/Pt/TiO₂/SiO₂/Si multilayer heterostructures prepared at annealing temperatures in the rather wide range (from 550 to 900 °C). Perovskite grain nucleation in PZT films occurs at about 550 °C: rounded (111) grains grows on platinum surface with the same (111) orientation in this case. The height of perovskite grains comprises a half of the film thickness. Disordered perovskite grains (on the order of smaller size) and pyrochlore grains (2 ...15 nm) are formed in the bulk of the film as well. At annealing temperature 600 °C the perovskite grains grow through the whole film thickness, the amount of pyrochlore phase is significantly reduced and practically disappears when the annealing temperature rises up to 700 °C. At the same time an amount of (100) oriented perovskite grains increases and dominates over (111) oriented ones after annealing at 900 °C. The reason is activation of diffusion processes in the layers of heterostructure that leads in particular to formation of TiO₂ inclusions on the Pt surface. Dielectric hysteresis, permittivity, capacitance-voltage and current voltage dependences are studied to establish correlation between crystalline structure and main electrical phenomena in the films. Different components of crystalline structure (orientation, grain size, pyrochlore inclusions etc.) have different effect on polarization switching, permitivitty and charge transport phenomena. For example, the maximum value of remanent polarization is observed after annealing at 600 °C, at the same time permittivity of the films increases up to annealing temperature of 750 °C.

The dielectric films of perovskite oxides play the most important role in passive element such as capacitors and gate insulators, and the requirement of high performance and miniaturized element is on the steady rise. The Ba1-xSrxTiO3 is successfully commercialized as dielectric materials, but their dielectric properties are drastically decreased with reducing thickness. This decline is particularly known for damage caused by the effect of thermal strain during post-annealing process, so this process will need to be modified to more closely match the latest requirement. Therefore, synthesizing high-k material undisturbed for thickness is key point to solve the problems.
Here we investigated dielectric properties of nanosheets thin film with formula of Sr2(1-x)Bi2xNb3O10(SBNO, x = 0 to 0.3) by Langmuir-Blodgett deposition method at room temperature. SBNO nanosheets were fabricated from layered perovskites KSr2(1-x)Bi2xNb3O10 through 2-step solution based cation exchange process. We also discuss dielectric properties of bulk precursors as well. Structural properties were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM). The dielectric constant and loss value were measured from an impedance analyzer. The experimental results show that SBNO film could be applied to a high capacitive multilayer ceramic capacitor (MLCC) because of its great dielectric properties without thickness effect and low loss value because of substituting Sr ions with Bi ions in the lattice.

In recent years, the need for new buffer architectures suited to implement in coated conductors has grown exponentially. These new buffer materials should exhibit excellent crystallographic and chemical compatibility towards both the substrate and the superconducting YBa₂Cu₃O_7-x (YBCO) layer. A material which fits these needs is SrTiO₃, shortly STO. The material has the potential to be used as single buffer layer and can replace the currently used cerium oxide/lanthanum zirconate buffer stack, hence reducing the total synthesis cost and increasing the reproducibility of the coated conductor design. To ensure the sustainability of the obtained coatings, strontium titanate is synthesised starting from concentrated aqueous solutions, which allow the deposition of 150 nm thick layers in a single coating step. First, we investigated the influence of different starting materials on the stability and decomposition behavior of the precursor solution. We have deposited these solutions on single crystal LaAlO₃-substrates via dip-coating and explored the influence of the different steps in the heat treatment and the gas atmosphere on the final morphological and crystallographic properties of the layers. Highly epitaxial layers were achieved, which could allow the subsequent deposition of YBCO layers.

There is an alarming increase of a variety of new chemicals that are now being discharged into the wastewater system. This is predominantly due to the rapid emergence of technological developments within industries (e.g., pharmaceuticals) and is causing increased concern for public health and safety because many are not removed by typical wastewater treatment practices. Degradation of organic compounds by oxidation via hydroxyl radicals is a new potential treatment technology that degrades a wide range of organic compounds to complete mineralization with no selectivity. Titanium Dioxide (TiO2) is of significant interest due to its semiconducting properties that enable its use as a heterogeneous photocatalytic material, rapidly and completely mineralizing organics without harmful byproducts.
Mineralizing biological organisms demonstrate how nature can produce elegant structures at room temperature through controlled organic-mineral interactions. These organics exist as either soluble forms or as insoluble scaffolds that are often used to control size, shape, and phase of deposited mineral.
We utilize biologically-inspired scaffolds to template the nucleation and growth of TiO2 particles and porous membranes with controlled crystallite size and phase. In addition, cation and anion doping is performed to control band structure. Subsequently, the photocatalytic activity of the mixed phase particles and membranes are characterized via degradation of an organic dye. The optimal activity is discussed by anatase-rutile synergistic effect, band gap, and photocatalyst solution conditions.

Hafnium oxide hydroxide sulfate (HafSOx) with the chemical formula (HfO)_1-x-z/2(OH)_z(SO₄)_x has recently been demonstrated in applications including high-performance dielectric in thin-film transistors, and as high-sensitivity, high-resolution inorganic resists using either electron or photon irradiation. The HafSOx films are deposited using aqueous-based chemistries without the use of bulky organic ligands, which allows rapid, facile condensation with minimal volume change resulting in dense atomically smooth thin films. This method offers a solution-based, environmentally friendly route to high quality films and inorganic resists. In this study we have characterized the formation of nm-sized HafSOx clusters in solution, and the resulting films formed from these solutions. Dynamic light scattering (DLS) was used to investigate cluster stability in solution over time as a function of precursor concentrations, while high resolution transmission electron microscopy (HRTEM) imaging and scanning transmission electron microscopy energy dispersive x-ray spectroscopy (STEM-EDX) mapping were used to investigate the structural and chemical composition of the resulting films. The films were subjected to air anneals ranging from 80-300 °C, and we found chemical variation throughout the film cross-section with significant segregation toward the interfaces. X-ray photoelectron spectroscopy (XPS) confirms the presence of a composition gradient and provides information on the various chemical states in the film. X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE) are also used to help develop a model consistent with TEM data that describes the chemical and structural composition of solution-processed HafSOx films.

Chemical syntheses of nanocrystals (NCs) are known to provide a wide range of materials dispersed in colloidal solutions that are solution processable to form large assemblies of NCs in order to create solid-state devices such as field-effect transistors or solar cells. Among them, chemically doped NCs present high interest as they allow the modification and tuning of the physical properties of these assemblies. Doping of metal oxide NCs such as Zinc Oxide allows tailoring the bandgap, optical properties, carrier concentration thus conductivity.(1) Regarding conductivity properties, high quality aluminum-doped ZnO (AZO) colloïdal solutions have been published by several groups showing high conductivities in combination with high transparency (2) making AZO NCs promising materials for printing of transparent electrodes. After deposit high annealing temperature above 400°C is required in order to burn the insulating surface ligands (used during NCs synthesis to stabilize them) and to sinter the NCs into a continuous film. However, this annealing procedure is not permissible when temperature sensitive compounds or substrates are involved (i.e. organic/inorganic hybrids materials or flexible substrates). In this context, a new chemically AZO NCs synthetic method allowing high concentration of Al doping is presented within this work in addition with a ligand-exchange procedure to remove the bulky insulating ligands, avoiding any post-treatment annealing to remove them.
The synthetic route is thus described and shows the parameters involved to control both the aluminum doping level and the NCs morphologies (spheres, triangles or hexagons). Characterizations of the doped nano-materials are discussed comparing systematically before and after the ligand-exchange procedure for structural properties, optical properties and surface state. Thin films made by different deposition techniques of AZO NCs solutions were realized and studied to evidence changes in charge transport toward highly conductive transparent films.
(1) Yizheng Jin et al. Journal of Nanomaterials, 2012, 985326
(2) Tran V. Thu et al. Journal of Applied Physics, 2010, 107, 014308

Ceramic based nanocomposites have recently demonstrated the ability to provide enhanced permittivity, increased dielectric breakdown strength, and reduced electromechanical strain making them potential materials systems for high energy density applications. A systematic characterization and optimization of barium titanate and PLZT based nanoparticle composites employing a glass or polymer matrix to yield a high energy density component will be presented. This work will present the systematic characterization and optimization of barium titanate and lead lanthanum zirconate titanate nanoparticle based ceramics. The nanoparticles have been synthesized using solution and pH-based synthesis processing routes and employed to fabricate polycrystalline ceramic and nanocomposite based components. The dielectric/ferroelectric properties of these various components have been gauged by impedance analysis and electromechanical response and will be discussed.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Chemical solution growth of YBCO nanocomposite thin films with spontaneously segregated oxide second phase nanoparticles are shown to be an excellent low cost processing option with huge isotropic pinning forces at large magnetic fields. We will report on the growth mechanisms of solution-derived trifluoroacetate-YBCO nanocomposites with BaZrO3 and Ba2YTaO6 second phase nanoparticles. Atomic scale investigation shows that the presence of mainly randomly oriented nanoparticles generates incoherent interfaces within the epitaxial YBCO matrix which dramatically increases the density of planar defects in the form of Cu-O intergrowths. Associated partial dislocations generate a ramified network of inhomogeneously distributed nanostrained regions where the crystalline perfection of the superconductor is perturbed. We will present the effect on nanoparticles morphology, density, distribution, coarsening and orientation by modifying the processing conditions. Using advanced X-Ray and Scanning Transmission Electron Microscopy (STEM). In particular, we have observed a tendency of nanoparticles to aggregate in specific facets at high concentrations. Modifications of the processing parameters to control this phenomenon have been undertaken and will be evaluated. Comparison between different nanocomposites will be done. The correlation between processing parameters, microstructure and superconducting properties will be discussed for the different nanocomposites.

One dimensional nanostructure network composites, such as metallic/semiconducting nanowires and nanotubes, are promising candidates for low cost electronic devices. In this work, we report the charge transport analysis of the percolated network with one dimensional nanostructure having multimodal length distributions using Monte-Carlo simulations. The simulation was first validated with the excluded volume theory and experimental results under single length network conditions. We find that the bimodal length distributed network provides the significant percolation threshold reduction and the charge transport improvement. We have also found that the increasing the standard deviation of length dimension decreases the percolation threshold because of increasing long length contribution within the network. Based on the simulation, we suggest that the percolation threshold with multimodal lengths follows the weighted harmonic mean of single length percolation threshold. Finally, we present how multimodal system can affect the electrical and optical properties. This fundamental understanding may lead to the development of novel nano network electronics with multi component systems with different dimensions, such as metallic/oxide/carbon hybrid nanowire transistors and transparent conductors.

La0.6Sr0.4Co0.2Fe0.8O3-δ-Ce0.8Gd0.2O1.9 (LSCF-CGO) composite thin film cathodes were produced by spraying a single precursor solution of nitrate salts onto dense yttria stabilized zirconia electrolyte substrates at 235°C. Films annealed at 600°C contained a mixture of amorphous regions and crystalline regions composed of fine crystallites (< 5 nm). Annealing above 600°C increased the ratio of crystalline to amorphous material, led to the segregation of the films into distinct LSCF and CGO phases, and promoted grain growth. The electrical behavior of the films depended on annealing temperature. At testing temperatures of 400°C and below, the polarization resistance of films with lower annealing temperatures was larger than the polarization resistance of films with higher annealing temperatures. However, at testing temperatures of 500°C and above the polarization resistance of films with lower annealing temperatures was equal to or lower than the polarization resistance of films with higher annealing temperatures. This was reflected by the activation energy that decreased with increasing annealing temperature. The varying electrical behavior may be related to microstructural changes that caused bulk diffusion to be the rate-limiting step in films with lower annealing temperatures and oxygen dissociation to be the rate-limiting step in films with higher annealing temperatures.

Flexible and transparent barrier coatings are essential for the protection of sensitive electronic devices against oxygen and water vapour, as in inorganic and organic thin-film photovoltaic cells and organic light-emitting diodes (OLEDs). Photochemical approaches to inorganic barrier layers offer an attractive alternative to sol-gel techniques or vapour deposition techniques because neither temperatures above 100 °C nor high vacuum are required. Roll-to-roll coating processes become technically feasible.
Almost carbon-free thin aluminum oxide layers have been prepared by irradiation of solid aluminum precursor layers with a xenon excimer lamp. Results of XPS, XRD, XRR, and spectroscopic ellipsometry investigations as well as quantum chemical calculations will be presented. The process will be evaluated with regard to different precursors, reactand gases and irradiation doses.
The potential of photochemical conversion of metal complexes into oxides at ambient temperature and pressure will be presented as an alternative method to sol-gel techniques.

Semiconductor nanoparticles have attracted much interest during the past decades in both fundamental researches and technical applications due to their unique size dependent optical, electronics properties [1]. Polymer-semiconductor nanoparticle-composites offer the promise of a new generation of hybrid materials with a numerous possibilities of applications such as in optical limiting [1], optical data storage, optical computing, optical displays, catalysis, photovoltaics, gas sensors and light emitting diodes (LED). To fabricate nanoparticle-composites, carbon nanotubes (CNTs) are one of the potential candidates to be incorporated into the resins, since they can reinforce polymers and support the nanoparticles. However, when it comes to synthesis CNT-based composite materials, there are still the obstacles to overcome. Especially, the uniform dispersion of the nanoparticles into the matrix, which is enormous importance for the overall properties of the composites materials, is still challenging and is more difficult.
In this study, we have adopted a facile route to synthesis of Polyaniline (PANI)/CNT- CdS nanocomposites at room temperature by in-situ polymerization of aniline [2] in the presence of multi-walled carbon nanotubes (MWCNT) and negatively charged CdS nanoparticles. The nanocomposites have been characterized by HRTEM, FTIR, UV-VIS absorptions spectroscopy, photoluminescence (PL) spectroscopy and Raman spectroscopy. HRTEM observation showed that CdS nanoparticles were well distributed over CNT surfaces and the average CdS particle diameters were ~2.74 nm. UV-VIS and PL measurements indicateds that the incorporation of CdS nanoparticles in PANI-MWCNT enhanced the PL emission intensity and showed red shift with the increase in particles size. Raman measurement indicateds the good optical properties of nanocomposites, which were caused by well incorporation of CdS nanoparticles within the matrix of PANI and MWCNT.
This work was partially supported by the Japan Society for the Promotion of Science (JSPS), Grant-in-aid for Scientific Research (c) 21510119 and the Instrument Center of the Institute for Molecular Science (IMS).
References
1. M. J. Soileau, S. Guha, and E. V. Stryland, SPIE 540, 520-527 (1985).
2. M. Ghoswami, R. Ghosh, G. Chakraborty, K. Gupta, and A.K. Meikap, Polymer Composites, 32, 2017-2027 (2011).

Ytterbium films with low concentrations of iron (0.3-5.0 at%) have been prepared by co-deposition of atomic beams of the pure elements. The films were deposited onto Kapton substrates kept at room temperature under high vacuum. Iron is immiscible in ytterbium and various iron species are expected to occur.
The XRD reveals a mixture of fcc and hcp ytterbium. The several Mössbauer spectra are interpreted with contributions from two types of iron aggregates with different size and shapes. The first one is attributed to iron dimers or small clusters and the other to clusters formed upon diffusion. It is possible that the smaller aggregates, with low values of the isomer shift and large values of quadrupole splitting, are related to the mixture of fcc and hcp Yb phases. It is important to be noted that cluster formation is associated at low values of quadrupole splitting which would suggest that is going to iron bcc, despite the low temperature spectra do not show indication of α-Fe hyperfine field.
In addition, one singlet line is observed that is attributed to iron monomers, that is same found in early works. Mössbauer spectra in an applied magnetic field indicate clusters moments on the order of 90 mu;_B. Unlike previous work we found that cluster formation is increasing systematically with iron concentration.
This work was supported by CAPES, FAPERJ, Brazilian-German research program financed by CNPq and DFG 444BRA-113/55/0-1.

Mesoporous silica materials with ordered pores have received a great deal of attention because of their exceptionally large specific surface area, which can be used for a wide range of applications in various fields. Mesoporous silica thin films also have been studied as potential ultralow k materials, where inclusion of ordered pore structure in the silica matrix decreases the dielectric constant. In order to apply this excellent material in various fields, it is important to obtain mesoporous silica films with uniform porosity as well as film thickness. This paper describes the synthesis of thin films of mesoporous silica with a two-dimensional (2D) hexagonal structure using TEOS and Pluronic P-123 difunctional block copolymer surfactant. Initial reactants such as concentrations of TEOS as well as pluronics used affect the pore size and the film thickness of mesoporous silica. Mesoporous silica channels with uniform lateral spacing were fabricated by employing a lithographic mask followed by etching into silica. ICP dry etch methods are an advanced and sophisticated processes to provide highly anisotropic profiles with excellent control over selectivity to mask materials using low pressure plasmas which generates high density ion fluxes resulting no damage or disruption of the pore arrangement of the mesoporous silica thin films within the channels. The crystal structure, morphology, pore arrangement and sizes were determined by XRD and SEM. Ellipsometry measurements and cross sectional SEM images determine the thicknesses of mesoporous silica thin films.

One type of inverted type-Ι core shell In2O3/In2S3 nanostructures was prepared by in-situ anion exchange via a hydrothermal process at low temperatures. Ultra violet photoelectron spectroscopy (UPS) shows that the In2O3/In2S3 interface is an inverted type-Ι heterojunction. The energy potential in this structure would drive both the photo-generated holes and electrons towards the shell to facilitate photocatalytic H2 generation. The conversion process of In2O3 core to shell In2S3 nanostructures can be observed by scanning electron microscope (SEM) and transmission electron microscopy (TEM). Different thickness of In2S3 shell layers is controlled by different temperatures and furthermore, a hollow In2S3 nanotube consisted of nanoflakes are obtained due to Kirkendall effect. Compared with some reported Indium-based photocatalysts, the core shell In2O3/In2S3 obtained at 90 degree exhibits good H2 evolution rate of 61.4 mu;mol/h/g, which is due to the inverted type-Ι structure. This work may open avenue for application of inverted type-Ι materials.

In the fabrication of PCBs (printed circuit boards) and other electronic devices, copper (Cu) and/or Cu alloy plating are widely used for metallization. By recent studies, the characteristics of electroless Cu-Ni alloys such as thermal stablility, corrosion resistance, solderability, magnetic and electrical properties, are superior to that of the electroless Ni plating.
In high power LED, the thermal problem that is brought by heat generated within the LED itself is still a bottleneck that limits the stability, reliability and lifetime of high power LED. Accordingly, a ceramic Al2O3 layer is used as heat sinks of high power LED devices.
Commercial electroless Cu and/or Cu-Ni alloy plating solutions are operated at pH values above 9~11 [1,2]. However, a near neutral (~pH 7) process is required in circuit formation on Al2O3 substrate for high-power PCB because Al2O3 substrate can be damaged by a strong acid and/or strong alkali solution. Although elelctroless Cu-alloy plating has been studied by some researchers, there is not report of electroless Cu alloy plating on PCB included ceramic Al2O3 layer for high power light-emitting diode (LED).
In this study, we controlled the pH of electroless Cu-alloy plating solution to minimize a damage of substrate Al2O3 layer. According to various pH and plating temperature of electroless Cu-Ni plating solution, the characteristics of Cu alloy films were analyzed by XRD, XPS, and FE-SEM, etc.
Reference
[1] J. Li, P.A. Kohl, J. Electrochem. Soc. 150 (2003) C558.
[2] L. Zhu, L. Luo, J. Luo, J. Li, and Y. Wu, Int. J. Refractory Metals and Hard Materials, 31 (2012) 192.

High power LED is a strong candidate for the next generation of general illumination applications, and it is attracting interest due to its significant impacts on solid-state illumination industry. However, the thermal problem that is brought by heat generated within the LED itself is still a bottleneck that limits the stability, reliability and lifetime of high power LED.
In recent year, a ceramic Al2O3 layer is used as heat sinks of high power LED devices. Currently, a printed Ag paste was mainly used on anodizing insulator film as forming a metal PCB. Thus, film growth of electroless Ni, Cu, and Au etc, for formation of circuits on printed Ag pattern / anodized Al substrate is very important. Among the various types of electroless deposition, electroless Ni-B has gained immense popularity due to its ability to provide a hard, wear and corrosion resistant surface.
However, Al2O3 substrate can be damaged by a strong acid and/or strong alkali solution for electroless metal plating. Thus, a near neutral (~pH 7) process is required in circuit formation on Al2O3 substrate for high-power PCB because However, there is not report of electroless Ni-B plating on PCB included ceramic Al2O3 layer for high power light-emitting diode (LED).
In this study, we investigated a growth of electroless plated Ni-B film on screen printed Ag pattern with anodized Al substrate, by using XPS and XANES tools which are excellent methods to monitor surface chemistry and charge distribution and chemical bonding in Ni-B films because a understanding of interface and surface in this system is very important. All processes were carried out in electroless solution of ~pH 7 to minimize damage to the alumina substrate. In order to have direct local electronic and/or chemical structural information of the samples, we employed X-ray photoelectron spectroscopy (XPS) analysis and NEXAFS (near edge X-ray absorption fine structure; 10D XAS KIST beamline of the Pohang Light Source in Korea) In addition, AFM (Atomic Force Microscopy), SEM (Scanning Electron Microscope), and XPS (X-ray Photoelectron Spectroscopy) data analysis tools to determine the surface morphology and chemical properties of each sample.
[1] Sheng Liu and Xiaobing Luo “LED Packaging for Lighting Applications; Design, Manufacturing and Testing” (2011 Chemical Industry Press. Singapore).
[2] K. M. Kim, S. H. Shin, Y. K. Lee, S. M. Choi, and Y. S. Kwon, Electronics Letter 44(1), 24-25 (2008).

Antimicrobial properties of polymer materials are required in many applications. Silver nanoparticles can be used on common polyurethane foams to obtain particular properties like antifungal and antibacterial activity. A series of nanocomposites (PU-Ag) from a urethane-type polymer (PU) incorporated with various amounts of silver nanoparticles (with an average size of 20 nm) were prepared in this study. The surface morphology and the thermal and mechanical properties as well as the antifungal ability of the nanocomposites were investigated. Different surface morphology in PU-Ag nanocomposites materials was found. The latter nanocomposite showed enhanced thermal and mechanical properties, compared with the original PU. It was found antifungal activity against Trichophyton mentagrophyetes fungus at a specific concentration of silver nanoparticles. The silver nanoparticles have demonstrated its effect on microorganisms like virus and bacteria, there are, however, only few reports in the literature about the effect of silver nanoparticles on fungi. The antifungal activity of silver nanoparticles has not been studied extensively, this encourage us to study the effect of silver nanoparticles on fungus.

Nanocomposites of multi-walled carbon nanotubes(MWCNT) and polyaniline(PANI) were synthesized and used as reducing agents in the formation of Au nanoparticles. The average of Au nanoparticle size was 20-50 nm and it was easily controlled by just varying the concentration of MWCNT-PANI. The redox states of PANI were monitored by IR and UV-Vis and these results confirmed that the oxidation of PANI on the MWCNT caused the reduction of gold. The solubility and the surface of the nanocomposite were changed significantly due to the oxidation of PANI on the surface of MWCNT.

Size-dependent structural and optical properties were investigated for graphene quantum dots (GQDs) prepared by thermal deoxidization and hydrothermal cutting of graphene oxide sheets made from natural graphite powder. High-resolution transmission electron microscopy images demonstrated that GQDs appeared as the circular shape with mixed edges of zigzag and armchair for average sizes (d) le; ~17 nm, but as the polygonal shape mostly with armchair edges for d > ~17 nm. Atomic force microscopy images/height profiles of GQDs showed that the average thickness of GQDs increased with increasing their size, consistent with the electron energy loss spectroscopy results. With increasing d from 5 to 35 nm, the absorption peak energy of GQDs decreased from 6.2 to 4.6 eV, consistent with the quantum confinement effect, but the continuous-wave and time-integrated photoluminescence (PL) peak energies unusually showed non-monotonic behaviors having a minimum at d = ~17 nm. Size-dependent time-resolved PL traces were well fitted to biexponential functions with lifetimes of tau;1 and tau;2, possibly resulting from size-independent fast band-to-band transition and size-dependent slow transition, respectively. Size-dependent properties of Raman shifts and intensities were similar to the anomalous PL behaviors. These results were attributed to the size-dependent shape and corresponding edge variations of GQDs at d = ~17 nm as d increases.

We present a facile one-pot synthetic route for the preparation of silver nanocrystals via a simple proton beam irradiation process at room temperature. Size- and shape-controlled silver nanostructures were prepared in an aqueous phase-based solution without the addition of any harsh reductants. Morphologies of the prepared nanostructures were controlled just by changing the stabilizer and by controlling the molar concentration ratios of surfactants to metal precursors. It was observed that the size of the resulting Ag nanocrystals was easily varied by changing the stabilizer from hexadecyltrimethylammonium bromide to sodium dodecyl sulfate. We also found that the size of the prepared silver nanocrystals was decreased as the molar ratio of hexadecyltrimethylammonium bromide to silver ion was increased.

Ferromagnetic iron sulfides, such as pyrrhotite (Fe₇S₈) and greigite (Fe₃S₄), are important for biomagnetic, paleomagnetic and environmental magnetic studies [1, 2]. To develop a cost-effective and facile method for the synthesis of magnetic nanoparticles (NPs), we present a one-step synthesis to directly and quickly produce the pyrrhotite (Fe_1-xS) and greigite (Fe₃S₄), and study their structural and magnetic characteristics.
Fe₃S₄ and Fe_1-xS NPs were synthesized via thermal decomposition of iron nitrate and sulfur powder in octadecylamine (ODA) at temperature between 240 °C and 310 °C. As the heating temperature increases, the crystalline structure of the synthesized iron sulfide NPs undergoes a transformation from single cubic spinel phase (240 °C) to the pure hexagonal pyrrhotite with a NiAs-type structure (310 °C). The mean crystallite size of synthesized Fe_1-xS and Fe₃S₄ are 23.0 nm and 31.6 nm, respectively. TEM images indicate that the synthesized iron sulfide NPs are mainly hexagonal nanosheet structure with an opposite side distance of 100-300 nm. Saturation magnetization M_S decreases as the synthesized temperature increases, and the M_S value of spinel phase is clearly higher than the hexagonal phase. However, the hexagonal phase dominated samples have a high coercivity during structural evolution. This variation of magnetic properties is probably caused by the atomic rearrangement of Fe and S in the temperature range from 240 °C to 310 °C. Detailed magnetic behavior of iron sulfide NPs during structural evolution was discussed in terms of iron vacancies distribution over the crystal lattice.
References
1. D. Rickard and G. W. Luther, Chem. Rev.107, 514 (2007).
2. W. Bosum et al., J. geophys. Res. 102, 18307 (1997); A. P. Roberts, Earth Planet. Sci. Lett. 104, 48 (1991).

Copper chromite, CuCr₂O₄ is a tetragonally distorted normal spinel with a c/a ratio of 0.910, referred to a face-centered unit cell [1]. The Cu²⁺ ions are on the tetrahedral sites of the spinel-type structure and the Cr³⁺ ions are on the octahedral sites. In addition, the environment for copper ions is a distortion from a tetrahedron towards a square and is also slightly rotated about the c-axis. The chromium ions are slightly displaced from their ideal positions [1].
In this paper, CuCr₂O₄ nanoparticles were successfully synthesized by the combustion of mixtures of copper nitrate, chromic nitrate, citric acid, and glycine. The mean crystallite sizes (d) of the samples, annealed in air at 200-885 C for 1hr, are in the range from 2 to 50 nm. Samples were characterized by the X-ray diffraction, TEM, and SQUID. Magnetic measurements showed that the Curie temperatures T_C and initial permeability mu;₀ increase as the crystallite size increases. The saturation magnetization M_S, magnetic anisotropy field H_A and magnetocrystalline anisotropy constant K₁ of the particle assemblies were estimated by the law of approach to saturation. The coercivity H_C and M_S, determined from the hysteresis loops for the samples cooled in zero-field down to 5K, have a striking dependence on crystallite size. As the crystallite size is reduced, it is found that the M_S increase, go through a maximum, and then decrease. Moreover, we found an unusual behavior in the magnetization curves (H); the virgin curve extends outside the hysteresis loop. This phenomenon has been observed in spin glasses system. It is suggested that there is an irreversible field induced anisotropy in the CuCr₂O₄ nanoparticle surface state. Based on CuCr₂O₄ structure, the details of the mechanism leading to the observed results are discussed.
Reference
1. E. Prince, Acta Cryst. 10 (1957) 554.

Fluxgates are general use vectorial magnetometers with good trade-off between sensibility, power consumption, thermal offset and easy of use. They are able to measure from static magnetic fields up to low frequencies in the 10^-10 to 10^-4 T range [1]. Besides the small size, the advantages of miniaturizing this kind of sensors are the small weight, high geometrical selectivity, low cost in mass-production and on-chip electronics integration. But the sensor noise increases drastically for the smaller devices. Several planar and/or miniature type sensors have been reported, usually making use of two types of planar coils, spiral [2] or 3-dimensional solenoids [3]. The former are found in numerous works that dispose the coils in two or more metal layers (up to four). The later results in a better coupling with the core and allow ring-core sensors, but it also needs at least two metal layers and presents other process disadvantages. We are interested in developing a high resolution miniature fluxgate with a simpler process that uses just one layer of spiral planarized coils and rectangular NiFe electroplated cores. This approach leads to half core with evanescence excitation, increasing the noise level. An adopted mitigation solution was to insert the excitation coils parallel to the pick-up ones. A macro-scale millimeter-sized prototype was already developed to test the hypothesis [4]. For core fabrication we used an optimized current density of 14 mA/cm² and an electroplating solution bath of NiSO₄ (0.7 mol/l), FeSO₄ (0.03 mol/l), NiCl₂ (0.002 mol/l), H₃BO₃ (0.4 mol/l) and sodic saccharine (0.016 mol/l). For this work we build and characterized miniaturized planar fluxgate sensors (10.8 x 3.7 mm² surface area) using the single layer coils layouts with the optimized electroplated 3 µm thick NiFe core. The coils had 30 spires, which spacing was 30µm. The spires were 30 µm wide and 15 µm thick. Responsivity up to 16V/T and noise levels down to 6 nT rms (in the 0.015 to 10 Hz range) were obtained for a 1.6 kA/m excitation field amplitude. Despite the simpler process, this noise level is better than most reported sensors with about the same size. Core fabrication, sensor development, sensor characterization and future optimizations will be discussed in this presentation. Work supported by CAPES, CNPq and FAPESP. References: [1] P. Ripka, Magnetic Sensors and Magnetometers. Artech House Publishers, Jan. 2001.
[2] L. Rovati and S. Cattini, IEEE Transactions on Industrial Electronics, vol. 59, pp. 571-578, Jan. 2012.
[3] E. Delevoye, M. Audoin, M. Beranger, R. Cuchet, R. Hida, and T. Jager, Sensors and Actuators A: Physical, vol. 145-146, pp. 271-277, July 2008.
[4] T. Heimfarth and M. Mulato 219th Electrochemical Society Meeting, Montreal, ECS Transactions 2011.

The hydrophobic Au nanoparticles can produce a size change of 440% from 10 nm to 54 nm through the control of the volume ratio of the co-surfactants. In our system, the size change within a wide range is attributed to the high controllability of a surfactant in particle growth. It is very important to size change Au nanoparticles in one synthetic system because the surface energy and the optical properties of gold nanoparticles depend considerably on their size.
The as-prepared hydrophobic Au nanoparticles could be transferred into a water phase, and the hydrophilic Au nanoparticles were employed as a sensing agent for HCl in a colorimetric system. Consequently, our colorimetric technique shows the color transition of an HCl concentration up to 10 ppm. In addition, identical procedures for HCl detection are applied to other acid and salt species, but these showed a color change of the solution from 100 ppm and changeless color at any concentraions, respectively. These results reveal the high sensitivity and selectivity of an as-worked system toward HCl.

A general synthetic protocol for colloidal 2-D layered transition metal chalcogenide (TMC) nanocrystals with size tunability is developed. After introducing the synthesis of IV and V transition metal sulfide (TiS₂, ZrS₂, HfS₂, VS₂, NbS₂, and TaS₂) nanocrystals, especially titanium sulfide with well-defined single crystallinity and lateral size controllability, our synthetic protocols are extended to metal selenide (TiSe₂, ZrSe₃, HfSe₃, VSe₂, NbSe₂, and TaSe₂) nanocrystals. We discover that the use of suitable chalcogen source is important for synthesis of well-defined 2-D layered TMC nanocrystals. For 2-D layered metal sulfide nanocrystals, CS₂ is an efficient chalcogen precursor while elemental S is not appropriate due to the generation of reactive radicals. Interestingly, elemental Se is useful for 2-D layered metal selenide nanocrystals regardless of Se radical generation. Compared to S radicals, less reactive Se radicals have no adverse effect on the formation of metal selenide nanocrystals.

There are growing interests in the development of novel optical materials/ engineering process based on sol-gel hybrid glasses doped with inorganic materials and particles to satisfy a set of our multidisciplinary demands. In this work, we introduce a highly fluorinated sol-gel glasses doped with nano-scaled inorganic phases. It was molecularly designed and then synthesized for optical device materials, especially laser device materials. By modifying the Si-O-Si polymeric network, we prepared sol-gel glasses to homogeneously dope inorganic functionalities. We prepared fluoroalkylene-bridged polysilsesquioxane doped with both of Er+3 ions and CdSe nano-particles. In photoluminescent study, a significant enhancement in fluorescent intensity at 1540 nm has been observed from the sol-gel glass doped with Er+3 ions and CdSe phases. The presence of CdSe nano-particles, by virtue of their low phonon energy, also appears to significantly influence the nature of the surrounding environment of Er+3 ions in thosesol-gel glasses, resulting in the increased fluorescent intensity. It is a functional modification for the chemical environment of Er+3 ion-fluorescence.

