Traditional superhydrophobic coatings are soft in nature, with a Teflon-like surface chemistry, which results in reduced adhesion and durability. By combining vapor phase deposition together with wet chemical processes to produce differentially-etched, nanostructured glass materials, we have overcome many of these common problems. Here we describe the formation of atomically bonded, optical-quality, nano-textured porous thin glass film coatings on glass plates, utilizing metastable spinodal phase separation in a low-alkali borosilicate glass system. As formed, these coatings are structurally superhydrophilic (i.e., display anti-fogging functionality) and demonstrate robust mechanical properties. After appropriate chemical surface modification, they exhibit exceptional superhydrophobic performance, hence self-cleaning properties, with water droplet contact angles reaching to 172^o. Moreover, these nanostructured surfaces can be engineered to provide graded index anti-reflectivity with broadband and omnidirectional transparency. In particular, when applied to solar cover panels, we show that these coatings couple more light into the photovoltaic cells and substantially reduce the light energy lost to reflection, yielding an increased power output of the photovoltaic modules ~3-5% while preventing dust/pollution accumulation.

Interest in surface engineering has been increasing in recent years. There are several methods which can be used to modify the properties of surfaces. Some of these techniques include sol-gel method, plasma, chemical vapor deposition, atomic layer deposition, and also traditional wet chemistry methods. Some novel materials for surface modification are Polyhedral oligomeric silsesquioxanes (POSS) silanols. These materials possess some of the surface modification characteristics of other silicon-based materials. The POSS silanols were deposited by immersion methods on glass surfaces. Several concentrations and curing temperatures were evaluated. Contact angle measurements of water and other liquids were used to calculate the surface energy. Dynamic capture mode was used to calculate the hysteresis of advancing and receding contact angles. The hysteresis provided information regarding the wettability properties of the obtained surfaces. The results showed that POSS silanols were capable of impart hydrophobicity to surfaces at low concentration in solutions. The unique properties of POSS silanols for surface modification are also discussed and surface modification properties of these novel materials were also explored in the textile area.

Copper-chitosan (Cu-CS) nanoantimicrobials are a novel class of bioactive nanosized agents, providing enhanced/synergistic efficiency in the prevention of biocontamination in several application fields, ranging from food packaging to the prevention of nosocomial infections [1]. Designing bioactive materials, with controlled metal ion release, exerting significant bioactivity and associated low toxicity for humans, is nowadays one of the most important challenges for the scientific community [2]. In this work, we propose a new material combining the well-known antimicrobial properties of CuNPs [1] with those of bioactive CS, a cheap natural polymer widely exploited for its biodegradability and nontoxicity [3]. Here we exploited ultrafast femtosecond laser pulses to disgregate, via laser ablation, a Cu solid target immersed into aqueous CS solutions [4]. Homogeneously dispersed Cu-CS colloids were obtained by tuning the Cu/CS molar ratios, according to the initial chitosan concentration, as well as other experimental parameters. Cu-CS colloids were characterized by several techniques. UV-Vis and Fourier Transform Infra-Red (FTIR) spectra were used to study copper complexation with the organic matrix. X-ray Photoelectron Spectroscopy (XPS) allowed us to assess copper surface chemical speciation, by the accurate curve fitting of both photoelectronic Cu2p3/2 and Auger CuLMM high-resolution regions. Transmission Electron Microscopy (TEM) was used to morphologically characterize the novel nanocomposites. We also obtained well-dispersed nanocomposite thin films by spin coating these hybrid nanocolloids on several substrates. The effectiveness of the proposed nanocoatings as novel antimicrobial agents was demonstrated in bioactivity experiments performed on several target microorganisms.
References:
[1] N. Cioffi, M. Rai Eds., “Nano-antimicrobials. Progress and Prospects”, Springer-Verlag Publisher, 1st Edition, ISBN 978-3-642-24427-8 (2012).
[2] N. Cioffi et al., Chem. Mater., 17, 2005, 5255.
[3] M. Kong, et al., Int. J. of Food Microbiol., 144, 2010, 51.
[4] A. Ancona et al., Mat. Lett., 136, 2014, 397.

Incorporating metal-organic frameworks (MOFs) in polymeric structures is an important step in applying these porous crystals to industrial scale gas separation applications. Nanoscale MOF coatings on polymer membranes can promote selective transport and act as molecular sieves, but facile and scalable syntheses for these coatings are still in development. Here, a method to synthesize sub-micron MOF coatings from metal oxide nanocrystal precursors on porous polymer thin films is demonstrated. The coatings&’ morphologies and grain sizes were controlled through changes to the reaction conditions. Grazing incidence x-ray diffraction was used to confirm the presence of crystalline MOF in the thin films. These bilayer structures are promising as next-generation gas separation membranes.

Graded porous inorganic materials directed by macromolecular self-assembly are expected to offer unique structural platforms relative to conventional porous inorganic materials. Their preparation to date remains a challenge, however, based on the sparsity of viable synthetic self-assembly pathways to control structural asymmetry. Here we demonstrate the fabrication of graded porous carbon, metal, and metal oxide film structures from self-assembled block copolymer templates by using various backfilling techniques in combination with thermal treatments for template removal and chemical transformations. The asymmetric inorganic structures display mesopores in the film top layers and a gradual pore size increase along the film normal in the macroporous sponge-like support structure. Substructure walls between macropores are themselves mesoporous, constituting a structural hierarchy in addition to the pore gradation. Final graded structures can be tailored by tuning casting conditions of self-assembled templates as well as the backfilling processes. We expect that these graded porous inorganic materials may find use in applications including separation, catalysis, biomedical implants, and energy conversion and storage.

The fast civilization accompanying huge dependence on the fossil fuels consumption has never aroused such world-wide concern of energy depletion together with devastating consequences for the global economy and quality of human life. Carbon dioxide emission, as a result of burning fossil fuels for energy, has also raised an ever-increasing attention because of its greenhouse effect that could incur global warming and human nutrition deficiency. Although researchers nowadays are aiming at developing new technologies to physically capture CO₂ and chemically utilize CO₂ as a raw material in the production of commercially important chemicals, it is still a temporary solution since how to dispose large amount of captured CO₂ in an effective fashion remains the big challenge. In the long term, developing new and sustainable energy resources, such as solar energy and biomass, will play the major role. Metal-organic frameworks (MOFs), as a new class of crystalline inorganic-organic hybrid materials composed of inorganic metal nodes and organic linkers, have recently emerged as an ideal platform for engineering novel functional porous materials for clean energy applications because of possessing a diversity of coordinated models of metal ions and functional organic linkers, high porosity and rich pore functionalities. In this work, we aim to engineer one of the most promising MOF, UiO-66(Zr), through modular hydrothermal synthesis as advanced adsorbents for CO₂ capture and highly efficient heterogeneous catalysts for biomass conversion. We have chosen two model ligand, 2, 5-dicarboxylic-1, 4-benzenedicarboxylic acid (DCBDC) and sodium 2-sulfoterephthalate (SSBDC), to synthesize isostructural UiO-66 MOFs with different chemical functionalities (UiO-66-(COOH)₂ and UiO-66-SO₃H) via both traditional hydrothermal and modular hydrothermal reactions. Powder X-ray diffraction (PXRD), field-emission scanning electron microscope (FE-SEM) and gas sorption isotherms were applied to characterize the phase purity, morphology and gas adsorption properties, respectively. Compared to traditional hydrothermal synthesis, our modular synthesis has successfully lead to microporous UiO-66-(COOH)₂ with much higher BET surface area (~500 m²/g) and more than doubled CO₂ uptake (8% w/w) as well as mesoporous UiO-66-SO₃H with higher BET surface area (~420 m²/g) and highly efficient catalytic activity toward fructose conversion (>99%) to 5-hydroxymethylfurfural (5-HMF, ~80% yield). Our highly tuned modular hydrothermal synthesis method has provided a paradigm to synthesize novel functional porous materials for clean energy applications.

Mesoporous structures can steadily provide many functional sites, which are critical for solving emergent problems. Especially, metallic mesoporous materials can exhibit rather high carrier density and thus remarkable optical response and catalytic performance, which are not attainable by using other compositions of mesoporous materials (e.g., silica- and carbon-based compositions), and even other nanostructed metals. The rational design of mesoporous metals with tunable pore size toward practical applications is a most attractive and challenging objective. Although many well-developed approaches have been investigated in the fabrication of mesoporous silica, carbon, and other transition metal oxides, few of them are competent in obtaining mesoporous noble metals.Fortunately, we recently have succeeded in obtaining mesoporous metals, i.e., Pt, Pd, and Pt-based alloys, by using micelle assembly of non-ionic surfactants (or block copolymers). This work provides an exclusive facile and efficient strategy in obtaining mesoporous metals. Further, we extended the effective way to prepare mesoporous Au films, which have been proved to be fairly difficult by using the soft-templating method, by utilizing spherical micelles of polystyrene-block-poly(oxyethylene) (PS-b-PEO) diblock copolymers as soft-templates for the first time. The pore sizes of the obtained Au films could be well controlled in a wide range, and the various pore sizes surely brought tunable surface-enhanced Raman scattering (SERS) for molecule detection due to multiple ‘hot spots&’ built up in the mesopores as well as in the vicinity of narrow walls between the pores.

In the modern strategy of designing and synthesizing novel materials, versatility is one of the key concepts pursued with high priority. The design concept includes the development of clean, facile and sustainable methods as well as simultaneous controls over the structural and chemical properties for various applications. Zirconium phosphate (ZrP) has been focused as a multifunctional versatile material for different applications. Since its first report on synthesis in the laboratory scale and the ion exchange behavior by Clearfield and co-workers, ZrP has been attracting a great deal of interest due to its extended applications in various possible utilizations such as catalyst and catalyst support for different chemical reactions, proton conductor for fuel cells, and ion exchanger for water purification.In order to fulfill the requirements for applications in different fields, ZrP has been prepared into various forms such as micro/nanoparticles and thin films.Traditional synthetic routes, however, find their limitations in designing a mechanically stable monolithic shape combining hierarchical porosity in ZrP materials. Well-controlled hierarchically porous structures are advantageous for its applications as adsorbent, catalyst and catalyst support due to better accessibility of reactants to active sites and ease for recycle and reuse.
We herein present a low-temperature, one-step liquid phase synthesis of hierarchically porous ZrP monoliths with tunable compositions (from Zr(HPO₄)₂ (Zr:P = 1:2) to NASICON (Na super ionic conductor)-type ZrP (Zr:P = 1:1.5)) as well as macropore size (from 0.5 to 5 µm). The hierarchically porous structure has been obtained as a result of polymerization-induced phase separation (spinodal decomposition) during the sol-gel transition. Co-continuous macroporous structure is stable against heat treatment, which yields pure ZrP₂O₇ phase at 1000 °C, while treatment at even higher temperature (1400 °C) leads to further transformation.The as-synthesized ZrP monolith with high reactive surface area (600 m² g^minus;1) and relatively high mechanical strength (Young&’s modulus 320 MPa) has been applied to ion adsorption and catalysis. A simple syringe device inserted tightly with the ZrP monolith as a continuous flow setup has been demonstrated to remove various toxic metal ions in aqueous solution, which shows promising results for water purification. Meanwhile, ZrP monolith as an acidic heterogeneous catalyst also provides a platform for the catalytic dehydration of xylose, and high selectivity toward furfural production has been confirmed in water as the “green” solvent.
The synthetic method we have developed here would be further applied to the synthesis of other metal phosphates with hierarchically porous structure. The hierarchically porous ZrP and derivative monoliths may find high potentials in more sustainable applications such as enrichment and recycling of precious metals and fuel cells.

In addressing the issue of prosthetic infection, the present work demonstrates the synergistic effect of the application of static magnetic field (SMF) and utilizing magnetic properties of substrate on affecting the bactericidal property in vitro. For this purpose, HA-xFe₃O₄ (x: 10, 20 and 40 wt.%) powder compositions were sintered using uniquely designed spark plasma sintering conditions (three stage sintering with final holding temperature of 1050 °C for 5 mins). During bacteria culture experiments, 100 mT SMF is applied to growth medium (with immersed on HA-xFe₃O₄ substrate) for 30, 120 and 240 min. A combination of MTT assay, membrane rupture assays, live/dead assay and fluorescence microscopic analysis showed that the bactericidal effect of SMF increases with the exposure duration as well as increasing content of Fe₃O₄. Importantly, the synergistic bactericidal effect is found to be independent of bacterial cell type, as similar qualitative trend is measured with both gram negative (E.coli) and gram positive (S.aureus) strains. The reduction in E.coli viability is 83% higher on HA-40 wt%Fe₃O₄ composite after 4 hrs exposure to SMF as compared to non-exposed control. Importantly, all the HA-Fe₃O₄ composites demonstrated bactericidal property by rupturing the membrane of E. coli bacteria, while supporting cell growth of metabolically active human fetal osteoblast cells over 8 days culture. A systematic decrease in bacterial viability with Fe₃O₄ addition is consistent with a commensurate increase in reactive oxygen species (ROS). Overall, the present study illustrates significant role being played by magnetic substrate compositions towards bactericidal property than by magnetic field exposure alone.

Block copolymers (BC) represent a multifunctional tool for hierarchical structure fabrication down to the nanoscale. Due to the incompatibility of the homopolymer blocks, thin films of BCs can phase separate to form diverse periodic structures like spheres, cylinders or lamellae. It has been shown that by carefully matching the surface functionalization of nanoparticles to the polymer subunits in BCs, well-ordered hybrid materials can be achieved in which nanoparticles are selectively enriched in one of the BC phases. ^[1]
We provide metal oxide nanoparticles with different shell functionalities based on molecules with phosphonic acid anchor groups. ^[2] With this approach we are able to seamlessly fine-tune the surface properties of the nanoparticles from ultra-hydrophobic to extremely hydrophilic. This enables us to selectively target one or both of the BC phases. In our experiments, ambipolar polystyrene-b-polyethylene glycol diblock copolymers (PS-b-PEO) with high Flory-Huggins interaction parameter serve as organic matrix. We examine the phase-separation behavior of the BC films as a function of the nanoparticle surface energy, their size and the amount of particles in the polymer layer. The applied methods include electron microscopy and scanning probe microscopy as well as electrical characterization.
The nanoparticle/ PS-b-PEO hybrids are applied as dielectric layers in organic transistors, where they simultaneously serve as non-volatile charge storing layer to yield organic thin-film memory transistors (OTFMTs). Phase boundaries created by the BC lead to spatial separation of the embedded nanoparticles, which enhances charge storing performance. The hybrid dielectrics exhibit increased relative permittivity without compromised insulating properties.
[1] H. Zhang, Y. Liu, D. Yao, B. Yang, Chem. Soc. Rev.2012, 41, 6066.
[2] L. Portilla, M. Halik, ACS Appl. Mater. Interfaces2014, 6, 5977.