Inorganic nanoparticle/organic hybrid materials attract increasing attentions because of their beneficial properties of each phase. Zinc oxide is an n-type semiconductor with wurtzite structure and its nanoparticle is used for luminescent materials and photocatalysts. The authors reported the syntheses of Fe- and Er-doped ZnO particle/organic hybrids from metal-organics [1,2]. ZnO is an appropriate host oxide for many visible photoluminescence (PL) centers. ZnO nanoparticles doped with rare-earth ions are expected to be novel optical materials because of their sharp and intense optical emission spectra. This paper describes the synthesis of Yb-doped ZnO particle/organic hybrid with water solubility and biocompatibility. Zinc-organic and ytterbium -organic dissolved in ethanol were hydrolyzed and polymerized under controlled conditions. The hybrid was analyzed by FT-IR, DTA-TG, powder XRD, UV-visible and luminescence spectroscopy. The formation of ZnO nanoparticles in an organic matrix was confirmed by XRD analysis. The crystallite size of ZnO increased with increasing hydrolysis time. The size of ZnO particles dispersed in the hybrid was controlled by selecting the hydrolysis conditions. The hybrid had a water dispersability by adjusting organic polymer matrix. Yb-doped ZnO particle/organic hybrids were confirmed to generate the characteristic emissions of Yb ion at 980 nm. Yb-doped ZnO particle/organic hybrid injected in a mouse showed an emission at 720 nm. Yb-doped ZnO particle/organic hybrid has a potential of application in bioimaging materials.
1. T. Yogo, T. Nakafuku, W. Sakamoto and S. Hirano, J. Mater. Res., 20, 1475(2005).
2. M. Kachi, M. Ichida, T. Wada, H. Ando, W. Sakamoto, and T. Yogo, J. Mater. Sci., 47, 5128
(2012).

Inorganicminus;organic hybrid materials with one-dimensional structures have received much attention because of their tremendous potential in providing enhanced materials properties that are not easily achievable with either organic or inorganic materials alone. For example, II/VI-based one-dimensional hybrid semiconductors, MQminus;(L)_n (M =Zn, Cd, Mn; Q =S, Se, Te; L =hydrazine, ethylenediamine (en), cyclohexylamine; n =0.5 or 1) have been demonstrated to be a new family of multifunctional hybrid materials. We have developed a one-pot and solvent-assisted solvothermal process to synthesize ZnS(en)_0.5 (en = ethylenediamine) hybrid nanobelts having controlled length-to-width (aspect) ratios. While typical hybrid nanobelts synthesized at 180 °C for 6 h have an average width of 130 nm, a mean thickness of 55 nm, and an average length of 16 mu;m, their aspect ratios have been varied by adjusting solvent volume ratios of hydrazine monohydrate (hm) to en. A sufficient amount of sulfide from the reduction of sulfur by hm has been found to be essential for the efficient anisotropic one-dimensional growth of highly crystalline ZnS(en)_0.5 hybrid nanobelts. The photoluminescence spectra of ZnS(en)_0.5 hybrid nanostructures exhibit three bands located at 327, 415minus;430, and 587minus;654 nm, which are assigned to band-edge emission, trap sites-related emission, and anion-vacancy emission, respectively. The mean lifetime of photoluminescence having three decay components of 30, 170, and 2700 ps decreases with the volume ratio of hm to en due to the decrease of defect sites with the increase of the aspect ratios of ZnS(en)_0.5 hybrid nanobelts. Compared with bare-ZnS nanobelts prepared by the hydrothermal treatment of ZnS(en)_0.5 hybrid nanobelts, the hybrid nanobelts have intrinsically high flexibility and shown enhanced optical properties that would give them potential for soft (flexible and stretchable) electronic devices.

Pb(Zr_xTi_1-x)O₃ (PZT) is a technologically important material due to its high piezoelectric and ferroelectric properties [1]. In the past few years, a considerable amount of research has been focused on the growth of PZT one-dimensional (1-D) nanostructures for potential applications in miniaturized non-volatile random access memory devices, nanoscale piezoelectric transducers and actuators [2]. In this end, PZT nanowires and nanotubes were mostly prepared by template assisted modified sol-gel process on conducting substrates [3], and hydrothermal process on Ti metal foils [4]. However, limitations in applicability of this technology exists because of the difficulties in controlling the dimensions and alignment of these nanostructures, and due to the lack of suitable processing techniques. We have developed a novel two-step bottom-up approach for fabricating low-D PZT nanostructures of different shapes and sizes on conducting substrates without using any template. The approach involves depositing an ultra thin PZT seed layer on single crystal conducting substrates by Pulsed Laser Deposition (PLD) followed by direction oriented growth of PZT nanostructures by facile solution based synthesis processes. Alternatively, Ti seed layer was deposited by sputtering on different substrates and hydrothermal process was used to orient the growth of PZT nanostructures. These approaches discussed here allow improved tunability of the size, shape, and orientation of PZT nanostructures as investigated by X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. Electronic properties such as field emission properties and ferroelectric properties of the nanostructured films were measured and the results are discussed in context of understanding the potential of these nanostructures for advanced device applications.
[1] L.W. Martin, Y.-H. Chu, and R. Ramesh, Mater. Sci. Eng. R 68, 89 (2010).
[2] A.N. Morozovska, E.A. Eliseev, and M.D. Glinchuk, Phys. Rev. B 73, 214106 (2006).
[3] J. Kim, S.A. Yang, Y.C. Choi, J.K. Han, K.O. Jeong, Y.J. Yun, D.J. Kim, S.M. Yang, D. Yoon, H. Cheong, K.-S. Chang, T.W. Noh, and S. D.Bu, Nano Lett. 8, 1813 (2008).
[4] Y. Lin, Y. Liu, and H.A. Sodano, Appl. Phys. Lett. 95, 122901 (2009).

Sol-gel derived NiFe2O4/Pb(Zr0.52Ti0.48)O3 (NFO/PZT) thin film multilayer composites, with and without an intermediate layer of platinum, are grown on silicon, sapphire and platinum substrates. X-ray diffraction and scanning electron microscopy show phase-pure spinel cubic NFO and tetragonal perovskite PZT in the single component films and the multilayered structures. Texture studies are performed to evaluate the effect of textured (111) NFO layer on orientation of the PZT layer in different multilayer configurations. Transmission electron microscopy (TEM) reveals a sharp interface between the NFO and PZT layers in the Si/NFO/PZT multilayers. The presence of an intermediate Pt layer between the NFO and PZT reduces Pb diffusion into the NFO and silicon substrate, as evidenced by TEM and secondary ion mass spectroscopy. The saturation magnetization of Si/NFO/PZT multilayers with and without the intermediate Pt layer increase by 20% and 25%, respectively, relative to the Si/NFO films. The intermediate Pt layer (Si/NFO/Pt/PZT) also reduces the leakage current with respect to Si/NFO/PZT. A maximum remnant polarization of 22 mu;C/cm2 at 100 Hz is measured for Si/NFO(310nm)/Pt(100nm)/PZT(475nm) composites.

Bottom-up synthesis of electronic materials has attracted a great attention to lead innovation in the field of industrial technology. Nanometer-sized single crystals in cube shape (nanocubes) are expected to be candidates as building blocks for the electronic devices. Nanocubes of perovskite compounds such as BaTiO3 and SrTiO3 were synthesized by the hydrothermal method using aqueous sources of Ba, Sr and Ti, and organic additives. TEM and HRTEM images indicated that each 15 nm-sized single crystal had a cubic shape with sharp edges and high lattice coherence. Since the organic surfactant including long chains of C-C bond were adsorbed at the {100} surfaces of nanocubes, they were easily dispersed in non-polar solvents. Based on the highly dispersing properties and the volatility of solvents, the nanocubes were arranged into orderly structures by the capillary force assisted self-assembly method. In the BaTiO3 nanocube assemblies, the ordered region was over a wide range in tens of micrometers. The nanocubes were attached each other in face to face so that the assembly was quite dense. After the heat treatment at 1123 K, the original cube shape remained in the grains and a number of sharp interfaces run parallel in three dimensions. The piezoresponse behavior of the assemblies was identified by PFM. The d33-V curves of BaTiO3 nanocube assemblies showed hysteresis due to the ferroelectricity. In contrast, SrTiO3 nanocube assemblies showed the paraelectric linear relation, which was identical to the property of the constituent block. However, the mixture assemblies showed a distinguished behavior, which was a combination of non-linear and stepwise changes against the poling field. The results suggested that BaTiO3/SrTiO3 heterogeneous interfaces existing parallel and perpendicular to the surfaces of top and bottom electrodes affected the dielectric properties. The grain and interface-designed structures consisting of cube-shaped dielectric building blocks have potentials to tune the properties and would open for future dielectric device applications.
This work was supported by the Collaborative Research Consortium of Nanocrystal Ceramics, and the Advanced Low Carbon Technology Research and Development Program (ALCA) of Japan Science and Technology Agency (JST).

In recent years, weight reduction of aerospace vehicles has become critically important for improved efficiency and reduced operating costs. Aerospace structures typically consist of multiple systems each performing diverse functions with corresponding subcomponents. Significant weight savings may be achieved, however, by using materials that simultaneously perform multiple functions. These so-called multifunctional materials provide an approach for increased efficiency by integrating functions such as energy storage, or sensing, into structural materials. Polymer-matrix composites (PMCs), which have been widely used for aerospace structures because of their outstanding specific strength and specific stiffness, lend themselves naturally to the concept of multifunctionality. Because of the way that PMCs are processed, it is convenient to incorporate various kinds of fillers into polymer matrices to perform multiple functions for overall system weight reduction.
In this talk, the processing of three types polymer-matrix nanocomposites and their multifunctional properties will presented. The first one is a polystyrene-capped barium titanate (BaTiO3) nanoparticles with sizes of 11 nm and 27 nm. The nanoparticles were synthesized using amphiphilic star-like diblock copolymer templates. The crystal structure evolution of these nanoparticles over a wide temperature range (10-428 K) was investigated by powder X-ray diffraction. The Rietveld refinement indicates that the abrupt structural transitions observed in micron-sized powders become broad as particle size is reduced to a few tens of nanometers. The orthorhombic phase (Amm2) is observed in the range of 10-388 K, coexisting with the rhombohedral phase (R3c) at lower temperatures and with the tetragonal phase (P4mm) at higher temperatures. At room temperature (300 K), polystyrene-capped BaTiO₃ nanoparticles, both 11 and 27 nm sizes, primarily adopt the tetragonal phase, transforming to the cubic phase ( ) at 398 K during heating. The phase evolution of the nanoparticles correlates well with their dielectric behavior.
The second type is a ternary PMCs with SiO₂ coated Fe3O4 sub-micron spherical particles (a conducting core/insulating shell configuration). The spheres were fabricated using a hydrothermal method and are loaded at 10 and 20 vol.% into a bisphenol E cyanate ester (BECy) matrix for synthesis of multifunctional composites. The dielectric constant of the resulting composites is found to be enhanced over a wide frequency and temperature range while the low dielectric loss tangent of the neat cyanate ester polymer is largely preserved up to 160 oC due to the insulating SiO₂ coating on individual conductive Fe₃O₄ sub-micron spheres. These composites also demonstrate high dielectric breakdown strengths at room temperature. Dynamic mechanical analysis indicates that the storage modulus of the composite with a 20 vol.% filler loading is twice as high as that of neat resin, but the glass transition temperature slightly decreases with increasing filler content. Magnetic measurements reveal a large saturation magnetization and negligibly low coercivity and remanent magnetization in these composites.
Finally, polymer-matrix nanocomposites with dispersed Si nanoparticles have been fabricated and investigated for their dielectric and mechanical properties. It is found that Si nanofillers significantly enhance the dielectric constant of the nanocomposites while preserve the low loss tangent of the BECy matrix. Meanwhile, incorporation of Si nanoparticles effectively stiffens the polymer, as manifested by the large increase in the storage modulus. Furthermore, the AC conductivity of the composite is observed to decrease under compressive mechanical stresses due to the piezoresistive effect of Si. Therefore, these novel Si/BECy nanocomposites simultaneously display mechanical load-carrying, electric energy-storing and stress-sensing capabilities, very promising for multifunctional devices such as structural capacitors.

Use of reducing atmospheres during processing of electronic ceramics is attractive to enable dissimilar materials integration on base metals for enhanced performance and decreased device cost. Application of reducing atmospheres to three classes of materials will be presented in this talk: (1) base metal integration of high permittivity dielectrics on copper and nickel, (2) integration of solid state electrolytes on copper for high performance lithium batteries, and (3) optimal processing of metal-insulator transition materials such as VO2. Fundamentals of reduction-oxidation behavior of metal substrates, thermodynamics of complex oxides, and microstructural engineering of films will be summarize. Engineering of film microstructure will is critical to optimize permittivity, dielectric tunability, temperature stability and loss in materials such as (Ba,Sr)TiO3 [BST] films on base metal electrode (BME) substrates including Ni and Cu. Experimental and modeling effects of changing film grain size, density, and orientation will be discussed with regard to film properties such as permittivity and electric field tenability. Permittivity values up BST films on Ni substrates, and permittivity values up to 3000 have been obtained in BaTiO3 and BST films on copper substrates. A comparison of solution-deposited versus sputter-deposited film properties will be presented for identical annealing conditions and substrates. Thermodynamic methods to avoid nickel and copper substrate oxidation, such as growth at low P(O2) (< 1 ppt O2), will be compared to alternative kinetic methods. Methods to extend this approach to solid state batteries and thermochromic VO2 smart windows will also be presented. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy&’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

An indirect magnetoelectric coupling is observed via strain in composite materials, where the magnetostrictive materials (such as CoFe₂O₄) and piezoelectric materials (such as PbZr_xTi_1-xO₃) order parameters are in separate but intimately connected phases. In this work the synthesis and characterization of several magnetoelectric composite thin films are discussed. A mixed precursor solution method is utilized to fabricate the composite films of PbZr_0.52Ti_0.48O₃ (PZT):CoFe₂O₄ (CFO) on platinized silicon substrates. X-Ray diffraction studies show a clear phase separation in the PZT:CFO composites. The two phases are polycrystalline in nature. Atomic force microscopy revealed the low roughness of the films, while piezo-force microscopy showed the distribution of the 342 nm diameter PZT grains. The effect of molar fraction of the magnetic phases (with respect to the PZT phase) on the ferroelectric and magnetic properties of the composite films will be presented in detail. Preliminary results show that composite films with low molar fractions of CFO phase exhibit large magnetoelectric coupling. The optimization of this strain mediated magnetoelectric coupling with respect to molar fraction will also be presented.

Materials which simultaneous exhibit ferroelectric, ferromagnetic and ferroelastic orders in the single phase or composites are called multiferroics. These materials are potential candidates for applications in multifunctional devices. New alternate efficient memory storage sources are very much needed to overcome the future storage device applications. To overcome the scarcity of natural multiferroic materials, artificial ME composites consisting of ferroelectric/ferromagnetic were developed in thin film form. The scientific and technological interest towards magnetoelectric multiferroic composites motivated us to work on this BZT-BCT/CFO/BZT-BCT tri-layered pulsed laser deposited thin films. Recently, lead-free barium zirconium titante- barium calcium titante (BZT-BCT) has been gaining more attention owing to its ferroelectric piezoelectric properties. We have observed multiferroic behavior in tri-layered BZT-BCT/CFO/BZT-BCT thin films. Scanning probe microscopy has become very important technique for the visualization of piezocontrast and local hysteresis loop measurement in BZT-BCT/CFO/BZT-BCT films. Structural, magnetoelectric multiferroic, piezoresponse, magnetic force microscopy studies will be presented.

Multiferroic materials hold enormous potential for a variety of applications, including tunable microelectronics and multiphase memory. The development of novel complex oxide-based composite materials provides an opportunity to fabricate multiferroic materials with performance suitable for real-world applications. In composite multiferroics, the resultant magnetoelectric effect arises from coupling at the interface between a piezoelectric and a magnetostrictive phase. Therefore, it is desirable to assemble a composite such that the interfacial contact area between each phase is maximized for increased performance. Here, we present the first example of a composite nanostructured building block with a Janus-type morphology for multiferroic applications synthesized by coupling sol-gel synthesis with electrospinning and electrospray to form nanofibers and nanoparticles, respectively. This composite is composed of piezoelectric BaTiO3 and magnetostrictive CoFe2O4 in an architecture that simultaneously provides access to the bulk and surface properties of both phases. These Janus-type nanocomposites combine the large contact area of a core-shell material with the segmented ordering of a thin film, and allow for the control of both composition and surface anisotropy, providing additional degrees of freedom in the design of composite materials. In this talk, we will present the effects of synthesis conditions on the size, crystallinity and morphology of these novel composites. Magnetization measurements reveal multiferroic coupling in these individual nanostructures through changes in magnetization at the various structural transitions for barium titanate. Results from magnetic, dielectric, and magnetoelectric measurements will also be presented.

The microelectronic technology is now demanding cost-efficient, high-tech devices that push through the integration of active thin layers with flexible substrates. Applications envisaged with flexible and large-area substrates are calling for low thermal budgets, with processing temperatures even lower than those required for the manufacture of CMOS devices. Strong efforts are being made in this direction for semiconductor dielectric oxides, the most used inorganic materials in electronics. Thus, thin-film transistors have been integrated directly by solution methods onto polymers, as amorphous or crystalline dielectric oxide layers. These studies have shown the possibility of reducing the processing temperature, for some of the high-tech dielectric oxides, to the limit of 200 degrees C. But now, there is the need to integrate other active layers on polymers to increase functionality. This is a major opportunity for ferroelectric oxide thin films, since their intrinsic multifunctionality (ferro-, pyro-, piezoelectricity) would allow diverse operations in electronic devices. To date, just organic ferroelectrics have been processed at low-temperatures. However, these compounds, as well as organic semiconductors, still suffer from their process-dependent and limited performance. Inorganic ferroelectrics require high processing temperatures (>600 degrees C). These temperatures exceed by far the thermal stability of plastic flexible substrates. So, not only alternative materials, but also large-area, cheap-solution processing technologies are required to achieve high-performance active layers directly deposited onto polymeric substrates.
This conference shows different strategies in solution for the reduction of the processing temperature of ferroelectric oxide thin films, thus to get the direct integration of large-area coatings of these active layers with plastic substrates. PhotoChemical Solution Deposition (PCSD) has demonstrated to be an efficient technology for the low-temperature processing of inorganic ferroelectric films. The characteristics of this process have made possible its combination with other solution methods, whereby the fabrication of inorganic ferroelectric films at temperatures compatible with flexible polyimide substrates has been achieved. The functional properties of the resulting materials reveal these inorganic ferroelectric films on plastic as alternative high-tech active layers of potential applicability in flexible electronics and Si-technology, not only competitive to the multifunctional organic ferroelectrics but also to organic/inorganic semiconductors.
Work financed by the Spanish Project MAT2010-15365.

The development of YBa₂Cu₃O_7-δ (YBCO) high-temperature superconductors has reached the level of high performance applications such as magnets, generators and transformers. However, the critical current density J_c remains too low for optimal application in high magnetic fields. Moreover, the dependence of J_c on the orientation of the magnetic field poses problems for practical application. These problems can be circumvented by the introduction of various structural and morphological defects, or artificial pinning centers (APCs), in specific directions along the YBCO film. Recently, BaZrO₃ and Y₂O₃ in-situ created nanostructures have proven their effectiveness. However, our research focuses on the ex-situ addition of nanosized BaZrO₃, Ta₂O₅ and HfO₂ of which the latter have never been used as APCs up to date.
We explored solvothermal, microwave and hot-injection bottom-up synthesis methods for the creation of these nanostructures. We try to restrain the use of organics in those synthesis routes and use as much as possible environmental-friendly, even water-based precursors. Final goal of this research is to incorporate these synthesized nanoparticles into YBCO precursors solutions, being water or TFA-based. In order to do this, we need to carefully assess the surface chemistry of the different types of nanoparticles, and study the influence of ligand exchange on the stability of the nanoparticle/YBCO precursor mixtures. In the end, these mixtures will be used as inks in order to deposit ex-situ pinned YBCO on selected substrates through ink-jet printing.

YBa2Cu3O7-x, one of the most promising oxide superconductors, is currently fabricated by metal organic deposition using trifluoroacetates (TFA-MOD), a non-vacuum process. Although TFA-MOD is related to metal organic deposition (MOD), the growth scheme is quite different. Fluorine atom plays a major role in TFA-MOD and fluorinated liquid phase during the firing process assists biaxial orientation of the resulting films. Such atomic orientation connects for several hundred meters without a vacuum process. Superconducting tape amounting to 1,000 kilometers has recently been fabricated by TFA-MOD.
YBa2Cu3O7-x superconductor was discovered in 1987. The MOD process has long been studied for fabrication of this superconductor. The films derived from MOD have a serious problem in terms of their orientation. If calcined films contain nanocrystallites, the nanocrystallites cause random orientation during the firing process, which decreases superconducting properties. TFA-MOD has no such problem. Calcined film apparently contains a large amount of CuO nanocrystallites. Quasi-liquid converts the crystallites and forms well-oriented superconductors.
TFA-MOD provides only 300 nm-thick superconducting film without the use of crack-preventing chemicals. The thickness is much greater than that of film obtained by the other MOD processes. However, the thickness is inadequate for superconducting applications. With regard to TFA-MOD, film whose thickness exceeds 1 micron is eagerly awaited. In the MOD process, repeated coatings are applied to obtain a film whose thickness exceeds 1 micron. However, in TFA-MOD, strong acidity of the coating solution attacks the formed layer. Decomposed or reacted material between old and new layers causes random orientation, which leads to unstable superconducting current in long tape.
In the MOD process, use of a crack-preventing chemical having -(CH2)n- carbon chain is effective for increasing the thickness of the films formed by a single deposition. However, the chemical is harmful in the case of TFA-MOD because chemical reaction between hydrogen and fluorine leads to carbon residue and segregation of metal contents. A newly proposed chemical having -(CF2)n- carbon chain and carboxylic base and terminated hydrogen atom solves this problem. Only by adding the chemicals to coating solution, single-coated thick YBCO film is obtainable by TFA-MOD. These technologies strengthen the position of TFA-MOD as the most promising 2G wire process.
The presentation also includes related discussion.

Internal environmental control of buildings is responsible for the majority of electrical energy use in the United States. While highly desirable, the presence of windows in buildings leads to unwanted heat gains and losses at various times of year and have a significant detrimental impact on overall building energy use. Energy efficient “smart” windows are able to change their properties depending on conditions throughout the day and year in order to improve building energy efficiency. One method to accomplish this employs electrochromic (EC) metal oxide films, which allow window transmission to be modulated to pass or block incident sunlight by applying a small voltage. The most commonly used materials for such devices are tungsten and nickel oxides as shown in the below figure. These layers are separated by an ion conductor that shuttles, in our devices, lithium ions between the two materials. In a typical metal oxide based electrochromic device, tungsten colors upon lithium ion intercalation while nickel oxide acts as the complementary electrode and colors when lithium ion is removed from the film. This produces a more efficient electrochromic device as both electrode materials color and leads to a more neutral tone in the final tinted device.
Electrochromic windows are currently available in the market place; however, the current price point is limiting adoption. A significant portion of our current research program is focused on cost reduction methods for the production of metal oxide based electrochromic windows. In this presentation we will feature our progress on solution phase processing of electrochromic materials for integration into “smart” windows. We will highlight solution phase routes to produce both electrochromic nickel and tungsten oxide films showing improved performance over state of the art vacuum processed materials. In addition, we will discuss our efforts to integrate these materials into a complete device using solution processed ion conductor films.

Recently, the electrochemical depositions of nickel-tungsten (NiW) are in a great interest due to their unconventional physical properties as high tensile strength, strong hardness, and good corrosion resistance to aggressive liquid environment. Therefore NiW alloy is one of the potential candidates to substitute of chromium, which is not eco-friendly. The contents of tungsten in the alloys by the electrodeposition are the main factor to control physical properties of NiW alloys. Unfortunately, it is well known that tungsten have not been deposited from the aqueous solution, and it needs to be combined with nickel and complexers as a ligand to deposit on a substrate. It is possible to deposit NiW alloys from the aqueous electrolyte by regulating the DC(direct current) or PC(pulsed current), and most of previous researches reported that the hardness and the corrosion resistance of the deposits in the alloys increases with increasing tungsten contents, and the ductility of the deposits in the alloys increase with increasing the nickel contents. However, it is very difficult to find the proper ratio of Ni/W for satisfying the property of the hardness and the ductility to substitute Cr thin films.
In this research, the simple and effective process is suggested to obtain the unique properties of the NiW thin films by altering the overpotential during the deposition process. The properties of deposits of NiW alloys could change by the applied current density and the type of current, and by altering the applied current with short period of time we could be achieved the superlattice structure of NiW thin films. Each layer in the NiW superlattice structure has different composition and microstructures.
The net physical properties of NiW superlattice layers would be strongly influenced by the thickness and composition of each layer in superlattice structures.

In order to meet with the demand of increasing speed and improving performance, but also in view of new technologies in various fields, functional oxides with nanostructured morphology are key.
Mostly, these materials are deposited on a solid support whereby strong control over the composition, nanostructure and phase formation is required. New fundamental questions related to composition-morphology-property relations at the nanoscale need to be addressed as well. For this, it is required that candidate nanostructured oxides are synthesized with the desired purity and in the specific appearance in which their functional properties need to be established. This tendency towards nanostructured materials, together with the increasing economical and environmental awareness on production processes, imposes important opportunities for solution based synthesis methods. They are put forward as an economically efficient alternative for high temperature solid state synthesis or vacuum based methods.
In our group we study the chemical solution based synthesis of monometal (TiO2, ZnO, VOx) as well as doped and complex oxides (transparent conducting oxides, ferroelectric & multiferroic oxides, high-k oxides) by means of sol(ution)-gel, thermal decomposition, hydro/solvothermal and precipitation methods. In this presentation our experimental strategies towards lowering thermal budgets, nanosize structuring and controlling the nanoscale properties are presented for recent examples of our current work.
The research presented is supported by the Flemish Research Foundation (FWO-Vlaanderen), The Flemish Methusalem Program, The SoPPoM program of the Flemish Strategic Initiative Materials (SIM) and the Hercules Foundation of Flanders.

Graphite oxide (or graphene oxide, GO), which was once noted as an important precursor to graphene, has been established as an important and technologically relevant material in the last five years. There now exists an extensive literature regarding the synthesis, chemical structure, reactivity, properties of GO, as well as its use in multiple applications. However, GO has recently been reported to degrade after about a month at room temperature. Loss of epoxide groups is believed to be the major structural change during the degradation process of GO. This structural change presents a significant challenge for all potential applications of GO. In my presentation, I will discuss our work using films of GO as a proton conductor in both supercapacitors and hydrogen fuel cells and how its properties may change over time. I will also show that degraded GO can regain epoxy groups with ozone treatment as indicated by solid-state 13C NMR. The measured proton conductivity of ozone treated GO (OGO) is 75% higher than that of GO aged for more than a month in solution. It is anticipated that 1H and 2H NMR investigations will elucidate the proton hopping mechanism in GO and OGO and 2D NMR 13C{1H} heteronuclear correlation experiments will reveal unprecedented microstructural information. Overall, free-standing OGO films offer improved device performance when used in supercapacitors and hydrogen fuel cells as proton conductors.

Metal oxide thin films display a broad range of physical properties and technological applications. For this reason intensive research has been devoted to set-up suitable synthetic approaches, combining simplicity with low cost and process flexibility. Solution synthesis of metal oxide thin films presents several advantages over other approaches like sputtering and evaporation: for instance, low cost of the precursors and apparatus and easier control of the layer composition. A remarkable breakthrough is obtained if the films can be fully integrated into electronic devices. The compatibility of the solution deposition process with the silicon/silicon dioxide substrate, however, requires careful investigation of the film uniformity and adhesion to the substrate. Metal alkoxides are a versatile class of precursors for the solution synthesis of metal oxide materials. Alkoxides are known for a large number of elements and are easily available for technologically relevant elements like Si, Ti and Zr. Apart for these notable exceptions, in general metal alkoxides suffer from some limitations in their use due to high cost, high reactivity to moisture and limited time stability. It is then interesting to explore alternative, inexpensive precursors, capable of overcoming the problems of metal alkoxides, while at the same time retaining important features of the latter, like the processability. A class of precursors with such features emerges when considering the solvolysis of anhydrous metal chlorides, available for a broad range of elements such as Sn, Ti, Zr, Si, Mo, V, W, Hf etc. Precursors are obtained which have the general formula: MCl_x(OR)_y. In some important cases, like SnO₂, even the chloro-alkoxide method may result ineffective, as concerns the film adhesion and uniformity, and further alternative deposition processes need being developed. In this work we will present a review of the synthetic routes that we developed to metal oxide thin films. TiO₂ will be a case study for conventional thin film processing from commercial metal alkoxides. As case studies of metal chloro-alkoxides the syntheses of WO₃, MoO₃, V₂O₅, Nb₂O₅, Ta₂O₅ thin films (thickness from 50 to about 110 nm) will be presented. Finally, the synthesis of SnO₂ from Sn (II) 2-ethylhexanoate solutions will be presented. The general features of the underlying chemistry will be discussed. Detailed characterization of the resulting thin films and, for selected systems, the microelectronic processing of gas-sensing devices will be discussed. It will be shown that a broad variety of oxide materials can be prepared from simple precursors, by spin-coating technique in atmospheric conditions. Gas-sensing devices can be produced using conventional microelectronic processing, demonstrating the potential of solution processes for the preparation of miniaturized, fully integrated gas-sensing devices. Examples of TiO₂ and SnO₂ based devices will be shown.

Solution-derived n-type oxide semiconductor thin film transistors (TFTs), such as indium-gallium-zinc oxide (IGZO), indium-zinc-tin oxide (IZTO), gallium-tin-zinc oxide (GTZO), zinc-indium oxide (ZIO), and zinc-tin oxide (ZTO), have recently received a lot of attention because of their simplicity, low cost and high throughput in comparison with vacuum-based techniques. However, the solution processed oxide films generally possess high concentration of defects, such as pores and lattice defects (i.e., the oxygen vacancies), which play an important role in trapping charges and lead to decreasing stability of thin film transistors.
In our previous study, ZTO semiconductor is chosen as the channel layer of the metal oxide TFTs to avoid the expensive cost of In and Ga. Zinc acetate or Zinc nitrate and tin chloride are dissolved in 2-methoxyethanol to form ZTO solutions, which are then spin-coated on SiO₂/p-Si substrate to form the TFT channel layers. After spin-coating, the ZTO films are baked at 500 ^oC (zinc acetate) and 250 ^oC (zinc nitrate) in ambient for 1 hr, respectively. The ZTO (zinc acetate) TFT shows a mobility of 2 cm²/Vs, while the ZTO (zinc nitrate) TFT shows a mobility of 1 cm²/Vs. In this study, we investigate the role of metal precursors (zinc acetate vs. zinc nitrate) on the chemical structure and electrical stability of ZTO TFTs. The instabilities of ZTO TFTs originating from positive, negative gate-bias stress and light illumination are examined. The shift of threshold voltage under bias stressing or light illumination is fitted by the stretched exponential equation to verify the mechanism producing the instability of ZTO TFTs. The correlation between the mechanism of ZTO TFT instability and metal precursor (zinc acetate or zinc nitrate) is also investigated.

Ordered arrays of crystalline complex oxides nanostructures were synthesized onto single crystal insulating substrates using a polyvinyl alcohol based electron beam resist precursor. The same precursor was shown to be nanoimprintable allowing for duel processing of the nanostructures. The precursor consists of a stoichiometric amount of La, Sr, and Mn in an aqueous nitrate solution, yielding La_0.7Sr_0.3MnO₃ (LSMO), along with 2-15 wt% polyvinyl alcohol. The irradiated zones are insoluble in water (negative-tone resist) due to the electron induced cross linking. The high temperature treatment of the developed precursor samples leads to the formation of ordered arrays of nanodots for low irradiation doses and to the growth of epitaxially oriented nanowires for high irradiation dosages. The insulating single crystal substrates SrTiO₃, LaAlO₃, and yttria stabilized ZrO₂ (YSZ) were used to promote various amounts of localized strains on the grown nanoislands and nanowires.
A local characterization of the generated patterns was performed by atomic force microscopy (AFM) and high resolution TEM. The nanoislands showed dimensions which are dosage dependent and on the order of 25 nm in height with a diameter of 100 nm. The nanowires are 30 nm in height and up to 10 mu;m in length. The TEM analysis showed an epitaxial growth and the EELS analysis showed the nanostructures to be depleted of manganese which falls in line with previously reported results derived from other methods [1, 2]. By using SEM images at various stages of thermal treatment, the nanowires growth mechanism was studied and revealed to form at 800 °C and have a fast non-linear growth rate of 3 mu;m/hr for the first thirty minutes.
This technique&’s applicability was also confirmed by writing nanoislands and nanowires with a SrTiO₃ precursor solution. Furthermore, both the LSMO and STO precursors were shown to be nanoimprintable on single crystal substrates. This allows for future duel processing of a single precursor film gaining nanostructuration from both EBL and NIL methods.

1. C. Moreno et al Adv Func Mat 19, 2139 (2009)
2. A. Carretero et al Adv Func Mat 20, 892 (2010)

We acknowledge the financial support from MICINN (MAT2008-01022, Consolider NANO-SELECT) and Generalitat de Catalunya (Catalan Pla de Recerca 2009 SGR 770 and XaRMAE). A. Calleja acknowledges financial support from Spanish Ramoacute;n y Cajal program. J. Malowney acknowledges financial support from the AGAUR, Generalitat de Catalunya grant resolution IUE/2681

Material systems based on hydrogels are of great interest for bio-medical applications as they are bio-compatible. For these applications, mechanical properties play an important role. In this study, we investigate the mechanical and electro-mechanical properties of composite hydrogels, made of polysodium acrylate with two different forms of cellulose fillers. Commercially obtained microcrystalline cellulose (MCC, particle size 20mu;m) and cellulose nanocrystals (CNC) prepared through acid hydrolysis were used. The length and width of CNC ranges from 200-400nm and 10-25nm respectively. Composites with different filler concentration were characterized for electro-mechanical behavior, this included dielectric properties such as relative permittivity, loss tangent, piezoelectric coefficient, mechanical strength and stiffness. The electro-mechanical properties of the composites were compared to that of the standard piezopolymer poly vinylidene fluoride (PVDF). The prepared composites need to be investigated for their potential as sensors and actuators for different applications.