Due to the increase of world energy consumption, energy-saving technology has been attracting a lot of attention of scientists. Silica aerogels, which can be obtained by drying wet gels using supercritical drying methods, are candidate materials for high performance thermal-insulating window, because of their low thermal conductivity and high light transmittance. However, the practical use of aerogels is highly restricted by their low mechanical properties. In order to improve their mechanical properties, various kinds of organic-inorganic hybridization have been studied so far. Our group has reported the synthesis of aerogels composed of methylsilsesquioxane (MSQ, CH₃SiO_1.5), which show higher elastic behavior on compression, as well as high light transparency and low thermal conductivity comparable to those of silica aerogels. With silsesquioxane (RSiO_1.5) materials, there is a possibility of obtaining transparent aerogels possessing a new property.
The aim of this work is to investigate the properties of silsesquioxane aerogels with substituent groups other than methyl. Since reactive substituent groups such as vinyl can be chemically modified even after the gelation, tuning of the properties of aerogels with these groups are available. Thus, we mainly focused on vinylsilsesquioxane (VSQ, CH₂=CHSiO_1.5) aerogels in this report. Although any other silsesquioxane aerogels, except for MSQ, have not been reported so far, we successfully obtained VSQ aerogels by utilizing acid-base 2-step reaction in surfactant-based solution. Obtained aerogels were evaluated in terms of their structural, optical and mechanical properties and availability of post treatment (e.g. radical reaction, thiol-ene reaction, etc.).
In the VSQ system, dilute nitric acid was added into vinyltrimethoxysilane (VTMS) and the mixed solution was stirred for hydrolysis. After a few minutes, a liquid surfactant was added into the solution, and then a strong base solution was added for polycondensation. The reaction solution was subsequently transferred into an incubator and gelled at given temperature. Obtained wet gels were aged for a few days and washed with alcohols, followed by supercritical drying.
With optimized starting composition, the VSQ aerogels were obtained in a transparent monolithic form. The VSQ aerogels showed flexible behavior on uniaxial compression; however, resilience after the removal of applied load was smaller than that of MSQ aerogels. Post treatment on wet VSQ gels was effective to improve their mechanical properties and highly flexible aerogels against compression were obtained without losing their transparency.

The syntheses of porous materials with controlled structure, porosity, surface functional groups and morphology can bring the materials into a myriad of unique properties and possible applications.
We have recently reported a synthesis of a unique type of macroporous hydrogen silsesquioxane (HSiO_1.5, denoted as HSQ) monolith, which possesses reductive hydrosilyl groups on the pore surface. The HSQ materials are synthesized via the sol-gel process accompanied by phase separation, which is a reliable technique to tailor well-defined macropores in the material. The resulting HSQ monoliths were used both as a reductant and host to produce monolith-supported Ag, Au, Pt, Pd, Ru and their alloy nanoparticles by simultaneous reduction of these metal ions and embedment. In a different example, because of the hydrosilyl groups on the pore surfaces, the HSQ monoliths were successfully used as highly efficient, selective, fast, metal-free catalytic grafting of alcohols to develop a new alternate process of surface modification of silica.
It is interesting to impact the HSQ monoliths with periodic mesopores, because those materials would show high specific surface area, high mesopore volume and uniform-sized mesopores, leading to the ideal materials for catalysis, sensors, and biomedical applications. While many types of periodic mesoporous silica materials such as MCM41 and SBA-15 have long been studied, there have been only a few periodic mesoporous HSQ materials reported so far. This is because the three-dimensional (3-D) network of the HSQ materials is not robust enough, as their precursors have only three linkers. We herein we report our attempt in a synthesis of the first example of macroporous HSQ monoliths with ordered periodic mesopores.
The synthesis of the periodic mesoporous HSQ monoliths was conducted by combination of the sol-gel process and supramolecular templating method. We used triethoxysilane (HTES) and tetraethoxysilane (TEOS) for strengthening the siloxane frameworks. In a typical experiment, polymeric surfactant such as F127 and Brij78 was dissolved into HCl solution. After complete dissolution of the surfactant, the mixture was kept stirring for several minutes in an ice bath. Then TEOS was then added under vigorous stirring at 0 °C. After a clear solution was obtained, HTES was added under vigorous stirring at 0 °C until a clear solution was obtained. #12288;After these processes, the solution was kept at room temperature (RT) until gelation, followed by aging at RT for 1 day. The wet gels thus obtained were subjected to solvent extraction using acetone. The washed gels were finally dried at 40 °C for 12 h. The porous and molecular-level structures of the obtained dried gels were investigated by scanning electron microscopye, Fourier transform infrared spectroscopy and N₂ adsorption-desorption.

Titanium phosphate is studied for extended applications, for example ion exchanger, adsorbent, fuel cell cathode, and solid acid catalyst. Hierarchically porous gels of several metal phosphate compositions, such as aluminum phosphate, zirconium phosphate, and calcium phosphate, have been synthesized via the sol-gel process accompanied by phase separation using metal salt and phosphoric acid as the precursors. In this work, hierarchically macro/mesoporous titanium phosphate monoliths have been synthesized from titanium(IV) oxysulfate (TiOSO₄) and phosphoric acid as the precursors with poly(ethylene oxide) (PEO) and polyvinylpyrrolidone (PVP) as phase separation inducers in the solvent system of water, glycerol and dimethyl sulfoxide (DMSO).
In a typical experiment, titanium oxysulfate, PEO (M_w = 100,000), and PVP (M_w = 55,000) are dissolved in the mixed solvent of water, glycerol, and DMSO. Concentrated phosphoric acid is then added to that solution in an ice bath, after two solutions are cooled. The solution is kept 0 °C about 2 minutes until gelation. The obtained gel is then aged for 1 day at room temperature. The wet gels are solvent-exchanged with several solvents, such as 2-prapanol, methanol, and water. Some of the xerogels are calcined at the temperature of 300 °C to 1000 °C. Other wet gels are solvothermally treated at the temperature of 100 °C to 200 °C with ethylene glycol as the solvent, after the gels are solvent-exchanged with ethylene glycol. The macropore structure of the xerogels and heat-treated gels is observed by SEM. The BJH pore size distribution and the BET specific surface area are evaluated by nitrogen adsorption-desorption analysis. The crystal structures are analyzed by XRD.
We obtained co-continuous macroporous xerogels by employing proper amounts of PEO and PVP. The phase separation tendency, which determines the macropore size, can be changed by the amount of PEO. The increase of PEO amount causes an increase in porosity. The macropore size can also be controlled by the amount of PVP; the macropore size becomes larger as the PVP amount increases. The XRD patterns of as-dried xerogels show no sharp peaks, indicating amorphous structure. The XRD patterns of the gels calcined below 600 °C also do not show sharp peaks. The XRD patterns of the gels calcined over 800 °C exhibit sharp peaks attributed to titanium pyrophosphate (TiP₂O₇). The patterns of the solvothermally treated gels cannot be attributed to either titanium phosphate or titanium pyrophosphate. The BET specific surface area becomes the highest, 260 m² g^minus;1, in the as-dried xerogels prepared with a large amount of PVP and solvent-exchanged with 2-propanol. The modal mesopore size is about 30 nm. If calcined over 800 °C, the BET specific surface area is lowered to 4 m² g^minus;1. The BET specific surface area of the solvothermally treated gels becomes lower with increasing temperature, because the pore size grows larger at high temperature.

Synthetic opals are suitable as a scaffold for the fabrication of inverse opal structures with a complete photonic band gap. The band gap is tunable by the geometry of the opal's building blocks, usually ceramic or polymeric spheres with a diameter of several hundred nanometers up to a few micrometers. The final structures can be effectively tuned to act as thermal barrier coatings with a complete photonic band gap in the infrared region. The optical features of these photonic crystals, however, are not only determined by the chosen building blocks, but also by their spatial arrangement or crystallinity.
In this work, the influence of a patterned template on the crystallization of an opal structure fabricated by means of vertical convective self assembly or with a slide coating technique is studied. Lines, cubic arrangements as well as hexagonal structures with periodicities in the range of 300 - 900 nm are chosen as lithographic patterns. These are introduced by one-step or two-step UV laser interference lithography applied to a single photoresist layer on top of a simple glass substrate. In this way, the pattern geometry—depth of the holes, periodicity at multiple angles—can be easily and precisely adjusted to the dimensions of the respective polymeric spheres used for opal deposition. After infiltration of the structure with a ceramic layer by Atomic Layer Deposition (ALD), a sequential self-limiting process used to conformally coat arbitrarily shaped structures with nanometer precision, the spheres are removed and the remaining inverse opal structure can be optically characterized.
Additionally, with these low cost substrates a comprehensive statistical study of the influence of a patterned template on the crystallization of opaline structures is feasible for the first time. We utilized the fast fourier transform of scanning electron micrographs to determine the resulting structure and quantify the degree of order depending on various deposition parameters for each pattern: pattern periodicity, wettability of patterned substrate and substrate angle during deposition. In this presentation, the influence of variations of the pattern periodicity on the crystallization of opal structures is highlighted and the results are compared to optical measurements on the respective direct and inverted opal structures.
We gratefully acknowledge financial support from the German Research Foundation (DFG) via SFB 986 "M^3", projects C1, C3 and C4.

Introduction and control of pore structure in materials has been studied, because adequately controlled pores will enhance the functionality and extend the possible applications. In particular, synthesis of porous tin dioxide (SnO₂) has been attracting considerable attention because of their possible applications such as gas sensors, optical devices and catalysts. Since previous studies have shown that structural features, such as pore size, surface area, and crystalline phase have a great influence on functionality, it is important to prepare desirable porous structure and control these parameters. Although there have been reports on preparation of SnO₂ nanostructures, most of them have reported the synthesis of low-dimensional materials and few reported three-dimensional macroscopic porous materials. In this study, we have succeeded in preparing macroporous SnO₂ monoliths and investigated the relationship between starting compositions and the structural features.
The synthetic procedure is as follows. Tin(IV) chloride pentahydrate as a tin source was dissolved in N,N-dimethylformamide (DMF) in the presence of the water-soluble polymer at 0 °C (in an ice bath), followed by an addition of propylene oxide (PO) to the solution at 0 °C. The solution was left in the ice bath until gelation. The polymer acts as a phase separation inducer to develop macropores, and PO was used as the acid scavenger in the sol-gel process, driving the hydrolysis and polycondensation of the hydrated Sn⁴⁺. After aging for 3 hours, some of the wet gels were processed by solvothermal treatment at temperatures from 80 °C to 200 °C for 24 hours under an autogenous pressure. After the solvent exchange by 2-propanol (IPA) or methanol, the obtained gels were dried by evaporation at fixed temperature. We characterized as-dried samples by using scanning electron microscopy (SEM) to observe the gel morphology in the micrometer range, X-ray diffraction (XRD) to examine the crystal phase and nitrogen adsorption-desorption to characterize mesoporous structure.
We prepared monolithic gels with co-continuous macropores by using SnCl₄middot;5H₂O (2.80 g, 8.0 mmol), PO (2.25 mL, 32.2 mmol) and poly(propylene glycol) (PPG) with number-average molecular weight (M_n) of 4000 as the water-soluble polymer. From the SEM images, the increase of the macropore size in the micrometer range was observed as the PPG content in the starting composition was increased. With increasing PPG, phase separation tendency became higher, resulting in larger macropores. Moreover, after the solvothermal treatment at various temperatures, mesopore has been developed in the dried gels. Mesopore was developed above a certain critical temperature, and the mesopore size become larger with increasing the temperature. After solvothermal treatment, in addition to the introduction of mesopores, crystallization into (tetragonal) rutile-type SnO₂ phase was also observed by XRD.

Porous metal foams are a fascinating class of materials because they combine unique properties of metals with extreme structures of porous materials such as ultralow density, high surface area, and a high strength-to-weight ratio. In this study, Cu foams with low density (down to ~10% density relative to the bulk density) and uniform pore morphology were successfully synthesized from a templating approach. Micrometer-sized polystyrene (PS-COOH) with carboxylic acid groups was used as a pore-generating template. Conformal nanometer-sized Cu layers were coated onto the Pd-seeded PS surface from electroless Cu deposition reaction. A suspension of the copper-coated PS (PS-Cu) particles was casted to form cylindrical PS-Cu monoliths with multi-millimeter diameter and height. The sacrificial PS templates were removed after baking the PS-Cu monoliths at 400°C with a flow of H₂/Ar (4%). Formation of monolithic Cu foams with density as low as ~0.9 g/cm³ (~10 % relative density) was achieved, which will be a good candidate for fabrication of low density metal foam targets for laser-driven fusion energy experiments and high-energy-density physics experiments at the laser facility. In this presentation, we will detail the effect of experimental condition on the formation of low density porous Cu foams. Our results expand the potential of the templating approach from previously being restricted to thin film and small monoliths to a facile and versatile technique for preparing macroscopic uniform metal monoliths.

If fully-printed TFTs are to be made, electrodes and gate dielectrics should be solution-processed. Most research papers have reported on oxide TFTs either with thermally-grown SiO₂ on a highly-doped silicon wafer, with gate dielectrics fabricated by using a vacuum process or with solution-processed semiconductors. High-k gate dielectric layers in TFTs increase the capacitive coupling between the gate electrode and the semiconductor layer, improving the subthreshold gate swing and the operation voltage range and resulting in low power consumption in display devices. Well-known potential high-k materials for oxide TFTs are Al₂O₃, HfO₂,Y₂O₃, ZrO₂, and TiO₂. There are several reports on Al₂O₃, Zr₂O, and HfO₂ as gate dielectrics, but none on TiO₂ fabricated by using a solution process. Therefore, a study of high-k TiO₂ fabricated by using a solution process combined with an oxide semiconductor fabricated by inkjet-printing is worthwhile because no research on the application of a TiO₂-based hybrid gate dielectric to inkjet-printed oxide TFTs has been reported yet. We synthesized sol-gel TiO₂ and coated it on SiO₂ to make a hybrid gate dielectric for inkjet-printing ZTO TFTs for the first time.
Sol-gel TiO₂ was synthesized and used as a gate dielectric for oxide thin-film transistors (TFTs). A hybrid gate insulator composed of sol-gel TiO₂/thermally-grown SiO₂ was applied to the inkjet-printed zinc-tin oxide (ZTO) TFTs for the first time. The electrical properties of an inkjet-printed ZTO TFT with a hybrid gate insulator show a mobility of 0.17 cm²/Vs, an on-to-off current ratio of 5x10⁴, a subthreshold slope of 0.8 V/dec, and a threshold voltage of 0.6 V. The hybrid gate insulator for the inkjet-printed ZTO TFT shows a much improved operating voltage and subthreshold slope and a lower mobility compared to the SiO₂ gate insulator. We found that the use of high-k materials as gate dielectrics was not the only solution for improving the electric properties in dielectrics. In solution-processed gate dielectrics, controlling the annealing temperature so that is below the crystallization temperature should be considered to obtain the desired properties by minimizing Coulomb scattering and by improving the surface roughness.

Transparent conducting oxides are critical in many optoelectronic devices such as solar cells, light emitting diodes and flat panel displays. Current aims in the field are to improve the standard requirement of optical transmittance above 80% in the visible region and electrical resistance below 10^-3 W.cm as well as obtaining coatings on a large scale at lower fabrication costs. Co-doping of metal oxides is a strategy employed as it enables the enhancement of both optical transparency and electrical conductivity often in a single step. And solution processing methods enable easy scale up.
Here we present the synthesis of co-doped ZnO and SnO₂ thin films with both cations (such as Al³⁺, Ga³⁺ and Mg²⁺) and anions (such as F-) via a solution-based route called aerosol assisted chemical vapour deposition (AACVD). This method is a specialized form of CVD that involves the transportation of the often commercially available precursor molecules (that are pre-dissolved in a suitable solvent) into the deposition chamber in the form of aerosol droplets. AACVD is inexpensive, scalable, and allows the use of precursors that are usually incompatible with traditional CVD methods.
The fabricated thin films have been extensively characterized for their material and functional properties which are on par with current industry standards. Hall effect measurements indicate n-type conductivity with resistivities of 10^-3 W.cm or lower and UV-Vis shows transmittance in the visible region to be between 80-90%. Furthermore UV-Vis also shows the plasmonic edge to be shifted to shorter wavelengths making them applicable as heat mirrors. SEM of the films show structured morphologies that enable efficient light scattering which is ideal as electrical contacts in photovoltaic devices.

In the present study, silver was added to barium titanate powders by alkoxide-hydroxide sol-gel process in inert atmosphere to obtain the high dielectric constant; low conductivity and low tangent loss. It is also used to investigate the effect of adding a conductive phase on dielectric and sintering properties of barium titanate. The composites were sintered in microwave furnaces at 1100°C for 20 min and compared it with conventional sintering. The basis behind using microwave sintering is to take improvement in the densification of ceramic composite in short sintering time. XRD, FE SEM, Raman spectroscopy and TGA were performed to confirm the phases of BaTiO₃ and Ag, the morphology and tetragonal crystal structure of BaTiO₃ and the weight loss. The average grain size of the dense BaTiO₃-Ag composite was in the range of 0.6-1.3 µm. Dielectric constant and tangent loss increased with increasing Ag content until percolation threshold was achieved and the adhesion of silver to BaTiO₃ suppressed the formation of conducting path in the composite. In addition, the highest dielectric constant (~9.2x10⁴ with tangent loss ~0.06 much higher than pure BaTiO₃) at T_c of BaTiO₃-Ag (3.5 vol %) was achieved. The enhanced dielectric properties of the BaTiO₃-Ag composite are due to the well-dispersed silver particles in the BaTiO₃ matrix.

A number of novel technologies have been discovered to improve the quality of our lives. Nanotechnologies are also widely investigated to bring new techniques. Chemists have been seeking for novel synthetic routes, which can produce novel materials with unconventional properties. Microfluidic synthesis has taken a considerable attention due to special advantages that can&’t be achieved by conventional synthesis. For example, high surface-to-volume ratio and small volume expedite the chemical reaction in microfluidic devices and improve the product yield. Microfluidic devices also offer the capability of continuous, multi-step chemical synthesis at small scales. The overall goal of microfluidic synthesis is to carry out all operations, including synthesis, processing, purification, and analysis on designed microfluidic devices efficiently and economically by using micro-scale reagents. A high-efficiency microfluidic device to synthesize novel inorganic materials/particles is presented in this study. We designed a micro-channel pattern, which was able to alternately generate droplets, generating under controlled droplet ratios. The controlled droplet fusion is adjusted by passive control based on the channel geometry and liquid phase flow. Novel microfluidic synthesis of CdS nanoparticles utilizing each fused droplet as a microreactor for rapid and efficient mixing of reagents is demonstrated. Following alternating droplet generation, the channel geometry allows the exclusive fusion of alternate droplets with concomitant rapid mixing and produces supersaturated solution of Cd ²⁺and S^2- ions to form high performance CdS nanoparticles for multifunctional device fabrications.

Oxygen and iodine are two key elements used for activating the photoconductivity of PbSe films regardless of how the PbSe film is made, either by chemical bath deposition (CBD), thermal evaporation or MBE [1,2]. The sensitization which is the process of heat treating the PbSe films under the oxygen and iodine atmospheres seems to cause recrystallization of PbSe polycrystals in the grown films, making them photosensitive to infrared [1]. In this study, we tried to clarify how the morphology of a PbSe film changes during sensitization in the oxygen and iodine atmospheres. A PbSe film was grown on a thermally oxidized (111) Si substrate by chemical bath deposition. Solutions of lead acetate and sodium selenosulfate were mixed together to make up the growth solution. The Si substrate was dipped in the growth solution for 1 hour at 60#730;C to grow an 800 nm thick PbSe film. The as-grown PbSe film observed by SEM consists of a large number of two dimensional amorphous-like clusters of about 200nm in diameter and the relatively uniform thickness. The substrate with a PbSe film grown was cut into pieces, and the pieces were annealed at different conditions. The first piece was annealed at 380#730;C for 30 minutes under an oxygen atmosphere. After this annealing, most of the boundaries between clusters became smeared with the clusters becoming bigger in size. Other pieces were annealed at 380#730;C for 30 minutes under the oxygen atmosphere, and then under an iodine plus nitrogen atmosphere for different durations. minutes sensitization under the iodine plus nitrogen atmosphere made new single crystalline particles with faceted surfaces larger than 100 nm in diameter formed on the underlying PbSe layer. The underlying PbSe layer also experienced a slight morphology change. After 5 minutes sensitization, the diameter of the particles becomes bigger to approximately 300 nm. After 10 minutes sensitization, the faceted morphology of the particles became more pronounced and the particles became interconnected both sideways and vertically. After 20 minutes sensitization, the particles grew in size to about 500 nm and became fully joined together, forming grain boundaries. We will discuss how these morphological changes affect the electrical and optical properties, especially detectivity of the PbSe film.
References
1. Jijun Qiu, Binbin Weng, Zijian Yuan, and Zhisheng Shi, J. Appl. Phys., 113, 103102 (2013).
2. M.C. Torquemada, M.T. Rodrigo, G. Vergara, F.J. Sanchez, R. Almazan, M. Verdu, P. Rodriguez, V. Villamayor, L.J. Gomez, and M.T. Montojo, J. Appl. Phys., 93, 1778 (2003)

Polynuclear oxo/hydroxometal clusters under acidic conditions provide a unique route to the formation of dense and atomically smooth thin oxide films. Extraneous cations are eliminated under these conditions, enabling direct cluster-to-solid condensation with minimal volume change. Niobium salts are commonly known to be insoluble under acidic conditions. In combination with hydrogen peroxide and phosphoric acid, niobium is found to be readily soluble in water, forming unique peroxophosphatoniobium clusters. These clusters can be spin coated to produce thin films of a new family of niobium phosphates covering the range of P:Nb compositions from 0.5:1 to 2:1. Thermal, structural, optical, and electrical measurements reveal a new class of amorphous insulator with dielectric constants near 17 and loss tangents as low as 0.1%. At elevated temperatures, films can crystallize and lose P₄O₁₀. This loss of P₄O₁₀ coincides with a decrease in density and formation of porous structures. Also, niobium phosphate thin films from these clusters can be patterned by electron beam lithography.

In recent years, the search for alternative cathode materials, which have better reliability and capacity with low cost become very important priority of lithium ion battery technology. Lithium transition metal orthosilicates cathode materials have been viable candidates for the alternative cathode material since they can store and release two lithium ions per a transition metal redox couple reaction. This work discusses the hydrothermal synthesis of Li₂MnSiO₄ for cathode materials. At first, Li₂MnSiO₄ is prepared with various hydrothermal conditions, such as different temperatures, times, and starting solutions, and their physical and electrochemical are characterized to seek the best synthesis condition. In order to overcome the inherent poor electronic conductivity of Li₂MnSiO₄, the in-situ carbon incorporation is employed by the addition of carbon precursor into the starting solution for hydrothermal synthesis. The effect of different hydrothermal conditions on the powder morphology as well as electrochemical performance is also discussed in detail.

Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) powders comprising nanocrystallites were synthesized via oxalate precursor method. The calcined powders were sintered in the 1200-1500^oC temperature range for an optimized duration of 10h. The concomitant grain enhancement in grain size was from 0.5mu;m to 32mu;m. Interestingly the one that was sintered at 1450^oC/10h having a grain size of 30mu;m exhibited well resolved Morphotrophic Phase Boundary (MPB). These ceramics were found to possess higher domain density mostly associated with 90^o twinning. Large strain of about 0.2 % and piezoelectric coefficient as high as 563pC/N were obtained for 30mu;m grain sized ceramics with improved ferroelectric characteristics.

Organic-inorganic hybrids derived from partially substituted alkoxysilane precursors can offer a variety of monolithic porous materials via a sol-gel process when their hydrolysis-polycondensation reactions are appropriately controlled to parallel the polymerization-induced phase separation. Some of our recent developments are described below.
Poly(methylsilsesquioxane) Aerogels
Using methyltrimethoxysilane, MTMS, as a single precursor, monolithic poly(methylsilsesquioxane), PMSQ gels are prepared in the presence of surfactants via acid-base one pot reaction route. Through the preparation optimized for low-density, pure PMSQ aerogels are obtained to exhibit comparable properties with those of tranditional silica aerogels. Moreover, the monolithic PMSQ aerogels can reversibly recover to the original size when uniaxially compressed. Utilizing this “spring-back” property, PMSQ aerogels can be prepared by drying at ambient conditions.
Marshmallow-like Macroporous Monoliths
Based on PMSQ monoliths, a co-polymerization with dimethyldimethoxysilane, DMDMS, produces softer materials. With an increase of DMDMS/MTMS ratio, the Young&’s modulus drastically decreased to give very soft reversibly deformable monolith (marshmallow-like monolith) with larger macropores. Due to its inherent surface hydrophobicity, the marshmallow-like monolith can selectively absorb nonpolar liquid from a physical mixture of oil/water. Additional modification with fluorocarbon moieties produces superamphiphobic soft monoliths.
Hydrogen-silsesquioxane Monoliths from Hydrosilane Precursors
The simplest silsesquioxane, hydrogen silsesquioxane HSQ, has been studied for a long time. Using the polymerization-induced phase separation technique, we have succeeded to prepare monoliths with well-defined continuous macropores while preserving all the Si-H bonds contained in the precursor. Liquid-phase contact of noble metal ions onto the Si-H resulted in an instantaneous formation of pure metal or alloy nanoparticles firmly immobilized in the mesopores of HSQ monoliths, which were applicable to various catalytic reactions with excellent efficiency and recyclability. A novel surface modification has been developed using similar reagents.

The problem of water contamination due to the Fukushima nuclear plant accident following the tsunami which occurred on March, 11th 2011 makes ¹³⁷Cs extraction a topical issue¹. Several studies have been done on the removal of cesium with insoluble ferrocyanides or also called Prussian blue analogues (PBA) showing that they are highly selective for these ions^2-4. However, their use as a powder-bulk compound in column process decontamination is limited due to clogging problems produced by its powder nature. Therefore it is necessary to employ a porous support to carry out the precipitation of the PBA within the porosity and confer a suitable bed for the correct operation of ion-exchange columns. A new synthesis of inorganic monoliths functionalized with different PBA: K_xCoFePBA, K_xCuFePBA or K_xZnFePBA using high internal phase emulsion (HIPE) as soft template and PBA precipitation after liberation of monolith mesopores was achieved by our team at the "Institut de Chimie Separative de Marcoule" (ICSM) at the "Laboratoire des Nanomateriaux pour l'Energie et le Recyclage" (LNER). The use of an emulsion with high internal phase (> 50% vol) followed by the fully PBA precipitation in the procedure allows to considering innovative ways of functionalizing in order to obtain materials with both hierarchical porosity and nanoparticles immobilized for decontamination purposes as ¹³⁷Cs removal. The obtained functionalized monoliths were test in Cs⁺ ions removal from aqueous solutions containing largest Na⁺ concentration. The functionalized monoliths are highly selective to Cs⁺ being KZnFePBA-monolith the sample which presents the biggest quantity adsorbed Q_Cs (mmol/gZnFC) = 2.3.
Funding: French ANR - RSNR “Demeterres”
1. D. Klein and M. Corradini, Fukushima Daiichi: ANS Committee Report, 2012.
2. S. Szoke, G. Patzay and L. Weiser, Radiochim. Acta, 2003, 91, 229-232.
3. T. Sangvanich, V. Sukwarotwat, R. J. Wiacek, R. M. Grudzien, G. E. Fryxell, R. S. Addleman, C. Timchalk and W. Yantasee, J. Hazard. Mater., 2010, 182, 225-231.

Smart materials with responses to external stimuli have attracted attention due to potential applications in optical systems, microfluidic, and biosensors. Tremendous effort has been devoted to the fabrication of stimuli-responsive organic/inorganic materials, as well as many studies into stimuli-responsive functional organic polymers. Silica-based hybrid materials are especially promising thanks to their chemical/thermal stabilities and bio inertness. Here, we focus on the combination of hybrid silica and poly(N-isopropylacrylamide) (PNIPAM) to achieve active microwrinkles working as liner actuators by thermal stimulus.
The active microwrinkles were prepared on the surface of composites of PNIPAM and hybrid silica. The composites were synthesized via a sol-gel reaction. Hybrid silica with ca. 1 mu;m thickness was processed such that it covered the surface of monolithic PNIPAM gels. The microwrinkles formed on the surface of composite in the course of releasing the stress mismatch between the two layers (PNIPAM and hybrid silica). The hybrid silica layer swells/shrinks depending on temperature, which reversibly generates various surface structures such as folding and nested wrinkle structures. More interestingly, the microwrinkles move to a targeted-direction by patterning the hybrid silica coating. The anisotropic movement of surface microwrinkles can convey particles with mu;m sizes which are well-matched to periodic lengths of wrinkles.
The presentation will also include the discussion on 1) the synthesis parameters to control the morphology and dimension of microwrinkles and 2) mechanism of producing active wrinkles.

Exfoliated layered clays, nanoscale silicate platelets (NSP), were previously prepared from the exfoliation and extraction process and suitable candidates for preventing heat penetration and flame propagation. In this study, we synthesized the phosphazene-silicate (HCP-NSP) through the hexachlorocyclotriphosphazene (HCP) which were covalently bonded on sodium nanoscale silicate platelets and chloride was exchanged for the silicate and removed. The optimal fraction of HCP and silicate were characterized by using FTIR, and energy dispersive x-ray spectrometry (EDS). We have also prepared the HCP-MMT hybrids by HCP covalently bonded on sodium montmorillonite. Subsequently, the relative thermal stabilities of the epoxies cured with the HCP-silicate were studied. The effect of silicate clays was evaluated by blending the HCP-silicates into a two component epoxy system (diglyidyl ether of 4,4&’-isopropylidenediphenol (BPA) and a diamine) and fully cured to form solid materials. The analyses by SEM-EDS, X-ray diffraction, and transmission electronic microscopy (TEM) indicated that the HCP-NSP/Epoxy composites had a more homogenous silicate and phosphorus distribution in the polymer matrix than HCP-MMT/Epoxy. Thermal gravimetric analysis (TGA) indicated an enhanced thermal stability for the HCP-NSP epoxy composites, with a delayed weight-loss pattern (temperature of weight loss at 10% (T_10wt%) from 350 to 370 ^oC and temperature of weight loss at 85% (T_85wt%) from 520 to 580 ^oC), compared to pristine epoxies. The co-existence of HCP and silicate platelets at various ratios demonstrated a synergistic effect on the improvements of thermal stability.