In this report, we make an effort to address certain fundamental issues of nanomaterial synthesis. These issues directly affect the promising device based applications. We demonstrate and develop a novel synthesis technique that paves the path for fabrication of ultra-pure inorganic nanostructures in large quantities. The method of Electro Explosion of Wire (EEW) [1, 2], as adopted by us for synthesis of nanomaterials, also serves as a generalized method for the synthesis of undoped and transition metal doped metal oxide nanocrystals with high yield [2]. In this article, we focus on synthesis and characterization on copper oxide nanocrystals due to several reasons. Nanostructures of oxides of copper are widely reported for their p-type semiconducting behaviour [3]. It is a benchmark material for industries based on nano-electronic, nanodevices, photovoltaic, plasmonics and photonics. Thermoelectric, catalytic and superconducting doped oxides based on copper are also of importance due to its large excitonic binding energy (140meV) [4, 5]. Till date, issues pertaining to synthesis of pure phase and mono-disperse nanomaterials are unabated. To understand these crucial issues related to fabrication, characterization, phase quantification of nanostructures of copper; we have developed a method of EEW for preparing highly uniform nanocrystals of copper oxide. The nano-characterization of Cu/Cu2O nanocrystals includes the XRD analysis for structural parameter, phase quantification by Rietveld Simulations, electron microscopy. Investigations for optical properties related to band gap structure probing size quantization effect and bond composition of Cu-O/Cu2-O were done through UV-visible and FTIR spectroscopy, respectively. The aim of this work is to develop a novel method of synthesis, bridging the experimental results of XRD and TEM with the simulated parameters obtained through Rietveld analysis. The optical and vibrational properties for probing the possible applications in the field of nanostructured semiconductors for future high-impact science and technology related to copper oxide nanostructures are also investigated.
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Iron oxide microspheres possess a wide range of applications in lithium storage batteries, sensors, photocatalysis, environmental remediation, magnetic resonance imaging and drug delivery. The most commonly used method for the preparation of iron oxide microspheres is hydrothermal synthesis. Besides this, other synthetic methods such as co-precipitation, electrostatic self- assembly, microwave and sol-gel have been reported. The reported synthetic methods usually require longer time (2 to 48 hours) and expensive experimental set up. In the present study, a novel low temperature thermal decomposition approach for the synthesis of iron oxide microspheres has been reported. Thermal decomposition of an iron-urea complex ([Fe(CON₂H₄)₆](NO₃)₃) in a mixture of diphenyl ether and dimethyl formamide at 200^oC for 35 minutes lead to the formation of iron oxide microspheres. The microspheres were characterized using a variety of analytical techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and magnetometry. The XRD results indicated amorphous nature for as prepared iron oxide, whereas after calcination at 500^oC, crystalline α-Fe₂O₃ phase is obtained. The SEM images indicated uniform spheres with an average diameter of 1.2 ± 0.3 mu;m. The DRS results too gave evidence for the formation of α-Fe₂O₃ on calcination of the microspheres at 500^oC . The field and temperature dependent magnetic measurement results indicated superparamagnetic behavior for the as prepared iron oxide microspheres indicating that the microspheres consist of iron oxide nanoparticles. On the other hand, an antiferromagnetic behavior was observed for the microspheres calcined at 500^oC . The present synthetic method is a novel method to produce magnetic materials with controlled morphologies.

Yttrium aluminum garnets (YAG: Y3AL5O12) doped with rare-earth elements are complex oxides with excellent properties for next-generation lighting industry, display systems and radiation detection. In this work, Undoped and Ce doped YAG nanopowders of homogenous composition, good crystallinity and pure phase were synthesized using the sol-gel method. X-ray diffraction (XRD) measurements showed no evidence of any secondary phases. The average particle size was determined from the XRD measurements and the particle size distributions and morphology were evaluated using SEM. The wet chemical method allowed the synthesis of single-phase YAG at low temperatures, which is not possible by solid state reactions. This relatively low temperature synthesis method permits better control for particles sizes, impurities and defects. Luminescence measurements were conducted to study of the effect of grain size on emission.

Galvanic replacement reactions provide a simple and versatile route for producing hollow nanostructures with controllable pore structures and compositions. However, they have previously been used for the chemical transformation of metallic nanostructures only. We herein demonstrate that the galvanic replacement reactions can occur in metal oxide nanocrystals as well. When manganese oxide (Mn3O4) nanocrystals were reacted with iron(II) solution, hollow box-shaped nanocrystals of Mn3O4/γ-Fe2O3 (“nanoboxes”) were produced. These nanoboxes ultimately transformed into hollow cage-like nanocrystals of γ-Fe2O3 (“nanocages”). These nanoboxes and nanocages showed excellent performance as anode materials for lithium ion batteries owing to their non-equilibrium compositions and unique hollow structures. Our approach of using a galvanic replacement reaction is an effective method for simultaneously manipulating the morphologies and compositions of oxide nanocrystals in a large scale.

In the last decade, thin film solar cells based on CdTe and CIGS (Cu, In, Ga, and S) have achieved promising efficiencies of up to 20.3% [1]. However, these technologies utilise materials that are toxic (Cd) or low in abundance (In), which severely limits their long-term potential as a clean energy source. One solution to this problem is the use of earth-abundant and non-toxic elemental materials, which can be found in CZTS (Cu, Zn, Sn, S) solar cells [2]. Despite being a new class of thin film solar cell, efficiency values of 11.1% have recently been reported [3]. Currently, CZTS solar cells undergo a sulfurization step to increase the sulphur content for stoichiometric CZTS films [4]. However, existing methods of sulfurization involve H2S gas, either as a by-product or as a source of sulphur. The use and production of H2S has to be carefully managed, especially for large-scale manufacturing when environmental legislations have to be adhered to.
In this study, we present a green alternative to conventional sulfurization methods. We employ a one-bath electrochemical approach, in which metal ions are reduced and sulphur is simultaneously incorporated into the metal matrix. Through this method, we managed to obtain films with Cu, Zn, Sn, and S without gas phase sulfurization. The role of bath composition and cell parameters in controlling the film stoichiometry and homogeneity will be discussed. The method presented in this study may replace traditional sulfurization methods to produce CZTS solar cells without the use of toxic H2S.
[1] P. Jackson, D. Hariskos, E. Lotter, S. Paetel, R. Wuerz, R. Menner, W. Wischmann, and M. Powalla, "New world record efficiency for Cu(In,Ga)Se2 thin-film solar cells beyond 20%," Progress in Photovoltaics: Research and Applications, vol. 19, pp. 894-897, 2011.
[2] H. Katagiri, "Cu2ZnSnS4 thin film solar cells," Thin Solid Films, vol. 480, pp. 426-432, 2005.
[3] T. K. Todorov, J. Tang, S. Bag, O. Gunawan, T. Gokmen, Y. Zhu, and D. B. Mitzi, "Beyond 11% efficiency: Characteristics of state-of-the-art Cu2ZnSn(S,Se)4 solar cells," Advanced Energy Materials, 2012.
[4] H. Araki, A. Mikaduki, Y. Kubo, T. Sato, K. Jimbo, W. S. Maw, H. Katagiri, M. Yamazaki, K. Oishi, and A. Takeuchi, "Preparation of Cu2ZnSnS4 thin films by sulfurization of stacked metallic layers," Thin Solid Films, vol. 517, pp. 1457-1460, 2008.

A low cost, aqueous solution synthesis process carried out in a continuous stirred-tank reactor (CSTR) produces nanoparticles of three common polymorphs of TiO2 - anatase, rutile and brookite. A dilute aqueous solution of titanium tetrachloride (TiCl4) acts as the feed to the CSTR. The process is subjected to variable conditions of inlet TiCl4 concentration (0.1-1.5M), temperature (70-90°C), agitation (500-1500 RPM), and residence time (1-3 hours). The steady-state nanotitania crops (characterized using XRD, BET, SEM and TEM) differ from those obtained through batch reactor synthesis [1], a characteristic that needs to be taken into account for successful nanomaterial development and transfer beyond laboratory scale. The particles show variability in anatase/rutile/brookite mass ratios, particle size, morphology, and surface area for different operating conditions, allowing for production of desired nanotitania phases for different applications. One of the applications considered here is the production of hybrid nanotitania pastes for single layer screen-printed dye-sensitized solar cells (DSSCs) photoanode films [2].
1. C. Charbonneau, R. Gauvin* and G. P. Demopoulos, 2011, “Aqueous solution synthesis of crystalline anatase nanocolloids for the fabrication of DSC photoanodes”, J. Electrochem. Soc., 158 (3), H224-H231.
2. Kee Eun Lee, Cecile Charbonneau, George. P. Demopoulos, 2012, Thin single screen-printed titania layer photoanodes for highly performing DSSCs via a novel dual-function paste formulation and process, J. Materials Res. Soc. (accepted for the special issue on TiO2-February 2013).

The SnO2 is employed as the sensitive layer material in various modern sensors. The choice of selecting a gas sensor is based on its sensitivity, selectivity and stability. Metal oxide thin films have been widely used for detecting NO2 gas [1]. However, most of these sensors lack high sensitivity and operate only at high temperature (300-500C) [2, 3, 4, 5]. The gas sensing mechanism in SnO2 based sensors is influenced by the surface composition of SnO2. In this paper we demonstrate that the sensor based on Polyaniline (PAni) nanofibers, simply prepared by the interfacial polymerization, has the advantages of sensitivity, spatial resolution, and rapid time response for NO2 gas at room temperature [6]. Although PAni is one of the most studied conducting polymers due of its good electrical conductivity, environmental stability and relative easier synthesis [5, 7, 8, 9], yet due to poor solubility of PAni, it is difficult to form the film adopting conventional methods. Nonetheless, nanomaterials of conjugated polymers are found to exhibit superior performance as compared to conventional materials due to their larger exposed surface area [9]. The objective of this work is to study the PAni doped SnO2 nanocomposite as novel sensing system and to probe the NOx sensing characteristics of this sensor at room temperature. Here we focus on the effect of doping ratio of sensor material, gas flow time and response time of the sensor. PAni (EB-powder form) with different amounts has been stirred with SnO2 solution to obtain SnO2/PAni mixture. SnO2/PAni thin films were deposited on different substrates. In present work, sensors with different PAni doping ratio were prepared and characterized so as to ascertain the favorable conditions for higher sensitivity, selectivity and better gas sensing characteristics. The as-grown films were studied employing an assortment of characterization techniques. It is revealed through our study that the PAni/SnO2 nanocomposite show good gas sensitivity at 30-100C.
References:
[1] K.Thomas, H.Starke, G.S.V.Coles, H.Ferkel, Sensors and Actuators, B 85, pp.239-245(2002)
[2] T.Waitz, B.Becker, T.Wagner, T.Sauerwald, C.D.Kohl, M.Tiemann, Sensors and Actuators, B 150, pp. 788-793(2010)
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[9] S.Bhadra, D.Khastgir, N.K.Singhaa, J.H.Lee, Progress in Polymer Science, 34, pp. 783-810(2009)

We like to report a low-temperature silver melting process for fabricating Ag/graphene films with high electric conductivity. The fabrication required first the preparation of a homogeneous dispersion comprising of Ag nanoparticles and graphene nanohybrids by using the poly(oxyethylene)-imide (POE-imide) dispersant. The silver nanoparticles (AgNPs, 10-25 nm in diameter) in aqueous 2D-graphene dispersion were characterized and subsequently subjected to solution coating into thin films. Under the annealing temperature as low as 160 °C, the films exhibited a high electric conductivity or low sheet resistance at 2.4×10-1 Omega;/sq (equivalent to 7.9×104 S/cm). The dried films with Ag networks on surface were analyzed by transmission electron microscopy and scanning electron microscope for morphology and ultraviolet-visible spectroscopy for transparency. The formation of Ag network was explained by the simultaneous occurrences of water evaporation, AgNP migration to the upper surface and melting into Ag interconnected network at the annealing temperature. The control experiments without using the dispersant and the sole graphene film without Ag had showed the importance of the graphene presence. It is noteworthy that the process of low-temperature annealing at 160-170 °C is attributed to the fast deterioration and degradation of the POE-imide organics before the AgNP coalescence and melting. The interconnected Ag networks are primarily responsible for the electric conductivity. The details in the solution compositions of graphene/silver nitrate/reducing agent and the annealing temperatures higher than 170 °C were also investigated. Furthermore, the comparisons of using the selected silicate clays and carbon nanotubes in replacing the 2D graphene had revealed the different morphologies of these supports in generating Ag networks.
The process involving the coating of AgNP/graphene homogeneous dispersion the polyimide substrate could lead to the functions of Ag films. A video movie showing the large-scale, flexible and robust film enabling to connect the electricity in illuminating a series of light-emitting diode lamps will be presented. The findings of using the polymeric dispersion for the synthesis of nanohybrids may open up a new avenue for making films with integrated properties of flexibility, transparency and high conductivity for a host of electronic applications.

We have investigated the processing windows for self-ordered growth of anodic porous alumina formed on {001}, {101}, and {111} grain surfaces of aluminum by changing the anodization electrolyte concentration, temperature, voltage, and time. The ordering qualities of the nano-porous patterns are quantitatively characterized by a novel method based on the orientations of triangles connecting three neighboring pore centers of the pattern. An alternative anodization condition, which is different from the well-known mild anodization (MA) and hard anodization (HA) methods, is found, under which porous alumina with better ordering qualities are fabricated on {001} Al at growth rates 10 to 25 times faster than the MA condition. The inter-pore distance to anodization voltage ratio is nonlinear which is different from the linear behavior under MA or HA conditions.

In the context of newly appeared environmental legislations and growing societal awareness, there is nowadays a large interest in the use of new catalysts that could assess environmental issues such as CO2 emissions. RuO2/TiO2 catalysts are here presented for the hydrogenation of CO2 into methane. This catalytic reaction, under mild condition, allows highly selective CO2 recycling, as methane can be further converted to chemicals or directly used as a fuel benefiting of the existent infrastructure for transport and storage.
We use two advanced green methods to synthesize RuO2 nanoparticles on TiO2 support. The first one involves the fast addition of excess H2O2 to an aqueous solution of RuCl3 in order to form stable colloidal suspensions of monodispersed 2 nm-sized RuO2 nanoparticles.[1] Hydrogen peroxide allows an immediate oxidation of the ruthenium precursors in solution and a faster hydrolysis/condensation in aqueous media, provoking a rapid nucleation that leads to highly dispersed amorphous ruthenia nanoparticles. RuO2/TiO2 catalysts were thus prepared via the deposition of the as synthesized RuO2 nanoparticles suspensions on TiO2 support [1]. The second method was performed by anchoring the Ru precursor on the support and adding H2O2, controlling the “in situ” growth of supported ruthenia. Both methods were applied on lab-made TiO2 supports of pure crystalline phase (anatase, brookite, and rutile). Catalysts were heat treated (450°C), reduced in H2 and tested in the CO2 methanation reaction performed at low temperature [2].
Catalytic performances clearly depend on the TiO2 crystal phase and on the method of deposition of RuO2 on the support: the first method (RuO2 NP deposition), leads to more active catalysts compared to the second one (direct growth). Ru/anatase catalysts are the most active, whereas Ru/brookite shows the poorest performance.
This is confirmed by the activation energy values (independent from the deposition methods) which are lower (13kcal/mol) for Ru/anatase than for the other supports (around16 kcal/mol). The crystallographic phase of the support plays an important role in the faceting of more active ruthenia particles. Oriented attachment, epitaxial growth, sintering, solid state solutions or demixion are carefully studied as the most possible phenomena involved in the stabilization of Ru particles which exhibit such contrasted activities.
[1] C. Sassoye, G. Muller, D.P. Debecker, A. Karelovic, S. Cassaignon, C. Pizarro, P. Ruiz, C. Sanchez, Green Chem. 13 (2011) 3230.
[2] M. Jacquemin, A. Beuls and P. Ruiz, Catal. Today, 157 (2010) 462.

The key requisite to increase energy and power density in electrical storage systems is the rational design of nanocomposite structures. Porous transition metal (oxide) carbon nanocomposites are synthesized and characterized towards a designed structure for supercapacitor application. The combination of depth profile Auger electron spectroscopy (DP-AES) and energy filtered transmission electron microscopy (EF-TEM) is used to quantify the 3D nanocomposite material in case of localization and homogeneous distribution of the nanoparticular transition metal (oxide). Employing these nanoscale characterization tools to study one of the most promising future electrode designs for energy storage devices is a novel trend-setting step towards the understanding of the correlation between a locally varying chemical composition and the electrochemical performance. The developed nanocomposites overcome the limitations in energy storage performance of their carbon base material over the well-aimed functionalization at the nanoscale. For example a thin layer of iron (hydr)oxide embedded into the surface of a porous carbon material contributes with a pseudocapacitance of 375 F/g to the nanocomposite and therefore almost triples the capacitance of the electrode material. Moreover a novel supercapacitor electrode concept will be presented including porous nickel carbon nanocomposites.

Thin film photovoltaic absorbers such as CdTe and Cu(In,Ga)Se₂ (CIGS) can achieve solar conversion efficiencies of up to 20% and are now commercially available, but the presence of toxic elements (Cd and Se) and expensive materials (In and Te) is a real issue as the demand for photovoltaic solar cells rapidly increases. To overcome these limitations, there has been substantial interest in developing viable alternative materials such as Cu₂ZnSnS₄ (CZTS). CZTS is an emerging solar absorber that is structurally similar to CIGS, but contains only earth abundant and nontoxic elements. It has a near optimal direct band gap energy of 1.4-1.6 eV and a large absorption coefficient of ~10⁴ cm^-1. CZTS absorber has been prepared by various methods, such as thermal evaporation, sputtering, electrodeposition, sol-gel, and hydrothermal synthesis. Among them, wet-chemistry methods are of great research interest because of their low fabrication cost. However, most wet-chemistry based CZTS film formations have been based on the synthesis of CZTS particles, followed by collecting and spin-coating them on a substrate and thermal treatment. Little information is available on a direct synthesis of CZTS film using wet-chemistry method. In the present work, we report a direct formation of CZTS film on a substrate using chemical bath deposition method. CZTS films were deposited on glass and Mo/glass substrates in an ammonia solution of CuSO₄, ZnSO₄, SnCl₂2H₂O, thiourea, and triethanolamine (TEA). The results showed that this inexpensive and relatively benign process produced CZTS thin films exhibiting uniform composition and kesterite crystal structure. The ratio of TEA and ammonia, and temperature strongly affected on the morphology of CZTS film. We will further discuss the synthesis of CZTS films depending on such key experimental factors and the properties of CZTS based solar cells.

Hybrid alumina-silicone nanolaminate films were synthesized by plasma enhanced chemical vapor deposition (PECVD) process. PECVD allows digital control over nanolaminate construction, and may be performed at low temperature for compatibility with flexible substrates. These materials are being considered as dielectrics for application such as capacitors in thin film transistors and memory devices. In this work we present the temperature dependent current versus voltage (I-V) measurements of the nanolaminate dielectrics in the range of 200- 310 K to better asses their potential in these applications. Various models are used to know the different conduction mechanisms contributing to the leakage current in these nanolaminate films. It is observed that space charge limited current (SCLC) mechanism is the dominant conduction process in the high field region whereas Ohmic conduction process is contributing to the leakage current in the low field region. The shallow electron trap level energy (Et) of 0.16 eV is responsible for SCLC mechanism whereas for Ohmic conduction process the activation energy (Ea) for electrons is about 0.22 eV. An energy band diagram is given to explain the dominance of various conduction mechanisms in different field regions in these nanolaminate films.

For Earth and /planetary orbiters satellite application, payload power consumption is trending higher to meet exponentially increasing satellite communication capacity requirements. Advanced battery is need with High energy density and beyond 15 years of operational lifetime. This can be up to 60,000 cycles for low Earth orbiting satellites. There are number of ways to improve cycle life, such as use shallow depths of discharge (< 30%); additives in electrolyte [1-3]; zero-strain insertion material, Li[Li1/3Ti5/3]O4 (LTO) as anode [4]; electrochemical stable coating on cathode materials[5,6].
Here we report a synthesis method for preparing fast ionic conductive coating on cathode material. Lithium lanthanum titanate (LLT), perovskite (ABO3), is the highest bulk lithium ion-conducting solid electrolyte.[7] The coating was prepared via sol-gel process. The coating homogeneously conformed on the surface of the cathode particles with a thickness in the range of 2- 10 nm. The electrochemical study of coated cathode was published elsewhere [8]. Results showed that LLT coating really increases the cyclic performance compared to the pristine electrodes. Rate studies indicate that use of a LLT coating is effective in achieving an enhanced rate capability for the cathode material. Based on PITT test, it is clear that the LLT coating increase the lithium diffusion coefficient even by several magnitude at some voltage value (3.5 V-3.8 V) based on PITT measurement, which is also demonstrated by computational studies on both high and low lithium concentration LLT materials. The lithium diffusion barrier is lower than 250meV, which can easily happen at room temperature.
This research was supported by Air Force SBIR funding with contract number of FA9453-10-M-0115.
References:
1) Kusachi, Y.; Kato, T.; Ishikawa, H.; Utsugi, K.: 208th Meeting of Electrochem. Soc., 2005, 364
2) Hyung, Y. E.; Vissers, D. R.; Amine, K.; J. Power Sources, 2003, 383, 119-121
3) Abouimrane , A.; Belharouak, I.; Amine, K.; Electrochemistry Communications, 2009, 11, 1073-1076
4) Sawai, K.; Yamato, R.; and Ohzuku, T.; Electrochimica Acta, 2006, 51, 1651-1655
5) Chen, Z.; Qin, Y.; Amine, K .; Sun - J, Y.K.; Mater. Chem., 2010, 20, 7606-7612
6) West, W.C.; Soler, J.; Smart, M.C.; Ratnakumar, B. V.; Firdosy, S.; Ravi, V.; Anderson, M. S.; Hrbacek, J.; Lee, E.S.; and Manthiram, A.; J. Electrochem. Soc., 2011, 158, A883-A889
7) Stramare, S.; Thangadurai, V.; and Weppner, W.; Chem. Mater. 2003, 15, 3974-3990
8) Qian, D.; Xu, B.; Cho, H.M.; Hatsukade, T.; Carroll, K.J.; and Meng, Y.S.; Chem. Mater. 2012, 24, 2744minus;2751

It is known that the origin of degrading the electrical performances and the negative bias stress (NBS) stability of solution-processed amorphous indium-gallium-zinc oxide thin film transistor (a-IGZO TFT) is defects related oxygen vacancy. To reduce these defects, we added hydrogen peroxide to a-IGZO thin film and as a result a-IGZO TFT showed the improved electrical performances and the stability against NBS. The field effect mobility, on-off current ratio, and subthreshold swing were improved from 0.37 cm^2/Vs, 1.71x10^6, and 0.86 V/dec. to 0.97 cm^2/Vs, 5.17x10^7, and 0.58 V/dec., respectively. When NBS was applied to pristine a-IGZO TFT, it showed a large negative shift in threshold voltage (ΔVth= -3.47V), while a-IGZO TFT with hydrogen peroxide showed superior NBS stability (ΔVth= -0.01V). The rich oxygens supplied from hydrogen peroxide which decomposed during annealing process compensate defects related oxygen vacancy. Consequently, adding hydrogen peroxide to a-IGZO thin film enhances dramatically both the electrical performances and the stability against NBS in a-IGZO TFT by supplying oxygen into thin film

In this work we used impedance spectroscopy (IS), differential scanning calorimetry (DSC) and infrared spectroscopy (IR) techniques to study the polymer electrolyte membranes based on poly(vinyl alcohol) (PVA) and hypophosphorous acid (H3PO2) with different titanium oxide nanoparticles (TiO2) concentrations. The polymer systems were prepared using solution casting method. The impedance spectroscopy studies were obtained from 100 Hz to 5 MHz over the temperature range of 20 to 120 oC. The results show dielectric and conductivity relaxations as well as a change in dc ionic conductivity with the TiO2 content. The order of the ionic conductivity is between 10-5 to 10-3 Scm-1 at room temperature, being about 5x10-3 Scm-1 for 5.0% of TiO2 . FTIR spectra show changes in the profiles of the absorption bands with the addition of different concentrations of titanium oxide nanoparticles.

Effect of the annealing temperature on device performance of solution processed silicon-indium-zinc oxide (SIZO) thin-film transistors (TFTs) has been investigated. At the annealing temperature of 250C, the SIZO TFTs were showed on/off ratio of 1.6 × 10e7 with a subthreshold swing (S.S) of 0.07 V/decade. The threshold voltage (Vth) is shifted in a negative direction and a field-effect mobility (mu;FE) was increased as the increase of annealing temperature. Chemical, physical and electrical analyses analysis on SIZO films and TFTs at various annealing temperatures were performed and compared.

For high performance electronic devices, low energy barriers between source-drain electrode and semiconductor interfaces are critical to the device performances. There was no report regarding transition metal interlayer between source and drain metal (S-D) and oxide transistors. The main reason is supposed to be a not-matched work function between oxide layer and S-D. We tried to introduce such a transition metal between oxide semiconductor and electrode to investigate the effect on the electrical property for the first time.
As an interlayer for the S-D in a solution processed zinc tin oxide (ZTO) thin-film transistor, MoO3 was introduced beneath of aluminum metal. Various thicknesses of interlayer were tested to find an optimum level for electrical characteristics in ZTO TFT. Interlayer of 0.5 nm between ZTO and Al displayed better properties: a mobility of 5.6 cm2/V s, a Vth of -1.3 V and a subthreshold slop of 0.9 V/dec. Voltage bias stability and hysteresis were also improved by very thin interlayer. This improvement is attributed to the MoO3&’s reduction to a conductor, MoO2, and the inter diffusion of interlayer between active channel and S-D layers, those were confirmed by XPS spectra and by TEM analysis, respectively.

In recent years, the need for new buffer architectures for coated conductors has grown exponentially. With the conventional CeO2 buffer layers problems regarding reproducibility and chemical inertness are observed, giving rise to the formation of intermediate phases and a strong decrease in superconducting properties. A promising material for replacing the cerium oxide appears to be yttrium bismuth oxide (YBiO3 or YBO) as it shows excellent crystallographic and chemical compatibility with YBa2Cu3O7-x. To ensure the sustainability of the obtained coatings, the YBO thin film is synthesized starting from aqueous solution. First, the formation of YBiO3 starting from the new water-based precursor was studied in bulk under different processing conditions. The decomposition of this precursor was studied with thermogravimetric and differential thermal analysis (TGA-DTA) and the reaction products were identified with X-ray Diffraction (XRD). Secondly, we deposited these solutions on a single crystal LaAlO3-substrate via dip-coating and explored the influence of the heat treatment on the final morphological and crystallographic properties of the layers. Highly epitaxial and smooth layers were achieved, allowing the subsequent deposition of superconducting YBCO with critical current densities up to 3.6 MA/cm2, indicating the potential of this material as an alternative for CeO2 in the CeO2/La2Zr2O7/Ni-5%W and CeO2/YSZABAD/SS coated conductor architectures.

Acoustic wave (AW) sensors play an important role in chemical and biological recognition. Generally AW sensor material reflects a coupling between two physical fields, such as piezoelectric material (PZT, quartz) that produces an electric field by changing dimensions and vice versa. With an alternating voltage the material deforms periodically, which results in the propagation of acoustic waves. Similar with piezoelectric materials, magnetostrictive materials can provide an easy, stable, fast transduction mechanism for acoustic wave sensors. Magnetostrictive materials have the property of coupling between magnetic and mechanical fields. Magnetostrictive materials convert magnetic energy into mechanical energy or vice versa. When a magnetostrictive material is magnetized, its length changes and if a functional wave is applied, the material will keep stretching and shrinking, forming a mechanical vibration with a resonant frequency. Since the resonant signal of a magnetostrictive material can be wirelessly obtained through magnetic field, a simple configuration without any wire connection is possible for the implementation as a sensor platform. Among magnetostrictive materials, Fe-B amorphous material has low magnetocrystalline anisotropy, high megnetomechenical coupling efficiency and high level of magnetostriction. Such properties make it possible for Fe-B magnetostrictive materials to perform with high sensitivity by operating at high frequency with minimal loss.
In this study, Fe-B thin films were fabricated by electrochemical deposition. The method has advantages for obtaining multi-component iron-boron thin films in large quantity with low costs. A systematic parameter study was conducted by investigating current density, concentration, temperature, and the amount of precursors during electrochemical deposition. The results show that traditional nucleation and growth mechanism can explain the formation of amorphous and crystalline phases of Fe-B thin films. Structural and magnetic properties were examined to understand the relationship between the process parameters and the growth of Fe-B systems. We also demonstrate the possibility of synthesized Fe-B magnetostrictive thin films for biosensor platform.

Thin film transistors (TFTs) based on metal oxide gate insulators have been widely studied with the goal of low voltage operation and high electrical performance. To drive TFTs at low voltage, high electrical capacitance of gate insulator that can be achieved with high permittivity should be required. Therefore, it is important that the gate insulator has a high dielectric constant (K). Accordingly, various researches have been studied using high K binary oxides as a gate insulator such as hafnium, lanthanum and zirconium oxide. Also, the formation of smooth, dense, and pinhole-free layer are important to achieve good dielectric properties with low leakage currents and high breakdown strength. However, the binary oxides have a tendency to crystallize and produce the grain boundaries that contribute to impurity inter-diffusion and increase leakage currents. For this reason, it is important to produce amorphous phase for gate insulator with wide band-gap and high dielectric constant (K). Herein, we demonstrated that an amorphous metal oxide gate insulator showing high electrical permittivity using mixture of hafnium (Hf) hydroxide and lanthanum (La) hydroxide solutions by simple spin-coating method and annealed at 500 °C. Since we mixed two binary oxides, those metal oxides showed amorphous phase and high K value with low leakage currents. The spin-coated amorphous metal oxide gate insulator had a high dielectric constant and operated well as a dielectric layer for transistor at low voltages. According to the results, the dielectric constant (K) of the Hf-La oxide dielectric layer was ~11 in frequency range from 1 kHz to 100 kHz and showed the low leakage currents as 10-7 A cm-2. The thickness of Hf-La oxide dielectric layer was around 40 nm. For the electrical performance test of solution processed TFT except electrodes, TFT device with Si / 40 nm Hf-La oxide / 7 nm ZnO / 100 nm Al was fabricated as a bottom gate and top electrode structure. The on/off current ratio of the TFT with Hf-La oxide dielectric layer was characterized by transfer characteristics and was ~107 at 5 V operating, ~104 at 1 V operating. The calculated charge carrier mobility of this solution processed TFT with Hf-La oxide dielectric layer was 1.5 cm2 V-1 s-1 at 5 V operating and 0.15 cm2 V-1 s-1 at 1 V operating. In this method, our amorphous metal oxide gate insulator showed good performance and stability in ambient conditions. Those properties sufficiently meet the performance requirements of gate insulator in TFTs. Specially, the solution processed TFTs are possible to operate at low voltages by the hafnium-lanthanum oxide gate insulator. Therefore, this amorphous metal oxide dielectric material has a good potential for high energy efficiency of TFTs.

The fabrication of electronics on a flexible polymer substrate has been highlighted as a pathway to low cost and large area electronics. However, many processes for conventional IC fabrication, photolithographic patterning and subsequent vacuum metal deposition for metal patterning in particular, are not suitable for large area flexible electronics. In order to solve this problem, metal nanoparticle ink-based direct metal patterning methods such as micro-contact printing, aerosol jet deposition and screen printing have been developed. They succeeded in patterning the metal nanoparticles onto flexible substrate in a single step, but their resolution has been limited to few tens of microns. Moreover, the flexible substrate occasionally shows thermal degradation after these approaches as it undergoes considerable amount of bulk heating to melt patterned metal nanoparticles.
To overcome these problems, we introduce Digital direct metal patterning (DDMP) process for rapid, low-temperature and high resolution metal patterning for flexible electronics. For a typical DDMP process, the metal nanoparticle ink is first coated on the flexible substrate in advance using solution process such as spin casting or slot die coating. The focused laser beam is then utilized as a local heater to achieve selective melting of the metal nanoparticle ink. By using focused laser as a heat source, the thermal damage to the substrate is minimized while the resolution of the metal pattern is greatly enhanced, thus enabling very small metal patterns even at sub-micron width. An arbitrary metal pattern is achieved by raster scanning of the focused laser beam using 2D galvanometric mirror with CAD data. Being a direct writing method, DDMP process does not require any pre-made mask and thus greatly reduces the overall cost.
Through combinatorial study on laser power and scanning speed, Ag metal pattern is successfully achieved over 4 inch wafer size on PI, PET and glass substrate without any damage on the substrate. The minimum resistivity of DDMP processed Ag electrode is measured to be as low as 2.1mu;m, which is only 130% of its bulk counterpart. The reliability of the DDMP processed metal electrode is also verified through 100,000 bending deformation cycles.
The electrode fabricated by DDMP process can be readily applied to the flexible electronics. As an example, DDMP process is applied for multilayered structures to fabricated gate, source and drain of organic field effect transistor (OFET) array on a PI substrate. The resultant OFETs show clear output characteristics before and after the mechanical bending cycles. We expect that the metal electrode fabrication by DDMP process is also promising in many other applications in high performance flexible optoelectronics, portable flexible electronics and wearable computers.