Effective bonding of organic/inorganic interfaces by means of adhesion promoting hybrids is paramount to the structural reliability of modern multilayer device technologies, such as flexible electronics, photovoltaics, and 3D microelectronic devices, where organic/inorganic interfaces are ubiquitous. These interfaces are notoriously weak in the presence of reactive environmental conditions, such as moisture, leading to implications for reliability.
Hybrid molecular materials containing organic and inorganic components that are resistant to such environmental species and synthesized via sol-gel chemistry are uniquely capable of addressing these challenges. The intimate nanometer length-scale mixing of these components can be leveraged by coupling chemistry and processing parameters to synthesize hybrid molecular structures with targeted functionalities, such as the ability to form a high-performance moisture-insensitive bond between an organic layer and an inorganic substrate.
We synthesized a hybrid organic/inorganic system using an epoxy-functionalized silane, (3-glycidoxypropyl)trimethoxysilane (GPTMS), and a zirconium alkoxide, tetra-n-propoxyzirconium (TPOZ) [1]. We unravel the kinetics of the underlying hydrolysis and condensation reactions of the precursors in order to optimize the hybrid molecular structure for high adhesion as well as resistance to moisture. We carefully control the hydrolysis and condensation reactions of the zirconium precursor to understand the role of the inorganic network in the deposited films towards mitigating moisture-assisted degradation.
We find that the increase in zirconium hydrolysis leads to an increase in the overall molecular network connectivity in the deposited film, resulting in a hybrid organic/inorganic film with a highly crosslinked molecular network. As a result, these films are capable of inhibiting moisture-assisted degradation between a silicon substrate and an epoxy layer while tripling the adhesion of the bare epoxy/Si interface.
[1] Marta Giachino, Geraud Dubois, and Reinhold H. Dauskardt, ACS Applied Materials & Interfaces20135 (20), 9891-9895

Interfaces between passivated substrates like silicon and epoxy fillers are common features in compact 3-D electronic circuitry. The stability of 3-D architectures requires that these interfaces exhibit suitable adhesive strength and moisture resistance to maintain structural integrity. We have previously demonstrated that the presence of zirconate-organisilicate hybrid layers at these types of interfaces can dramatically improve the interfacial adhesion, even in moist environments, preventing delamination.
The preparation of such hybrid layers via sol-gel chemistry is a remarkably complex process with a myriad of variables influencing the structure and properties of the interfacial hybrid layer produced. Due to the low concentrations at which the sol-gel syntheses of these layers are typically conducted, conventional analytical techniques including visual observations, FT-IR and NMR spectroscopy are difficult or time consuming, inhibiting efficient film optimization. Therefore, to develop a deeper understanding of the dynamics of the underlying hydrolysis and condensation reactions of the precursors on hybrid network formation, we conducted the initial steps of the sol-gel process under more concentrated conditions. This enables a way to evaluate the influence of system variables, such as solution aging time, stoichiometry, temperature and pH on the resulting adhesive/cohesive properties of the films.
Through this approach, we have identified the crucial reaction conditions for an aqueous sol-gel system of TPOZ and GPTMS that are necessary for obtaining hybrid layer films with good interfacial and cohesive properties. Utilizing our well-established thin-film adhesion/cohesion technique we have gained insight to the hybrid organic network connectivity of these films by correlating the observations of the concentrated sol-gel to the adhesive/cohesive properties of the films and have mapped the influence of solution synthesis variables on the cohesive/adhesive fracture energies that range from approximately 20 J/m² up to values as high as 80 J/m².

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. We present a novel class of hybrid nanocomposites created through a unique backfilling approach in which selected polymers are homogeneously infiltrated into the pores of a sol-gel nanoporous glass scaffold, leading to uniform mixing at unprecedentedly small length-scales (~1nm) and confinement of polymer chains to dimensions far smaller than their bulk radius of gyration. The second-phase material may be chosen from an extensive library of polymers, allowing for the development of composites with novel electrical, optical, and mechanical properties. This synthesis technique is versatile and can produce uniform, high-quality films over large areas.
We show that it is possible to dramatically improve the mechanical and fracture properties of a nanoporous organosilicate matrix by filling the porosity with a polymeric second phase. The degree of toughening is shown to increase with the polymer molecular weight, and is also found to depend on synthesis conditions. These studies of confined polymers enable us to explore the fundamental limits of nanocomposite toughening in terms of molecular strength, molecular size, and degree of confinement. We describe a novel toughening mechanism based on the molecular bridging and pullout of individual confined polymer chains from the porous matrix, distinct from the more common entanglement-based crazing mechanisms exhibited by bulk polymers. This mechanism is supported and quantified with a model that describes the nanomechanical processes occurring on the length scale of individual polymer chains. The toughening model is further leveraged to calculate the tensile strength of individual polymer chains and find it in agreement with our own independent estimates of molecular strength. This study provides new insight into the mechanical behavior of polymer chains under nanoscale confinement and suggests potential routes for increasing the cohesive strength of multifunctional nanocomposites, where the traditional bulk toughening mechanisms may be absent.

Hybrid organic-inorganic solids processed from organically-functionalized silane precursors via sol-gel chemistry represent an important class of engineering materials as the combination of organic and inorganic species at the molecular scale can lead to novel properties ranging from oxides to polymers. Of the numerous silanes used to process hybrid materials, 3-glycidoxypropyltimethoxysilane (GPTMS) is one of the most common. Hybrid films processed from GPTMS and metal alkoxides precursors (e.g. TPOZ) are used as adhesive coupling layers to form strong and durable interfaces between metal oxides and epoxy adhesives in structural joints and fiber-metal laminates. While the mechanical properties of GPTMS-based materials have been studied, many questions remain regarding the link between the molecular structure of these films and their mechanical properties. Thus, we have developed computational tools to generate an accurate molecular model of Zr/GPTMS. Using NPT molecular dynamic simulations to implement simulated annealing, we obtain the global energy minimum of the high-dimensional configuration space. We found that the inorganic species segregate to form ZrO_x clusters, while the GPTMS precursors decorate the inorganic clusters via Si-O-Zr bonds and crosslink to form an organic mesh between clusters. Due to the variable Zr coordination, network connectivity cannot be completely quantified, so we introduce a simplified model. With a low energy structure, we simulate the bulk modulus under both compressive and tensile hydrostatic pressure. Surprisingly, we report asymmetric elastic behavior due to the presence of the inorganic clusters, which create a difference in free volume under compressive and tensile loading conditions. We systematically investigate important parameters of the molecular structure including composition, cluster size, connectivity, and crosslinking of the organic network. Our molecular model provides valuable insight into the molecular origins of the mechanical properties and creates a framework from which experimental studies can optimize mechanical properties.

Solution-based fabrication methods have been widely used for depositing uniform functional coatings. These coatings can be utilized in a variety of applications such as optoelectronics, biomedical, and energy. However, such fabrication techniques are not appropriate for directly depositing patterned micro/nano-scale features, which are required in many contact-based applications such as in MEMS.
In this work we propose the direct writing of hydrophobic silica-based sol-gel patterns with sustained functionality and their subsequent tribological characterization. Such an approach may be an advantageous alternative to current lithography-based methods due to the relative ease of processing and no material waste. There are few studies on the tribological and mechanical performance of such directly deposited coatings, and in particular the effect of feature geometry and edge quality on the tribological performance of the patterned surface.
This investigation involves the abrasive wear and frictional analysis of various pattern geometries of fluorinated silica sol-gel coatings that are directly printed onto glass substrates with a robotically controlled pneumatic nozzle system. Measurements of friction coefficient and contact angle are used to elucidate the effect of geometry and deposition parameters on the composition and performance of the deposited features. Mild abrasion is conducted using an in-house built reciprocating wear apparatus. The sustained hydrophobic functionality of the worn patterns is analyzed using contact angle goniometry. Furthermore, lateral force microscopy is used to assess the small-scale tribological response of the printed features. In addition, nano-scratch and nanoindentation are performed to investigate the relationship between the patterns&’ mechanical and tribological properties. Finally, X-ray photoelectron spectroscopy and scanning electron microscopy are used to assess the chemical and microstructural characteristics of both pristine and worn patterns. Such work sheds light on the tribological properties of lithography-free processed hydrophobic patterns for applications spanning from micromotors to biomedical fluidic devices.

Engineering bio-inspired antifouling surfaces is of importance for a wide range of applications.^1,2 Water-repellent surfaces, owning so many unique properties such as self-cleaning, anti-contamination, and drag reduction are highly desirable to achieve this goal. Herein we report the development of a novel superhydrophobic surface featured with hierarchical architecture that exhibits enhanced antibacterial activity. The superhydrophobic surfaces is patterned with lattice arrays of submillimetre-scale posts decorated with uniformed nanotextures. We found that an impacting drop could detach from the surface close to its maximum lateral extension with a pancake-like shape, resulting in a four-fold reduction in the contact time compared to that on the conventional superhydrophobic surfaces.³ We also found that, on the tilted surface with an appropriate tilt angle, the impacting drop bounced off the surface in a pancake shape with a much shortened contact time and left the field of view before bouncing again. This exclusive property, characterized by minimized contact of the liquid with the solids, not only endows a minimal bacterial adhesion in the static condition, but also in the dynamic conditions relevant to practical applications. We envision that the antibacterial surface reported here will find promising applications in dropwise condensation, heat exchangers, and biosafety where requires environmentally friendly antifouling coatings.
References:
1. Kirschner, C. M. & Brennan, A. B. Bio-Inspired Antifouling Strategies. Annual Review of Materials Research, Vol 4242, 211-229 (2012).
2. Shivapooja, P. et al. Bioinspired Surfaces with Dynamic Topography for Active Control of Biofouling. Adv Mater25, 1430-1434 (2013).
3. Liu, Y. H. et al. Pancake bouncing on superhydrophobic surfaces. Nat Phys10, 515-519 (2014).

Engineering robust artificial biomaterials that can resist bacterial colonization and biofilm formation is of importance for a wide range of applications such as in marine, petroleum pipelines, textiles, and medical implants, yet has proved challenging.^[1] Since the adhesion of bacteria to the substrate represents the first step in the bacterial colonization and subsequent biofilm formation, the creation of novel surfaces which prevent the initial attachment of bacteria to the substrate emerges as an appealing alternative to traditional chemical-based approach. Many natural surfaces, including plant leaves, gecko foot, shark skin, insect wings, fish scale and spider silk, are capable of resisting bacterial colonization. Inspired by these natural surfaces, numerous superhydrophobic surfaces have been extensively developed over the past decade. Although artificial superhydrophobic surfaces can maintain anti-fouling in the dry conditions for a long time, however, the desired anti-fouling property is prone to being compromised in the wet environment due to the breakdown of their water repellency. ^[2]
Herein we develop a novel superhydrophobic surface featured with hierarchical architecture and bimetallic Cu/Ag composition that exhibits enhanced antibacterial activity. The surface is created using a facile galvanic replacement reaction followed by a simple thermal oxidation process.^[3] Interestingly, we show that the surface&’s superhydrophobic property naturally allows for a minimal bacterial adhesion in dry environment, and also can be deactivated in the wet solution to enable the release of biocidal agents. In particular, we demonstrate that the higher solubility nature of the thermal oxides created in the thermal oxidation process, together with the synergistic cooperation of bimetallic composition and hierarchical architecture allows for the release of metal ions in a sustained and accelerated manner, leading to enhanced bacterial performance in the wet condition as well. We envision that the easy of the fabrication, the versatile functionalities and the robustness of our surface will make it appealing for broad applications.
References
[1] Hasan J., Crawford R. J., Ivanova E. P. Antibacterial Surfaces: The Quest for a New Generation of Biomaterials. Trends Biotechnol. 2013, 31, 295-304.
[2] Papadopoulos P., Mammen L., Deng X., Vollmer D., Butt H. J. How Superhydrophobicity Breaks Down. Proc. Natl. Acad. Sci. U. S. A. 2013, 110, 3254-3258.
[3] Zhang H., Jin M. S., Wang J. G., Li W. Y., Camargo P. H. C., Kim M. J., Yang D. R., Xie Z. X., Xia Y. N. Synthesis of Pd-Pt Bimetallic Nanocrystals with a Concave Structure through a Bromide-Induced Galvanic Replacement Reaction. J. Am. Chem. Soc. 2011, 133, 6078-6089.

Solution based synthesis routes using metal alkoxides and organically coordinated metal salts have been developed for synthesis of complex oxides, nano-composites and nano structured metals. Oxides systems of varying complexities including doped and non-doped iron-, titanium-, and zinc oxides, as well as spinels and perovskites were prepared in the forms of thin and ultra-thin films on flat and nano-structured surfaces at temperatures typically in the range 270-500^oC. The influence of the precursor, reaction kinetics and thermal treatment in relation to the structures and properties obtained will be discussed. The possibility of greatly extended, metastable doping-levels in semiconductor oxide hosts such as Fe2O3 and ZnO will also be discussed. Further the processing using organically coordinated metal salts developed to yield metals and alloys will be described. This route allows for nano-crystalline metals and alloys to be prepared with crystallite sizes below 10 nm, as well as thin- and ultra-thin coatings on nano-structured oxides, including nano-porous structures, wires and powders. Synthesis temperatures in the range 150-500^oC were used and no reducing gas was necessary. Similar systems were used for synthesis of metal-in-ceramic composite films and thin or ultra-thin coatings on wires and porous oxide electrodes with a wide range of metal nano-inclusions and oxide matrixes will be described. The metal inclusion sizes were down to a few nm and loadings were up to over 80%. The syntheses and products were studied with a wide array of analytical techniques including; SEM, TEM, XRD, TGA, DSC/DTA, IR and Raman spectroscopy. Such simple low cost synthesis routes to highly complex nano-materials are required for practical application in many areas of sustainable energy conversion and storage, catalysis and magneto-electric applications.

We have recently proposed a new technique for realizing crystalline oxide thin films on plastic substrates. The technique is based on the sol-gel thin film deposition and the transfer process, i.e. it comprises (i) deposition of a polymer layer on a silicon substrate, (ii) deposition of a precursor gel film on the polymer layer by spin- or dip-coating, (iii) conversion of the gel film into a crystalline oxide film by firing, and (iv) transfer of the crystalline oxide film onto a plastic substrate. The transfer is realized by heating the oxide film on a hot plate and pressing the plastic substrate onto it where the softened or molten surface of the plastic substrate acts as an adhesive. The technique is significant in that the "firing" step guarantees the crystallization and densification of films, which are the key factors for their superior functionalities, and that the principle of the technique is available for any combinations of oxide thin films and plastic substrates.
The crystalline oxide thin films thus fabricated on plastic substrates are crack-free and optically transparent, and have smooth surface both in scanning electron and scanning probe micrographic scales. 60 nm thick anatase thin films with high optical reflectivity, 660 nm thick ITO thin films with electrical conductivity, and 85 nm thick ZnO thin films with (002) orientation have been prepared on plastic substrates including polycarbonate, acrylic resin and PET. Patterned ITO thin films have been prepared on plastics simply by using a mother silicon substrate with periodic grooves. Alternating ITO and ZnO ribbons have also been fabricated on plastic substrates.
In order to make the technique more applicable especially for those who are interested in utilizing it, many fundamental issues are left to be studied systematically and clarified quantitatively; for instance, how the polymer layer, the types of plastic substrates, the bending and the temperature change could affect the quality and/or performance of the oxide thin films transferred on plastic substrates. In the present work we have studied (i) the effect of the polymer layer on the microstructure and crystallinity of the oxide thin films fired on it, (ii) the effect of the types of plastic substrates on the transfer performance and the adhesion of the oxide thin films, and (iii) the factors that determine the bendability of the oxide thin films on plastic substrates.