Including portable electronic devices, flexible display, wearable computer and artificial skin, next generation electronics fundamentally require flexible electrodes. The flexible electrodes can be made by depositing electrically conductive materials on a flexible substrate. The substrate materials typically used for this process are plastic. Recently, however, attention is drawn to paper as a substitute for the plastic materials. The paper substrate is lighter, inexpensive, and easily accessible than plastic in addition to its highly flexible mechanical properties, which even allow complete folding and excessive bending. Lately, Cui et al has developed paper electrodes for energy storage devices using CNT, and Whitesides et al has demonstrated fabrication of paper electrode by utilizing spray deposition method. Including these two papers, there are many other published research papers in which advantages of paper substrates are shown.
However researches on paper electrode fabrication using Aluminum have not yet been conducted so far. Al is a material that has great electrical conductivity and an edge in price competitiveness. In fact, Al has highest conductivity to material cost ratio than any other metals. Al is widely used at OLED fabrication as electrode material. However, high temperature and vacuum processes such as thermal evaporation deposition is required for Al electrode fabrication. Unfortunately, paper electrodes cannot be made by using these processes. Even if it is possible, cost of using these processes is very high.
In this study, we have developed a solution based Al electrode fabrication technique, which can be used with paper substrates. This technique utilizes thermal decomposition of Al precursor ink at relatively low temperature (110 degrees celsius). The Al electrodes on the paper substrate showed good electrical conductivity as well as mechanical durability. The electrical conductivity of this Al electrode is similar or even better than those made by thermal evaporation deposition process. Even though this technique is operated at low temperature (110degrees celsius) and under atmospheric pressure, the produced electrodes shows reasonable electrical conductivity. Therefore, it is very competitive against conventional techniques involving high temperature or vacuum process. The electrodes made by using this technique endure 30,000 cycle bending test and results in only 20~60% resistance increase. These electrical and mechanical properties varied by employed paper materials. The Al electrodes on inkjet printing paper substrate among various paper materials, shows the best electrical and mechanical properties.
Until today, Al has been considered unusable for the solution based process due to oxidation problem, however we have showed in this study, good electrical and mechanical properties can be obtained through solution based Al electrode fabrication on paper substrate, and it is very applicable to various applications

Understanding nucleation and growth of nanoparticles on high curvature nanowire surfaces is necessary to develop controlled assemblies with enhanced multifunctionality. Towards this end, coating silicon nanowires with gold nanoparticles is of particular interest as it results in an interesting Schottky device geometry. In addition, silicon nanowire-gold nanoparticle heterostructures have recetly generated interest for sensor appliations. However, it is critical to evolve gold nanoparticles with controlled morphologies and spacing on such nanowire substrates and remains a significant challenge to date. Here, we report a detailed fundamental study on morphological and structural evolution of gold nanoparticles onto silicon nanowires by combining chemical vapor deposition method with wet-chemical synthesis. This resulted in controlled spatial densities, inter-particle spacing, and diameters of gold nanoparticles on high curvature silicon nanowires. Interestingly, it was observed that there were diffused interfaces between gold and silicon, which can potentially alter the chemical, plasmonics, and electronics properties of such heterostructures. These nanowire heterostructures were characterized using high resolution electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Such controlled nanowire heterostructures hold promise for future analytical devices as well as NEMS/MEMS architectures.

We have investigated the effects of two different strain-relief bilayer shell structures on the luminescence properties of colloidal CdSe quantum dots (QDs). CdSe QDs with a strain-compensated ZnS/ZnCdS bilayer multishell were synthesized using the successive ion layer adsorption and reaction technique. The crystallinity of was determined by X-ray diffraction, which revealed three distinct diffraction peaks corresponding to the crystalline planes of cubic CdSe. The QDs enjoy the benefits of excellent exciton confinement by the ZnS intermediate shell and strain compensation by the ZnCdS outer shell. The resulting CdSe/ZnS/ZnCdS QDs exhibited a 40% higher photoluminescence quantum yield and a much smaller peak redshift upon shell growth compared to conventional CdSe/ZnCdS/ZnS core/multishell QDs with an intermediate lattice adaptor. CdSe/ZnS/ZnCdS QD light-emitting diodes (LEDs) had a luminance of 556 cd/m2 at 20 mA/cm2, 28% higher than that of CdSe/ZnCdS/ZnS QD-LEDs. The former also had better spectral purity at high injection currents. These results suggest that nanocrystal shells may be strain-engineered in a different way to achieve QDs of high crystal and optical quality well suited for full-color display applications.

Nanoporous gold thin films, produced by a dissolution-based self-assembly process, offer high electrical conductivity, catalytic activity, tunable pore morphology, and compatibility with conventional micropatterning techniques, which are critical for a number of technologically important applications including biosensors, fuel cells, and photonics. Thermal annealing has been the most frequently used method for modifying the pore morphology, in which surface diffusion of gold atoms leads to ligament thickening and pore coalescing, consequently increasing the average pore size. However, the percentage porosity decreases two-fold when the annealing temperature increases from 200°C to 400°C and in turn the effective surface area necessary for enhanced sensor and catalyst performance also decreases. We report a novel technique for increasing the average pore size with minimal variation in percentage porosity. This technique involves a halide-based wet etching mechanism that controllably reduces gold ligament thickness and increases overall film porosity. Dilute etchant solutions with concentrations at 1 M and 0.5 M, combined with shorter etch durations on the order of 35 seconds to 90 seconds yield films with higher average pore size and minimal change in overall morphology. We discuss the effect of etchant concentration, etching duration on the morphology of nanoporous thin films with sub-micron thicknesses. The results include morphological and elemental analysis of modified nanoporous gold films, obtained by scanning electron microscopy and energy dispersive spectroscopy. We expect that this solution-based technique will allow the production of high-porosity thin film coatings for sensor and catalysis applications.

Silver nanostructures have been investigated entensively due to their broad applications in catalysis, biological labeling, and plasmonics. Particularly, much attention has focused on the controleld synthesis of different morphology with tunable surface plasmon resonances (SPR). Herein, we present the synthesis of three novel silver structures, flower-like mesoparticles, nanorice and nanocarrots , and their application in plasmonics.[1,2]
Flower-like silver mesoparticles, which could generate huge electromagnetic (EM) field, were first obtained by reducing AgNO3 with ascorbic acid. Micro-manipulation method was implemented to create mesoparticle dimers.[1] The surface enhanced Raman scarterring (SERS) of flower-like silver mesoparticle dimers with large hot area is 10~100 times stronger than that of the individual ones. Incident polarization measurements illustrate that, even in the rough-surface mesoparticle dimer system, coupling effect dominates the SERS. More importantly, our work shows that the micro-manipulator can be used to form dimers with high SERS intensity in a controlled mannor.
Silver nanorice structures with interesting, tunable resonances in the wide near infrared region were synthesized by polyol method. Their growth process and plamonic properties were investigated.[2] Oriented attachment was found to dominate the morphology. The longitudinal SPR is highly sensitive to the refractive index of surrounding media, which predicts their promising applications as chemical or biological sensors. The multipolar resonance in individual rice is mapped in real space by electron energy-loss spectroscopy (EELS) for the first time.[2]
Novel asymmetric silver nanocarrot structures were synthesized through a polyol method. The crystals feature mixed twins and stacking fault domains along the <111> longitudinal direction. Multipolar plasmon resonances up to fourth order were measured by optical extinction spectroscopy and EELS and are in agreement with theoretical calculations. EELS maps show an asymmetric distribution of the resonant plasmonic fields in the nanocarrot, and the compression of the resonance node spacing towards the tail. The longitudinal SPR peaks are red-shifted and the intensities increase with increasing length.
[1] H. Y. Liang, Z. P. Li, Z. X. Wang, W. Z. Wang, F. Rosei, D. L. Ma, H. X. Xu, , Small, DOI: 10.100
[2] H. Y. Liang, H. G. Zhao, D. Rossouw, W. Z. Wang, H. X. Xu, G. A. Bottom, D. L. Ma. Chem. Mater. 2012, 24, 2339-2346.

Colloidal pyrite FeS2 nanocrystals (NCs) have recently become a promising candidate in optoelectronic applications because it has a narrow band gap < 1 eV and the advantages of earth-abundance and non-toxicity. This study demonstrated that soluble pyrite FeS2 nanocrystals were successfully synthesized with a controlled size and a heterojunction photodiode consisting of a device structure of ITO/ZnO/FeS2 NC/MoO3/Au with visible to near infrared (NIR) photoresponse was fabricated. The formation of FeS2 NCs heterojunction structure with satisfied band alignment by the insertion of metal oxide layers effectively suppresses the leakage current and reduces the series resistance of the device. The device exhibited an excellent photoresponse with a spectral response extended to NIR wavelengths of up to 1150 nm and a high photocurrent/dark current ratio of up to 8000 at -1 V under A.M. 1.5 illumination (100 mW-cm-2). The promising optoelectronic performance of the FeS2 NC/metal oxide heterojunction device has provided a crucial step toward the success in producing colloidal pyrite NCs thin films for low-cost and large-area photoelectronics.

The development of conducting metallic inks and pastes for printable electronics is based on Ag nanoparticles due to their highest electrical conductivity and high resistance to oxidation. However, the electrochemical migration of silver is considered to cause short circuit failures in electronic devices, especially under high humidity conditions. An alternative conducting material considered suitable for similar use is copper, if it is made oxidation resistive. To make copper oxidation resistive, alloying with easily reducible metal such as nickel, which has lower reduction potential than copper, is considered viable. Thus in this study, Cu-Ni nanoparticles were prepared by co-reducing Cu and Ni metal salts with long alkyl chain alcohols such as 1-heptanol or 1-octanol in the presence of oleylamine expecting a copper-rich core and a nickel-rich oxidation protective shell. The overall percentage of nickel was set to 20 %. The TEM-EDX of the particles obtained confirmed the formation of copper-rich core with a nickel content of about 2.6 atomic % and the nickel-rich shell with a copper content of about 48.9 %. The results showed that the product constituted of particles with an average size of about 15 nm and well-dispersed in organic solvent such as toluene. Subsequently, these particles were tested for their stability in oxidizing atmosphere and proved to be stable and the formation of oxide layer was not observed even after several weeks. The above results confirmed that the synthesis protocol is a viable technique to produce oxidation resistive conducting nanoink with potential physical characteristics to replace silver. However, on the premise of using these particles for nanofabrication of conducting elements, it is necessary to minimize the nickel content in the oxidation resistive shell.

Zn-Co alloy coatings were electrodeposited on AISI 1018 steel substrate from an alkaline bath containing glycine as a complexing agent, and by a using pulse current. Corrosion behavior of Zn-Co alloy coatings was studied by using a potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) in a 3.5 wt.% NaCl solution. Scanning electron microscopy (SEM), energy depressive spectroscopy (EDS) and X-ray diffraction (XRD) analysis were used to study surface morphology, chemical composition and phase structure of the coatings. The results showed that corrosion resistance of deposits was highly influenced by the composition and morphology of the coatings. Overall, Zn-Co deposit containing 2.35 wt. % Co showed the highest corrosion resistance among the coatings. This was due to its single phase structure and its finer morphology.

Semiconductor nanorod (NR) and nanotube (NT) arrays have been demonstrated to be excellent photocatalysts since the minority carriers have to travel a maximum distance equal to the nanorod radius (or one half the nanotube wall-thickness for NTs) to achieve charge separation and react with redox-active species at the NR/NT surface. For many semiconductors, this transit distance is smaller than or comparable to the minority carrier diffusion lengths in the respective materials thus enabling high charge separation efficiencies. In addition, the NR and NT arrays possess high surface areas and can be engineered to exhibit strong light trapping effects. While the high oxidizing power of the holes in large band-gap n-type semiconductors such as TiO2 and SnO2 have been exploited in high-rate oxidative photocatalysis and oxidative photoelectrochemistry using NT/NR arrays [1], there is a paucity of similar p-type nanostructures to perform photoreductive reactions. Cu2S is a p-type semiconductor extensively researched for high-performance photovoltaics, and later discarded due to phase stability and copper ion diffusion issues in a dynamic, high current operating environment. There has been a recent resurgence in the study of phase-stable Cu2S nanocrystals and photovoltaic device designs [2-4]. In the context of photocatalysis, we may be able to avoid the limitations of Cu2S while benefiting from its many desirable properties such as p-type behaviour, low band-gap (1.21 eV), a high optical absorption coefficient, a moderate minority carrier diffusion length, earth-abundance and non-toxicity. We report on the synthesis of vertically oriented phase-pure chalcocite nanorod and nanowall arrays on plastic substrates using solution processing, and demonstrate control over the nanostructure shape, size, phase and composition by altering the conditions of growth. The Cu2S nanorod and nanowall arrays were found to be excellent visible-responsive photocatalysts for the sunlight-driven conversion of CO2 into methane with CH4 production rates as high as 38 µmol m-2 h-1 obtained under AM 1.5G illumination. Device performance was correlated to electron-hole recombination behavior in Cu2S nanorod arrays, studied by time-resolved photoluminescence.
1. Zhang, X.; Han, F.; Shi, B.; Farsinezhad, S. F.; Dechaine, G. P.; Shankar, K. Angewandte Chemie 2012 DOI: 10.1002/anie.201205619.
2. Kruszynska, M.; Borchert, H.; Bachmatiuk, A.; Rümmeli, M. H.; Büchner, B.; Parisi, J.; Kolny-Olesiak, J. ACS Nano 2012, 6, (7), 5889-5896.
3. Zheng, H. M.; Rivest, J. B.; Miller, T. A.; Sadtler, B.; Lindenberg, A.; Toney, M. F.; Wang, L. W.; Kisielowski, C.; Alivisatos, A. P. Science 2011, 333, (6039), 206-209.
4. Kriegel, I.; Jiang, C.; Rodríguez-Fernández, J.; Schaller, R. D.; Talapin, D. V.; da Como, E.; Feldmann, J. J. Am. Chem. Soc. 2011, 134, (3), 1583-1590.

The synthesis of hybrid organic/ inorganic materials has been a subject of strong research owing to their fascinating structural chemistry and potential applications in different areas such as adsorption, ion exchange, catalysis and new physical properties of material. Between these kinds of materials, bimetallic complex have multiple compositions and crystal structures, which results in a variety of properties leading to a vast variety of potential applications.
Here we report new synthesize of bis(acetylacetonato κ 2-O,O') [zinc(II)-coper(II) (0.67/0.28)] by the reactions of Cu(NO3)2.3H2O and Zn(NO3)2.6H2O with acetylacetonate (acac) in ethanol/water in very mild conditions. This bimetallic complex was formulated as C10H14 Cu0.28O4 Zn 0.67, and it was crystallizes with the central portions partially occupied by Zn and partially by Cu, with the refined Zn:Cu occupancy ratio of 0.67 :0.28. The distribution of two kinds of metals in the complex is random, which suggests that all the molecules would contain Zn and Cu atoms.
The atomic structure of the new bimetallic complex is square planer characterized by single crystal x-ray diffraction, where two ligands coordinating to the metal atoms are located in the same plane, and the metals have octahedral coordination. The metal to oxygen (O1, O2) bond lengths [1.9174 and 1.9191 Å] are slightly longer than those in Cu(acac)2 [1.9182 Å] but shorter than the average value found in Zn(acac)2 [2.0147Å]. Besides single crystal X-ray diffraction, Infrared spectroscopy (IR), Inductively coupled plasma (ICP) , X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), mass spectroscopy (MS), Thermogravimetric analysis (TGA)and transmission electron microscopy (TEM) also confirm the structure with this composition.

While 2-dimensional (2D) layered nanostructures are emerging as next-generation functional materials, there is lack of understanding in use of nanoscale chemical stimuli for tailoring the materials properties. Here, we exposed 2D layered titanium disulfide (TiS₂) nanocrystals to water (H₂O) to induce the regioselective structural transformation into heterogeneous TiS_2(disc)-TiO_2(shell) nanostructures. The chemical principles obtained here can serve as a new design concept for functionalizing 2D layered nanostructures to tune materials properties. For example, heterogeneous TiS_2(disc)-TiO_2(shell) nanocrystals constitutes a high performance type II heterojunction which not only has remarkably high (~80%) solar energy coverage with near infrared absorption edge (0.76 eV), but also brings significantly enhanced electron transfer property.

Carbon nanotubes (CNT) are attractive candidates due to their structural characteristics and promising electronic and mechanical properties for the use as nanomaterials and nanodevices. Composites of carbon nanotube with metal nanoparticles are particularly useful for use in catalysis, energy storage, and nanotechnology. Among them, CNT-Ag nanocomposites drew significant attention due to their potential applications as catalyst, and advanced materials. In this study, a new synthetic route to decorate carbon nanotube (MWCNT) with silver nanoparticles (Ag-NPs) is presented via a simple proton beam irradiation process at room temperature. The characterization of the MWCNT-Ag composites has been done by using FE-TEM and EDS analysis.

In the past two decades, many efforts have been made in the synthesis of metal nanoparticles because of their unusual properties and potential applications in optical, electronic, catalytic, and magnetic materials and so on. Since copper is the most widely used material due to its low cost and very high electrical and thermal conductivities, nanocopper have attracted a great deal of research attention because of their catalytic, optical, and conducting properties . Therefore, the synthesis of Cu nanoparticles has become a subject of great interest from scientific as well as industrial point of view.
In this paper we report a one-step chemical synthesis of preparation of copper nanostructures. This synthesis achieved in aqueous solution using sodium borohydride as a reductant and tartaric acid as the surfactant and capping agent. This green chemical route utilizes an environmentally friendly reaction medium and does not require the use of a protective inert gas and its production of copper nanostructure with reasonably uniform size and relatively higher yield. Our experiment shows nanocopper may crystallize in the form rod or amorphous nanoparticle that they were stable more than four month period in ethanol by using this method.
While changing the reaction parameters, including the molar ratio of reactants, pH reaction time, and temperature, amount of stabilizing agent in the synthesis was found to be beneficial to produce pure copper nanostructure and have better control in the size and shape of the nanocopper. The resulting copper particles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and UV-Vis . Also transmissions electron microscopy (TEM), fuel emission scanning electron microscopy (FESEM) show the size and morphology of nanostructure respectively.

In this study, we employed the polyelectrolyte separation method (1,2) to reduce multi-wall carbon nanotubes in THF and Na/naphthalene salts, followed by dispersion in N-N dimethylformamide and Tetrahydrofuran. The modified MWCNTs were added to the organic precursor of siloxane-PMMA (poly(methyl methacrylate)) hybrids to improve their mechanical strength and thermal stability. The hybrids were prepared via the sol-gel route from radical polymerization of methyl methacrylate (MMA) with 3-metacriloxipropiltrimetoxisilano (MPTS) followed by acidic hydrolysis and condensation of tetraethoxysilane (TEOS). (TEOS).(3) Hybrid films, prepared by dip-coating on carbon steel, were characterized using X-ray photoelectron spectroscopy, thermal analysis and atomic force microscopy. The corrosion resistance of the coatings was evaluated using electrochemical impedance spectroscopy during immersion in standard saline and acidic solutions. The obtained results have shown that the used approach led to a hybrid matrix with high degree of connectivity, containing highly dispersed MWCNTs, which provided thermally stable films with high mechanical strength, determined by traction tests. In addition, these nanocomposite coatings acted as a very efficient diffusion barrier, with a corrosion resistance in the range between 100 - 1000 MOmega; after long-term exposure in aggressive environments.
1. D. Voiry, O. Roubeau, A. Pénicaud. Journal of material chemistry 20 (2010) 4385-91.
2. A. Pénicaud, L. Valat, A. Derré, P. Poulin, C. Zakri, O. Robeau, M. Maugey, P. Miaudet, E. Anglaret, P. Petit, A. Loiseau, S. Enouz. Composites Science and Technology. 67 (2007) 795-797.
3. P. Hammer, F.C. dos Santos, S.H. Harb, B.M. Cerrutti, S.H. Pulcinelli, C.V. Santilli. Carbon nanotube-reinforced siloxane-PMMA hybrid coatings with corrosion resistance. Progress in Organic Coatings. In Press

Silver is known to exhibit high toxicity to a wide range of microorganisms and therefore, silver-based compounds have been used extensively in many applications bactericides, such as antimicrobial fabrics, curatives for wounds and water filtration systems. Preparation of silver nanoparticles mostly consists of two steps: reduction of silver cations mainly from solutions of AgNO3 and stabilization of silver nanoparticles. Accordingly, the montmorillonite clay has been studied as a carrier due to its properties intercalation, swelling and ion exchange, making it possible to replace its exchangeable ions (Na+, Ca2+ and Li+) existing in the interlayer space by silver ions. The aim of this study was to investigate the adsorption of silver cations on montmorillonite modified with a quaternary ammonium salt that was intended to expand the interlayer spacing of the clay. Experimental development consists of the following steps: purification, with hydrogen peroxide, and modified, with cetyltrimethylammonium bromide, of the sodium bentonite clay natural with cation exchange capacity (CEC) of 100 meq/100 g clay. The adsorption process is the addition of 200 mg of clay in a solution of AgNO3 0.005 M, 0.01 M, 0.02 M, 0.05 M and 0.1 M followed by vigorous stirring for 24 hours. The characterization of modified and unmodified clay was performed using infrared spectrometer (FT-IR) and x-ray diffractometer (XRD). The basal spacing (d001) was calculated. In FT-IR analysis was verified the modification of clay with quaternary salt, it showed two intense bands at 2930 and 2847 cm-1 corresponding respectively to the asymmetric and symmetric vibrational modes of the CH2 group, and a band at 1475cm-1 characterized by asymmetric deformation of the CH group. The increasing the concentration of AgNO3 in the adsorption of silver ions in the clay resulted in a reduction of purified basal spacing, thus varying from 1.35 to 1.17 nm. This is due to the replacement of exchangeable cations present in the interlayer space of the clay by silver ions exhaustively, thus causing the exfoliation of layered structure, whereas there was a reduction of the peak intensities. In the modified clay the structure remained intact, since it occurred only the adsorption of silver ions and the quaternary salt has not been removed from the interlamellar spacing. The basal spacing ranged only from 1.37 to 1.42 nm. The silver ions present in purified and modified clay (AgNO3 0.01 M) were reduced by sodium borohydride 0.01 M. We observed that the basal spacing for modified clay was unchanged 1.42 nm, whereas while for purified was 1.25 nm. The metal silver nanoparticles have to be located on the layer surface and crystal edges of the clay. The mean size of the Ag0 crystallites was calculated as L111 = 7.59 nm for purified and L111 = 7.67 nm for modified clay. Therefore, the modified clay had a positive result for the same combination with various types of material for future industrial applications.

The addition of nano-fillers in an organic polymer matrix can reinforce it and cause an interaction between the organic and inorganic materials [1]. However, agglomeration of these nanoparticles has been the most difficulty in their wide applications. Surface-modification in situ with some silane coupling agents were found to make nano-SiO2 disperse well and steadily in many organic mediums [2,3]. Furthermore, silica core/organic shell can improve the interaction at the organic/inorganic interface and have been mostly applied in different fields such as solid carriers for the immobilization of biological substrates [3]. In order to improve interfacial interaction in nanocomposites, silica surface was modified with 3-trimethoxysilyl propyl methacrylate (MPS) and then covered with a polymeric shell prepared by a polymerization reaction between styrene and divinylbenzene monomers in the presence of AIBN as an initiator. Nanocomposites based in commercial polymer matrix, as carboxylate nitrile rubber (XNBR), were prepared by the insertion of silica by means of simple mix of components using the colloidal route. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed SiO2 nanoparticles prepared by a modified procedure originally described by Stöber et. al, with narrow size distribution of 250 nm, and then covered by a polymeric shell with thickness greater than 20 nm. All the nanocomposites were characterized by differential calorimety scanning (DSC), X-ray diffraction (XRD and small angle X-ray scattering (SAXS). The presence of nanoparticles increased the correlation volume (Lc) associated to the spatial distribution of XNBR nanodomains at q=0.010Å, calculated by the Scherrer equation for SAXS. These results are directly related to a high dispersion of silica in the polymer matrix. Guinier plots of the materials showed that increasing SiO2 concentration, the size of large and small XNBR crystallites were reduced, specially the Rgsmall of the one in the presence of SiO2/polymer shell, which can have improved the interaction at the organic/inorganic interface. Furthermore, these decreases can be related to correlations volumes (Lc) at q = 0.16 Å, which appear in the presence of SiO2-MPS and are reduced with increasing the nanoparticle amount, indicating that a nano-organized structure was formed, as shown in the XRD. These results evidence that nanoparticle surface was satisfactorily modified by MPS and polymeric shell, which softened the final material (slightly Tg reduction) and distinct modifications of silica surfaces resulted in different organizations in the XNBR matrix.
Work supported by FAPESP, CMDMC/Cepid, CNPq and CAPES.

[1] Chiu, Y. C.; Tsai, H.C. ; Imae.T.; J. Appl. Polym. Sci., DOI 10.1002/app.36277 (2012).
[2] Liu, L.; Li, L.; Yang, X. ; Dai Z. ; Polym. Adv. Technol., 19, 1922 (2008).
[3] Li, X.; Cao, Z.; Zhang, Z.; Dang, H.; Appl. Surf. Sci., 252, 7856 (2006).

To enhance the electrical performance, various metal-alloy zinc oxides such as IZO and IGZO, which are still solution-processible, have been reported to compensate for the poor electrical performance of intrinsic ZnO semiconductors. Although devices based on these metal-alloy oxide zinc semiconductors have shown good electrical performance capabilities, the massive use of indium (In) as a dopant causes some problems, which is becoming expensive and strategically important. To address these issues, we previously introduced alkali metal dopants, particularly focused on lithium (Li) and sodium (Na), to fabricate the low-temperature and solution-processed ZnO TFTs with remarkably enhanced the field effect mobility values and on/off current ratios.[1] Herein, we discussed the exact mechanism and a detailed analysis of the alkali metal doping effects by structural, optical and electrical characterizations.
From the HR-TEM analysis, we observed that the structures of all of the solution-processed Li-doped ZnO films are polycrystalline. A strong direct correlation between the morphology or crystallinity of ZnO semiconductor films and the electrical performance was not observed. However, we demonstrated that the optical bandgap energy, Eopt, is correlated with the enhancement of the electron mobility of alkali metal-doped ZnO TFTs. The broadening of the Eopt values, which are strongly related to the amount of excited electrons from the Fermi level in the valance band to the conduction band, was observed from Li-doped ZnO 0 mol% film to Li-doped ZnO 10 mol% film. The increase in the electron donor concentration was the dominant reason for the enhancement in the electron mobility of the alkali metal-doped ZnO TFTs.
In addition, doping with alkali metals considerably improved the electrical stability of ZnO TFTs. In high and continuous gate biases (Vg) of 50 V over 6,000 seconds, alkali metal (Li) doped ZnO TFTs showed a highly stable threshold voltage and no degradation in the field effect mobility. The higher activation energies for interface trap creation induced by alkali metal doping in ZnO reduced the amount of charge trapping sites in the ZnO matrix and led to stable operation of the device. Although the processing temperature of this method was lower than the processing temperature of typical sol-gel methods, ammonia-ZnO as a precursor could be transformed easily into ZnO films which did not contain any residuals owing to the volatile ammonia ligand. Both XPS and EDS analyses showed that there were no residuals in the alkali metal-doped ZnO films. We believe that in-depth study of the crystal structure, morphology, and optical bandgap of alkali metal-doped ZnO films make a great contribution to next-generation high-performance TFTs for flexible, printed and transparent electronics.
[1] S. Y. Park, B. J. Kim, K. Kim, M. S. Kang, K. H. Lim, T. Il Lee, J. M. Myoung, H. K. Baik, J. H. Cho and Y. S. Kim, Adv. Mater., 2012, 24, 834.

Optimal electrocatalyst discovery remains one of the most crucial yet laborious tasks in modern catalysis. Here, we integrate Ink-Jet Printing (IJP) synthesis with Scanning Droplet Cell screening (SDC) to significantly accelerate optimal solid-state electrocatalyst discovery. Tens of thousands of continuous landscape of candidate quaternary catalysts has been generated by IJP system. With a large volume of resulting candidate catalysts, the SDC system was applied to identify catalytic acitivities at an unprecedented rate of 4 s per catalyst. The effectiveness of the approach was validated using a benchmark optimal catalyst identification case, which utilized the electrochemical water oxidation. An inexpensive and efficient quaternary catalyst NiFeCoAl has been discovered for electrocatalytic oxygen evolution in less than one week.
This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993.

Melting gels are silica-based hybrid gels with the curious behavior that they are rigid at room temperature, but soften around 110C. A typical melting gel is prepared by mixing methyltriethoxysilane (MTES) and dimethyldiethoxysilane (DMDES) in molar per cents between 70 MTES:30 DMDES and 50 MTES:50 DMDES. MTES has one methyl group substituted for an ethoxy, and DMDES has two substitutions. The methyl groups do not hydrolyze, which limits the network-forming capability of the precursors. The precursors are reacted in a sol-gel process involving hydrolysis and condensation polymerization to form a monolithic gel. The hydrolytically stable substitutions are retained in the rigid gel. When the rigid gel is warmed up to 110C, it can be poured like syrup. When the gel cools to room temperature, it becomes rigid again. This cycle of warming and cooling can be repeated. When the gel is warm, it can be poured onto a substrate to make a bead or a line of gel. When a second material is place on top, the gel becomes a bond. Gel seals have been formed between two pieces of copper, aluminum and stainless steel, along with other substrates. Finally heat treatment to a higher temperature (>135C) leads to consolidation of the gel and forms a permanent seal, which no longer softens.
To gain insight into the molecular structure of the melting gels, differential scanning calorimetry (TA Q-2000, using a 5C/min heating rate in nitrogen flow (20 ml/min)) and oscillatory rheometry (TA AR-G2, using a 3C/min heating rate in air) studies were performed on melting gels before consolidation. According to oscillatory rheometry, at room temperature, the gels behave as viscous fluids, with a viscous modulus, GPrime;(t,omega;omicron;) that is larger than the elastic modulus, Gprime;(t,omega;omicron;). As the temperature is decreased, gels continue to behave as viscous fluids, with both moduli increasing with decreasing temperature. At some point, the moduli cross over, and this temperature is recorded as the glass transition temperature Tg. According to calorimetry, the only feature seen on the low temperature DSC curves is the inflection indicating glass transition behavior. The Tg values obtained from both methods are in excellent agreement. The Tg decreases from -0.3C to -56C with an increase in the amount of di-substituted siloxane (DMDES) from 30 to 50 mole %. A decrease of the Tg follows an increase of the number of hydrolytically stable groups, meaning a decrease in the number of oxygen bridges between siloxane chains. In addition to the determination of Tg, the complex viscosity (eta;) was estimated from the values of viscous modulus, GPrime;, and the angular frequency, omega;omicron; (eta;=GPrime;/omega;omicron;). The viscosity at room temperature decreased with an increase in DMDES content. The temperature dependence of the viscosity diverged from a simple Arrhenius behavior in compositions with more DMDES, suggesting more complicated relaxation processes.

Chemical nanotechnologies have played, in the past few decades a major role in the convergence of life, physical and engineering sciences leading not only to simple collaboration among the disciplines but to a paradigm shift based on true disciplinary integration. The successful synthesis, modification and assembly of nanobuilding units such as nanocrystals and wires of different materials have demonstrated the importance of chemical influence in materials synthesis, and have generated great expectations for the future. Implications of chemistry as an innovation motor are now visible for knowledge leap forward in various sectors such as materials engineering for energy, health and security.
Inorganic nanostructures inherit promises for substantial improvements in materials engineering mainly due to improved physical and mechanical properties resulting from the reduction of microstructural features by two to three orders of magnitude, when compared to current engineering materials. This talk will present how chemically grown nanoparticles, nanowires and nanocomposites of different metal oxides open up new vistas of material properties, which can be transformed into advanced material technologies. The examples will include microwave-assisted synthesis of superparamagnetic iron oxide nanoparticles for drug delivery applications, and chemically controlled production of heterostructures for sensing and light-harvesting application.

Despite tremendous untapped potential, solar cells provide only a tiny fraction of the world-wide energy supply because they are uncompetitive with fossil fuels on a cost-per-unit-energy basis. Ongoing research and manufacturing improvements continue to slowly chip away at this cost gap for current solar technologies. Meanwhile, there has been an increasing amount of effort devoted to so-called “third generation” solar conversion approaches [1], which seek to exploit advanced physical phenomenon to achieve high conversion efficiencies in devices fabricated using low-cost materials and methods. One prominent example are the “quantum-dot cells,” which are based on solution-synthesized semiconductor nanocrystal quantum dots (NQDs), particularly those made of lead chalcogenides (PbE, where E=S or Se). In addition to being inexpensive to make, PbE NQDs offer high absorption cross sections, excellent photostability and size-tunable effective band gaps, due to the effects of quantum-confinement, that span the ideal energy region for single-junction solar cells (~0.9 - 1.5 eV). Moreover, they are the first materials to demonstrate efficient carrier multiplication, a process in which absorption of a single ultraviolet photon can create two or more electron-hole pairs in an NQD, both in spectroscopic studies [2] as well as in real, functional devices [3].
Despite already impressive performance, there are still a number of outstanding issues for PbE NQDs that need to be resolved in order for them to reach their full potential as photovoltaic materials. For instance, PbSe NQDs are particularly sensitive to oxidation under ambient conditions, which leads to uncontrolled changes in their effective band gap and carrier recombination dynamics. In addition, effective methods for controlled electronic doping, a key capability that allows the formation of charge-separating p-n junctions in most solar cells, are still at the relatively early stages of development for essentially all NQD materials. In this presentation, I will survey the current status of NQD-based devices, and describe solution-based methods for addressing some of the remaining issues in PbE NQDs that are being investigated within the Center for Advanced Solar Photophysics, a DOE Energy Frontier Research Center devoted to NQD-based third-generation solar cells. Specifically, I will discuss post-synthesis treatments for the elimination of active surface sites responsible for both instability toward oxidation and fast carrier recombination in PbE NQDs. I will also describe our recent work in chemical methods for persistent electronic doping of these materials. Finally, I will summarize recent performance studies of devices using these new methods, and outline related future directions.
[1] M.A. Green, Third Generation Photovoltaics: Advanced Solar Conversion, Springer (2003). [2] R.D. Schaller and V.I. Klimov, Phys. Rev. Lett. 92, 186601 (2004). [3] O.E. Semonin, et al., Science 334, 1530 (2011).

Vanadium oxide compounds with different stoichiometries are receiving special interest for their exceptional structural, (electro-)chemical and physical properties. VO₂ exhibits a temperature induced insulator to metal transition at 68 °C. Its integration in novel MOSFET and memories is currently explored. Additionally, V₆O₁₃ and V₂O₅ are candidate cathode materials for rechargeable Li-ion batteries. Here, we report a new, aqueous, and hence environmental friendly route for the deposition of these vanadium oxides on various substrates.
Prior to the deposition process, a stable and suitable aqueous vanadium precursor is developed and profoundly analyzed using Magnetic Resonance and Spectroscopic techniques. The oxovanadate(IV) species present are structurally identified as mononuclear, octahedral citrato-oxovanadate(IV) complexes with a four R-CO₂^- ligation at the equatorial positions and likely a fifth R-CO₂^- ligation at the axial position, each originating from citrate species present in the aqueous solution.¹
Subsequently, the developed aqueous oxovanadate(IV) precursor is successfully used for the formation of VO₂, V₆O₁₃ and V₂O₅ nanostructures. Through an elaborated study of the deposition and processing parameters - including substrate choice, layer thickness, O₂ partial pressure and temperature - specific conditions are derived for the formation of respectively crystalline VO₂, V₆O₁₃ or V₂O₅. The crystallinity, morphology and topography of the obtained structures are studied using X-Ray Diffraction, Scanning Electron Microscopy and Atomic Force Microscopy, respectively. Additional information about the vanadium oxidation state is obtained by Grazing angle Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy.
In summary, a new aqueous based synthesis route for the formation of VO₂, V₆O₁₃ and V₂O₅ nanostructures is reported including a detailed study on the precursor synthesis, the processing parameters, the crystallinity and the morphology of the obtained vanadium oxide nanostructures.
Nick Peys & Christopher De Dobbelaere are funded by the Research Foundation-Flanders.
¹N. Peys et al., V₆O₁₃ films by control of the oxidation state from aqueous precursor to crystalline phase, Dalton Transactions, DOI 10.1039/C2DT31857A

Due to their large surface charge, oxides offer a valuable alternative to carbon-based electrochemical capacitors for high-rate energy storage. In addition to conventional charge accumulation at the double layer interface, transition metal oxides with mixed valence properties allow some redox reactions in their outer layers that largely increase the capacitance value [1]. This effect can be further increased in the case of open-structure materials which present a good ionic conductivity and fast ionic intercalation and exchange properties. This work will particularly focus on cobalt oxides and vanadium bronzes presenting a lamellar-structure.
For specific x values, the cobalt bronze NaxCoO2 phase is electronically conductive [2, 3]. It therefore is a good candidate for supercapacitor applications. Nanoparticles of NaxCoO2 with high specific area (above 100 m2/g) can be synthesized by rapid precipitation in an aqueous alkaline oxidizing medium at room temperature. For NaxCoO2,yH2O deposited onto a glassy carbon substrate in an aqueous electrolyte, at slow cycling rates (1 mV/s), charges as high as 900 C/g can be measured similar to that obtained for the expensive ruthenium oxide [4]. This high capacity can be attributed to the reversible insertion of 0.5 sodium, associated to a pseudocapacitance contribution in addition to the double layer capacitance. Indeed electrochemical studies with transition metal oxides have shown that pseudocapacitive charge storage becomes more prominent with nanoscale particles [5,6].

Vanadium bronzes MxV2O5 (M=Li, Na, K) are known to be better electronic conductors than most oxides and their 2D lamellar structure allows a good ionic mobility and an easy insertion of alkaline ions [7]. Nanofibers of about 10 nm in diameter and one micron long of V2O5 are obtained thanks to a sol-gel synthesis using a sodium metavanadate solution [8]. Then intercalation of alkaline ions is obtained in solutions of alkali iodides (with redox insertion reaction) or of alkali sulfates (limited to simple ionic exchange). Electrochemical measurements have been performed in organic electrolytes. For instance, LixV2O5 showed a high capacity of 500 C/g at 1 mV/s. And even at very high sweep rates, the capacity remains above 125 C/g.
[1] B.E. Conway, Journal of Electroanalytical Chemistry 524-525 (2002) 4-19
[2] F. Tronel, L. Guerlou-Demourgues, M. Basterreix, C. Delmas, Journal of Power Sources 158 (2006) 722
[4] J.W. Long, K.E. Swider, C.I. Merzbacher, D.R. Rolison, Langmuir 15 (1999) 780
[5] X. Pétrissans, A. Bétard, D. Giaume, P. Barboux, B. Dunn, L. Sicard, J.-Y. Piquemal, Electrochimica Acta 66 (2012) 306-312
[6] J. Wang, J. Polleux, J. Lim, B. Dunn, J. Phys. Chem. C 111 (2007) 14925
[7] I.D. Raistrick, R.A. Huggins, Solid State Ionics 9-10 (1983) 425-430
[8] N. Gharbi, C. Sanchez, J. Livage, J. Lemerle, L. Nejem, J. Lefebvre Inorg. Chem. 21 (1982) 2158-2165

Progress in the development of energy-efficient coatings on glass has led to the study of smart glass with special functional coatings that can regulate solar energy in response to an external stimulus. Thermochromic smart windows are considered attractive because they are visibly transparent and can intelligently control the amount of solar heat (mainly in the near-infrared region) in response to changes in ambient temperature. Discovered over 50 years ago, VO2 is the most promising thermochromic material; however, related materials have not been commercialized because of problems related to cost-efficient preparation, stability and performance. To date, gas-phase deposition methods, such as sputtering and chemical vapor deposition, are the most common methods for the fabrication of VO2 films, but these methods are still dependent on innovative technologies to meet the requirements of practical applications and are excluded from the topic of the current paper. This paper reviews the state-of-the-art solution processes used top prepare VO2 films on glass and polymer substrates, with a special emphasis on polymer-assisted deposition methods. The VO2 films prepared by these methods show controllable morphology and thickness and complex optical properties compared with those prepared by gas-phase methods. In fact, single-layered films exhibit the highest integrated visible transparency (43%) and solar-energy modulation ability (14%). These studies suggest that chemical preparation is inexpensive, easy to scale up, and best suited for the practical applications of the fabricated materials.

Vanadium oxides thin films with variable oxidation states have attracted great attention due to their unique electrical and optical properties and many important applications in microelectronics, infrared optical devices, and energy harvest systems. However, to fabricate vanadium oxide thin films with controllable phases and desired transport properties is still a challenge by using a chemical solution deposition (CSD) technique. In this presentation, we will report that vanadium oxide thin films with well controlled phases such as rhombohedra V₂O₃ and monoclinic VO2 could be synthesized on Al₂O₃ (0001) substrates using a CSD technique ---- polymer assisted deposition (PAD). Both V₂O₃ and VO₂ thin films can be well controlled with good epitaxial quality by optimizing the fabrication parameters. The electrical resistivity changes four orders of magnitude at metal insulator transition for both epitaxial V₂O₃ and VO₂ thin films. The correlation between the physical properties and the microstructures of the films will be discussed.

The issue of global warming and the finite lifetime of conventional fossil fuels stimulate the world wide effort for renewable and green energy production, predominantly based on using energy from our sun either indirectly by wind and water power, or by direct conversion of sun light to electrical power or chemical fuel. Photoelectrochemical (PEC) water splitting yielding hydrogen which can be stored and used as clean fuel is one promising approach. Due to their abundance, nontoxicity and electrochemical stability wide-band gap semiconducting metal oxides such as TiO2, WO3, and Fe2O3 are often studied materials but each of them has its advantages and disadvantages. Hematite (α-Fe2O3) possesses a band gap of ~ 2.2 eV suitable for visible light, but still has low photon conversion efficiency (IPCE) due to short hole diffusion lengths of 2-4 nm, low absorption coefficient and very short excited state lifetime. On the other hand TiO2 performs better but uses only a part of the solar spectrum due to the band gap in the UV range (3.2 eV). Thus in order to optimize the IPCE of these materials nanostructure and bandgap engineering are required. Chemical solution deposition (CSD) offers large potential because of cost efficiency, possibility of micro-/nanostructure control, and flexibility with regard to composition including the ease of dopant addition for tuning the bandgap.
In the present work stable CSD routines using TiO2 nanoparticle dispersions and molecular precursor solutions for TiO2 and hematite have been developed which enabled the addition of dopants such as W, Ni, Si etc. Thin films photo anodes with different nanostructures and compositions have been fabricated on FTO coated glass and characterized by scanning electron microscopy, X-ray diffraction and UV/VIS spectroscopy. The determined band-gaps were in good agreement with the literature.
In order to characterize the PEC response of the various thin films a multipurpose solar-simulator was built. Here the required artificial sunlight was generated by a LED array consisting of 20 high performance LEDs with different wavelengths, ranging from 300 nm to 1100 nm. The generated spectrum could be manipulated by computer controlled drivers for each LED. Adjacent to the light guide of the solar simulator a self-constructed electrochemical measuring cell was placed with the ability to hold and electrically contact 1”x1” samples with an illuminated area of 3 cm2 and a working- to counter electrode distance of 14 mm.
Thus the reaction of the various CSD derived photo anodes was studied depending on individual wavelengths, times, and intensities and compared to the literature. In addition to typically published parameters which influence the IPCE, further factors which are often not taken into account, such as “degree of electrolyte stirring”, moment of measurement after bringing the film into the electrolyte, etc. will be discussed with regard to their significant impact on the IV-characteristics.

Large mesopores have been demonstrated as a size-selective platform for applications in biosensing. Unfortunately, there are few methods available for producing large-mesopores in the biological size range. Here, we utilize designer cross-linked micelles generated from block copolymers as a pore generating species capable of producing large mesopores. The cross-linked micelle contains an organosilicate incompatible core and compatibilizing periphery to create large domains from samples that can be easily spun from solution. Further, we demonstrate that pore morphology can be controlled by tuning the interactions of the periphery block with the organosilicate. After thermal vitrification and pore generation, the organosilicate is hydrophobic and lacks silanol functionality rendering the pores inaccessible to water or surface modification even when interconnected. While oxidative treatments for transforming organosilicates to silica-like structures are known (e.g. UV/ozone and O2 plasma), they create non-uniform films where the most damage/silanol creation occurs at the interface. Unlike the organosilicate, these highly damaged, oxide-like, portions of the film dissolve in aqueous solutions. To circumvent these problems, we have developed a process that oxidizes the interface of the pore wall. This allows us to create a uniformily oxidized material with respect to the film thickness while controlling the overall level of carbon within the film.

Organization of silica/silicate mesoporous materials through self-assembly is important topic in nanoscience. For synthesis and fabrication of these materials, many methods and techniques have been developed in recent years. A well ordered silica porous topology has been mostly achieved in powder type by a combination of sol-gel and supermolecular chemistry that involved an amphiphilic BCPs (block copolymers) micelle templated self-assembly process using silica precursor. But, using these binary mixtures continuous thin film with vertically aligned mesopores has been suffered to be fabricated.
Herein, we have developed silazane based novel inorganic-organic BCPs (PS-b-PVCSZ, PMMA-b-PVCSZ and PEO-ss-PVCSZ) using controlled living polymerization techniques as a single precursor for both powder and thin film type of mesoporous SiCN and silicate, depending on the precursor and treatment conditions. In particular, the PEO-ss-PVCSZ was converted to vertically aligned, functionalized silicate nanoporous thin film with chemical and thermal robustness. The thiol (-SH) functionalized inner surface of the mesoporous silicate thin films was decorated with Au, Pd and Ag metals in a site-selective manner. Furthermore, the confined Au nanometal in the nanopores showed excellent catalytic activity in microchemical platform, with no aggregation even after annealed at 250 degree centigrade. These organic-inorganic based BCPs has open new way to fabricate the continuous silicate thin films and it is plausible to further extend into other applications like nanosives, nanotemplate, biosensors etc.

Vertically-oriented polymer grafts and carbon nanotubes on substrates have been reported recently as a new class of functional materials with shape-derived unique properties. Those materials are so-called “nanobrush” because their distinctive microscopic morphologies look like brushes. Strong structural anisotropy and large grafting density of nanobrushes make them useful for potential applications in electronics and photonics. We present the synthesis of vertically-oriented titanate nanotubes (TNTs) prepared by hydrothermal treatment of amorphous TiO2 thin films from sol-gel method. Given the unique shape of such nanostructure, we named it “TNT brush”. The surface morphology can be tuned from nanosheets to nanofunnels by controlling the NaOH concentration during the hydrothermal treatment. Vertically-oriented titanate nanosheets are formed in lower pH conditions. The edges of the nanosheets are rolled-up to form nanotubes in higher pH conditions, resulting in the formation of inverse funnel-shaped titanate structures positioned on top of the nanosheets. The nanotubes at the top of the nanosheets are well-oriented and perpendicular to the precursory film surface, leading to the formation of TNT brushes. The unique morphology enables us to control its surface chemistry for the fabrication of functional interfaces. As an example of such an interfacial application, we functionalized TNT brushes so that they can be used as a superhydrophobic adhesive surface for small water droplet delivery. The fabricated surface can possibly be used as a new tool in microfluidics, drug delivery, lab-on-a-chip and other applications in which the handling of precise amounts of solutions on semiconductor oxides is crucial.

Thin films with nanometric grain size, nanorods and hierarchical nanostructure have been actively investigated in the last few years as key component in several technologically relevant applications such as gas sensing. Some effective solution synthesis techniques have been proposed for these nanostructures. However, most of these approaches do not allow a direct and accurate patterning. This represent a significant limitation in their use in actual devices. We recently developed a new approach towards the synthesis of these materials based on the use of metal-loaded poly(ethylene glycol) based hydrogels. The method has been applied to the preparation of patterned SnO2, In2O3, ZrO2 and TiO2 and other complex oxides, ZnO nanorods and ZnO hierarchical nanostructures. In this approach the hydrogel-based precursors have been embossed using polydimethylsiloxane molds, then photopolimerized and thermally and/or photochemically degraded producing crack-free and highly transparent ceramic patterns of high lithographic quality. The thin films are characterized by a very fine nanostructure characterized by grain size ranging between 5 and 30 nm. These films represent an ideal seeding layer for the growth of micropatterned ZnO nanorods arrays through hydrothermal synthesis. The arrays of nanorods show a relevant vertical alignment , while the nanorod characteristics can be partially controlled varying the grain size of the seeding layer. Hierarchical nanostructures based on ZnO nanorods have been obtained as well. The overall procedure allows to overcome some drawbacks associated to other soft-lithographic approaches to the synthesis of ceramic patterns and rely completely on the use of very inexpensive, environmentally friendly chemicals and of simple experimental apparatuses.

Conventional thin film deposition processes such as chemical vapor deposition (CVD) or sputtering, etc require severe conditions like high temperature or high vacuum, which limit their applications that needs soft/mild processes on delicate substrates (e.g., plastic, electric circuits, etc). Self-assembly techniques are one of the powerful and efficient methods to the synthesis of nanostructured materials in soft/mild conditions. Using these techniques and their combination with top-down fabrication processes such as lithography, materials with hierarchical feature can be produced with form and function in multiple length scales. In this presentation, I will discuss on our recent progress in the development of a wet-solution-based process employing self-assembly as a new method to produce optical, electrical, and magnetic coatings. The technology combines self-assembly, sol-gel process, and nanocrystal colloid chemistry to produce engineered multifunctional films. Through introduction of a variety of functional elements, this technology enables the development of engineered coatings with tunable properties, such as hydrophobic, mechanical robustness, etc. This new process not only meets the demanding requirements of conventional film deposition technologies but also expands the functionality of these films to deliver performance on multiple metrics concurrently.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy&’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Among soft chemistry approaches, non-aqueous sol-gel routes are elegant routes for the synthesis of metal oxide nanocrystals,[1] ordered organic-inorganic hybrid materials,[2] inorganic heterostructures.[3] These routes, involving the reaction of metal oxide precursors in organic solvents (e.g. benzyl alcohol) at moderate temperature and pressure, offer advantages such as high crystallinity of the as synthesized oxides, high purity, high reproducibility and the ability to control the crystal growth without the need of using additional ligands. Moreover, non-aqueous sol-gel is particularly suitable for the syntheses of multi-metal oxides and doped materials.[4] In this presentation, after a short introduction to non-aqueous sol-gel chemistry, we will focus on our recent work on the assembly of metal oxide nanoparticles in surfactant-free media [4] and on the fabrications of heterostructured materials (based on metal oxides) targeting energy and environmental applications.[5]
References:
[1] N. Pinna, M. Niederberger, Angew. Chem. Int. Ed., 2008, 47, 5292
[2] N. Pinna, J. Mater. Chem., 2007, 7, 2769
[3] N. Pinna, M. Karmaoui, M.-G. Willinger, J. Sol-Gel Sci. Technol., 2011, 57, 323
[4] A. Pucci, et al. ACS Nano 2012, 6, 4382
[5] P. A. Russo et al. Angew. Chem. Int. Ed. 2012, DOI: 10.1002/anie.201204373

A variety of self-assembly techniques has been developed since decades, however, device-scale assembly of highly ordered anisotropic nanoparticles is still challenging. We developed a simple coating method for a shear-directed assembly of rigid colloidal nanorods over a large area without size limitation. Hydro-thermally synthesized lanthanum phosphate (LaPO₄) nanorods were used as base material considering their single crystalline rodlike geometry, high colloidal stability, and superior anisotropic optical properties.^[1] By tuning the nanorod suspension into a thixotropic gel phase, the fundamental problems of shear-directed assembly such as orientation relaxation, defect generation, and texturing could be eliminated. And a macroscopic mono-domain film structure (7.5cm x 2.5cm) associated with a very high orientational order (S>0.99) was obtained and verified by polarization optical microscopy, SEM, and XRD analysis. As-prepared thin films exhibit remarkable birefringence (Δn=0.13) together with high transparency on the entire UV-Vis-IR range.^[2] Such a large birefringence is found to be an optimal combination of form birefringence from the ordered structure and the intrinsic birefringence of the LaPO₄ crystal itself (Δn_LaPO4=0.05), which is a novel way to obtain high birefringence. It is also possible to modulate optical properties by filling the pores with other inorganic media such as silica or TiO₂ by sol-gel route. This film can be directly used as an inorganic thin film wave plate for a variety of optical applications (e.g., UV optics, high power laser devices, large flux displays, and telecommunication). And its fabrication process is very simple, cost-effective, and all solution-based from synthesis to assembly.
[1] J. Kim et al., Adv. Funct. Mater. doi: 10.1002/adfm.201200825 (2012)
[2] J. Kim et al., Submitted to Adv. Mater. (2012)

We introduce the facile route for preparation of solvent-free metal (i.e., Ag, Au) and quantum dot (QD) nanoparticle fluids with highly improved electrical, optical and rheological properties. In our system, we used hydrophobic Ag, Au and QD nanoparticles which were synthesized using hydrophobic stabilizers such as palmitic acid, tetraoctylammonium bromide and oleic acid in organic media (i.e., 1-octadecene, toluene) respectively. The solvent-free nanoparticle fluids based on hydrophobic nanoparticles can be produced by phase-transferring the hydrophobic nanoparticles showing the high affinity with thiol group to thiol-containing imidazolium-type ionic liquid (TFI-IL) medium. The prepared Ag nanoparticle fluids exhibit the noticeable electrical properties such as low sheet resistance (~ 40Omega;/sq.) due to the short chain length and low molecular weight of TFI-IL stabilizer, which enable the close contact of between nanoparticles. These phenomena can also be supported by optical properties of QD nanoparticle fluids such as high photoluminescence, strong energy transfer. In addition, their optical, electrical and rheological properties can easily be controlled by changing the amount of inserted nanoparticles in TFI-IL medium. These solvent-free nanoparticle fluids all display the liquid-like behavior at room temperature without addition of any solvent. We also explain how to prepare the TFI-IL-QD-based multilayers (red, green and blue emission) using layer-by-layer (LbL) self-assembly method in aqueous solution. If DI water is added in TFI-IL-QDs, the positively charged QD solution can be prepared due to the protonated imidazolium group of TFI-IL stabilizer and easily controlled their concentration. Therefore, the positively charged TFI-IL-QDs can be electrostatically self-assembled with negatively charged polyelectrolyte such as poly(sodium, 4-styrene-sulfonate) (PSS) using LbL self-assembly method. The prepared optical multilayers for each-colored red, green and blue QDs show the strong photoluminescence due to high relative quantum yield and adsorption amount of QDs, compared to the previous water-dispersible QDs using hydrophilic ligands such as cysteamine (CA) and mercapto acetic acid (MAA).

Engineered metamaterials with novel properties that are not present in conventional systems are gaining considerable attention. A major target of metamaterials research is tunability and low loss, especially in the visible and infrared regions of the electromagnetic spectrum. Loss is generally caused by absorption of the building blocks (plasmonic metals such as Au and Ag, for example). One of the proposed solutions is to include a gain medium in the system to compensate for this loss. This approach has demonstrated to be valid for example in the preparation of visible-light lasers or for the stimulated emission of Au-based structures at sub-wavelength dimension, in both cases using organic fluorophores as gain media. Quantum dots (QDs) are ideal candidates for this application because, compared to organic fluorophores, they show higher stability against photobleaching, they can be potentially integrated on a large-scale and they can be not only optically but also electrically pumped. However, their interaction with plasmonic building blocks is still poorly understood.
In this contribution, we analyze the interactions between plasmonic and semiconductor materials where we carefully tune the composing building blocks, their composition, morphology and distance with a set of different chemical and physical tools. The local field enhancement is analyzed and related to the structural properties of the assemblies, such as physical distance and electronic structure. We will investigate the use of plasmonic metals of different shapes and semiconductor quantum dots and films of all these materials. The spacers will be either organic or inorganic, and either semiconductors or dielectrics. All this wealth of information will be rationalized by careful experiments at varying parameters.

Future availability of high-temperature power inverters will advance the market share for hybrid vehicles that are highly fuel efficient and environmentally friendly. An integral part of vehicle power inverters is the DC buss capacitors, which have a significant influence on inverter lifetime, reliability, cost, and temperature of operation. The drive train and backup systems in electric vehicles utilize AC power drawn from a battery via a power inverter. Similarly, the battery is charged from the utility grid (AC power) via a rectifier. Large ripple currents are produced due to imperfect inversion and rectification. Ripple currents reduce the battery performance, lifetime, and charge/discharge efficiencies. Capacitors are thus used in the power electronic systems to block the ripple currents from reaching the power source. Advanced power inverters require capacitors that operate at high voltage and under-hood conditions and yet have minimal footprint. This need can be realized by embedding high-permittivity dielectrics within a printed wire board (PWB). Embedding capacitors into PWBs frees up surface space, increases device reliability, minimizes electromagnetic interference and inductance loss, and reduces manufacturing cost. However, the integration of high-permittivity ceramics into PWBs is challenging because of the incompatibility of the different processing conditions involved. The “film-on-foil” approach, where the high-permittivity ceramic dielectric is first deposited on base-metal foil, is the most viable fabrication method for embedding the capacitors within a PWB. We have deposited high-permittivity lead lanthanum zirconium titanate (PLZT) ceramic dielectric films on Ni foils by a chemical solution deposition technique. These prefabricated “film-on-foil” dielectric sheets can be embedded into PWBs. For PLZT films deposited on Ni foils, the measured dielectric constants varied with temperature: from asymp;700 at -50°C to asymp;2200 at 250°C. The dielectric loss remained fairly constant at asymp;0.05-0.08. For 300 V bias, we measured a dielectric constant of asymp;110 and loss asymp;0.004 at room temperature, and a dielectric constant of asymp;185 and loss asymp;0.008 at 200°C. Leakage current densities of 6.6 x 10^-9 A/cm² at 25°C and 1.4 x 10^-8 A/cm² at 150°C were also measured. The breakdown field strength of PLZT films deposited on LNO-buffered nickel foils was 2.6 MV/cm. Hysteresis loop analysis showed an energy density of asymp;85 J/cm³. These results suggest that Argonne&’s film-on-foil capacitors have the potential to operate at high voltage in an under-hood temperature environment and yet have minimal footprint. The fabrication procedures and dielectric properties of film-on-foil PLZT samples will be presented in this talk.
Work supported by the U.S. Department of Energy, Vehicle Technologies Program, under Contract DE-AC02-06CH11357.

In addition to their intrinsic physical properties due to their electronic band structure, photocatalytic materials must display a relatively high specific surface and a good stacking of atoms constituting the crystalline structure to display high activity. Indeed, defects may act as recombination center between photogenerated electrons and holes and consequently decrease photocatalyst efficiency.1 When different polymorph of the same composition of photocatalyst is available another challenge is to form selectivly during the synthesis the most active. With a solid background in oxide nanoparticles tailoring from metallic salts in aqueous solution,2 our research group succesfully transferred conventionnal syntheses of titanium dioxide and bismuth based oxides to microwave assisted thermohydrolyses.
In the case of TiO2, pure anatase could be obtain through microwave heating where brookite is usually observed as secondary phase in traditionnal oven.3 The use of organic additive was thus avoided and good photocatalyst with clean surface were consequently more rapidely obtained.4 Photocatalysts obtained by microwave synthesis were compared to their conventionnal counterpart in order to check whether significant improvement in Rhodamine B degradation in aqueous solution was observed. Additionnaly time resolved microwave condutivity (TRMC) was used to probe the crystalline improvement of the materials.
References
1. G. Benko, B. Skarman, R. Wallenberg, A. Hagfeldt, V. Sundstrom, and A.P. Yartsev, J. Phys. Chem. B, 2003, 107, 1370.
2. J.-P. Jolivet, C. Froidefond, A. Pottier, C. Chanéac, S. Cassaignon, E. Tronc, and Patrick Euzen, J. Mater. Chem., 2004, 14, 3281
3. A. Pottier, S. Cassaignon, C. Chanéac, F. Villain, E. Tronc, and J.-P. Jolivet, J. Mater. Chem., 2003, 13, 877
4. F. Dufour, S. Cassaignon, O. Durupthy, C. Colbeau-Justin, and C. Chanéac, Eur. J. Inorg. Chem., 2011 submitted.

Transition metal oxides (TMOs), duo to the rapid surface redox reaction related pseudocapacitance, can provide at least ten times higher capacitance than the electric double layer of porous electrodes. However, the application of TMOs for supercapacitors is significantly limited due to their high resistivity. Nanostructured oxides supported by graphene sheets, simultaneously achieving high conductivity and large surface area, is a very promising approach to overcome this limitation. Here we report our study of vanadium oxide/graphene composite based high performance supercapacitors.
In this work, vanadium oxides with different morphologies including nanoparticles, nanosheets, and nanowires, were synthesized via hydrothermal method with vanadyl acetylacetonate and graphene oxide sheets as precursors. The reduction of graphene oxide and formation of vanadium oxide was conducted in the same process to achieve intimate bond between these two materials, facilitating electron transport and enhancing the nanomaterial porosity. The composite was further thermally processed to minimize resistance. The structural, chemical, electrical, and optical properties of the hybrid were studied based on SEM/TEM, micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and resistance measurement. The supercapacitor performance based on these composite nanomaterials were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge measurements.

With the particular optoelectronic characteristics and excellent physicochemical properties, ZnO nanocrystals have been applied to extensive fields ranging from photoelectronic physics to material chemistry. However, the large band gap of ZnO prohibits it from effective light absorption under sunlight irradiation, which further limits its applicability in relevant photoelectric processes. To render visible light absorption thus becomes an essential task for the further advancement of ZnO. In this work, an environmentally benign antisolvent method [1,2] has been developed to prepare transition metal ion-doped ZnO nanocrystals. A room-temperature ionic liquid, known as deep eutectic solvent (DES), was used as the solvent to dissolve ZnO powders. Upon the introduction of ZnO-containing DES into a bad solvent which shows no solvation to ZnO (e.g. water), ZnO was precipitated and grown due to the dramatic decrease of solubility. By adding transition metal ions such as Cu2+, Ni2+ and Co2+ in the bad solvent, the growth of ZnO in antisolvent process was accompanied by metal ion doping, resulting in the formation of metal ion-doped ZnO nanocrystals. The thus-obtained metal ion-doped ZnO showed additional absorption band in visible range (400-800 nm), attributable to the doped ions which invoke the interband transitions within the energy gap of ZnO to render ZnO visible-light responsive. Furthermore, due to the significant sp-d interaction between doped ions and ZnO [3], the doped ZnO samples exhibited obvious hysteresis loop at 300K with the saturated magnetization increasing with the increase of metal ion concentration. With the unique visible-light responsive and room-temperature ferromagnetic properties, the present transition metal ion-doped ZnO nanocrstals may find potential use for unique optomagnetic applications especially when magneto-optical effect is exerted.
[1] J.-Y. Dong, Y.-J. Hsu, D. S.-H. Wong, S.-Y. Lu, J. Phys. Chem. C 2010, 114, 8867.
[2] J.-Y. Dong, W.-H. Lin, Y.-J. Hsu, D. S.-H. Wong, S.-Y. Lu, CrystEngComm 2011, 13, 6218.
[3] Q. Xiao, J. Zhang, Mater. Sci. Eng. B 2007, 142, 121.

Compared to classic fluorescent materials such as organic dyes and quantum dots, rare earth doped fluoride upconversion fluorescent materials possess a series of superiorities, such as long excitation wavelength, high physical and chemical stability, strong fluorescence intensity, large anti-Stokes shifts, narrow band emissions and high photo-chemical stability, along with the week auto-fluorescence, low cytotoxicity, deep penetration of light, minimal photobleaching and high signal-noise ratio. For these unique superiorities, rare earth doped fluoride upconversion fluorescent materials have a bright prospect in the biomedical applications. Hexagonal-phase sodium yttrium fluoride (NaYF4), known as one of the most efficient host materials due to the low lattice phonon energy and good thermal stability, has been usually used as host materials of upconversion materials.
Chelating ligand, as a part of the process of nanocrystal&’s growth, plays an important role during the growth of nanocrystals. There are two major roles of the chelating ligand: one is complexing with rare earth ions to reduce the concentration of the free rare earth ions and delay the nucleation of the nanocrystals; the other is combining with the nanocrystals&’s surface and guiding the growth of the nanocrystals. Carboxylic acids are good complexing agends for rare earth ions due to the high complexing quotient on rare-earth metal. Oleic acid (OA), sodium citrate and ethylenediamine tetracetic acid (EDTA) are the most commonly used chelating ligands.
In this paper, myristic acid was used as a novel chelating ligand to synthesize NaYF4: Yb, Er nanocrystals through a facile hydrothermal method. Field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD) and upconversion luminescence spectroscopy were used to characterize the product. It was found hollow nanorods of NaYF4: Yb, Er can be obtained. The size and shape are controlled through changing the reaction conditions (F-/Re, quantity of myristic acid and NaOH). What&’s more, the ratio of F-/Re, quantity of myristic acid and NaOH were all responsible to the fluorescence intensity.

High surface area, nanomaterial-supported adsorbents are highly promising composites with respect to specific cleaning and filtration of toxic off gases and as they can extend the capabilities of currently used bulk adsorptive agents. In this context, transition group metal oxides cannot only perform and enhance adsorptive processes for polar gases, they furthermore have the potential e.g. to specifically remove gaseous components and/or gain additional catalytic faculties.
Thus, a new and effective route for the formation of nanoparticle-containing, active adsorbents has been developed based on metal oxide/polymer nanocomposites. Representatively we want to show the preparation, characteristics and H2S adsorption capabilities of a FexOy nanoparticle containing, polymer based activated carbon.
Gas phase made iron oxide nanoparticles derived from liquid spray flame synthesis, were functionalized in liquid phase using organosilane coupling agents to change surface properties from hydrophilic towards lipophilic. A homogeneous inorganic/organic nanocomposite was formed by radical polymerization reaction of styrene containing the surface-modified iron oxide nanoparticles. Composite materials with up to 5 wt% of FexOy could be received. As a final step, thermal pyrolysis of the obtained polymerizate under N2-atmosphere at temperatures below 400 °C yielded activated, porous carbon/FexOy nanocomposites.
The materials were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD), IR-spectroscopy, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The characterization clearly shows the preservation of the iron oxide nanoparticle structure, size and morphology even after pyrolysis and their extensive distribution within the carbon matrix.
The desired overall product was investigated in particular by nitrogen adsorption (BET) and H2S adsorption/desorption measurements to probe the adsorption properties. The results reveal that load capacity of the composite is above 0.2 mol H2S per kg adsorbent and so beyond adsorption capabilities of common impregnated activated carbon, even though the hitherto materials have much smaller BET surface area values (A_BET) around 300 m2/g. Our new method prevents loss of micropore volume and available surface as it is observed for activated carbon impregnated with inorganic salts. In addition the potential of regeneration of the adsorbent and obtaining enlarged surface is given.

Zinc oxide nanorods were electrodeposited on conductive oxide-coated transparent glass at a potentiostatically controlled voltage with a single initial voltage-pulse.
Cadmium sulfide nanoparticles were coated on the as-prepared ZnO nanorods by chemical-bath deposition, forming ZnO/CdS nanoarrays.
The resulting nanoarrays were characterized by X-ray diffraction, X-ray spectroscopy, UV-Vis spectroscopy, Raman spectroscopy, and photoelectrochemical methods.
The short-circuit current density (J_sc) of some ZnO/CdS sample showed over 3.3 mA cm^-2 under solar-simulated illumination.
The ZnO/CdS nanoarrays showed promising photocatalytic activity with respect to the degradation of Eriochrome Black T (EBT) under visible light.
The nanoarrays' good photoelectrochemical and photocatalytic performance under visible-light illumination can be ascribed to the enhanced absorption of visible-light by CdS and the charge separation effected by the semiconductor/semiconductor interface.
The employed synthetic methods offered a fast and cost-effective way to produce medium aspect-ratio nanorod films dotted with nanoparticles at readily accessible experimental conditions.