Metal-oxide thin-film transistors (TFTs) have attracted considerable attention over the past decade due to their high carrier mobility and excellent uniformity. Besides, the solution processability and transparency have opened new horizons for low-cost printable and transparent electronics on flexible substrates. Firstly, a simple passivation method is developed to overcome the water susceptibility of solution-processed InZnO thin-film transistors (TFTs) by utilizing octadecylphosphonic acid (ODPA) self-assembled monolayers (SAMs). The unpassivated InZnO TFTs exhibit large hysteresis in their electrical characteristics due to the adsorbed water at the semiconductor surface. Formation of a SAM of ODPA on the top of InZnO removes water molecules weakly absorbed at the back channel and prevents water diffusion from the surroundings. Therefore, the passivated devices exhibit significantly reduced hysteretic characteristics. Secondly, We developed a simple and environmentally friendly spin-coating method for high-κ dielectrics (AlO_x, ZrO_x, YO_x and TiO_x). These materials were used as gate dielectrics for solution-processed nanocrystalline In₂O₃ or amorphous InZnO TFTs with a maximum processing temperature of 300 °C. The role of high-κ dielectrics in device performance was systematically studied. Among the high-κ dielectrics, the AlOx-based devices showed the best performance with mobilities of 21.7 cm² V^minus;1 s^minus;1 in an In₂O₃ TFT and 11.6 cm² V^minus;1 s^minus;1 in an InZnO TFT with the on/off current ratio exceeding 10⁶. Furthermore, the devices exhibited ultra-low operating voltages (<3 V) and negligible hysteresis. A comprehensive study suggests that the high performance of the AlO_x-based devices could be attributed to the smooth dielectric/semiconductor interface and the low interface trap density besides its good insulating properties. Therefore, the solution-processed AlO_x can be used as a promising high-κ dielectric for low cost, low voltage, high-performance oxide electronic devices.

Selective synthesis for the integration of nanomaterials with controllable morphology and composition represents an emerging field in nanoscience and nanotechnology given the intrinsic properties behind these nanostructures, which are generally phase-, shape-, and size-dependent. In this direction, the present work explores the capabilities of chemical solution deposition for the growth of epitaxial functional oxides nanostructures and thin films on different substrates [1,2]. Several examples will be presented such as (i) 1D and 2D epitaxial perovskite oxide (La_0.7Sr_0.3MnO₃, SrTiO₃, BaTiO_3hellip;) nanostructures on silicon and SrTiO₃ substrates, (ii) nanostructured epitaxial quartz thin films on silicon substrates [3] and (iii) single crystalline manganese based octahedral molecular sieves (OMS) nanowires on silicon and fluorite substrates [4]. Moreover, a first combination of soft-chemistry, track-etched polymer templates and molecular beam epitaxy (MBE) allow us to describe the synthesis of single crystalline titanate nanowires (BaTi₅O₁₁) epitaxially grown on LaAlO₃ substrates. This work provides a detailed study on the influence of the distinct growth parameters on the nanostructural evolution of the resulting nanostructures and their physical properties. As a result, here we demonstrate that the combination of soft-chemistry and epitaxial growth opens new opportunities for the effective integration of novel technological functional complex oxides nanomaterials on different substrates.
[1] A. Carretero-Genevrier et al. Chem.Soc.Rev, 43, 2042-2054 (2014)
[2] A. Carretero-Genevrier et al. Nanoscale, 20, 892-897. (2014).
[3] A. Carretero-Genevrier et al. Science, 20, 892-897. (2013).
[4] A. Carretero-Genevrier et al. Chem.Mater, 26 (2), 1019-1028 (2014)

Weakly-coupled relaxor dielectric systems based on solid solutions of BaTiO₃ and Bi-based perovskites which are unstable in pure form under ambient conditions (e.g., Bi(Zn_0.5,Ti_0.5)O₃, Bi(Mg_0.5,Ti_0.5)O₃, BiScO₃, BiAlO₃, etc.) have received a great deal of interest in recent years because of their large permittivity values (>1000) which are stable under large electric fields (>100kV/cm) and across broad temperature ranges (some as high as 400°C). While chemical homogeneity and large (columnar) grains have been shown to be critical to achieving bulk-like permittivity in pure BaTiO₃ thin films, parallel work suggests that the attractive permittivity stability of bulk Bi(Zn_0.5Ti_0.5)O₃-BaTiO₃ and related materials is due at least in part to chemical heterogeneity at the sub-grain scale. Here we report the fabrication of thin films in the Bi(Zn_0.5Ti_0.5)O₃-BaTiO₃ system which exhibit both the frequency dispersion that is characteristic of bulk weakly-coupled relaxor dielectrics and similar magnitudes of permittivity values when compared to bulk ceramic samples of the same compositions. This system provides an opportunity to explore the role of multi-scale cation distribution on permittivity scaling and relaxor response in addition to providing a Pb-free option for temperature- and field-stable high-permittivity thin film dielectrics.
This work was supported in part by the Energy Storage program managed by Dr. Imre Gyuk for the Department of Energy&’s Office of Electricity Delivery and Energy Reliability. 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.

Nowadays, the high performance and high integration electronic devices with minimum size are strongly demanded. And also, the environmental problems should be considered for all of the world. Therefore, the development of entirely new technologies using nano-sized materials are necessary to fabricate of the next generation electronic devices with eco-friendly process in near future. The bottom-up of single-crystalline nanocubes is quite ideally process to fabricate high orientation films independent of a kind of the substrates. Moreover, it is expected that the electrical properties will be enhanced by design of interfaces between neighboring nanocubes which exist a lot in the structure. In our previous study, single-crystalline barium titanate nanocubes, which were fabricated by hydrothermal method using water-soluble titanium complex and surfactants, have been focused on as the new nano-sized materials for dielectric devices. The size of barium titanate nanocubes have been tuned from 15 to 30 nm with narrow size distribution by changing the synthesis conditions. By using the 15 nm-sized nanocubes as building blocks, the ordered assemblies of barium titanate nanocubes were fabricated on various substrates by dip-coating method with a quite low withdrawal speed. The dielectric constant and loss of the barium titanate nanocube assembly after sintering at 1123 K were about 3000-4000 and under 0.07 from 1 kHz to 1 MHz. The values of dielectric constants were much higher than these of barium titanate thin films derived from conventional solution method. This enhancement was considered due to effect of interfaces between the nanocubes.
In this paper, the size dependence on dielectric properties of barium titanate nanocube assembled films will be discussed. The dielectric measurements were conducted on the metal-insulator metal (MIM) micro-capacitors consisting of the barium titanate nanocube assemblies. The relations between the size of nanocubes, thickness of the assembled films and dielectric properties will be addressed. Thereby, the potential of the barium titanate nanocube assemblies for the next generation dielectric devices will be notified.
This work was supported by the Advanced Low Carbon Technology Research and Development Program (ALCA) of Japan Science and Technology Agency (JST).

Since the production of the first electronic thin films in 1980 Chemical Solution Deposition (CSD) has emerged as a highly flexible and cost-effective technique for the fabrication of a wide variety of functional oxide films. Among the different application areas we have explored the CSD-MOD technique for the production of High Temperature Superconductors (HTSC). In this context, metal-organic decomposition has been established as the versatile methodology to grow low cost, scalable, high performance epitaxial YBa₂Cu₃O₇ films for coated conductors.
Although the Trifluoroacetate (TFA) approach has proved to be a feasible way to produce ReBCO layers with good superconducting properties, new designed solutions are proposed in accordance with the new requirements concerning environmental safety. Looking at these objectives we will present here our work in the preparation of precursor solutions with reduction or complete elimination of fluorine content, which should be adapted to the requirements of Superconducting ReBCO layers production, leading to high production rates with optimal performance. Solutions with low and non-fluorine precursors (acetates, ethylhexanoates) in different amounts of additives (triethanolamine, propionic acid) have been stabilized and their rheology modified for substrate wettability. Thermal decomposition analysis performed directly in films, have revealed differences in decomposition and growth steps. Upon optimization of growth process parameters, Tc and Jc(77K)of around 90 K and 3 MA/cm² are obtained.
Changes in solvent and use of inorganic salts and polymers produce changes in the rheological properties of the solution improving the thickness and homogeneity of the final layers. Besides, a deep understanding of the thermal decomposition process, represents a powerful tool to produce ceramic layers with improved structural properties.
It is also described a new approach to nanostructured YBCO layers. Preparation of colloidal solutions of oxide nanoparticles adapted to form stable solutions with Yttrium, Barium and Copper salts will be presented. The last results of the use of this “ex-situ” approach to the formation of YBCO-nanocomposite layers will be discussed.
The research leading to these results has received funding from EU-FP7 NMP-LA-2012-280432 EUROTAPES project and MAT2011-28874-C02 national project.

Bismuth based pyrochlores, Bi₂X₂O₇, have a large potential for a wide variety of applications due to the tunability of properties based on the identity of the X atom. Bismuth iridate, for example, is metallic with interesting magnetic properties and has been investigated as a oxygen evolution catalyst while contrastingly bismuth titanate possesses a band gap of 2.9 eV.¹ This flexibility with in this metal oxide system highlights the importance of the characterization of this type of materials.
Of the bismuth group IV ternary metal oxides with the stoichiometry of Bi₂X₂O₇, the bismuth titanate is by far the most extensively studied with little known about the respective zirconate and hafnate materials. Much attention has been focused on the electrical properties of Bi₂Ti₂O₇ due to its high dielectric constant and low dielectric loss.² Other research has investigated Bi₂Ti₂O₇ as a photocatalyst for the oxidation of organics and methanol reforming. The structure of Bi₂Ti₂O₇ is consistently described as a pyrochlore, with until recently a bismuth deficiency, which was required to avoid a mixture of Bi₄Ti₃O₁₂ and Bi₂Ti₂O₇ from forming.³ However in 2014, Oropeza et al. have grown stoichiometric epitaxial Bi₂Ti₂O₇ films - with the epitaxial stabilization credited with exceeding the stabilization offered by Bi vacancies.⁴
While the Bi₂Ti₂O₇ is a pyrochlore, there is debate if the structure of Bi₂Zr₂O₇ and Bi₂Hf₂O₇ is either pyrochlore or fluorite_. The pyrochlore structure can be described as a fluorite cell with a vacancy in the 8a wyckloff positions and is preferred when the A:B ratio of the ionic radii is above 1.42. The A:B ratios of ionic radii for Bi₂Ti₂O_7, Bi₂Zr₂O₇ and Bi₂Hf₂O₇ are 1.70, 1.43, and 1.45 respectively, suggesting the pyrochlore structure would predominate, however V. Sharma et. al concluded Bi₂Zr₂O₇ to have a fluorite structure.⁵
Pure phase powders via coprecipitation and spin-coated polycrystalline films of these three materials have been prepared with the thin films a first for Bi₂Zr₂O₇ and Bi₂Hf₂O₇, allowing for the first time comparison between the bismuth group IV ternary metal oxides together. We have been investigating these materials in terms of band structure via UV-vis and X-ray photoelectron spectroscopy, crystal structure as well as photocatalytic activity of the bulk material. For Bi₂Zr₂O₇ and Bi₂Hf₂O₇ this either provides new insight into the chemical and physical properties or clarifies conflicting/variable published results.
1. K. Sardar et. al., Chem. Matter, 2012, 24, 4192-4200.
2. C. G. Turner et al, J. Am. Ceram. Soc., 2014, 97, 1763-1768.
3. A. L. Hector et. al, J. Solid State Chem., 2004, 177, 139-145.
4. F. E. Oropeza et. al., J. Mater. Chem. A., 2014, 2, 18241-18245.
5. V. Sharma et al, RSC Adv, 2013, 3, 18938-18943.

Recently a lot of attention has been paid to the spinel systems cobalt oxide (Co₃O₄) and cobalt ferrite (CoFe₂O₄) due to their potential in advanced technologies, e.g. as gas sensors [1], electrode materials [2], or catalysts [3]. Cobalt ferrite, a ferrimagnetic material with moderate saturation magnetization, high coercivity, and good chemical stability, is particularly applied in magnetic recording. The combination of a ferrimagnet with a ferroelectric compound in a nanostructured composite material offers promising opportunities for the research on multiferroics, i.e. materials that simultaneously show at least two ferroic order phenomena [4]. Coupling between these dual order parameters, known as the 'magnetoelectric effect', makes them interesting for application in data storage, sensors, and microwave devices, as the magnetic memory can be controlled by an electric field or vice versa.

We present the synthesis of assorted mesoporous cobalt-based spinels with variable nanostructural properties [5]. The materials are prepared from aqueous solution inside the voids of a structural mold (such as porous silica); the mold is later removed by selective etching [6]. This leads to nanostructured materials with variable structural properties, such as surface-to-volume ratio, porosity, crystallite size, as well as particle size and morphology. The influence of these parameters on the magnetic behavior is systematically studied for various mesoporous cobalt oxide and cobalt ferrite spinel phases.
In addition, a periodically ordered, nanostructured composite material consisting of CoFe₂O₄ and BaTiO₃ is obtainable by a two-step synthesis procedure [7]. First, porous CoFe₂O₄ is prepared by nanocasting (as described above). In a second step, BaTiO₃ is subsequently created by the citrate route inside the pores of the CoFe₂O₄ material. This results in a well-ordered composite material of both phases. The two components are known for their distinct ferroic properties, namely ferrimagnetism (CoFe₂O₄) and ferroelectricity (BaTiO₃), respectively. Thus, this proof of synthesis concept offers new perspectives in the fabrication of composite materials with multiferroic properties.

[1] S. Vetter, S. Haffer, T. Wagner, M. Tiemann, Sens. Actuators B 206 (2014) 133-138.
[2] S. Trasatti, Electrochim. Acta 29 (1984) 1503.
[3] K. Sreekumar, S. J. Sugunan, Mol. Catal. A: Chem. 185 (2002) 259.
[4] D. Khomskii, Physics 2, 20 (2009).
[5] S. Haffer, T. Walther, R. Köferstein, S.G. Ebbinghaus, M. Tiemann, J. Phys. Chem. C 117 (2013) 24471.
[6] T. Wagner, S. Haffer, C. Weinberger, D. Klaus, M. Tiemann, Chem. Soc. Rev. 42 (2013) 4036.
[7] S. Haffer, C. Lüder, T. Walther, R. Köferstein, S.G. Ebbinghaus, M. Tiemann, Microporous Mesoporous Mater. 196 (2014) 300-304

Owing to the electrically active nature of living bone to regulae it&’s biochemical activities, the present study developed a new class of piezobiocomposite which potentially mimics the integrated dielectric constant, AC conductivity, piezoelectric strain coefficient, compressive strength and modulus values of bone. Further, two different aspects of the influence of electric field application towards stimulating the growth/proliferation of bone/connective tissue cells in vitro: (a) intermittent delivery of extremely low strength pulsed electrical stimulation (0.5-4 V/cm, 400 mu;s DC pulse) and (b) surface charge generated by electrical poling (10 kV/cm) of hydroxyapatite -BaTiO₃ piezobiocomposite have been demonstrated. It has been established that the cell growth can be enhanced using the new culture protocol of the intermittent delivery of electrical pulses within a narrow range of stimulation parameters. The negatively charged surfaces of developed piezocomposite are found to stimulate the cell growth in a statistically noticeable manner as compared to the uncharged or positively charged surfaces of similar composition. The concern of potential toxicity of BaTiO₃ has also been addressed in vivo using mouse model which confirms the absence of any trace of injected particles or any sign of inflammatory reaction in the vital organs, such as heart, spleen, kidney and liver. Importantly, the absence of any systemic toxicity response in any of the vital organs in the treated mouse model, other than a mild local response at the site of delivery, was recorded. Altogether, with the above responses as well as the absence of any inflammatory/adverse reaction will open up myriad of opportunities for BaTiO₃ based piezoelectric implantable devices as a new generation material for biomedical applications.

Size confinement is a promising technology to tailor the physical properties of multifunctional systems. Recently, Cr-based systems have shown simultaneous presence of ferromagnetic, ferroelectric, photoluminescence and catalytic properties which makes them important functional materials. We report a significant enhancement in the magnetic response of YCrO₃ nanoceramics below 10K [1]. Significant control over the particle size could be obtained by synthesizing the particle under droplet confinement in inverse miniemulsion. YCrO₃ nanoparticles shows antiferromagnetic characteristics below 140K with significant increment in the magnetic moment when the sample is cooled below 10K. The hysteresis loop nature shows a cross over to a weak ferromagnetic characteristics. This magnetic behavior can be explained using the concept of elongated grains or mesocrystals. Interesting modulation in the ferroelectric properties are also discussed by analyzing the frequency dependent dielectric and XRD data. YCrO₃ nanomaterials can be doped with Pr using the same synthesis strategy to modulate their ferroelectric response. All the obtained materials show crystalline nature upon calcination at optimized temperatures. A structural phase diagram of Y_1-xPr_xCrO₃ system is presented after careful rietveld analysis of x-ray diffraction patterns. Pr Doped YCrO₃ systems also show relaxor type behavior that can be explained using the concept of frustration introduced due to nano-grains or nano-polar regions.
References:
[1] I. Singh, A. K. Nigam, K. Landfester, R. Muñoz-Espí, A. Chandra. Anomalous magnetic behavior below 10 K in YCrO₃ nanoparticles obtained under droplet confinement. Applied Physics Letters2013, 103, 182902.

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 progresses in the development of a wet-solution-based process employing self-assembly techniques to produce multifunctional nanostructured thin films. The fabrication processes combine self-assembly, sol-gel process, and nanocrystal colloid chemistry to engineer multifunctional optical, electrical, and magnetic coatings. Through introduction of a variety of functional elements (e.g., nanoparticles), this technology enables tunable properties, such as hydrophobic and mechanical robustness. 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.

Solution processing provides a versatile and inexpensive means to prepare functional materials with specifically designed properties. One of the current challenges is to utilize such approaches to mimic the structural, optical and/or chemical properties of thin films fabricated by vacuum-based techniques and replace them within viable applications. In this view, we show how a simple aqueous-based deposition can be used to deposit ZnO thin films with tailored morphological, optical and electrical properties.
Firstly, we demonstrate how dense, thin layers of intrinsic ZnO can be deposited using a low-temperature aqueous bath method. Through careful control of the kinetic and thermodynamic reaction parameters, highly oriented and dense ZnO thin films, which mimic the structure and properties of sputtered coatings are grown. Through detailed microscopic and spectroscopic investigations, we show that the prepared films exhibit bulk-like optical properties, are intrinsic in their electronic characteristics, and possess negligible organic contaminants, especially when compared to ZnO layers deposited by sol-gel or from colloidal inks. These ZnO films are tested as buffer layers within inorganic Cu₂ZnSn(S,Se)₄ solar cells prepared using a nanocrystal ink route, obtaining identical performances compared to devices incorporating sputtered ZnO.
Secondly, we show how a different bath chemistry can be explored using a high-throughput automatic system. This enabled us to rapidly investigate the effect of dopants, organic ligands, temperature and time in the growth of transparent conductive ZnO films. Through this process, we have identified the optimal parameters for the low-temperature growth of dense, highly conductive ZnO films that are transparent in the visible range and show infrared plasmonic absorptions arising from free carriers.
These aqueous deposition methods constitute a step forward towards the realization of fully solution processed optoelectronic devices using earth abundant materials, with low-cost and low-toxicity processes.

Solution processing is an effective, low-cost, low-temperature means of creating amorphous oxide semiconductors (AOSs) for thin-film transistors (TFTs) used, for example, in flat-panel displays. Conventional solution processing methods are limited in their ability to create dense films at low-temperatures with good electrical properties because they use organic solvents, excess counter-ions, and stabilizing ligands, thus producing porosity in the final film when annealed. A new solution chemistry is therefore necessary to create “ink-precursors” that can yield higher-performance films. Here, we report the electrochemical synthesis of In-Ga-Zn oxyhydroxide nitrate clusters, which are used as an aqueous ink-precursor for solution-processed amorphous transparent IGZO thin films. The starting solution was prepared by dissolving In(NO₃)₃, Ga(NO₃)₃, and Zn(NO₃)₂ salts in 18 M#8486; water. Using a three-electrode electrochemical cell, a constant voltage of -0.49 V was applied with respect to the reference electrode to reduce the nitrate counterions as well as to meticulously control the solution pH during the cluster synthesis. No additional chemical reagents were used during this synthesis. The size and stability of the resulting cluster precursors were investigated and compared to the starting nitrate salt solution using dynamic light scattering (DLS). The electrolyzed precursors were stable for less than 2 h and displayed a cluster radius of 0.8-1.0 nm. The electrical, structural, and morphological properties of films deposited from both cluster and initial nitrate salt solution precursors were explored. The films are amorphous when annealed below 600 ^oC. Electron microscopy and x-ray reflectivity investigations indicate that the cluster films are uniform and crack-free with a film density of ~ 80%. TFT transfer curve assessment using the IGZO film as an active channel layer was performed in order to determine the average channel mobility, turn-on voltage, and drain current on-to-off ratio. Electrical characterization indicates that films made from electrochemically-generated cluster precursors have significantly larger mobility values compared to those made from initial nitrate salt solution precursors. Increasing both In content and annealing temperature caused the TFT device operation mode to change from enhancement-mode to depletion-mode with a higher drain current drive. The best electrical properties were observed by incorporating an ITZO interface layer prior to the deposition of a cluster film composed of In:Ga:Zn=33:33:33 and annealing at 550 ^oC in air, yielding an average channel mobility of ~30 cm²V^-1s^-1 and a turn-on voltage of ~-10 V. This new method allows for the development of aqueous ink-precursors to enable a wide variety of functional mixed-metal-oxide semiconductors/dielectrics.

Solution based printing and coating process is very applicable to preparation of functional films on both rigid and flexible substrates. In the solution based process, metallic colloidal inks consisted of silver(Ag) and gold(Au) with very excellence in both electrical conductivity and chemical stability are generally used. However, Ag and Au are expensive so that alternative materials with high electrical conductivity and low price should be necessary for low cost preparation of highly conductive metal films using the solution based process. Thus, recent researches use the solution based process to prepare highly conductive aluminum(Al) films on several kinds of substrates. To fabricate the highly conductive Al film via the solution process, AlH₃ etherates have been a unique Al source despite their chemical instability in solvents and lack of long-term sustainability. Herein, we suggest an innovative solution process to overcome the aforementioned drawbacks in AlH₃ etherates; AlH₃ aminates powder, which can be stored in low temperature surroundings and re-dissolved in solvents whenever it is needed. Since refrigeration of AlH₃ aminates, AlH₃{N(CH₃)₃}, was very effective to prevent its chemical degradation. Al film with excellence and uniformity in electrical and mechanical properties was successfully fabricated even by the 180-day stored AlH₃{N(CH₃)₃} dissolved in solvents. Moreover, the applicability of long-term stored AlH₃{N(CH₃)₃} to electronic devices was experimentally demonstrated by the successful operation of LED lamps connected to the Al pattern films on glass, PET, and paper substrates.

The solution syntheses of complex metal nanoparticles, such as ones having core-shell morphologies, have attracted the interest of the catalysis community due to their potential in providing particles with tailorable surface chemistry. However these nanoparticle systems are inherently difficult to scale-up due to the sensitivity of their growth kinetics towards changes in the reaction volume. Herein, we demonstrate a rapid and scalable synthesis by continuous-flow to form shape and size controlled platinum-ruthenium core-shell (Pt@Ru) nanoparticles, which have not been previously reported. We demonstrate that the particle&’s size and shape can be intricately controlled by temperature, surfactants, and gaseous reducing agents. We describe how to tailor the particles&’ morphology from being dominated by low index facets in the ruthenium shell, to forming dendritic growths on the platinum seed. Lastly, we discuss the relationship between the Pt@Ru nanocrystal&’s structure and its catalytic properties in preferential carbon monoxide oxidation (PROX).

Currently, novel nanotechnology-based inks made with metals such as silver and gold are widely used because of their excellent conductivity, stability, and sintering efficiency under conventional processing conditions. However, these noble metals are too expensive for widespread commercialization. For this reason, copper nano-inks have received considerable attention as a low-cost alternative to silver or gold nanoinks for printed electronics.
In this work, the copper nanoparticles were fabricated by an electrical explosion method of metal wire. In this method, a high current passes through the metal wire with the high voltage, evaporating the metal wire followed by the formations of the metal nanoparticles. The diameter of copper nanoparticles was controlled by changing voltage condition. The fabricated copper nano-inks were printed on a flexible polyimide (PI) substrate, and sintered at room temperature via a flash light process using xenon lamp. The flash light was irradiated with various conditions such as energy, irradiation time and pulse number. The microstructures of the sintered copper nano-ink films were observed using a scanning electron microscope (SEM). To investigate the crystal phases of the flash light sintered copper films, X-ray diffraction (XRD) was performed. Also, the resistivity of the sintered copper films was measured using a four-point probe method and alpha step. From the result, higher electrical conductivity of the copper film could be obtained via optimization of the wire explosion and flash light sintering process.

In recent years, there have been a large number of studies showing that compositionally modulated or multilayer coatings have significantly higher corrosion resistance than monolithic equivalents, in a diverse set of environments. Electrodeposition is an attractive processing method for synthesis of multilayer coatings due to low cost, good scalability, and the potential to continuously adjust composition through modulation of deposition current density. However, although aluminum-zinc alloys are the most widely employed class of corrosion coatings, electrodeposition of aluminum-zinc coatings presents several unique challenges. It is well established that thin films of a range of aluminum alloys, including aluminum-zinc, can be electrodeposited from room temperature ionic liquid solutions. However, due to the lack of established leveling or brightening agents, in many cases it is difficult to obtain coatings with the desired composition, microstructure, and mechanical and electrochemical properties, and to avoid surface instabilities leading to formation of dendrites, pores, or other defects that degrade coating performance. This is a particularly significant issue for co-deposition of aluminum and zinc, due to the large electrochemical gap between the two elements, low solid solubility, and strong tendency for formation of zinc dendrites. In the case of pure aluminum electrodeposits, it has been shown that the addition of a low concentrations of the alloying elements Mn and Zr has a strong grain refining effect, in many cases producing coatings that are nanocrystalline or amorphous, as well as significantly harder, flatter, and more compact than pure aluminum. In this paper, we examine the effects of addition of Mn and Zr as ternary alloying elements during the electrodeposition of aluminum-zinc from AlCl₃/1-ethyl-3-methylimidazolium chloride solution. Aluminum-zinc electrodeposits, with and without addition of Mn or Zr, are characterized using SEM/EDS, XRD, surface contact profilometry, and polarization curves in NaCl solution. In this study, we present results showing that the addition of Zr, but not Mn, results in decreased grain size, surface roughness, and compositional homogeneity, and facilitates the electrodeposition of compositionally modulated aluminum-zinc alloy coatings with distinct and well defined layers.

The fabrication of a highly conductive silver film was demonstrated at room temperature without a post-annealing process via a continuous flow microreactor deposition system. Colloidal silver nanocrystals were prepared in a microreactor then directly delivered onto a soda lime glass substrate for the film deposition. Since the silver nanocrystals were synthesized in the absence of stabilizers, post-sintering processes were not required, which is generally needed to decompose organic stabilizers and achieve electrically conductive silver film. The silver nanocrystals completely covered the substrate without forming any voids, resulting in excellent electrical conductive paths. The electrical conductivity of the silver film reached the same order of magnitude as bulk silver. A silver line was also fabricated with the aim of pattering the silver film by incorporating the continuous flow microreactor with a micro-embosser and flow cell. The electrical conductivity of the silver line was demonstrated by an LED circuit. This study offers the possibilities of the continuous flow microreactor deposition to prepare highly conductive metal film more efficiently.

The rapid development of organic semiconductor materials that can be processed from solution opens up the possibility of printing organic field-effect transistors (OFETs) onto a wide range of substrates to enable the development of low-cost, large area electronics. However, typical solution-processed OFETs operate at voltages that are too high for use in wearable/portable electronic devices or notably as aqueous sensors (V > 5 V). For these applications, transistors working in the range of 1.5 to 1 V are highly desirable. Lowering the operational voltage of OFETs can be achieved by reducing the threshold voltage and the subthreshold swing. These device parameters are largely controlled by the gate dielectric and the density of charge traps at the dielectric-semiconductor interface. Therefore, to achieve ultralow-operational voltages, high-capacitance, solution-processable gate insulators that form trap-free interfaces are essential.
With great promise in hybrid materials, we developed a novel, high-k dielectric material based on alternative organic-inorganic nanocomposite materials that combine very high dielectric constant values intrinsic to ferroelectric metal-oxide materials (nanoparticles) with mechanical flexibility, low-cost and easy processing of polymers. Metal oxides, such as BaSrTiO3 and BaZrO3, have been incorporated into both low- and high-k polymer matrices to formulate highshy;-k nanocomposite dielectric suspensions. The uniformity of suspensions has been improved by nanoparticles surface modification in case of low-k polymers, while a combination of polymer choice, solvents and nanoparticle-to-polymer ratio led to homogenous suspension based on high-k polymers. The nanocomposite preparation technique was also unique to this work, and proved reproducibility and stability of all nanocomposite suspensions. Solution-processability on a variety of substrates and compatibility with most common semiconducting materials make such high-k nanocomposite dielectrics an unrivalled candidate for low-cost fabrication and integration of low-voltage electronic components and circuits on flexible substrates.
High-yield, ultralow-voltage OTFTs have been successfully demonstrated on rigid and flexible substrates by integrating nanocomposite bilayer dielectrics using a high-k fluorinated polymer. Bilayer dielectrics were formed by (partially) capping surface of the nanocomposite films with an ultrathin capping layer. The capping layer was the key to the operation of low-voltage OTFTs as it allowed remarkable use of nanocomposite surface roughness and improved dielectric-semiconductor surface roughness. Ultimately, low-voltage OTFTs using solution-processed, nanowire-based electrodes and high-k nanocomsposite dielectrics have been demonstrated. Using such solution-processed electrodes pave the way towards realisation of transparent, flexible electronic devices operational at low-voltages.