Earth abundant multicomponent copper chalcogenide-based, namely Cu2ZnSnS4 (CZTS), Cu2ZnSnSe4 (CZTSe), Cu2ZnSn(S1-xSex)4 (CZTSSe) and Cu2Zn(Sn1minus;xGex)S4 (CZTGS), have recently attracted a great deal of attention as direct band gap materials for the fabrication of high-efficiency photovoltaic devices. In particular, these compound (I2-II-IV-VI4) semiconductor material possess high optical absorption coefficients (105 cm-1), high energy conversion efficiencies, offer good photostability against long-term radiation and cause less environmental problems due to their relatively low toxicity. So far device efficiencies for these multicomponent kesterite based solar cells are significant lower than the best efficiencies achieved for chalcopyrite based solar cells, which has been related to the difficulty to achieve controlled stoichiometry in the currently applied vacuum-based deposition or precursor annealing techniques. Solution based methods are an attractive alternative to vacuum deposition processes due to their simplicity and cost effectiveness. We have developed a facile, low-cost method to synthesize CZTSSe and CZTGS nanocrystal with excellent monodispersity in shape, controlled stoichiometry and crystal phase by methods of colloidal chemistry. The crystal structure, shape and composition of the as-synthesized nanocrystal were investigated with transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, PL and energy dispersive X-ray analysis (EDX).

Recently transparent oxide semiconductor (TOS) materials for solution process have been widely developed. The typical sols as precursors to TOS are low-viscosity and mostly coated on a substrate by spin-coating for fabrication of electric devices. When electric devices are fabricated by printing technique, the appropriate viscosity of materials depends on the kind of printing methods. In this study, viscous sols as precursors to indium gallium zinc oxide (IGZO) were synthesized using various liquid amines by a simple and easy process and the thermal and electric characteristics were evaluated. Liquid amine was added to an aqueous solution containing metal salts and urea and the mixture solution was heated at 100 deg C with continuous stirring. The water was gradually evaporated and ammonia was formed by hydrolysis of the urea. The ammonia induced increase in pH of the solution and formation of metal hydroxides. Subsequent heating at 110-140 deg C provided viscous sols as precursors to IGZO. Especially the sols containing diethanolamine (DEA) are transparent and showed ca. 3 to 13 Pa s of viscosity depending on the concentration of metal salts. According to thermogravimetry-differential thermal analysis (TG-DTA) for the sol containing DEA with 3 Pa s of viscosity, mass decrease more than 80% occurred due to pyrolysis of DEA at 240 deg C and then drastic exothermic change was observed at 300-310 deg C due to dehydroxylation. The temperature giving the exothermic change depended on the kind of amines. A bottom-gate top-contact transistor was fabricated using the sol by coating on a silicon wafer with thermally oxidized film, sintering for 30 min, and vapor deposition of gold as source and drains electrodes. When the sintering temperature is higher than 350 deg C, the transistor demonstrated more than 10^6 of on/off ratio.

Ceramic high temperature superconductors (HTS) are near perfect conductors for electricity and promising materials for applications in magnets, generators and transformers which can be used in e.g. green energy generation and energy saving industrial devices. To allow for integration of HTS materials in for example conducting wires, we need to move from brittle bulk ceramics to thin films on flexible substrates. Chemical solution deposition uses precursors containing stoichiometric amounts of the different metal ions in solution. These can be coated on top of flexible metal substrates carrying suited buffer stacks e.g. by ink-jet printing. Good inks have to fulfill a number of requirements such as long time stability at more or less neutral pH, good gelation properties, compatibility with the substrate and suited thermal decomposition behavior.
The development of these precursors is a time consuming and non-straightforward job that might be simplified if we could predict the stability of precursor inks containing varying concentrations of different complexing agents, additives and metal ions as a function of pH. For aqueous YBCO precursors, often tri-ethanolamine is used to stabilize the metal ions in solution. Yet, the complexation of Cu²⁺ ions with this fourfold coordinating base remains a matter of debate and it is clear that earlier reported stability constants are not suited to describe our systems. We use both EPR, NMR, potentiometric titrations and complexometric speciation simulations to improve the understanding of the Cu-TEA solutions. For the model system used here, we find that at pH below 7, only acetates are actively complexing the Cu²⁺ ions, while when reaching higher pH levels both triethanolamine and ammoniak complexes are formed. By using the Evans&’ method, we were able to proof from NMR measurements, the presence dimeric species in solution at higher pH values. Larger data sets are being generated in order to extract exact complexation constants.

Large area ceramic thin films on plastics are strongly demanded in flexible electronic device technologies as well as in technologies that aim at replacing glasses by lightweight plastics. Many of the active functions of oxide thin films emerge in their crystalline states with high bulk density or small porosities. Crystallization as well as densification, however, is driven in principle by atomic diffusion at high temperatures where plastics cannot survive. This is why great efforts have been made for over thirty years to develop "low-temperature" deposition techniques, where how to crystallize and densify the films without "firing" has been focused on. Here we report a totally different route that guarantees crystallization and densification by firing. The technique comprises (i) the deposition of a polymeric release layer on a single crystal silicon substrate, (ii) the deposition of the precursor gel film by spin- or dip-coating, (iii) the conversion of the gel film into a crystalline oxide ("ceramic") film by firing, and (iv) the transfer of the crystallized film onto a plastic substrate. The transfer was realized by melting or softening the substrate surface. The ceramic thin films transferred onto plastic substrates were crack-free and had smooth surface. Transparent, 60 nm thick anatase thin films with high optical reflectivity could be prepared on PMMA and polycarbonate (PC) substrates. Transparent, electrically conductive, 660 nm thick ITO thin films on a PC substrate are another example. Patterned ITO thin films could also be prepared on plastics by using a mother silicon substrate with periodic grooves.

Ba0.8Sr0.2TiO3/ZrO2 heterostructured thin films with different individual layer ZrO2 thicknesses are deposited on Pt/Ti/SiO2/Si substrates by a sol-gel process. The current versus voltage (I-V) measurements of the above multilayered thin films in metal-insulator-metal (MIM) device structures are taken in the temperature range of 310 to 410K. The electrical conduction mechanisms contributing to the leakage current at different field regions have been studied in this work. Various models are used to know the different conduction mechanisms responsible for the leakage current in these devices. It is observed that Poole-Frenkel mechanism is the dominant conduction process in the high field region with a deep electron trap energy level (phi;t) whereas space charge limited current (SCLC) mechanism is contributing to the leakage current in the medium field region with a shallow electron trap level (Et). Also it is seen that Ohmic conduction process is the dominant mechanism in the low field region having activation energy (Ea) for the electrons. The estimated trap energy level and activation energy for electrons are increased with the increase of ZrO2 sub layer thicknesses. An energy band diagram is given to explain the dominance of the various leakage mechanisms in different field regions for these heterostructured thin films.

Transparent conducting oxides (TCOs) are essential for many electronic devices such as photo-electric converters, light emitting diodes, liquid crystals, or fenestration applications [1]. Commonly used TCOs are wide band-gap oxide semiconductors such as Tin doped Indium oxide (ITO), Fluorine doped Tin oxide (FTO), or Aluminum doped Zinc oxide (AZO). The application of AZO as transparent front contact in thin film solar cells is already the norm due to its low cost and high material abundance. However, until now high performance AZO transparent conductive layers are deposited by magnetron sputtering or chemical vapor deposition, both employing sophisticated vacuum or reactive gas handling equipment. Thus, for a more economic deposition of AZO thin films, a non-vacuum, solution-based technique would be favorable.
This work presents the development of a chemical bath deposition (CBD) method for the formation of AZO thin films applicable as transparent front contacts in Cu(In,Ga)Se₂ thin film solar cells. The main focus is set on a low-temperature ( le; 200°C) processing to obtain transparent and conducting AZO thin films. Systematic investigations on the influence of the precursor solution pH, temperature, organic modifier and dopant concentration on thin film quality and opto-electronic parameters are discussed. With a novel doping and post-treatment strategy high-quality polycrystalline films with an optical transmission of ge; 90% (in the 400-800 nm range) and resistivity of le; 10^-2 Ohm cm have been obtained.
[1] C.G. Granqvist, "Transparent conductors as solar energy materials: A panoramic review", Sol. Energy Mater. Solar Cells 91, 1529 (2007).

In optoelectronic applications, the reduction of light reflection from device surfaces is a critical issue. Simple calculations suggest that this can be achieved using anti-reflection (AR) coatings with a low refractive index of ~1.2. However, such low refractive indices cannot be obtained by dense thin film materials; moreover, single-layer AR coatings can obtain minimum reflectance only at a specific wavelength. In contrast, a graded-refractive index AR coating can achieve very low reflectance in a wide wavelength range. Thus, AR coatings with discrete multi-layer stacks with different refractive indices have been studied and demonstrated. Recently, highly porous block copolymer (BCP) thin films were applied to AR coatings because the refractive indices of the nanostructures derived from BCPs can be easily tuned by controlling the volumetric ratio of the pores generated by the selective removal of one block. Here, we demonstrate that an excellent AR coating in the visible wavelength range can be achieved using double-layered poly (styrene-b-dimethylsiloxane) (PS-PDMS) BCP thin films. By the selective etching of PS-PDMS BCPs using O2 plasma, PS chains are removed and PDMS chains are converted to highly porous thin silica films. The refractive indices of the porous silica films can be systematically controlled from 1.111 to 1.346 by adjusting the volume fraction of the PDMS in the BCPs. Our double-layered nanoporous thin silica films show outstanding broadband and omnidirectional AR characteristics with an average transmittance that exceeds 99% in the visible wavelength range (400 - 700 nm). Outstanding thermal and chemical stability levels stemming from their inorganic properties were also confirmed. Moreover, an anti-fogging capability is possible due to the superhydrophilicity of the nanoporous thin films, leading to significantly improved transmittance in a highly humid atmosphere. The facile fabrication process, excellent AR characteristics and good durability make these porous silica thin films very practical for many optoelectronic devices, such as flat panel displays or solar cells.

In recent literature, nanocrystal inks have emerged as promising candidates for the solution deposition of inorganic thin film materials. These inks are colloidal suspensions of nanocrystals that, upon pyrolysis, recrystallize into polycrystalline films, relinquishing their unique nano-scale properties. This general deposition method exploits advantages of a controllable stoichiometry, low volume contraction, and mechanical robustness as well as the other benefits of solution processing, with applications in photovoltaics, solid state lighting, and other large area electronics. Here, we extend this method by applying recent developments in nanocrystal surface chemistry, using chalcogenide systems including ZnS and ZnSe for demonstration. These developments include ligand exchanges on colloidal nanocrystals, replacing long-chain organic ligands with small molecular species of similar stoichiometry to the crystal itself. We demonstrate successful nanocrystal syntheses, efficient ligand exchanges, and the preparation of dense polycrystalline thin films from these ink solutions. We confirm the efficacy of small molecule ligand exchange in preparing higher quality material versus control studies using more traditional surface treatments. The thermodynamic and kinetic basis for these improvements are discussed, accompanied by electrical, optical, structural, and morphological properties of the resultant thin films, confirming our hypothesis that the film properties are a strong function of nanocrystal surface chemistry.

As an efficient, inexpensive and scalable technique, inkjet printing offers an ideal answer to the emerging trends and demands of depositing small volume (in picoliter range) droplets of precursor liquid inks into functional thin films and device components with high degree of pixel precision. Compared to other techniques of film deposition, this method is fast, simple, precise, material-saving and suitable for any type of substrates, which is promising for new flexible and/or stretchable electronics. One challenge that remains open is to design the inks with long term stability for effective deposition of specific materials of industrial importance like ZnO, MgO, TiO2 .
In this presentation we introduce a reliable method of producing stable inks for ‘in-situ&’ deposition of oxide thin films by inkjet printing. The inks were prepared from metal-acetates solutions and printed on a variety of substrates. The acetate precursors were decomposed into oxide films during the following calcination process to achieve the deposition of oxide films in-situ on the substrate. With this approach high quality ZnO, MgO, and indium tin oxide (ITO) films have been printed from their acetate(s) solutions. In order to obtain room temperature contamination free ferromagnetic spintronic materials defect induced and Fe doped MgO and ZnO have been synthesized ‘in-situ&’. It is found that the origin of magnetism in these materials is intrinsic. For a 28 nm thick film of Fe-doped ZnO we observe an enhanced magnetic moment of 0.47 µB/Fe atom while it is 0.11 µB/Fe atom for the doped MgO film of comparable thickness. The origin of magnetism is attributed to cat-ion vacancies. We have also fabricated highly transparent ITO films with a transparency >90% both in the visible and IR range which is rather unique compared to films grown by any other technique. The films have a nano-porous structure, an added bonus from inkjetting that makes such films applicable for a broad range of applications.

The structural, optical and magnetic properties of Zn_1-xCo_xO (x=0.0, 0.0625) thin films deposited onto fused quartz substrates via a simple sol-gel method, are reported. X-ray diffraction measurements revealed that pure and Co-doped ZnO films exhibited the hexagonal wurtzite structure. The XRD pattern of the pure ZnO film evidenced a preferential growth of the (002) plane, whereas other planes typical of the wurtzite phase were developed only in presence of the Co species. UV-vis spectroscopy analyses confirmed the high transparency of the films (higher than 85%). Besides, the presence of absorption bands corresponding to the d-d transitions were clearly identified, which confirmed the actual incorporation of Co ions into the ZnO host lattice. The increasing of the Urbach&’s energy, from 57meV, for pure ZnO, up to 200.6meV, for Co-doped ZnO, suggested the augment of disorder in the oxide lattice induced by the incorporation of Co ions. Room-temperature VSM measurements evidenced that the magnetic behavior of Co-doped films were anisotropic in nature; the films exhibited a ferromagnetic behavior when the magnetic field was applied in parallel to the film orientation whereas a clear paramagnetic trend was observed when the field was applied perpendicular to the film.

The self-cleaning technology has recently received a lot of attention in commercial anti-fouling applications. Anti-fouling coatings can protect materials from environmental pollution, keep the performances and reduce maintenance costs. In the current applications, due to the concentration of appearances and durability, self-cleaning glass is highly desired for buildings, trains, showers, solar-cells and so on. There are a lot of organic and inorganic pollution in our environment. The super-hydrophobic and photo-catalytic coatings can both offer the self-cleaning function. However, the former prevents adhesion of inorganic dust mainly and the latter decomposes just organic compounds. In this study, a transparent self-cleaning coating combined super-hydrophobic with photo-catalytic properties has been reached.
The nano-roughness structure will lower the surface energy but not interfere the light transmission, so it is the key to making surfaces both transparent and super-hydrophobic. In this study, the nano-needle structure on transparent super-hydrophobic film was established by coating the nano-alumina on glass, and subsequently treated with hot water to make the crystallization. After building the needle-like layer, the fluoro-modified nano-silica has been coated on it to acquire the super-hydrophobic property. Finally, the anatase type nano-titania was coated as outer surface to give photo-catalytic function. All nanoparticle coating used in this paper are synthesized via sol-gel reaction, and their sizes have been controled under the nano-degree (<20nm) to maintain film&’s transparency. The problem of adverse properties between super-hydrophobic and photo-catalyst, has been solved by optimizing the contents of them. When 0.2 wt% anatase type nano-titania doped, the film&’s water contact angle is still above 160°, and its light transmission is larger than 95% averagely. The SEM and AFM morphologies show that the film thickness ranges from 100 to 200 nm, while the needle&’s height and roughness range from 20 to 50 nm. Based on the methylene-blue adhesion and decomposition test, the dual-function coating can first reduce about 80% dye adhesion by the super-hydrophobic property, and then totally decompose the residue after being exposed to UV light for 4hrs because of the photo-catalytic function.

Thin films of pure silica (silicalite-1) and titanium doped (TS-1) zeolite MFI were synthesized on seeded glass substrates. Two different sized pure silica seed crystals were used, 80nm and 200nm, and their effect on secondary growth was compared. All synthesis gels used for secondary growth contain fluoride and use the same structure directing agent (TPA-F) and silica source (TEOS). Such gel compositions inhibit nucleation in the bulk such that, over the relatively short synthesis times employed in this study, the bulk gel remains amorphous and nearly all crystallization occurs on the seeded glass substrates. The resulting films continue to grow with the orientation of the seed layer which is random for the 80nm seeds and highly 'b' oriented for the 200nm seed crystals. Removal of the structure directing agent (SDA) was carried out by UV/Ozone under heating. Seed layers and resulting continuous films were characterized using gXRD and SEM. SDA removal was confirmed by optical spectroscopy. Attempts at EBSD will be shown but this technique is problematic for zeolite films due to radiation damage during analysis. The purpose of this study is to refine efficient techniques for the synthesis of thin zeolite films to use as low-k dielectrics, an important area to advance as the need for better insulation increases with ever shrinking CPU's.
In a similar line of research, TS-1 films may demonstrate photocatalytic activity toward the reduction of CO2 in the presence of H2O to methanol, methane, and other light hydrocarbons. Air borne pollutants such as NOx may also be reduced to N2 and O2. Previous research1,2 has shown that TS-1 powders are effective photocatalytic reductants; however, TS-1 films have yet to be tested. TS-1 films also present the opportunity for fundamental studies, such as the binding of small organic compounds to the tetrahedrally coordinated Ti4+. In this work, we have developed a methodology for the synthesis of TS-1 with low defect (silanol) concentrations and variable amounts of Ti. Just as for silicalite-1, the TS-1 films prepared from the fluoride route have a strong b-axis texture. The films were characterized by XRD, SEM, EDS, and FTIR and the results will be described.
1. Anpo, M.; Takeuchi, M.; Sakai, S.; Ebrahimi, A.; Matsuoka, M. Top. Catal. 52 (2009): 1651-1659.
2. Anpo, M.; Yamashita, H.; Ikeue, K.; Takewaki, T. Journal of Physical Chemistry B. 105 (2001): 8350-8355.

In this work we used the technique of chemical bath deposition (CBD) at low temperature for preparing thin films on Cd_1-XZn_XS with low zinc content on glass substrates. The CBD process was totally ammonia free using precursors of metallic salts like CdCl₂ and ZnCl₂, in alkaline solution stabilized with KOH, and replacing the ammonia with trisodic citrate (C₆H₅O₇Na₃) as complexing agent. Thin films were obtained with proportions of precursors in solution x = 0.04, 0.12 and 0.2, where x = ZnCl₂/[CdCl₂ +ZnCl₂]. The deposition conditions were optimized to obtain homogeneous and uniform films at a temperature of 60^oC. Under these conditions it was possible to investigate the effects of adding Zn²⁺ ion precursor to the reaction solution on the properties of the as deposited films. Subsequently, the films were annealed at 400^°C. The X-ray diffraction analysis showed that the films crystallize under a wurtzite-type hexagonal structure. By applying the annealing treatment, films with x = 0.04 and x = 0.2 exhibit high crystallinity, with the exception of x = 0.12 which showed a slightly amorphous structure. The elemental composition of the films was determined by Energy Dispersive Spectroscopy (EDS) analysis. From this analysis we observe that the intensity peaks identifying the Zn content in 1 and 8.5 keV of the spectrogram increases with the annealing treatment of the samples. The sample with the higher content of Zn was that with x = 0.2, which has 48 at% of Cd, 13 at% of Zn and 39 at% of S. The superficial morphology, grain size and the thickness of the films were determined by Scanning Electron Microscopy (SEM). Those as deposited films showed agglomerates in the form of flakes whose size increased with the content of Zn. The agglomerates of the annealed films were densified taking a spherical-like shape with larger grain size on the surface compared to that of the as deposited films. The analysis by UV-VIS spectrometry showed that the optical transmittance values for films with x = 0.04 and 0.12 before and after annealing was almost the same. However, for the case of x = 0.2, a decrease in the value of the optical transmittance of about 10% was observed after annealing treatment. The calculation of the energy band gap showed a shift due to changes in the concentration of Zn. The higher is the content of this element, the greater is the value of the band gap energy. For annealed films we detected a slightly decrease in the bandgap energy. For example, in the case of the films with x = 0.2 the bandgap value decreased from 2.65 (calculated for the as deposited film) to 2.56 eV. In summary, the anneal treatment produced morphological and structural changes in the Cd_1-XZn_XS thin films and in some cases favored to better cristalinity but the optical transmittance and bandgap values were reduced.

Many applications of optoelectronics require materials with tailored properties, specifically, those referred to get a desired electrical conductivity and optical transparency. Most investigations in the literature correspond to the development of n-type transparent metallic oxide semiconductors. However, optoelectronics applications also require p-type semiconductors. Recently, chalcogenide metallic materials have become an important research field in order to get transparent p-type semiconductors. For such a case, CuS thin films with low thicknesses ~70nm have been proposed. However, the maximum transmittance achieved with these films in the visible region of the optical spectrum is about 65%. Ternary alloy compounds are materials whose optical and electrical properties can be modified for a variety of applications. Specifically, Cu _1-xZn _x S is a promising material for device applications such as electroluminescent, photoconductors and photovoltaic devices. Here, we show preliminary results on Cu _1-x Zn _x S films with low content of Zn obtained by a chemical bath deposition method. For the reaction solutions we used cupric Nitrate (Cu (NO ₃ ) ₂ ) as source of Copper (Cu) ions, Zinc Acetate (C ₄H ₁₀ O ₆ Zn) as source of Zinc (Zn) ions, Thiourea as source of Sulfur (S) ions and triethanolamine (TEA) as complexing agent. Ammonium hydroxide (NH ₄ (OH)) was used to adjust pH. Clean glass substrates were vertically immersed into the solution, contained in a beaker at low temperature, and were taken out after 25 minutes. In order to get a content variation of Zn in the reaction solution, we established the proportions of Cu and Zn as x =(C ₄ H ₁₀O ₆Zn)/[ (Cu (NO ₃) ₂) +(C ₄H ₁₀O ₆Zn)]. In this way, the Zn precursor content had a variation of x=5, 10, 15 and 20%. At first, it is noted that the higher the content of Zn, the thin films obtained are more transparent and thinner. For all the cases, the results from X-ray diffraction shows that Cu _1-xZn _xS thin films are amorphous. A study was made in all the Cu _1-xZn _xS thin films to obtain the surface morphology by scanning electron microscope. The resulting surface particles were agglomerates of spherical particles. The size of the agglomerates is larger as the content of Zn is increased. An additional consequence of adding Zn to the films is an increasing of the transmittance up to 85%. From energy dispersive spectroscopy analyses obtained evidence of the presence of Zn which in the case of the films with x=15% the content in of Zn is 29.88at%, Cu is 31.45at% and S is 38.67 at%. The electrical characterization showed that Cu _1-xZn _xS thin films are more resistive when as the content is higher going from 2 KOmega;/square for the films with x=5% to 16 KOmega;/square for the films with x=20%. Because it is possible to obtain various optical an electrical characteristics of the Cu _1-xZn _xS, the obtained thin films can be potentially used in various devices that require p-type transparent semiconductors.

This oral presentation will introduce our recent work on understanding the roles played by citrate and poly(vinyl pyrrolidone) (PVP) as capping agents in seed-mediated syntheses of Ag nanocrystals with controlled shapes. We have demonstrated that citrate and PVP selectively bind to Ag(111) and Ag(100) surfaces, respectively, and thus favor the formation of Ag nanocrystals enclosed preferentially by {111} or {100} facets. In addition, we have quantified the coverage density of PVP adsorbed on the Ag(100) surfaces. Based on the mechanistic understanding, a series of Ag nanocrystals with controlled shapes and sizes have been successfully synthesized by using different combinations of seeds and capping agents: single-crystal spherical/cubic seeds with citrate for cuboctahedrons and octahedrons or with PVP for cubes and bars; and plate like seeds with citrate for enlarged thin plates or with PVP for thickened plates. The shape-dependent optical properties of the as-prepared Ag nanocrystals are also discussed.

Laser-induced chemical liquid phase deposition (LCLD) used for metal deposition from solutions onto surfaces of dielectrics is based on the local impact of laser beam focused at the interface of a solution and a dielectric surface. This results in the initiation of metal reduction within the focal zone of laser beam yielding metal structures of a micrometer range at the interface of the solution and the surface.
LCLD is known to be a perspective method for manufacturing of metal interconnections for printed and flexible electronic devices. It is maskless technology, promising cost-effective environmentally friendly manufacturing process for prototyping and small-scale production of high precision PCBs.
Copper was deposited onto dielectric substrates made from glass ceramic “Sitall CT-50-1” widely employed in microelectron-ics; its composition is as follows: SiO2 (60.5%), Al2O3 (13.5%), CaO (8.5%), MgO (7.5%), TiO2 (10%).
The experiments for copper deposition at different laser powers were performed. The scanning speed of laser beam was 0.01-01mm/s, DPSS laser (532nm) working in continuous mode was used for irradiation of samples, power of laser beam was 200-1000mW, diameter of focal spot was 10-50 mkm). The dependance of copper lines width on laser power was clarified for each dielectric material. Copper lines were analyzed by optical reflectance microscopy and scanning electron microscopy. Composition of copper lines was examined with EDX microanalysis. Copper as a general component of deposited lines was defined. The a.c. impedance spectra were recorded with an impedance meter Z-2000 (Elins Co.) in the frequency band of 20 Hz to 2 MHz at the signal amplitude of 125 mV.

Zinc oxide (ZnO) nanoparticles (NPs) are being extensively studied due to their unique chemical and physical properties at the nanoscale and the numerous actual and potential applications. Doping of ZnO NPs also has been explored as an attempt to enhance and/or tune their functional properties and enable these NPs to find novel applications not only in spintronic but also in biology and medicine, including imaging and photo-dynamic therapy. Although the doping of ZnO with different transition metal ions has been reported elsewhere, the effect of the dopant oxidation state on the materials properties at the nanoscale has not been properly addressed yet. In this work, we have synthesized bare and (Fe³⁺ and Fe²⁺)-doped ZnO NPs in polyol medium at 180^oC. The synthesis in polyol allows a precise control of doping under size-controlled conditions. The Fe concentration varied in the 0-2 at. % range. As-synthesized samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR), Photoluminescence (PL) spectroscopy and Vibrational Sample Magnetometry (VSM). XRD measurements confirmed the formation of well crystallized wurtzite ZnO with absence of secondary phases in bare and doped samples; the average crystallite size was estimated at (8.4 ± 0.3) nm for bare ZnO NPs and (6.0 ± 0.3) nm and (7.8 ± 0.3) nm for the Fe³⁺ and Fe²⁺ doped ZnO samples, respectively. FT-IR analyses evidenced the presence of organic moieties on the surface of the nanoparticles that are associated to the functional groups of polyol by-products; these adsorbed species could explain the observed stability of the NPs when suspended in water. PL measurements for bare and doped ZnO NPs exhibited only the excitonic emission in the UV region at room temperature. Moreover, the doped samples in the 0.5-1 at. % range displayed an increase in the UV PL-emission intensity comparing with the pure material; the enhancement in the emission intensity was more pronounced for the Fe³⁺ doped samples. The quenching in the UV emission was observed above that doping range. VSM measurements at room temperature evidenced a weak but noticeable ferromagnetic response in doped samples; the coercivity values varied between 73 Oe and 123 Oe for the Fe³⁺ doped ZnO samples.

Introduction: We established a new reaction field named Solution plasma which can generate plasma in solution. The research on the solution plasma as metal nanoparticle synthesis method such as gold nanoparticles has been carried out in our laboratory.
Plasma can be generated in bubble formed from solution by applying pulse high voltage to the wire electrodes immersed in the solution. During plasma discharge the various radicals and electrons are generated and these activated species can promote the reduction reaction of metal ions in solution. The kinds of radicals are derived from the solution and its physical properties. Thus, we can control the kind of radicals and even control the reduction reaction by controlling the conditions of the solution. In this study, we synthesized gold nanoparticle by solution plasma in water - alcohol mixture solution.
Experimental methods and results: At first, for the evaluation of the effect of solution on the plasma, we measured the dependence of the breakdown voltage to occur plasma on the concentration of ethanol - water mixture solution through the oscilloscope analysis. As a result, the breakdown voltage increased drastically with the increase of ethanol mole fraction of 0~0.14, and in its mole fraction of 0.14~1.0 breakdown voltage decreased gently with the increase of concentration (Fig. 1). This is because composition and density in bubble varies, following the Henry-Raoult&’s law [1] when bubble is formed from solution by applying high voltage.
In next step, we added 0.3mM HAuCl4 to the solutions above described and synthesized Au nanoparticles by solution plasma. We calculated the reaction rate constant through UV-vis analysis. From Fig.2 a maximum reaction rate constant of 30×10-3s-1 was achieved at ethanol mole fraction of 0.14. The relationship between Fig.1 and Fig.2 will be discussed in the details during poster presentation.

Titanium dioxide is one of the most widely used materials across various applications including pigment, UV light absorber, memristor in electronics, and solar energy conversion. Herein, we report the successful synthesis of hollow N-TiO2 (nitridated TiO2) spheres with sizes down to a sub-micrometer scale by simple nitridation process of hollow TiO2 spheres. These hollow N-TiO2 spheres can be assembled into a monolayer film on a water surface, enabling the transfer onto a substrate which can be done, repeatedly, and on a large scale. We demonstrate that these assembled N-TiO2 sphere films show a great enhancement in electrochemical performance compared to TiO2 films without the need of any binder materials. Additionally, the areal capacitance of an N-TiO2 electrode shows a linear increase with the number of N-TiO2 layers. Furthermore, the deposition of MnO2 on the surface of an N-TiO2 sphere film remarkably improves the specific capacitance due to the interplay of the high electronic conductivity of N-TiO2 and high electrochemical activity of MnO2. The MnO2/N-TiO2 film supercapacitor displays great cyclic stability up to 1000 cycles as measured by acyclic voltammetry scans.

A major concern for the food industry is the development of more efficient and effective materials for food preservation and protection against human health-compromising microorganisms. More recently, the antimicrobial activity of environmental-friendly and chemically stable MgO has been suggested. Compared to others, MgO is expected to provide an improved food packaging solution under cost-effective conditions. Also, the capability of nanosize MgO to destructively adsorb chemical warfare agents and its bactericidal activity even in absence of UV illumination, coupled with its ability to block UV light, enable this nanomaterial to be considered for food preserving applications. Despite of the remarkable features of MgO, there is a lack of systematic research on its size-controlled synthesis, which could modify the size-dependent properties of nanoscale materials (e.g. bactericidal capacity).
On the above basis, the present work focuses on the development of a reproducible and cost-effective size-controlled synthesis route for nanoscale MgO and the assessment of its bactericide capacity as a function of crystal size. Nanoscale MgO was produced through the thermal decomposition of Mg-carbonate hydrate precursor synthesized in aqueous phase in presence of sodium oleate as surfactant. The thermal treatment temperature was set at 600°C based on the information provided by thermogravimetric analyses. The exclusive formation of the MgO phase, with an average crystallite size around 11 nm, was evidenced by X-Ray Diffraction. Fourier Transform - Infrared spectroscopy confirmed the evolution of the precursor into the desired MgO structure. The bactericidal tests were conducted in a Petri dish seeded with a certain volume of inoculums containing the tested bacteria (e.g. E. coli O157:H7, Salmonella and Shiguella) and MgO nanoparticles of specific sizes. The relationship between the functional properties and bactericidal capacity of MgO will be presented and discussed as a function of crystal size at the nanoscale.

Dispersion of hydrophobic particles in water is typically achieved by using surfactants or polymers that “camouflage” hydrophobic surfaces with hydrophilic groups. Aqueous dispersion of hydrophobic particles without the use of any surfactants has both technological and academic significance. In this study, we demonstrate that aqueous dispersion of hydrophobic particles without any “camouflage” is indeed possible with reengineering of the interfacial topography. We sculptured the surface of smooth polystyrene microsphere to feature hydrophobic and rigid Zinc Oxide (ZnO) nano-wires, termed the Hedgehog particles (HHPs). The HHPs not only dispersed in organic solvents but also in water while retaining hydrophobicity of ZnO spikes in the aqueous environment. We believe that the HHPs form a three-phase shell; radially distal portion occupied with water and the proximal portion filled with air cavity both of which are interdigitated with solid phase ZnO nano-spikes. Such arrangements reduce hydrophobic solid fraction at the HHPs interface, and in conjunction, create large surface area for hydrogen bonding that significantly increase the freedom of water molecules around the interface. The rigid ZnO nano-spikes function to localize and confine entropic loss in the HHP shell, while minimizing the entropic loss of the whole system and enable to circumvent hydrophobic interaction amongst the HHPs.

The sensitization with narrow-band gap semiconductor quantum dots (PbS, CdSe, CdS etc.) have been explored as next-generation solar cells owing to their unique characteristics comparable to those for conventional dyes such as using Ru-polypyridine complexes and organic dyes. In case of quantum dots, their optical absorption can be tuned by controlling their size and shape to cover the solar spectrum. They have a higher extinction coefficient and can utilize hot electrons to produce multiple electron-hole pairs per photon which may improve power conversion efficiency. Hence we have fabricated PbS sensitized ZnO samples for improving its performance of solar cells.
In the present paper, authors have sensitized ZnO nanoneedles with PbS nanoparticles using refluxing and chemical bath deposition method. The PbS coating time was varied from 5 to 30 min to cover complete ZnO nanoneedles. The sensitized samples were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Raman spectroscopy and optical absorbance. The size and density of PbS particles increases with respect to coating time, resulting in cube-like shape. The peaks corresponding to PbS and ZnO phases in XRD pattern revealed successful coating of nanoparticles onto nanoneedles. Further, Raman spectra exhibited peaks related to PbS and ZnO, which confirmed the successful sensitization using chemical route. Moreover, the optical absorbance increases in the visible region after PbS sensitization which is useful to increase power conversion efficiency of solar cells device. Hence, these PbS -sensitized ZnO samples may show better efficiency of quantum dots sensitized solar cells.