Solution synthesis methods allow low-cost fabrication of single phase bulk, thin films, and biphasic nanocomposites of many functional and multifunctional materials. Magnetoelectric (ME) material, which exhibit some magnetic and electric orders, are of great interest for memory and sensing applications. Such ME materials can be broadly divided into two categories: (i) single phase MEs and (ii) biphasic MEs. Among single phase MEs, materials like TbMnO₃ and BiFeO₃ have been well studied in the past. In this talk, structural, microstructural, and magnetic studies of bulk rare-earth chromites, such as DyCrO₃, a material with a potential of exhibiting strong ME coupling above 145 K, will be presented. In biphasic nanocomposites, concentration and connectivity of the two phases play an important role in defining their physical properties. In case of biphasic ME nanocomposite films prepared in our group, magnetic nanoparticles (NPs) were incorporated in the piezoelectric matrix in order to observe the ME coupling that is mediated through mechanical strain at their interfaces between the two phases. The detailed ferroelectric and ME properties of 3-0 type nanocomposite thin films with various concentrations of CoFe₂O₄ NPs dispersed in PbZr_0.52Ti_0.48O₃ matrix will be presented.

Hierarchical assembly of nanoparticles has become an important aspect in the field of nanotechnology for formation of hollow and porous nanostructures. Inorganic nanostructures with these geometries provide a high surface area, which is important for enhanced physiochemical properties and catalytic applications. Two-phase systems are often used for the formation of hollow nanostructures through self-assembly of nanoparticles at the interface. Inverse miniemulsions using surfactants as templates are one of such systems [1]. Individual identity of the droplets within the miniemulsion helps to obtain the independent chemical reactions within the confined space of a droplet, which results in reduced thermodynamic parameters for formation of the inorganic metal oxides. Furthermore, almost independent reactions within surfactant covered droplets lead to low aggregation of nanostructures and high surface areas in the resulting materials [2]. Parameters influencing the reactions at the interface include, among others, the type and concentration of the precipitating agent as well as of the surfactant, the molarity of the reaction precursors, and the reaction environment (i.e., temperature, pressure) [3].
In the present paper, we present our recent developments for synthesis of metallic oxide nanostructures in inverse miniemulsions and how the reaction conditions of the miniemulsions can be optimized to obtain the desired hollow and porous morphologies with high surface areas. We were able to achieve an interfacial crystallization in the case of CuO and CeO₂ systems. It is also shown how the different reaction conditions can affect the final morphology of the observed oxides. These systems can also be doped to increase the physical and chemical properties of the materials. We were also able to obtain interfacial precipitation in the case of ABO₃ type multiferroic systems such as YCrO₃ and SmCrO₃ [4]. All of the mentioned systems were characterized thoroughly to demonstrate their better electric, magnetic, and catalytic properties.
References:
[1] R. Muñoz-Espí, C. K. Weiss, K. Landfester. Inorganic nanoparticles prepared in miniemulsion. Current Opinion in Colloid and Interface Science2012, 17, 212-224.
[2] R. Muñoz-Espí, Y. Mastai, S. Gross, K. Landfester. Colloidal systems for crystallization processes in liquid phase. CrystEngComm2013, 15, 2175-2191
[3] M. Hajir, P. Dolcet, V. Fischer, J. Holzinger, K. Landfester, R. Muñoz-Espí Sol-gel processes at the droplet interface: hydrous zirconia and hafnia nanocapsules by interfacial inorganic polycondensation. Journal of Materials Chemistry2012, 22, 5622-5628.
[4] I. Singh, A. K. Nigam, K. Landfester, R. Muñoz-Espí, A. Chandra. Anomalous magnetic behavior below 10 K in YCrO₃ nanoparticles obtained under droplet confinement. Applied Physics Letters2013, 103, 182902.

Smart composite materials are attracting considerable interest in wind turbines, aeronautics and space applications due to their strength, rigidity and light weight. However, as time goes on, cracks and fractures appear in the structure of these composite materials due to thermal, mechanical, ballistic or external interventions. These cracks and fractures lead to the changes in mechanical properties and the reduction in the life time of composites. At this point, reliable and durable composite production is possible by integrating a self-healing capability into composite materials. Recently, self-healing materials are fabricated by a suitable catalyst and a healing agent. With these materials, the systems recovered their functionalities and repaired the damaged area with the healing agents, and healing catalysts embedded in the structure of nanofibers. In addition, ability of fabrication hollow structured multi-layer fibers with high specific surface area and ultra lightweight through multi-axial electrospinning process offers novel design for lightweight reinforcing agents. In the present study, it is aimed to fabricate self-healing agent filled core/shell nanofibers having three different walls via triaxial electrospinning technique. The fabrication process of multi-axial electrospun nanofibers is based on a nozzle containing concentric tubes allowing for the extrusion of different fluids to tip of the nozzle under high voltage power. Bending instabilities and whipping motions applied on polymeric jet in electric field between nozzle and collector result in the reduction of the jet diameter and this leads to the formation of fibers with diameter ranging from several nanometers to micron. This work investigates the fabrication and morphological control of multi-walled structured electrospun polymeric nanofibers by multi-axial electrospinning system. Different types of homopolymer and copolymers with different polarities were optimized for middle and outer walls of electrospun fibers. The diameter, surface morphology and layered structure of electrospun nanofibers were controlled by tailoring the solvent vapor pressure, degree of miscibility of solutions in each layer, polymer solution concentration, applied voltage, electrospinning distance, and flow rate. Hansen solubility parameters were used to systematically optimize the solvent selection for each layer and and control the degree of miscibility of layers with the purpose of tailoring the final wall morphology of nanofibers. Characterization studies were performed by Tunneling Electron Microscope, Scanning Electron Microscope, Energy-Dispersive X-ray Spectroscopy, Fourier Transform Infrared Spectroscopy, and Thermal Gravimetric Analyzer.

Nanoscale silicate platelets (NSP) in the dimensions of 100 nm x 100 nm x 1 nm were previously prepared from the exfoliation and extraction process of the naturally occurring phyllosilicate clays. The sol-gel synthesis involving tetraethyl orthosilicate (TEOS) in the presence of NSP in water yielded a three-dimensional silicate wires interconnected by NSP through covalent siloxane bonding. The optimal fraction of NSP and TEOS was essential for the formation of the novel wire networks which were characterized by using silicon nuclear magnetic resonance, transmission electron microscopy, and X-ray diffraction. Physical blending of the nanosilicate platelet-nanosilicate wire (NSP-NWS) nanohybrids in a waterborne polyurethane (PU) subsequently afforded the corresponded nanocomposites. With a 10 % loading of the nanohybrid, the nanocomposite films had a 30 % increase in the tensile strength when compared with that of the pristine PU film. The hybridized NSP with sol-gel condensation silicates could lead to a myriad of materials and structural reinforcements for new nanocomposites.

Transition metal hydroxides composed of earth abundant elements are a prominent class of electrocatalysts for alkaline oxygen evolution reaction (OER) at low overpotentials. However, it is challenging to control the structures and metal valence states of these systems, making it difficult to tune their electrocatalytic properties. Pulsed laser irradiation (PLI) of a liquid precursor is a less commonly reported approach for materials design, due to limited understanding of the laser chemistry in solution and the lack of useful materials being synthesized so far. In principle, laser irradiation can selectively induce electronic excitation, vibrational excitation and thermal decomposition of the reagent molecules, which can mediate the dynamics of chemical reactions. Due to the nature of fast reaction, non-equilibrium material growth is expected and materials with superior properties may be achieved. Controlling the laser solution chemistry has been a long-sought goal. Here we demonstrate the laser-chemical route for tailoring diverse transition metal (Ni, Co, Fe, Mn) hydroxide nanostructures in a liquid precursor solution for electrocatalysis of alkaline OER. The laser-induced hydrolysis reactions introduce a series of complex hydroxides such as [Li_xNi_0.65²⁺Mn_0.35-y²⁺Mn_y³⁺(OH)₂](NO₃)_0.19(ORO)_0.36middot;mH₂O, etc., and allow for fine control of the composition, structure, valence state and morphology of the material. Several new active OER catalysts have been identified that are with operate overpotentials less than 0.35 V under current density of 10 mA×cm^-2. Such controllable laser-chemical synthesis of complex nanostructures in liquids opens many opportunities to design other novel functional materials for advanced applications.
We performed laser synthesis experiments at Materials Sciences Division of Lawrence Berkeley National Laboratory. TEM characterization was done at 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.

Here we report the improvement of photocatalytic activity and surface plasmon ploriton (SPP) propagation length by our fabricated ultra-large single crystalline Ag microplates. The Ag microplates were synthesized by a modified HNO₃-asissted polyol reduction method, which can effectively increase the lateral size of Ag microplates from 5 mu;m to nearly 50 mu;m with highly single crystallinity. The resulting mechanism shows that the successive growth of micro-sized Ag plates is mainly contributed by the absorption of ethylene glycol (EG) reduced Ag⁰ and desorption of HNO₃ on the side (100) facets. In addition, based on these ultra-large single crystalline Ag microplates, we demonstrated two cutting-edge performances. The first one is to form a heterogeneous junction between the Ag microplates and ZnO nanowires, which provides a prominent activity of photodegradation with a figure of merit (FOM) of 1.02×10^-2 beyond the state-of-the-art of ZnO-based methods. The second one is to show farther propagation length of SPP. Due to the smaller intrinsic loss of the single crystalline Ag microplate, its propagation length is up to 11.22 mu;m under 534 nm laser excitation, which is two-fold longer than that of the E-gun evaporated Ag thin film (5.27 mu;m). In conclusion, we successfully fabricated ultra-large single crystalline Ag microplates, and expect the promising applications in photochemistry, optoelectronics and others.

Integration between sol-gel chemistry and extrusion process offers a versatile path to design on demand oxide macroscopic fibbers.[1,2]
Considering Titania, we described the generation and properties of TiO₂-based macroscopic fibers designed for the photodecomposition of volatile organic compounds (VOC).[3,4] We made use of a continuous industrially scalable extrusion process employing hybrid sols of amorphous titania nanoparticles, polyvinyl alcohol (PVA) and optionnally latex nanoparticles. This process allowed for the continuous generation of hybrid TiO₂/latex/PVA or TiO₂/PVA macroscopic fibers. Upon thermal treatment in air, we obtained biphasic porous fibers containing the Anatase phase of TiO₂ with 10-15% of Brookite. These fibers, which can be manufactured as several hundred meter of length reels, provide significantly improved phototocatalytic efficiency compared to our previous work.[3,4] Their efficiency is now comparable to the commercial Quartzel®PCO photocatalyst for gas-phase acetone mineralization.[5]
[1] Combining soft matter and soft chemistry: “Integrative Chemistry” toward designing novel and complex architectures.R. Backov. Soft Matter 2006, 2, 452.
[2]a) Designing width and texture of vanadium oxide macroscopic fibers toward controlling their mechanical and alcohol-sensing properties. H. Serier, M.-F Achard, N. Steunou, J. Maquet, J. Livage, C. Leroy, O. Babot, and R. Backov. Adv. Funct. Mat. 2006, 16, 1745. b) ZnO/PVA Macroscopic Fibers Bearing Anistropic Photonic Properties. N. Kinadjian, M.-F. Achard, B. Julián-Loacute;pez, M.Maugey, P.Poulin, E. Prouzet and R.Backov. Adv. Funct. Mat. 2012, 22, 3994
[3] Photocatalytic TiO₂ Macroscopic Fibers Obtained through Integrative Chemistry . N Kinadjian, M. Le Bechec, T. Pigot, F. Dufour, A. Bentaleb, E. Prouzet, S. Lacombe and R. Backov. Eur. J. Inorg. Chem.2012, 5350
[4] Varying TiO₂ Macroscopic Fiber Morphologies Toward Tuning their Photocatalytic Properties.
N Kinadjian, M. Le Bechec, E. Prouzet, C. Henrist, S. Lacombe and R. Backov. ACS Applied Materials sect; Interface2014, 6, 11211
[5] TiO₂ Macroscopic Fibers Bearing Outstanding Photocatalytic Properties Obtained through a Scale-up Semi Industrial Process. N. Kinadjian, M. Le Bechec, C.Henrist, E.prouzet, P. Poulin, W. Neri, S. Lacombe and R. Backov. Adv. Eng. Mat. 2014 DOI:10.1002/adem.201400327

Segmented heteronanostructures is of importance in applications including catalysis, electrocatalysis, and photovoltaics. Conventional methods often rely on molecular beam epitaxy or chemical vapor deposition techniques in order to precisely control the deposition thickness and create a lattice-matched interface. However, they are very complex and expensive. In this work, we develop a seeded growth method assisted by a mask for synthesis of segmented heteronanostructures. This solution-based approach uses silica as a mask to partially block the surface of a seed and subsequently deposits a second component on the exposed area, forming a heterodimer. In principle, additional components can be concussively deposited on either side of the heterodimers depending on the reactivity of components and ultimately form an oligomers containing desired materials at the nanoscale. The initial demonstration is carried out on the metallic system in which gold is used seed, followed by deposition of palladium or platinum on the seed to form gold-palladium and gold-platinum heterodimers. Palladium is found to spread out laterally on the seed while platinum tends to grow vertically into branched topology on gold seeds. Without removal of the silica mask, platinum can be further deposited on an unblocked palladium of the palladium-gold dimer to form a platinum-palladium-gold trimer. This method is further expanded to build metal-oxide heteronanostructures. These nanostructures that are finding tunable activity in electro-oxidation of alcohols are demonstrated. The mask-assisted seeded growth provides a general strategy for fabrication of nanoarchitectures in solution at large scale.