Permanent magnets, specifically those containing rare earth metals, are an indispensable component of many applications in electric, electronics, communications, and automobile industries. The emergence of green technology markets such as hybrid/electric vehicles (PHEVs and EVs), direct drive wind turbine power systems, and energy storage systems (eg: flywheels) has created an increased demand for permanent magnets. Unfortunately, recent market trends have made the production and procurement of rare earth permanent magnets more challenging and less cost efficient. We have discovered a new permanent magnet material, low carbon steels, which requires no rare earth elements, employs a simplified synthesis technique that lowers production costs, and has the potential to compete with the highest energy density permanent magnets currently produced. This new nanostructured material is synthesized using a modified polyol process which is scalable. The new material has a thermal coefficient of demagnetization of -0.04%/oC from 20 to 250oC. The intrinsic coercivity is 3500 Oe with a saturation magnetization of 75 emu/g.

Cadmium free quantum dots (QDs) such as CuInS2 have emerged as alternatives to the range of cadmium based QDs that have historically dominated the field, due to their excellent optical properties. A synthesis route towards hydrophobic CuInS2 QDs that display optical properties comparable to those of cadmium based QDs, although originating from trap state dynamics as opposed to band edge, is now well established. Passivating these surface trap states with a ZnS layer can improve the photoluminescence quantum yield significantly, although a small blue shift in the emission wavelength is observed as a result. We present data that may elucidate the nature of the CuInS2/ZnS boundary, a detail that has proved to be controversial in the literature. Despite significant interest in these technologically important QDs, their transfer into the aqueous phase still remains non-trivial. In this work, the molar extinction coefficient of these QDs is determined, a parameter that is vital for many applications, since it allows the concentration of a given QD dispersion to be accurately estimated through routine spectroscopic methods. This allows for the optimized coating of the QDs with an amphiphilic polymer, a method which has proved to be very effective for enabling the transfer of hydrophobic QDs into the aqueous environment. The stability of the resulting QD-polymer hybrid nanoparticles is assessed in relation to solution pH and ion composition, as well as temperature and prolonged UV exposure. Finally, the in vitro response of HaCaT cells to these nanoparticles will be discussed.

The efficient use of agrochemicals to supply the demand for nutrients is a key aspect in the agriculture productivity. However, effects such as leaching and volatilization are common in many agrichemicals, which impose significant losses and also, leading to serious ecological problems. In this scenario, the controlled release of agrichemicals has been studied to reduce these losses and manage the delivery of desired molecules in the environment in the proper moment in the agriculture cycle. In order to modify the release of herbicide ametryne from montmorillonite as also minimize the agro-environmental pollution, starch gel was incorporated into montmorillonite-ametryn formulations in order to obtain a biodegradable nanocomposite, where the starch phase acts as the matrix and montmorillonite as a diffusion barrier to control the release. Composites with ametryne 50 wt% and starch gel-montmorillonite (25 wt% each) were successfully produced and characterized. Analyses by scanning electron micrograph (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry (TG) showed the effective interaction between ametryn and starch gel - montmorillonite nanocomposite. The TG results showed that the initial loss of ametryn starts in 169 oC while the ametryne into montmorillonite starts in 310 °C. The increase of crystallinity can be attributed to the high thermal stability of the clay mineral and to the interaction between the clay and the ametryn. However, when starch gel (280 °C) is incorporated into montmorillonite-ametryne, the initial loss decreased to 248 °C, indicating that the interaction with starch reduced the ametryn crystallinity, imposing a slight reduction of the melting temperature. The total release of ametryn occurred in less than 1 hour (~ 650 mgL-1). However, when incorporated into the clay, the release decreases to 40 mgL-1. When starch is incorporated into montmorillonite-ametryn formulation, the release is decreased 25%. These results showed that the starch incorporation into montmorillonite controlled properly the ametryn release in water. The release from starch-montmorillonite-ametryne formulation was slower than from montmorillonite-ametryn formulation, due to the strong interaction between ametryn with starch and the clay, in a synergistic manner.

Aligned nanofibers of poly(ethylene oxide) (PEO), PEO/TiO2 nanoparticles, and PEO/Fe2O3 nanoparticles were deposited by an electrospinning process at ambient conditions. The main goal of this experiment is to investigate the possibility of producing conductive nanowires for potential applications in nanoelectronics, sensors, and actuators. Electrospinning is a method of creating nanofibers by using a high voltage to draw fibers from a blunt needle or spinneret to a grounded collector. The fiber material begins as a viscous liquid, typically a polymer solution or melt, which solidifies as it travels to the collector. Electrospinning aligned and conductive nanofibers remains a challenge due to electrostatic repulsion between the nanofibers during the electrospinning process and agglomeration of the nanoparticles within the fiber. Electrostatic repulsion causes the fibers to be misaligned when deposited. This can be corrected by optimizing the viscosity of the solution, finding the correct working distance, and using parallel plates as the collector with the insulated substrate mounted between the plates. PEO functions as a carrier for the metal oxide nanoparticles which are deposited as composite nanofibers. The PEO carrier can be removed via annealing to produce metal oxide nanowires. The consistency of the solution plays an important role in its spinnability. To effectively electrospin PEO (molecular weight = 300,000), the weight percentage is found to lie between 4% to 10%. Below 4%, the solution is too fluid and results in electrospraying of droplets or does not fully evaporate when deposited. Above 10%, the solution becomes too viscous and does not act in a predictable manner while electrospinning. This will either form fibers that do not reach the collecting plate or create a large strand of the solution that forms directly between the syringe and a single point on the collector plate. During the preparation of the solution, the sequence of mixing is critical to achieving the correct consistency. It was found that isopropyl alcohol will inhibit the solubility of PEO, however, if the PEO is dissolved in water first then diluted with isopropyl alcohol to the desired concentration the solution mixes in a more homogeneous manner. It is at this point that the metal oxide nanoparticles are added to the solution. It was found that the sum of dissolved PEO and suspended metal oxide follows the same trend as PEO alone in reference to concentration. The concentration of PEO and metal oxide are inversely proportional in that the total concentration must be below approximately 10%. The agglomeration issue may be solved by incorporating a surfactant in the solution while maintaining the viscosity necessary to electrospin the solution.

Solid polymer proton exchange membrane (PEM) made of poly (vinyl alcohol) (PVAL), hypophosporous acid (H3PO2) and Nafion® aqueous solution (10% w/w) with thicknesses between 40 and 150 µm were synthesized by solution casting method. Ionic conductivity and thermal properties were studied as a function of the Nafion® concentration by means of impedance spectroscopy (EIS), differential scanning calorimetry (DSC) and thermogravimetric (TGA) measurements. Morphological, vibrational and structural characterizations were also performed with SEM, FTIR and XRD, respectively. The dried membranes dc conductivity at room temperature varies between 10-4-10-3 Scm-1 when Nafion® concentration was increased. Thermal studies shows that the presence of Nafion® in the system PVAL+H3PO2 doesn&’t have appreciable effect on the membranes, thermal stability and water uptake. These results are discussed in terms of Nafion® concentration in the membranes and its modification to the ion-ion and ion-polymer chain interactions.

Quantum confinement effects in silicon nanoparticles (Si NPs) lead to unique optoelectronic properties which are different than in the bulk. Several approaches are reported in the literature for the synthesis of Si NPs, but most require elaborate techniques or require hydrofluoric acid (HF) etching. Colloidal synthesis provides an alternate route for synthesizing these materials and also gives control on the size of the nanoparticles obtained.
Herein, we will describe an alternative colloidal route for the synthesis of Si NPs of sizes from (2-10 nm) with surfactants such as 1, 2-hexadecanediol and oleylamine. Characterization of the NPs with transmission electron microscopy (TEM), UV/Vis and nuclear magnetic resonance spectroscopy (NMR) will be described. In addition, the effect of different precursor concentration on the effect of NP size will be discussed.

While progress in physical deposition techniques, such as sputtering and CVD, has allowed thin film deposition techniques to generally keep pace with the performance requirements of typical optical and semiconductor applications, this performance comes at a significant cost, impacting budget, logistics, and environmental, safety, and health areas. Development of solution processing methods for the synthesis of functional inorganic materials have opened up new avenues to achieve enhanced and/or novel properties in these materials. Among significant methods, self-assembly techniques are one of the powerful, efficient, and cost effective methods to the synthesis of nanostructured films. Using these techniques and their combination with top-down fabrication processes such as lithography, materials with hierarchical feature can be produced with form and function in multiple length scales. Here our recent progress in development of engineered multifunctional nanostructured coatings using self-assembly techniques will be presented. An interfacial self-assembly process is developed to synthesize multifunctional nanoparticles and to assemble them into ordered, three-dimensional, nanoparticle films. Through control of structural parameters of nanoparticle assemblies, we are able to fabricate uniform reflective optical coatings. Quarter wave stacking of self-assembled nanoparticle films are developed for near infrared reflectors, which overcomes the harsh conditions from conventional processing (CVD, sputtering, etc) with improved functionality. Reflectivity studies show high and reproducible reflectivity over controlled wavelength windows (1-12µm). Theory modeling shows very good consistency with experimental results. Following this method, development of nanostructured anti-reflective optical coatings is accomplished through a phase separation driven self-assembly process. 3D nanostructured films are synthesized and fabricated into uniform multiple layered films that exhibit a wide anti-reflective optical band.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy&’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

In this work, acetylacetone was induced as a fuel to realize low temperature fabrication of oxide transistors by solution process. InGaZnO transistor with spin-coated Al₂O₃ as dielectric was fabricated at a temperature as low as 200°C under ambient conditions. Al₂O₃ gate dielectric layer was successfully synthesized by spin coating process on highly doped silicon substrates, followed with an annealing treatment at 200°C. The thickness of as-prepared dielectric layer was 170nm after spin-coating twice. It showed a low leakage current density of less than 2×10^-5A/cm² under the bias voltage of 10V and an equivalent relative dielectric constant k of 11.5. InGaZnO solution was prepared by a mixture of nitrate precursors and a certain amount of acetylacetone which serves as a fuel. Due to acetylacetone&’s nature of high heat of combustion, self-energy-generation system was formed easily which meant only a moderate temperature was necessary to drive the reaction. Consequently, annealing temperature of InGaZnO can be definitely decreased to 200°C, the same temperature as the dielectric layer treated. With indium and gallium co-doped ZnO as the active layer, the fabricated field-effect transistors (FETs) exhibited high device performance. The mobility reached to 1.7 cm² / (Vs), the threshold voltage decreased to 1V due to the remarkable areal capacitance of Al₂O₃ dielectric, I_on /I_off was measured to be 10³. This performance implied that less small power consumption was anticipated. Our study demonstrated solution combustion process was a powerful technique to realize low-cost and low-temperature fabrication of oxide-based FETs without compromise of device performance. The low annealing temperature was also favorable in flexible devices manufacturing.
This work is supported by Research Grants Council of Hong Kong (Grant Nos. CUHK2/CRF/08, CUHK418209, and the National Science Foundation of China (Grant Nos. 60990314, 60928009 and 61106093).
*Jianbin Xu is corresponding author

Nowadays there is a high interest to shift semiconductor deposition processes from expensive vacuum technologies to cheaper solution processed approaches which have sufficiently high performance for low-cost applications. Metal oxide semiconductors were found to be suitable materials for wet-chemical deposition of high performance thin film transistors. Soluble precursor materials are available which are convertible into semiconductors forming volatile by-products even at low process temperatures. Since semiconducting devices are very sensitive to impurities and defects optimization of film growth is crucial. Chemical and physical mechanisms have to be investigated in order to develop controllable and reproducible deposition techniques which guarantee high-quality thin films.
In this work the growth and nucleation of zinc oxide thin films deposited by pulsed spray pyrolysis from aqueous zinc-precursor solution is investigated. The deposition behavior of the solution was correlated to the pool boiling curve of the solvent to gain further knowledge of the deposition mechanism leading to homogeneous zinc oxide layers. The Leidenfrost effect was found to be a crucial mechanism during film growth since the Leidenfrost temperature has to be exceeded to form high quality layers. Furthermore, it is concluded that 3D nucleation of ZnO nano-crystals takes place out of the gaseous phase by a CVD-like process on SiO2 as well as on ITO substrates. Surface roughness and crystal orientation of the zinc oxide layer are found be substrate dependent. Moreover an increasing grain size with film thickness is observed. These findings were utilized to optimize the deposition of the active layer in a zinc oxide thin film transistor (TFT) and investigate its semiconducting properties as degree of quality of the functional layer. Under optimized conditions the mobility was found to exceed 12cm2V-1s-1, the on-set was at 1V and the on-off current ratio was found to be higher than 108. Thus the morphology and the electrical parameters of the ZnO films deposited by pulsed spray pyrolysis from non-toxic aqueous zinc precursor solution above the Leidenfrost point show excellent properties as functional material for electronic applications.

Silicon nanoparticles (SiNPs) are one of the best candidates for anode materials to achieve high Li-ion battery performance owing to their outstanding theoretical capacity of 4200 mAh/g and large surface areas.[1] However, SiNPs still suffer from some critical drawbacks such as over 420% volume change (pulverization) and poor contact into a current collector.[2] To overcome such issues on Si pulverization and unstable solid-electrolyte interface formation,, carbon-coated Si nanoparticles or core-shell Si-C nanostructures have been proposed.[3,4]
Herein, hybrid carbon-SiNPs nanofibers were synthesized from electrospinning of aqueous PVA/SiNPs solution followed by carbonizing polyvinyl alcohol (PVA) to improve the capacity and cyclability of Li-ion battery using SiNPs. The carbon contents in the C-SiNPs nanofibers were controlled by changing the ratio of PVA to Si NPs as well as by the carbonization temperature. After the C-SiNPs nanofibers were characterized by SEM, XRD, TEM and TGA to investigate their microstructural properties, the nanofibers were used as the anode electrode in coin cell-typed Li-ion batteries. Cyclic voltammetry and electrochemical impedance spectroscopy were carried out to examine electrochemical properties of the C-SiNPs nanofibers such as lithiation and delithiation processes or charge transport resistance. Our hybrid nanofibers exhibited both an outstanding charge/discharge capacity and much stable cyclability, compared with SiNPs only. Such performance improvements in Li-ion batteries using our C-SiNPs nanofibers are attributed by one-dimensional nanostructures of the nanofibers and durable carbon backbones obtained from carbonizing PVA.
References
[1] S. D. Beattle, D. Larcher, M. Morcrette, B. Simon, J. M. Tarascon, J. Electrochem. Soc. 2008, 155 (2) A158
[2] X. Zhou, Y. -X. Yin, L. -J. Wan, Y. -G. Guo, Adv. Energy Mater. 2012, 2, 1086
[3] H. Kim, M. Seo, M. -H. Park, J. Cho, Angew. Chem. Int. Ed. 2010, 49, 2146
[4] H. Wu, G. Zheng, N. Liu, T. J. Carney, Y. Yang, Y. Cui, Nano Lett. 2012, 12, 904
Acknowledgment
This work was supported by AXIUM NANOFIBERS, LLC

Titanium (IV) oxide, TiO₂, has been the object of intense scrutiny for energy applications ever since Fujishima and Honda reported using it for the photolysis of water in 1972. TiO₂ is inexpensive, non-toxic, and has excellent corrosion when exposed to electrolytes. A major drawback preventing widespread use TiO₂ for photolysis is its relatively large band gap of ~3eV. Only light with wavelengths shorter than 400 nm, which is in the ultraviolet portion of the spectrum, fulfills this requirement. Less than 14 percent of the solar irradiation reaching the earth&’s surface has energy exceeding this. Adding dopants such as transition metals has long been used to reduce the gap and increase photocatalytic activity. The degree to which the band gap is reduced using transition metals depends in part on the overlap of the d-orbitals of the transition metals with the oxygen p-orbitals. An important milestone was the discovery that using anions such as nitrogen as a dopant also reduces the gap. Recent studies suggest that using a combination of transition metals and nitrogen as dopants introduces intermediate states within the band gap, effectively narrowing it. Here we report the synthesis of mesoporous TiO₂ spheres, co-doped with transition metals and nitrogen, which exhibit a nearly flat absorbance response across the visible spectrum, extending into the near infrared.
Research supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division. JEM was supported by ORISE through U.S. Department of Energy-Visiting Faculty Program (VFP).

We investigated the combination approach of self-pattern and low-temperature processing on the solution-processed oxide semiconductors and thin-film transistors (TFTs). An InGaZnO (IGZO) and In₂O₃ solutions that were chemically modified with benzoylacetone (BzAc) or acetylacetone (AcAc), whose chelate rings were decomposed owing to a π-π* transition with cross-linking as result of irradiation with ultraviolet (UV) light, was used for the self-patterning. The nitric acid (HNO₃) and AcAc modified In₂O₃ solution exhibited both a strong UV absorption and self-energy generation. This method not only resulted in the formation of the high-quality In₂O₃ film at a low temperature of 250^oC owing to the combustion of the chemically modified metal oxide solution but also allowed for photoreaction-induced self-pattern process. The resulting self-patterned In₂O₃-based TFT on the flexible polyimide substrate showed high performance with a field-effect mobility of 2.24 cm² V^-1 s^-1, sub-threshold voltage swing of 0.45 V/dec., and Ion/Ioff ratio of 10⁸.

Introducing additional functionalities onto inorganic nanoparticles (NPs) uniformly dispersed within polymers would provide the nanocomposite with multifunctional properties useful for important optical applications. Using a simple “grafting-to” approach, we first grafted bimodal polydimethylsiloxane (PDMS) brushes onto high-refractive-index (RI) ZrO2 NPs. The grafted ZrO2 NPs showed a homogenous dispersion within silicone matrices enabling the preparation of transparent high-RI ZrO2/silicone nanocomposites. The good dispersion can be attributed to the combined effects of enthalpic core-core screening from the densely grafted short brush and the favorable entropic stabilization from the sparsely grafted long brush that favors penetration of the matrix chains. Sequentially, organic phosphor molecules were attached onto the PDMS-grafted ZrO2 NPs via a facile ligand exchange process. The phosphor-modified ZrO2 NPs maintained good dispersion within silicones, and color-conversion capabilities were incorporated into the nanocomposites without sacrificing their high optical transparency feature. Functionalized NPs with ~50 wt% ZrO2 core exhibit a transparency of ~ 90% in the 600-800 nm wavelength range and a 0.08 increase in RI compared to neat silicone. It was further demonstrated that the photoluminescence properties of the functionalized NPs can be tuned by optimizing the bimodal PDMS brush design. The prepared nanocomposites could be used as high-efficiency, non-scattering light-conversion materials for advanced LED encapsulation.

We explore the adhesive and cohesive properties of a self-assembled and compositionally graded organic/inorganic hybrid layer produced via a low-cost sol-gel processing technique. This material serves as an interphase layer between an inorganic substrate and a polymeric material, and can dramatically improve the reliability of multilayer devices in microelectronic, photovoltaic and display technologies. The two primary precursors used to synthesize the hybrid include epoxy-functionalized silanes and metal-alkoxides which crosslink to form a molecular network consisting of a dense inorganic mixed-metal oxide as well as an organic network of poly(ethylene oxide) oligomers.
By unraveling the underlying hydrolysis and condensation reactions of the two precursors, we can manipulate the hybrid molecular structure formation to obtain a controlled graded composition. Through the optimization of the sol-gel parameters such as solution aging time, curing temperature and time, we achieved ~80 nm thick hybrid layers with a molecular structure optimized for adhesion to adjacent oxide and organic layers. We demonstrate that a short solution aging time results in a graded film structure, while a longer solution aging time created a homogeneous film, with no interconnected organic/inorganic molecular network. When such graded layers are properly optimized, the interface adhesion exceeds the cohesive fracture energy of the adjacent epoxy layer, exhibiting outstanding moisture-resistant adhesive properties even in high humidity environments.

Hybrid mixed oxide materials, which contain organic and inorganic molecular components, can be engineered over a wide range of length scales to exhibit unique combinations of mechanical, thermal, and optical properties. Hybrid materials are therefore ideally suited to a bottom-up materials design where molecular structure and resulting properties can be engineered and tailored to achieve desired property sets for applications in diverse fields including microelectronics, aerospace and energy storage.
We have previously demonstrated the efficacy of ZrOx/epoxysilane hybrid films synthesized using a low-cost, low-temperature sol-gel synthesis route as adhesion promoting interphase layers in Si/epoxy bondlines. Due to their compositionally graded structure, these films are capable of forming durable bonds between metal oxides and structural adhesive organic resins, demonstrating more than ten-fold increases in adhesion and the inhibition of moisture-assisted debond phenomena in extreme environments.
In this work, we explore beyond applications in microelectronics to investigate the influence of the various underlying substrates on the development and resultant fracture properties of these self-assembled, compositionally graded hybrid structures. A strong correlation between isoelectric point (IEP) and bondline adhesion has been established for acidic sol conditions, showing increasing adhesion with decreasing IEP. We will discuss the role of IEP on sol-gel reaction kinetics, composition gradient and hybrid film network connectivity to explain the observed trends in adhesion. By understanding the fundamental processing-nanostructure-property relationships that govern the performance and reliability of these hybrid structures, guidelines can be developed to achieve optimized mechanical and fracture properties for adhesion promotion in various material systems.

Hydrotalcite-like compounds are layered double hydroxides (LDHs) with the general formula of [M(II)]_1minus;xM(III)_x(OH)₂]^x+[A^nminus;_x/n]^xminus; zH₂O, where A^nminus; is charge compensating anion, M(II) and M(III) are di- and trivalent cations, respectively. A family of HLDHs has been investigated as one of the most promising layered crystals in the various application fields, such as adsorption, separation, catalysis, and electronics. In general, powdery products are obtained through typical synthesis routes of LDHs, which requires molding process for desired shapes for specific applications. However, conventional molding process with LDH powders and binders exhibits several drawbacks; activity of LDHs are spoiled by binders, and only surface can be used because of the diffusion limitation. Therefore, monolithic LDHs with hierarchical macro/meso channels are strongly required. In this contribution, preparation and some applications of cm-scale monolithic LDHs with improved diffusion efficiency can be achieved. The synthesis of LDH-based monoliths has been performed via a facile sol-gel reaction. Obtained xerogels have monolithic shapes and no need of further powder molding using binders. In order to overcome the diffusion limitation, macro and mesochannels with well-defined sizes have been introduced into the materials. The macro and mesochannels form via a spontaneous manner by controlling phase separation and aggregation of primary particles in the course of sol-gel reaction. The channel formation highly contributes to improve the diffusion efficiency in the monolithic materials. As a result, we have, for the first time, succeeded to obtain monolithic LDHs exceeding cm scale with considerable ion exchange efficiency.

Technological solutions to our challenges in clean energy, national security and human welfare require next generation materials with an extensive range of material performance and property combinations. As material properties result from the synergy between chemical and structural features, realization of such materials requires advanced manufacturing techniques with independent control over structure across multiple length scales. In addition, an approach to structural control that allows for the sustainable incorporation of a wide variety of building blocks, including nanomaterials and bioactive materials, will provide enhanced material performance for a wide variety of products across multiple sectors. Layer by layer (LBL) assembly is a material fabrication technique based on the sequential adsorption of nanoscale monolayers driven by attracting chemical forces. It is known to generate composites with superior properties due to its nanoscale structural control and applicability to many different building blocks. For realization of such properties into advanced technologies, this work describes a toolbox of three sustainable and versatile approaches to introduce 3D, multiscale architecture into the traditionally planar structure of LBL materials.
Such approaches include a template-based LBL technique used to create high strength, optically transparent micro-containers for high throughput analysis. Similarly, hierarchically tunable materials for controlled response to external stimulus are generated and shown to provide strict control over material thermal expansion properties. Alternatively, a direct-write approach based on inkjet technology is used to significantly accelerate the LBL assembly process while allowing for simple patterning of LBL nanocomposites for introduction into advanced devices such as flexible electronics or onto alternative substrates such as clothe, paper and, plastics. Finally, a rare pseudonegative thermal expansion property of a polyelectrolyte LBL film is presented and applied to create prescribed 2D to 3D transformations of nanocomposites through the introduction of spatially controlled heterogeneities. Inkjet deposition of such materials allows for low cost, high throughput processing for a fundamental understanding of the transcription of 2D patterns into complex 3D structures with applications in robotics, biomedicine, energy collection, and optics. The fairly independent structural control of each of these techniques provides the opportunity for extensive structure-property relationships to be obtained, and unique combinations of material properties applied to next generation material design.

The development of high performance flexible electronics requires dielectrics possessing high dielectric constant and enhanced mechanical stability. In this study, we report novel polymer nanocomposites dielectric based on n-octadecylphosphonic acid (ODPA) functionalized aluminum titanate (AT) nanoparticles as dopants in poly (4-vinylphenol) (PVP). The robust surface layer covering the nanoparticles induces improved dielectric properties of the resulted composite films due to better interfacial adhesion. The nanocomposite layer with tunable dielectric permittivity and low leakage current is highly compatible on flexible substrates and has been deposited via simple solution process. Air-stable p-type and n-type transistors fabricated on the composite dielectric layer exhibited superior electrical performance than those on the pristine polymer dielectric layer. The complementary inverters made from these transistors possessed large signal gain and sharp switching. We systematically studied the electrical performance of the capacitors, transistors and inverters under different applied strain on flexible substrates. From the flexibility test, all these devices were found to be mechanically stable and environmentally robust, demonstrating the composite dielectric layer is an excellent candidate for the future development on conformable sensors, portable displays and other flexible electronics application.

Low-density hybrid molecular materials with organic and inorganic components engineered at molecular length scales can be made to exhibit diverse mechanical, thermal and optical properties. The molecular hybrids are created through a unique backfilling approach in which selected polymers are homogeneously infiltrated into the pores of a nanoporous glass scaffold, leading to uniform mixing at unprecedentedly small length-scales (~1nm). The second-phase material may be chosen from an extensive library of functionalized organic and inorganic polymers, allowing for the development of composites with novel electrical and optical properties. In this work, we focus on the effects of polystyrene and poly(methyl methacrylate) second phases on the mechanical and fracture properties of a nanoporous oxycarbosilane matrix. We observe a significant increase in fracture toughness for the composite material as compared to the unfilled matrix. In addition, we find that the degree of toughening exhibits a maximum with respect to the molecular weight of the second-phase polystyrene, an effect that is not observed in bulk polymer. We discuss mechanisms based on molecular confinement and fracture mechanics that are responsible for this unique toughening behavior. We show that the effects of nanometer-scale confinement on second-phase polymers are important for optimizing the cohesive strength of nanocomposites, and suggest a potential route to mechanically robust nanocomposites films with dramatic improvements in fracture toughness.

Carbon-inorganic nanocomposites are important materials with potential applications in emerging technologies such as photovoltaics or energy storage. Here, we report how the nanoscopic morphology of such hybrid materials can be tailored by utilizing of carbon-rich amphiphiles as molecular carbon precursors that allow their subsequent carbonization under controlled conditions. To this end, we employed poly(ethylene oxide)-substituted oligo(phenylene)s as structure directing agents and carbon source. The oligo(phenylene) amphiphiles spontaneously self-assembled into lamellar phases with a varying degree of internal order within a wide range of temperatures. Moreover, they could straightforwardly be converted into carbon upon thermal treatment. Following a “soft templating” approach via infiltration with different inorganic molecular precursors, we demonstrated that the amphiphiles directed the formation of lamellar structures in the composite materials, which are retained at the carbonization temperatures. Our approach, hence, allowed us to prepare novel multifunctional carbon-inorganic hybrid materials from different inorganic precursors with tailored nanoscopic carbon layers.

Supercritical hydrothermal synthesis has been performed to produce metal oxide nanoparticles from metal ion aqueous solution in both batch-type and flow-type reactors. In the flow-type reactors, a stream of metal ion aqueous solution is mixed with a stream of supercritical water at a junction to promote hydrothermal reaction. We have shown that the size and distribution of hydrothermally synthesized metal oxide nanoparticles are largely affected by how the reactants and supercritical water streams are mixed. However, the visualization of the mixing behavior has been difficult, because the synthesis was performed above the critical point of water (374°C and 22.1 MPa) in a stainless-steel tubular flow reactors.
In order to visualize the mixing behavior of supercritical water and room-temperature water, we proposed neutron radiography method. Neutrons are effectively scattered by hydrogen atoms and have high permeability in heavier elements including Fe, Cr, and Ni. Therefore, neutron radiography should enable the detection of differences in water density, which is caused by the change in the temperature at a constant pressure in a stainless-steel reactor. Based on this idea, we performed neutron radiography on a tubular flow reactor for supercritical hydrothermal synthesis and visualized the mixing behavior of supercritical water (~400°C) and room-temperature water (~25°C) under high pressure (25 MPa) at a T-junction. The results showed that the difference in density between supercritical water and room-temperature water, as well as how the density changed during mixing, was clearly visualized. The partitioned flow in the side tube was also visualized while feeding room-temperature water. The results indicated the importance of buoyancy forces, as discussed by others in previous reports.
Reference: S. Takami et al., J. Supercrit. Fluids, 63, 46 (2012).

The properties of nanoparticles differ from those of their counterpart bulk form due to confinement effect caused by their size, structure or unusual shape. To optimize these properties for specific applications it is useful to carry out synthetic reactions with small volume and low cost. Microfluidic reactors are valuable tools for this application, due to their ability to rapidly dose reagents and to create homogenous mixtures on the scale of microns. We describe a microfluidic device with an integrated microwave heater specifically designed to dielectrically heat non-aqueous droplets using time-varying electrical fields with the frequency range between 700 and 900 MHz. The device is capable of precisely heating the non-aqueous solvents used for nanoparticles synthesis, for instance benzyl alcohol, n-butanol and ethylene glycol. The precise control of frequency, power, temperature and duration of the applied field opens up new vistas for multiplex experiments not attainable by conventional microwave heating. We use a non-contact temperature measurement system based on fluorescence to directly determine the temperature inside a single droplet. The desired temperature can be achieved in 15 ms. In addition we use an infrared camera to monitor the thermal characteristics of the device allowing us to ensure that heating is exclusively due to the dielectric heating and not to other effects like non-dielectric losses due to electrodes or contacts imperfection. This is crucial for illustrating the potential of dielectric heating of benzyl alcohol droplets for the synthesis of metal oxides. We demonstrate the utility of this technology for high-throughput optimization of metal oxide nanoparticle synthesis, achieving crystallization of tungsten oxide nanoparticles and remarkable microstructure, with a reaction time of 64 ms at 50°C a 5,000x improvement over conventional heating methods.

We have developed a nanocrystal synthesis strategy that employs atomic interdiffusion at a core/shell interface to produce alloy-terminated nanocrystals. These core/alloy nanoparticles have alloy compositions that are determined by shell thickness, processing temperature, initial core diameter, and surface capping ligand. As a proof of principle, we have fabricated an assortment of noble metal systems. The alloying is preceded by the layer-by-layer deposition of the shell material (i.e., Ag, Pd, Pt), followed by a microwave mediated hydrothermal annealing step, which induces core/shell inter diffusion and alloying. We have recently extended this approach to use the alloy phase behavior at the interface to drive asymmetric growth of heterostructures with janus-like interfaces. In addition, this approach has been extended to non noble metal alloys, whose rich oxidation behavior can be tuned by alloy shell composition and thickness. This results in tailorable Kirkendell diffusion and vacany coalescence, forming highly stable core-void-shell materials.

Colloidal silica particles are being intensively studied due to their potential applications in catalysis, intelligent materials, optoelectronic devices, photonic bandgap crystals, masks for lithographic nanopatterning, etc. Moreover, in nanoscale electronic, photonic and plasmonic devices, feature dimensions shrink towards a critical limit, and new experimental approaches have to be explored in lithographic patterning. For this work, spherical submicrometer-sized silica particles were prepared by the sol-gel technique and deposited as a self-assembled monolayer onto high-purity silica glass plates by means of a spin coater system. This monolayer is then used as a mask to create regular arrays of nanoscale features in the sample, either by MeV Ag ion implantation or by Ag evaporative patterning of metallic deposits. On the other hand, previously to the ion implantation or metal evaporation, the masks can be modified by Si ion irradiation to tailor the size and arrangement of these embedded features or metal deposits as a function of the ion fluence. Indeed, amorphous glassy materials like silicon dioxide can undergo extreme deformations under exposure to high-energy beams, which induce damage and structural changes in solids due to energy losses of MeV heavy ions via ionization events and atomic collisions. Some of the samples were irradiated at room temperature with 4 MeV Si ions under an angle of 90° with respect to the sample surface. After the irradiation the silica particles turned into oblate particles, as a result of the increase of the particle dimension perpendicular to the ion beam and the decrease in the parallel direction. By this way, the mask openings of the silica particle monolayer were modified down to the nanoscale and a subsequent Ag ion implantation or Ag thermal evaporation allowed the formation of ordered arrays of Ag nano-objects, after removal of the silica particles. The size, size distribution and shape of both the silica particles and the array of metallic deposits were determined by scanning electron microscopy as a function of the preparation and ion irradiation parameters. Finally, the long range order of the nanoparticle assembly and its plasmonics properties were characterized by means of a Fast Fourier Transform study and optical absorption measurements, respectively.

Nanocrystals have been extensively investigated in last two decades from fundamental science to practical applications. There is no ending quest for a facile synthesis of high quality colloidal nanocrystals with controlled shape, size, composition and crystal structure. The copper-zinc-tin-sulfide (CZTS) quaternary nanocrystal is recently discovered as an important material for solar energy applications owing to the advantages of optimal band gap, earth-abundant and nontoxic components, high absorption coefficient etc. through low cost wet-chemistry process. However, such complicated multi-components quaternary nanocrystals have challenge in adopting convenient one-pot heating up process. Namely, either using common cationic precursors (metal acetate, metal chloride, etc.) or organometallic precursors (metal-oleate, metal-diethyldithiocarbamate, etc.), the unbalanced reactivity or different thermal decomposition temperatures among the precursors should be taken into account for avoiding the formation of second phases such as copper sulfide, tin sulfide or zinc sulfide. Herein, we present a facile one-pot heating up synthesis of wurtzite based CZTS (w-CZTS) nanocrystals for the first time which is belonged to orthorhombic crystal system. This is a newly discovered crystal structure for CZTS rather than the typically reported zinc-blende (tetragonal) one that recently has attracted great attention for sustainable energy application. We adopted a simple one-pot heating up process to obtain high quality w-CZTS nanocrystals. The nano-crystal forming mechanism is thoroughly investigated and resolved by X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). It starts from nucleation of plasmonic djurleite Cu1.94S, subsequent growth of CZTS-Cu1.94S heterostructures and inter-diffusion of cations and then finally leads to single phase and single crystal w-CZTS nanocrystals. The mechanism of nanocrystal formation can be applied universally regardless the type of zinc and tin precursors for high quality w-CZTS nanocrystals. It overcomes the typical challenge of balancing cation reactivity in preparing multi-components nanocrystals through one-pot heating up reaction. The in-depth interpretations of reaction mechanism of this process significantly advance the current knowledge of multi-components nanocrystal formation. The developed method is scalable for high throughput and low cost w-CZTS sus-pensions which awaits practical photovoltaic applications.

In2S3 is an important member of III-VI group of semiconductors that possesses a cation-ordered structure [1], has a bulk band gap of 2.0-2.3 eV and a large Bohr exciton radius (33.8 nm) [2]. Structurally, In2S3 possesses intrinsic vacancies and defects that make this material attractive for optoelectronic and electrical switching applications [3]. Quantum-confined low dimensional nanostructures offer additional flexibility of tunability in the materials properties [4-5]. In this work, we have synthesized nearly monodisperse thin (~7 nm thick) nanoplatelets of In2S3 in high yield by 1-thioglycerol assisted low temperature polyol process. Structural properties investigated using X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy suggested high crystallinity and morphological homogeneity of the prepared nanostructures. The synthesized nanoplatelets were crystallized in bulk tetragonal structure and show preferential crystallographic growth within a range of diameters from ~75-85 nm. Quantum confinement was observed by spectroscopic analyses with a determined band gap of 3.4 eV. Strong UV luminescence corroborated valence-conduction band transition in these confined nanoplatelets. Room temperature photoconductance measurements performed on the prototype device fabricated from the In2S3 nanoplatelets for the first time revealed noticeable enhancement of conductivity under illumination as compared to the dark condition. The present study is intended to open up a new approach in the synthesis of monodisperse In2S3 nanocrystals for efficient optoelectronic applications, such as in solar cells and as phosphors.
[1] R. Diehl, and R. Nitsche, J. Cryst. Growth, 28, 306 (1975).
[2] J. Herrero, and J.J. Ortega, Sol. Energy. Mater., 17, 257 (1988).
[3] J. Bonnet, F. Touhari, M. Nouaoura, and L. Lassabatere, J. Appl. Phys., 89, 2766 (2001).
[4] A. Datta, G. Sinha, S. K. Panda, and A. Patra, Crystal Growth & Design, 9, 427 (2009).
[5] A. Datta, S.K. Panda, D. Ganguli, P. Mishra, and S. Chaudhuri, Crystal Growth & Design, 7, 163 (2007).

A controlled hierarchical CdS-ZnO heteroarchitecture has been synthesized via a facile single-step hydrothermal process. FESEM and TEM analyses revealed the formation of the hierarchical 3D structure of the as-prepared CdS-ZnO. This complex heteroarchitecture is composed of the single crystalline CdS nanoparticles (size ~ 8 nm) are highly decorated on the surface of self assembled ZnO nanorods. The optical studies reveal selective modification of ZnO with CdS. Furthermore, plausible growth mechanism has been proposed on the basis of experimental results. Interestingly, the global nanoparticles of CdS were only selectively grown on the tips of the ZnO nanorods which were not found on surface Zn substrate. Significantly, such hybrid CdS-ZnO heteroarchitecture is observed to exhibit enhanced field emission properties such as low turn-on field, high current density and better current stability in comparison to other ZnO based nanostructures. Herein, a simple soft-chemical approach is used for the first time to design CdS-ZnO heteroarchitectures in single-step process, which is otherwise accomplished with high temperature and multistep process, as reported elsewhere. Also, present work not only gives insight into understanding the hierarchical growth behaviour of the CdS-ZnO heteroarchitectures in a solution phase synthetic system, but also provides an efficient route to enhance the field emission performance of ZnO nanostructures, which could be extended to other potential applications, such as chemical sensors, optoelectronic devices and photocatalyst.

Metal selenide nanomaterials represent a class of compounds with properties of interest to a variety of applications. These materials are being developed for use in photovoltaics1, light-emitting diodes2, biomedical sensors3, and more. Nevertheless, despite the variety of uses for these compounds there are very few methods of fabrication. Selenide nanoparticles that have been formed rely on selenium sources that are either a toxic selenium containing chemical, or elemental selenium dissolved through the use of phosphorous or boron containing chemicals. For high-throughput manufacturing of metal selenide nanomaterials it would be best to avoid the use of both toxic selenium sources and expensive organophosphorus solvents. Dissolution of selenium through phosphorus and boron containing chemicals should also be avoided in order to prevent these chemicals from reacting or incorporating into the nanoparticles and hindering the variety of applications for these materials.
To address these issues, we have developed a robust method to fabricate a variety of selenide nanocrystals by utilizing elemental selenium dissolved in a new media. The process successfully avoids any organophosphorus solvents, boron containing chemicals, or toxic selenium sources. The route to be presented has allowed the formation of a variety of different selenide nanomaterials in organic media at our lab at Purdue University. The route enables size control, composition tunability, and the capability for subsequent surface modification of nanoparticles whose characterization will also be presented. The final nanocrystals can be used in a variety of applications, without hesitation from the chemicals used in formation.
1. Semonin, O. E. et al. Peak external photocurrent quantum efficiency exceeding 100% via MEG in a quantum dot solar cell. Science (New York, N.Y.) 334, 1530-3 (2011).
2. Talapin, D. V., Lee, J.-S., Kovalenko, M. V. & Shevchenko, E. V. Prospects of colloidal nanocrystals for electronic and optoelectronic applications. Chemical reviews 110, 389-458 (2010).
3. Hessel, C. M. et al. Copper selenide nanocrystals for photothermal therapy. Nano letters 11, 2560-6 (2011).

Ceramic materials prepared from soluble precursors via pyrolysis, often called polymer-derived ceramics (PDCs), have been attracting increasing attention, since they can be possibly obtained in complex shapes. In addition, precursors for ceramic composites can be prepared via combinations of different precursors. The control of chemistry and structures of precursors and that of pyrolysis conditions are particularly important. We have developed precursors for nitride ceramics to offer solution synthesis routes to nitride ceramics. This talk describes our research activities aiming at both design of precursors and application to high-pressure synthesis. In terms of the design of precursors, we have been utilizing cage-type oligomers possessing Al-N backbones for the preparation of aluminum nitride (AlN) and its composites. Despites relatively low molecular masses, these precursors can be utilized as AlN precursors mainly because Al-N bonds cleaved at relatively low temperatures to cause polymerization of cages. By combining with silazanes, soluble precursors for Al-Si-N-C ceramics can be prepared. In terms of high-pressure synthesis, we have utilized amorphous materials prepared by pyrolysis of precursors as starting materials, and have converted them into high-pressure nitride phases.

Indium Phosphide is an attractive material for use in photoelectrochemical (PEC) water splitting. The 1.35 eV direct band gap of Indium Phosphide allows it to efficiently utilize a large part of the solar spectrum while its conduction band edge position makes it suitable for use as a photocathode. However, the low earth abundance of Indium makes the use of single crystal InP wafers for PEC expensive and impractical. Nano-materials have a much higher surface to volume ratio than bulk materials and, as a result, large densities of reactive sites that allows for the use of much less material when constructing photoelectrodes. Zinc doped, p-type Indium Phosphide nanowires were synthesized via a novel solution phase self-seeded solution-liquid-solid (SLS) method. First, the wires were used for solar driven hydrogen production in an aqueous powder suspension. Next, p-InP nanowires were used to fabricate photocathodes for photoelectrochemical water splitting, using only ~1/3000 the amount of material of a bulk InP wafer. Zinc doping amount and co-catalyst deposition was optimized to achieve the best photoelectrochemical performance. The surfactant free synthesis offers scalability not available with vapor phase growth methods such as vapor liquid solid (VLS) growth or metallo-organic chemical vapor deposition (MOCVD) and the nano-structured morphology of the p-InP photocathodes allows for the use of minimum quantities of photocatalyst material for PEC

Metallates based on group 5 elements (V-Nb-Ta) generate a broad interest due to their numerous applications as f.i. ferroelectrics, ion conductors or heterogeneous (photo)catalysts. Vanadates and niobates constitute also widely spread host lattices for lanthanide- doped luminescent materials. There is consequently a clear demand for developing new chemical routes able to produce these materials with high chemical and crystallographic purity under various forms : bulk phases with adequate morphologies and textural properties, highly dispersed supported phases for catalytic applications, or thin films.
High denticity (polyamino)carboxylates constitute an ideal and versatile starting chemical platform to access a very wide range of chemical formulations under relatively soft conditions. To compensate more particularly for the poor availability of water-soluble Nb and Ta compounds, oxo- and peroxo-complexes of Nb(V) and Ta(V) with (polyamino)carboxylate ligands have been synthesized and used as molecular precursors for a wide series of Nb-M mixed oxides, with M = V, Mo, Ta, Y or Bi.
In the Y-Nb system, the cubic Y3NbO7 phase was obtained after calcination of the freeze-dried precursors at the moderate temperature of 650°C, and the distorted tetragonal YNbO4 phase was synthesized at 800°C and stabilized at room temperature without quenching. Similarly, the catalytically-relevant Nb2Mo3O14 phase was obtained as bulk or silica-supported phase (60-70 m2/g) from a mixture of Nb and Mo oxooxalate complexes. Phases like NbVO5 and the high temperature triclinic β-BiNbO4, that are difficult to prepare, could be stabilized after doping with small amounts of Ta. Solid solutions Nb-Ta-V-O and Nb-Ta-Bi-O were also obtained. In some favourable cases, heterobimetallic Nb-Ta complexes were obtained and used as single source precursors for NbTaO5 solid solutions displaying a disordered meso/macroporous character.These non conventional methods were also shown to stabilize scarcely reported distorted tetragonal LnNbO4 polymorphs and pyrochlore-type Ln3NbO7 compounds, for which a linear correlation between the lattice parameter a and the Ln3+ ionic radius was observed. A monoclinic distortion was evidenced which increases when the Ln3+ ionic radius increases. Scanning electron microscopy indicates the formation of mesoporous materials with pore sizes of about 20 nm.
We also describe an alternative method based on hybrid precursors consisting in homogeneous blends between inorganic species and hydroxypropylmethyl cellulose (HPMC) acting as a sacrificial matrix but also as a viscosity-modulating agent. These routes were both used for the preparation of a broad series of simple and mixed vanadates, AVO4 and Y1-xAxVO4 and the corresponding Ln-doped vanadates, as powders of thin films.

The Hall effect has been of a great interest because it is immune to ambient environment (e.g. dust, dirt, mud, and water) and does not require direct contact with or dismantling the system to measure the desired property (e.g. the speed of the object in motion, the number of charge carriers, the flow rate of the liquid, and pressure). Therefore, it has been applied to many devices such as sensors, logic gates and switches. However, since the Hall voltage (VH) is relatively small (usually less than on the order of milli-volts (mV)) it has not yet been practical for an application to highly sensitive sensors and often requires an amplifier. In this respect, researchers have investigated and shown metal-insulator composites - usually prepared by co-sputtering method, such as Ni, Fe, Co, Cu and others as a metal and SiO2, Al2O3 as an insulator, has a higher sensitivity to the magnetic field and therefore shows a “giant” Hall effect compared to that of a pure metal. Herein, we study the giant Hall effect in a more systematic way by controlling the size and spacing of nickel nanorods (NiNRs) encased in a polymer matrix; a class of nanostructured materials which shows the Hall voltage on the order of volts (V) even under the magnetic field as low as a few thousands Gauss (G). We believe such a high Hall effect results from the low charge carrier density (n) (therefore, a high Hall coefficient (RH)) of the polymer matrix, poly-dimethylsiloxane (PDMS), surrounding an array of metal nanorods, NRs. The overall picture that emerges from our experiments is that the NiNR/polymer arrays are a versatile class of nanostructured materials allowing for the manipulation of current and shows a giant Hall effect. One of the more outstanding properties which make our NiNR/polymer arrays unique is how traditional magnetic materials exhibiting giant Hall effect can be constructed on flexible and transparent substrates. This will allow devices (such as sensors, switches, or logic gates) that can operate in a much wider range of environments than traditional nanoelectronic or nanooptical devices.

The interest in laser-induced chemical deposition of metal from solution (LCLD) stems from the prospects of its use in microelectronics due to the ability to create extended localized metal structures 5-100 mm wide on dielectric surfaces. Scanning a dielectric surface with a focused laser beam in an electrolyte solution leads to locally initiated chemical reduction of copper.
Composition of plating solution is organic complexing agent, usually sodium potassium tartrate or EDTA, reducing agent (HCHO or polyalcohols), copper salt and alkali. The spot of locally initiated reaction can be moved along substrate using computer-controlled motorized translation stage.
LCLD is known to be a perspective method for manufacturing of metal interconnections for printed and flexible electronic devices. It is maskless technology, promising cost-effective environmentally friendly manufacturing process for prototyping and small-scale production of high precision PCBs.
An unsolved technical problem that prevents the practical application of LCLD is intense gas evolution occurring around the laser beam focus point on the dielectric surface. The formation of gas bubbles in the laser beam path leads to its defocusing. As a result, metal deposition from solution is uncontrollably discontinued, or it occurs in a refracted or reflected irradiation zone. In such a case, diffuse edges, areas with unsatisfactory topology, ruptures, tails of the metal deposited in a non-localized way, and other flaws are formed on the metal deposited structure.
In order to solve the problem of gas evolution in direct copper deposition process our group has developed a number of metallization solutions, containing nonionic surfactants, complexing agents which do not decompose through laser irradiation of solution. New oxidizing additions, accelerating deposition rate, were proposed. All reactions of copper deposition were found to be thermally initiated. The scanning speed of laser beam was 0.01-01mm/s, DPSS laser (532nm) working in continuous mode was used for irradiation of samples, power of laser beam was 200-1000mW, diameter of focal spot was 10-50 mkm). These series of experiments were performed with oxide glass as a model of transparent dielectric material.
Polyimide films were chosen for further experiments according to their perspective dielectric properties. However, direct laser metallization is not effective because of polyimide deformation under laser irradiation with high powers. In order to deposit metal on polyimide substrate involving two-stage process, photosensitive Ag-containing solutions were used. First stage was pre-deposition of Ag film using laser-induced process followed by autocatalytic copper deposition on the Ag seeds.
Current research work was supported by Federal Targeted Programme “Scientific and Scientific Pedagogical Personnel of the Innovative Russia in 2009-2013”, contracts 8684, 14.132.21.1473.

Lithium nickel manganese oxides (LNMO, {Lix}[LiyNinMnm]O2, (x le;1, y le; 1/3, (y + n + m) le; 1)) are considered as attractive cathode materials for 5 V lithium ion batteries. LNMO nanoparticles with large surface to volume ratio have the potential to be as the active material in improving the electrochemical performance of the cathodes. However, it has been a challenge to synthesize LNMO nanocrystals with fine sizes and/or high stoichiometry using hydrothermal colloidal chemistry. Laser irradiation in liquids (LIL), featured by laser irradiating the precursor solution, can produce nanoparticles through photochemical and/or photothermal reaction induced growth. LIL process generates non-equilibrium growth conditions, which provide the opportunity to synthesize materials that are hard to achieve using conventional synthetic methods. Here, we demonstrate that LNMO nanocrystals can be synthesized when a 532 nm nanosecond pulsed laser was employed to irradiate a mixed aqueous solution of lithium nitrate, nickel nitrate and manganese nitrate. LNMO nanocrystals with the diameter ranging from 10 to 50 nm can be achieved by controlling the LIL conditions and processes. The as-synthesized LNMO nanoparticles are crystalline without apparent phase segregation. Carbon/LNMO nanostructures and many other complex oxide nanoparticles can also be synthesized by varying the experimental conditions. The as-synthesized LNMO nanoparticles and C/LNMO nanostructures show promising properties for the applications as cathode materials for lithium ion batteries.
We performed TEM experiments at Materials Science Division and National Center for Electron Microscopy (NCEM) of the Lawrence Berkeley National Laboratory, which is supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-05CH11231. HZ thanks the funding support from U.S. DOE Office of Science Early Career Research Program.

Hollow-structured nanomaterials with a movable core, which are referred to as “rattle-structured nanomaterials,” have recently attracted tremendous attention because they allow the optical, electric, and magnetic properties of the core material to be added to the nanomaterial. Of the various rattle-type mesoporous nanomaterial systems, the rattle-structured nanomaterial composed of gold nanorods in mesoporous silica nanocapsule is expected to attract a great deal of interest. On one hand, the mesoporous silica shell possesses the advantages of low cytotoxicity, uniform size, high stability, easy functionalization, high pore volumes, and low cost. On the other hand, gold nanorods offer fascinating tuned surface plasmon resonance (SPR) properties, which make them well suited for diverse biomedical applications such as diagnosis, photothermal therapy, bio-imaging, and biological sensing.

We present a novel solution-based consecutive process for the fabrication of rattle-structured nanomaterial composed of gold nanorods in a mesoporous silica nanocapsule (AuNR@mSiO2). Uniform-sized Au NRs were encapsulated inside a silver nanoshell, followed by SiO2 coating through the sol-gel technique. After selectively etching away the silver inner layer, a rattle-structured nanomaterial was obtained. The inner hollow space and the thickness of the mesoporous silica layer were easily controlled by adjusting the amount of each chemical agent. The scanning electron microscopy and transmission electron microscopy images clearly demonstrated that the AuNR@mSiO2 rattle-shaped nanostructures were highly uniform in particle-size distribution. In addition, the as-synthesized nanostructured materials showed well dispersibility properties, just like the starting gold nanorods. The growth and removal of Ag on Au NRs drastically affects the UV-vis extinction spectra. However, the rattle structured AuNR@mSiO2 which had eliminated silver inner layer had almost identical absorption band of SPR with pure Au nanorods.
The drug-loading properties of the nanomaterial and the regrowth control of the core nanoparticles were also studied. Drug loading was studied using the material as a drug carrier and doxorubicin hydrochloride (DOX) as a model. In addition, Au NRs inside the confined mesoporous silica nanocapsules were further regrown in a controlled manner by simply adding HAuCl4 and ascorbic acid. This nanomaterial is anticipated to be used as nanoreactors as well as in a variety of biological applications.

Patterned metal films play fundamental roles in numerous applications, such as lithography, nano-electronics, sensors, and others. The predominant technologies for creating two-dimensional film architectures involve “top-down” techniques in which light, electrons, or ions are employed for creating surface structures. “Bottom-up” techniques, however, which rely on molecular self-assembly processes, have emerged as viable alternatives due to their flexibility, structural diversity, and much lower costs. We describe a novel approach in which a single-step crystallization / reduction of a water-soluble gold complex leads to the formation of unique nanostructured, crystalline metallic patterns on amine-displaying surfaces. The new technology, based upon aurophilic interactions of the metal ions coupled to internal reduction by the complex ligands, does not require pre-formation of metal nanoparticles or colloids as building blocks for the film patterns, nor the addition of reducing agents. As such, this generic approach could be applied for surface coatings, opto-electronic applications, sensing, and catalysis. We demonstrate application of the new metal patterning scheme on different substrates, length-scales, and practical uses.

In the fabrication of devices for practical purposes using nanoparticles, one of the key challenges is the patterned deposition of the nanoparticles on pre-defined areas by simple, fast and low-cost methods. Various “top-down” and “bottom-up” techniques with sophisticated equipment and chemicals have been used to achieve the goal of nanostructure patterning. Here we present a novel, simple, fast and low-cost method to enable patterned deposition of nanoparticles. In previous work we attempted to locally functionalize the surface with amino- and mercaptosilane molecules by means of microcontact printing. Although there was an apparent density difference, the selectively was limited.
The present approach we will present here does not require sophisticated equipment nor does it involve harsh chemical procedures. We show that pure water can be used to selectively “defunctionalize” mercaptopropyltrimethoxysilane (MPTMS) treated surfaces; the water molecules form a thin “capping” layer on exposed thiol molecules within the mercaptan self-assembled layer. This reversible capping of water molecules locally “deactivates” the thiol groups, therewith inhibiting the binding of metallic gold nanoparticles to these specific areas during self-assembled formation of nanogold monolayers from solution. We demonstrate that this amazing role of water molecules enables patterning of gold particles on flat as well as on microstructured surfaces with a remarkably high degree of selectivity. Since MPTMS is used as a binding agent not only for gold but also for other materials, the method described here can in principle be extended to enable patterning of other nanoscale materials.
In addition to the localized gold nanoparticle deposition, we describe the selective metallization by electroless gold deposition on the patterned seed arrays. The latter process gives rise to enlargement of the isolated seeds past the percolation threshold, to ultimately give rise to conducting metal structures. The obtained patterned gold films exhibit macroscopic conductivity values approximately a factor of three lower than that of bulk gold. The surface morphology of the films has been characterized by scanning electron microscopy and spectroscopic ellipsometry. We discuss the different regimes as observed in morphological, electrical and optical characterization in relation to each other.

The resonance interaction of surface plasmons in metal nanoparticles with incident and scattered light gives rise to the surface enhanced Raman scattering of molecules or conjugated polymers that are adsorbed at the NP surface or located in its close proximity. Aggregated Metal Nanoparticles are attractive for SERS sensors due to the strong enhancement of local optical fields arises at the interparticle junctions upon interaction with the incident light.
We report a simple and facile method for preparation of aggregated gold nanoparticles (AuNPs) induced by water soluble polythiophene. The influence of π-conjugated polyelectrolyte, poly {3-[6-(1-methylimidazolium-3-yl)hexyl] thiophene-2,5-diyl bromide}), (P3HT-IMB) on the morphology and optical properties of AuNPs assemblies were studied. It was found that P3HT-IMB concentration has strong impact on AuNPs assemblies and consequently, on the optical processes in the system. Borate-stabilized AuNPs (diameter ~ 6 nm) in water were prepared by chemical reduction method using NaBH4 as a reducing agent. Au sol/ P3HT-IMB composite sol were prepared by adding P3HT-IMB solution into the gold hydrosol at various concentrations. Upon addition of the P3HT-IMB to the Au sol, the optical extinction spectra showed second surface plasmon extinction (SPE) band towards longer wavelength that confirms the formation of NPs aggregates. The electrostatic nature of the NPs stabilization in the colloid and aggregation induced by P3HT-IMB was confirmed by the zeta potential (xi;) measurements.
At low P3HT-IMB concentration, the surface charge of the AuNPs is only partially compensated and small but stable aggregates are formed. On the other hand, at high concentration the NPs are spatially isolated by the polymer and no aggregates were observed.
Upon optical excitation with appropriate wavelengths (532 and 647 nm) within this second SPE band a well resolved and strongly enhanced Raman signal of the polymer was obtained originating from tightly bound aggregates. In SERS, the strong enhancement, assigned to a formation of "hot spots" of a strong optical field localized in aggregates, was dependent on the size and degree of aggregation of the NPs developed at various concentrations of P3HT-IMB. It was conclued that electrostatic interactions of negatively charged Au NPs with polycationic polymer chains play key role in the formation of systems showing surface enhanced optical effects.

Due to a combination of high magnetic susceptibility and low coercivity, superparamagnetic nanoparticles are promising materials in applications requiring high magnetization with low loss, for example as transformer cores. Amorphous Fe nanoparticles with size < 20 nm have been shown to exhibit superparamagnetic properties. Here, we use microwave heating to synthesize oleylamine-stabilized Fe nanoparticles with controlled size and measure their magnetic properties. Microwave heating of a solution of Fe(CO)5 and oleylamine in 1-octadecene at relative low temperatures (180-220 °C) enables the synthesis of Fe nanoparticles in as short as 5 min. Varying the reaction time between 5 min and 50 min at a reaction temperature of 180 °C tunes the resulting Fe nanoparticle size between 5 nm and 15 nm as determined by TEM and DLS. Increasing the reaction temperature to 220 °C does not change nanoparticle size, but increases reaction yield. From the dependence of size on reaction temperature and time, we will discuss the nanoparticle growth mechanism. Both XRD and TEM results show no diffraction peaks associated with BCC Fe, indicating that the Fe nanoparticles are amorphous. Amorphous magnetic nanoparticles are especially suitable for low-loss applications since they do not have hysteresis associated with magnetocrystalline anisotropy. Magnetic measurements using an AC magnetometer show that as the nanoparticle size increases, the maximum susceptibility increases, and the frequency where susceptibility falls off decreases. This confirms that particle size control is critical and must be optimized for the frequency of target applications. Due to the combination of inexpensive precursors, low reaction temperature, short reaction time, good magnetic properties, and systematic size control, we conclude that microwave-assisted synthesis of Fe nanoparticles represents a promising method toward low cost synthesis of superparamagnetic nanoparticles for high volume applications.

Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol-gel process. The porous materials made by silica sol-gel chemistry are typically insulators, however, which has restricted their application. Here we present a simple, yet highly versatile silica sol-gel process built around a multifunctional sol-gel precursor that is derived from the following: amino acids, hydroxy acids or peptides; a silicon alkoxide; and a metal acetate. This approach allows a wide range of biological functionalities and metals—including noble metals—to be combined into a library of sol-gel materials with a high degree of control over composition and structure. We demonstrate that the sol-gel process based on these precursors is compatible with block-copolymer self-assembly, colloidal crystal templating and the Stöber process. As a result of the exceptionally high metal content, these materials can be thermally processed to make porous nanocomposites with metallic percolation networks that have an electrical conductivity of over 1,000 S/cm. This improves the electrical conductivity of porous silica sol-gel nanocomposites by three orders of magnitude over existing approaches, opening applications to high-current-density devices.

Magnetic nanoparticles (MNPs) have many important technological applications, including cancer treatment, contrast agents, and high density data storage. For use in applications, these nanoparticles must have a uniform size and shape distribution to ensure that they have a consistent and known magnetic behavior. The synthesis of monodisperse MNPs usually requires the use of harsh chemicals and high temperatures, neither of which can be considered green. In nature, biomineralization proteins are able to direct the formation of about 60 different biomaterials to form specific crystal phases and structural morphologies, all under ambient synthetic conditions [1]. Some biomineralization proteins and bioinspired peptide mimics are also able to template the formation of consistent, uniform nanoparticles from aqueous precursors under mild reaction conditions in vitro [2]. Therefore, biomineralization proteins and peptides offer a far greener approach to nanoparticle synthesis than the techniques currently used in industry.
For data storage applications it is necessary that the MNPs are tethered onto a surface, often as part of a patterned array or thin-film. This usually involves the use of energy intensive and expensive patterning facilities, such as clean-room based photolithographic techniques and sputtering under vacuum, which is costly and unenvironmentally friendly. Soft-lithographic techniques, such as micro-contact printing, can be used to pattern biomineralizing proteins and peptides onto surfaces, which offers a cheaper and greener method of functionalizing surfaces for specific materials deposition. Recently, we have shown that a recombinant form a naturally occurring biomineralizing protein (Mms6) is able to template the formation of high quality magnetite nanoparticles when selectively patterned onto surface to form biomineralized arrays of MNPs [3]. However, as magnetite is magnetically soft, it is unlikely that the magnetite MNPs will be able to retain information for data storage applications. As such, methods to create much higher coercivity biotemplated MNPs on patterned surfaces will be discussed. This will allow us to create arrays of biotemplated magnetic materials using mild chemicals and low temperatures that could be used for electronic data storage.
[1] RA Metzler et al. (2008) Langmuir, 24, 2680-2687.
[2] JM Galloway & SS Staniland (2012) J. Mater. Chem., 22, 12423-12434.
[3] JM Galloway et al. (2012), Small, 8, 204-208.

Core-shell nanoparticles provide a unique access to bimetallic systems with unique interfaces and spatial distribution. This is of major interest for studying structure-property relationships in catalysis and magnetism on a fundamental level, but also to develop more selective catalysts and more robust nanomagnets.
We designed a new solution-route synthesis for Cu-Co and Ni-Co core-shell nanoparticles. The nanoparticles were obtained by coating Cu or Ni monodispersed cores with a shell of cobalt. Although a shell of oxide is formed when exposed to air, they could be reduced back to a metallic state at 330°C under 1 Torr of H2, as probed by in-situ ambient pressure XPS at the Advanced Light Source, Berkeley, CA.
Morphological changes were observed when exposing the nanoparticles to reactive gases such as oxygen, hydrogen, or carbon monoxide. In particular, upon the synergistic exposure to a syngas mixture (CO + H2), a profound change was identified by HRTEM and STEM-EELS for the Cu-Co system: new copper-rich nanoparticles were formed by reactive removal of cobalt on ca 5% of the nanoparticles. In the case of Ni-Co nanoparticles, the synthesis was found to favor a true core-shell structure over a Janus one when the coating step was conducted with a lower heating rate. This suggests a balance between surface energy and magnetic interactions during the formation of these metastable morphologies. In situ experiments evaluate the robustness of these Ni-Co structures upon heating and reactive gas exposure.

The chemistry of metallic cations in aqueous solution is a relevant method to the elaboration of nanometric scale metallic oxides. This method is extremely versatile and allows one to control many characteristics of materials like iron, aluminium and titanium oxides, in particular, the crystalline structure for polymorphic compounds, the particles size and shape. The main parameters being more relevant are the acidity of solution, the presence of specific anions, and the temperature. The synthesis process has been optimised in order to study each parameter separately. Two synthetic routes are currently being developed within the LCMCP team involving the nucleation-growth of the particles either by alkalization or by thermolysis of molecular precursors. The crystalline phases obtained by alkalinization are often metastable phases and we have shown that the size and morphology of particles were governed by surface energy. For thermolysis, the formation of solid is slower due to the slower generation of precursors of the solid and leads to the crystallization of a thermodynamically stable phase. In this case, the solubility and precursor concentration are the key parameters that will control the characteristics of the particles.
We have shown in the case of magnetite and anatase particles that the particles size decreases as the pH of precipitation departs more and more from the point of zero charge, PZC. For others materials such as brucite (Mg(OH)2) and boehmite (gamma-AlOOH), the variation of morphology occurs. These examples bring decisive experimental arguments allowing connecting the size and shape of nanoparticles to the acidity of synthesis medium. We have also investigated some experiments using weak complexing molecules and we have shown that the use of small quantity of polyols allowed also to tune surface energy for each crystallite faces involving some change in aspect ratio for a given particle shape.

Transparent conductive oxides (TCO) such as indium tin oxide (ITO) are a essential material to fabricate smart or touching displays, sensors and photocells for its high transparency, wide optical band gap (3.3 eV) and low electrical resistivity (10-4 #8486;-cm-2). At present, conducting ITO paste and ink prepared by chemical routes have gained great importance because low temperature processing of the same has allowed the preparation of films on low thermal stability substrates. Co-precipitation followed by the heat treatment of the products provides a versatile route to obtain large quantities of ITO powders. However, the post-heat treatment that is necessary to achieve highly crystalline and chemical homogeneity promoted the particle growth and subsequently lost their ability to be dispersed in solvents. In this study, large scale synthesis of ITO nanoparticles (>10 g per batch) with particle size less than 5 nm was achieved by heating metal hydroxides precursors in an acidified solution of 2-octanol at 180 oC. The results showed that long alkyl chain of alcohols has prevented the particle growth and provided an excellent media for dehydrating indium tin hydroxide powders prepared by the co-precipitation of their metal salts. In addition to the benefits in reducing the particle size, the presence of hydrochloric or acetic acid assisted the dehydration through of two steps: dissolution of precursor and formation of intermediate complexes. The crystal structure of the final product was similar to In2O3 with a tin content of ~ 10%. On the other hand, ITO pellets made using these nanoparticles by annealing in air at 200 oC showed an electrical resistivity of 1.0 #8486;-cm-2 which is comparable to the values obtained by other chemical routes. It should be noted that the main advantages of the proposed technique are the ability to prepare smaller sizes and large quantity of ITO nanoparticle dispersion.

In recent years, research in functional oxides have lead a huge transformation by exploiting the capabilities of combining two materials with distinct functionalities, the so-called nanocomposites. Most of this research has been undertaken by physical deposition methods, however, latest developments in chemical solution deposition (CSD) have demonstrated the unique capabilities that this cost effective method can offer. In particular, CSD superconducting nanocomposites have reached the highest isotropic superconducting properties as any superconducting material. The aim of the present contribution is to demonstrate the opportunities of combining nanoparticles synthesis with growth of YBa2CuO3 superconducting nanocomposites using the Metal Organic Decomposition procedure.
The need to control size, morphology, composition, distribution and strain of the embedded nanoparticles has raised the interest in trying new approaches like dispersing already preformed nanoparticles in a colloidal YBCO precursor solution and subsequently grow the nanocomposite layer. However, the alcoholic ionic environment of the YBCO precursor solutions makes this task rather difficult if high concentrated colloidal solutions are to be stabilized. Thermal and microwave radiation assistance procedures based on the polyol route have been studied in our laboratories to obtain nanoparticles [MFe2O4 (M=Mn, Fe, Co, Ni, Zn) and CeO2] dispersible in a huge range of polar dispersants in sizes ranging from 3 to 15 nm. Both methodologies produce high concentration of nanoparticles in solution (up to 256 mM of in Fe3O4), with low dispersion in sizes and high cristallinity. We have then successfully prepared stable colloidal solutions with well controlled nanoparticles characteristics into high ionic force trifluoracetate based Y, Ba, Cu solutions in methanol, and studied the adaptability to deposit the layers by Drop on Demand inkjet printing as a very appealing high throughput method. Special attention has been devoted to the water content of the solutions using appropriate additives and preparation conditions, since this is critical to obtain high performance superconducting films. Superconducting nanocomposite layers, in the range of 150-300 nm in thickness, have been grown using the different colloidal solutions and the obtained properties have been analyzed and compared for each particular case.