Powders containing metallic Al and B have attractive potential in solid fuel and hydrogen storage applications.[1, 2] However, metallic Al and B are extremely oxophyllic, leading to poor air stability. One avenue to overcome poor air stability is to alloy Al and B with other metals, such as titanium, to lower air and moisture sensitivity. Al-Ti and Ti-B alloys show decreased air sensitivity without a significant decrease in energy storage related properties.[3, 4] The synthesis of Ti-containing alloys commonly employs high temperature annealing of the base metals, high temperature solvothermal reactions, or through mechanochemical processes.[3, 5] Our approach to synthesize Ti-B composite powders is a solution-based method, utilizing sonochemical agitation at relatively low temperatures. In short, a Ti(BH₄)₃ adduct is formed from the addition of TiCl₄ and LiBH₄ in diethyl ether. The Ti(BH₄)₃ adduct is then further reduced by a catalytic amount of LiAlH₄, resulting in the formation of an amorphous powder of Ti and B. With a low temperature anneal (e.g. 150 °C), the amorphous powder is imparted with increased air stability. Future work will be focused towards developing a more comprehensive materials characterization of synthesized amorphous Ti-B powders, while assessing their capabilities in hydrogen storage and solid fuel applications. This work represents a large scale, low temperature solution-based process to attain promising Ti-B composites for energy storage applications.
[1] E. L. Dreizin, "Metal-based reactive nanomaterials," Progress in Energy and Combustion Science, vol. 35, pp. 141-167, Apr 2009.
[2] X. Fan, X. Xiao, L. Chen, X. Wang, S. Li, H. Ge, et al., "High catalytic efficiency of amorphous TiB₂ and NbB₂ nanoparticles for hydrogen storage using the 2LiBH₄-MgH₂ system," Journal of Materials Chemistry A, vol. 1, pp. 11368-11375, 2013.
[3] M. Schoenitz, E. L. Dreizin, and E. Shtessel, "Constant volume explosions of aerosols of metallic mechanical alloys and powder blends," Journal of propulsion and power, vol. 19, pp. 405-412, 2003.
[4] A. Epshteyn, B. L. Yonke, J. B. Miller, J. L. Rivera-Díaz, and A. P. Purdy, "Sonochemically generated air-stable bimetallic nanopowders of group 4 transition metals with aluminum," Chemistry of Materials, vol. 25, pp. 818-824, 2013.
[5] L. Chen, Y. Gu, Y. Qian, L. Shi, Z. Yang, and J. Ma, "A facile one-step route to nanocrystalline TiB₂ powders," Materials research bulletin, vol. 39, pp. 609-613, 2004.

Highly efficient, reproducible and scalable approaches for the exfoliation, processing and assembly of MoS₂ are critical for emerging electronic and energy applications. Additive free techniques, such as solvent assisted exfoliation, offer numerous advantages, including the potential to minimize chemical modification of the layer and the resultant introduction of opto-electronic defects. The mechanism of exfoliation and the role of the organic solvent, such as N-Methyl-2-pyrrolidone (NMP), however is not well understood. Based on systematic variation of solvent moisture content, environment (N₂/Air) and processing conditions (sonication time and centrifugation speed), we confirm that MoS₂ exfoliation in NMP is substantially enhanced by the in-situ formation of organic reductants during the sonication process. Oxidative by-products (5-hydroxy-N-methyl-2-pyrrolidone / N-methylsuccinimide) of NMP are redox active to transition metals, resulting in the formation of negatively charged MoS₂ layers and their subsequent electrostatic stability in solution. Higher NMP moisture content corresponds to more efficient exfoliation. Likewise, inert atmosphere (N₂) and no moisture are not suitable for exfoliation. The underlying exfoliation mechanism and reactivity of the solvent were confirmed by multiple characterization techniques, including GC-Mass, XPS, UV-Vis, Raman, and PL spectra as well as HR-TEM and AFM images. The identification of the role of organic reductants in the solvent-assisted exfoliation of MoS₂, and the recognition that MoS₂ exfoliation in NMP is more complex than surface energy equivalence, provides new routes to tailor transition metal chalcogenide exfoliation and control the layer defect structure for organic solvent -based opto-electronic inks.

New forms of silicon such as nanocrystalline or amorphous materials as well as novel allotropes attract increasing attention in current research. Such Si materials are of special interest in the search for better anode materials in Li ion batteries due to the tenfold increased theoretical capacity when compared to the commercially used graphite. Li₁₅Si₄ and amorphous Si have been shown to form during the charging and discharging processes.
In addition, new forms of silicon are examined as semiconducting materials, i.e. in transistor and photovoltaic technologies, potentially allowing improvements of performance and scalability. Zintl phases constituted of alkaline or alkaline earth metals and silicon or germanium are versatile precursors for such materials. The Zintl phase Li₃NaSi₆ which contains polyanionic silicon layers separated by alkaline metal cations is said to yield an allotropic form of Si in a topotactic reaction.^[1]
In order to chemically emulate the delithiation of Li₁₅Si₄ in Li ion batteries and to further investigate the formation and structure of so-called allo-Si from Li₃NaSi₆, we subjected these Zintl phases to chemical extraction of the alkaline metal component by liquid ammonia and ethanol, respectively. After washing we obtain black powders of amorphous silicon from both reactions. The products termed a-Si (from Li₁₅Si₄) and a-allo-Si (from Li₃NaSi₆) crystallize to α-Si at very different temperatures in DTA measurements of around 660°C and below 570°C, respectively. Using several different characterization techniques, we find (i) a porous microstructure for a-Si built from spherically shaped particles with sizes around 10 nm, (ii) partial surface oxidation of both materials and (iii) the presence of nanocrystalline Si in both materials. In addition, we can attribute the unexpectedly varying crystallization behavior of the two amorphous Si materials to differing concentrations of sub-Bragg nanocrystals.
The result of the protic oxidation of Li₃NaSi₆ to an amorphous product a-allo-Si is at variance with earlier findings reporting the formation of a crystalline allotrope of Si (allo-Si). Using quantum chemical calculations, we demonstrate that such a topotactic reaction as in the formation of allo-Ge from Li₇Ge₁₂^[2,3] is energetically highly unfavorable in the case of silicon. In addition, we can explain the published powder patterns of “allo-Si” with an NbSi₂ impurity which most likely stems from the synthesis of the precursor phase Li₃NaSi₆. We therefore conclude that the postulated bulk material allo-Si is not accessible from Li₃NaSi₆.
[1] von Schnering, H. G.; Schwarz, M.; Nesper, R. J. Less-Common Met. 1988, 137, 297.
[2] Kiefer, F.; Karttunen, A. J.; Döblinger, M.; Fässler, T. F. Chem. Mater. 2011, 23, 4578.
[3] Zaikina, J. V.; Muthuswamy, E.; Lilova, K. I.; Gibbs, Z. M.; Zeilinger, M.; Snyder, G. J.; Fässler, T. F.; Navrotsky, A.; Kauzlarich, S. M. Chem. Mater. 2014, 26, 3263.

Electrospinning is an efficient technique for fabrication of very thin, long and narrow diameter polymer nanofibers with potential applications in designing sensors. In our work, we demonstrate the effect of process parameters on nanofibers alignment both theoretically and experimentally. However, complexity of the process poses additional challenges in controlling the fiber length and diameter and distribution of nanofibers on substrates. The random distribution is due to bending and whipping instability in the jet arising from the solvent evaporation prior to collection. We investigated the effect of auxiliary electric field on jet stability. It was observed that the magnitude of auxiliary electric field dictates the nanofiber density and distribution/alignment. Another disadvantage is the need for high voltages (>20kV) to spin continuous polymer nanofibers. The presence of auxiliary electric field overcomes this challenge and continuous polyaniline nanofibers of uniform density and diameter was obtained with applied voltage of ±5 kV. The electro-spun nanofiber morphology was characterized using scanning electron microscopy (SEM). The fiber density decreased with decreasing field strength and increasing collector distance. The crossbar microelectrode pattern at the collector resulted in directed assembly of polyaniline nanofibers. These fibers were used as acting sensing area for detection of biological analyte, troponin-T, cardiovascular biomarker for early diagnosis. The interaction of biomolecules at electrically active area modulates the charge transport at the junction due to the surface charge associated with it. The net change in electrical signal can be measured either as change in diode current/source-drain current based on device architecture. The voltammetric current response of this nanodevice was measured between-2V and 2V. Experimental results suggest sensitivity of device for detection of troponin-T at 1 pg/mL.

Ensembles of free-standing two-dimensional (2D) materials, such as graphene, metal and semiconductor nanosheets have attracted great interest for their unique properties. Here we report the synthesis of Hanoi Tower-like multilayered Pd nanosheets via a rationally-designed synthetic route.¹ The synthesized Pd sheets have a unique multi-layered structure interconnected through a shared central core. Their atomically thin layers preferentially grow along <110> directions, forming continuum {111} surfaces as characterized by transmission electron microscopy (TEM) and atomic force microscope (AFM) techniques. The Pd layers are as thin as several angstroms, which is at the unit cell length of Pd and may only contain one single twinning defect. These layers are the thinnest possible Pd nanostructure that can tolerate multiple planar defects. Further characterization shows various inter-layer rotational mismatches, strongly correlated with the surface electronic structures. We propose a new anisotropic growth mechanism for the Pd nanosheets involving a Pd complex intermediate, Pd₄(CO)₄(CH₃COO)₄, identified via x-ray single crystal diffraction.² This mechanism was supported by density functional theory (DFT) calculation of adsorption energy of Pd intermediate complex on Pd low index surfaces.¹ DFT calculation shows that the adsorptions of Pd₄(CO)₄(CH₃COO)₄ is preferred over that of CO on Pd(110), and less favored than CO adsorption on Pd(111). This result agrees with the anisotropic shape of Pd(111) nanosheets. The mechanical properties of the multilayered Pd nanosheets are studied by nanoindentation and AFM force curve experiments. The multilayered structure of Pd nanosheets shows more compliance than bulk Pd upon exposure to applied force.
(1) Yin, X.; Liu, X.; Pan, Y.-T.; Walsh, K.; Tsao, K.-C.; Yang, H. Nano Lett.2014.
(2) Yin, X.; Warren, S. A.; Pan, Y.-T.; Tsao, K.-C.; Gray, D. L.; Bertke, J.; Yang, H. Angew. Chem., Int. Ed.2014. DOI: 10.1002/anie. 201408461.

Wet-chemical synthesis is a promising alternative to the conventional vapor-phase method owing to its advantages in commercial-scale production at low cost. Studies on nanocrystallization in solution have suggested that growth rate is commonly affected by the size and density of surrounding crystals. However, systematic investigation on the mutual interaction among neighboring crystals is still lacking. Here, we report on strong interactive growth behaviors observed during anisotropic growth of ZnO hexagonal nanorods arrays. In particular, we found multiple growth regimes demonstrating that the diameter of the rod is dependent on its height. Local interactions among the growing rods result in cases where height is (i) irrelevant to the diameter, (ii) increased with increasing diameter or (iii) inversely proportional to the diameter. These phenomena originate from material diffusion and the size-dependent Gibbs-Thomson effect that are universally applicable to a variety of material systems, thereby providing bottom-up strategies for diverse three-dimensional nanofabrication.

Micro- and nanolithography techniques are a key factor in pushing the limits of science and technology. This is especially true in the semiconductor industry which has made remarkable progress over the last 20 years. With the technology focus moving to progressively smaller scale, numerous lithography methods of manufacturing complex micro- and nanostructures (such as photo, nanoimprint, e-beam, soft and focused ion beam) have been developed. However, most of these techniques have limitations in the form of material choices, speed, cost and/or pattern shape/size. Clearly a fast, low-cost and versatile method of producing high quality surface nanostructures is needed.
Here, an approach that offers low-cost, fast manufacturing of complex patterns over large scale is presented. By utilizing existing and well known technology such as the optical disc drive and combining it with tools used in photolithography a novel manufacturing technique is made available. The method proposed can be used to directly scribe the desired pattern on the light sensitive material or create a master to be used for transferring a pattern to the appropriate material. In all cases the procedure is similar. First, the desired motif is drawn on a computer using any drawing program. Second, a label enabled media such as lightscribe or labelflash DVD is coated with the material to be inscribed (e.g. photoresist to create a master). The disc is then inserted in the appropriate labeling disc drive and the pre-drawn image is engraved in material/photoresist. If necessary the disc can be treated post-scribing to create the structures; e.g. develop the photoresist. Finally, the surface of the material is engraved with the predetermined pattern.
The method described here represents an affordable, fast and versatile way of manufacturing complex micro- and nanostructures without some of the design, throughput and material limitations faced by costlier techniques, making state of the art research more affordable and accessible.

Stability of nanofluids is one of the critical assessments for the efficient systems that the solid content of nanofluid should be stable and well dispersed for longer time. Production of a homogenous dispersion is real technical challenge due to strong van der Waals attraction among the nanoparticles, which preferring the formation of aggregates. Stable nanofluids can be achieved via recommended physical and chemical treatments such as addition of additives and surfactants, surface-active agents to disperse hydrophobic materials, adjusting the pH value to provide electrochemical stability.
Detailed investigations were carried out to identify the stability parameters, dispersion methods, application requirements, experimental investigation to determine the stability of nanofluids. Aluminum oxide (Al₂O₃), titanium oxide (TiO₂) and cerium oxide (CeO₂) were selected for these studies. Custom designed stability measurement setup was used to record the sedimentation rate. Aging test was performed in the heat transfer coefficient (HTC) setup to determine the erosion and corrosion properties. Thermal cycling was performed up to 80 ^oC with maximum heating cycles of 500 times. Dynamic light scattering (DLS) used to estimate the aggregate size before and after the thermal cycling and aging test. Results from the time depended DLS measurements, sedimentation rate and aging effects presents that Al2O3 nanofluids have better performance.

The printed electronics have attracted substantial interest as advanced alternatives to conventional photolithography due to its simple and environment-friendly process. However, for the real applications of printed electronics, there are several issues to be resolved. One of the important issues is the development of appropriate conductive inks. Currently, copper nanoparticles-based inks were employed because of its outstanding electrical properties (1.72 mu;Omega;#12685;cm) and low cost. However, copper nanoparticles are easily oxidized in room temperature. The oxidation of copper makes it difficult to sinter the nanoparticles during sintering process. Also, the pores between sintered copper nanoparticles inevitably yield low-electrical conductivity of films. For this reason, in this work, the bimodal sized copper nanoparticles ink was investigated. To fabricate the ink, the two different sizes of copper nanoparticles (40 nm and 70 nm each in diameter) were mixed with various ratios. For the sintering method, flash light sintering was employed because it can sinter the copper nanoparticle in milliseconds in room temperature and under ambient condition. Using this method, the sintering characteristics with respect to various irradiation conditions (irradiation energy density, pulse number, on-time, and off-time) were investigated. The morphology and crystal phase of flash light sintered copper ink was characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) technique. In addition, the sheet resistance of sintered copper film was measured using a four-point probe method and the thickness of sintered copper film was measured using an alpha step. From these results, it was found that optimal ratio of 40 nm to 70 nm of copper nanoparticles was 25:75 wt% which has the resistivity of 15 µ#8486;#12685;cm with smallest pores and damages on the polymer substrate.

Colloidal silica is used in many technologies like high temperature binder, carbonless paper, catalyst, and an abrasive for polishing silicon wafers. Generally, colloidal silica is suspended in an aqueous phase that is stabilized electrostatically. However, the dispersion stability is not ensured in acidic region since the IEP of colloidal silica is about 2.5. So we synthesized the colloidal silica which has high negative charge of its surface in acidic region. For mono-dispersed silica particle, we used means of hydrolysis of alkyl silicates and condensation of silicic acid in alcoholic solutions. In addition, Aluminum ion is used to control the surface charge of colloidal silica in acidic region. The aluminum ion has the formation of ortho-sialate molecule with silicon ion and becomes tetra-valent with an additional negative electrostatic charge. Furthermore, we could change the ratio of ion exchange between silicon and aluminum by different temperature. So we can control the degree of electrostatic charge of silica surface. These results suggest that we can assure the dispersion stability of colloidal silica in all pH ranges and enhanced dispersion stability could be applied for many applications.

In this paper, we present our recent progress in the synthesis of various rare-earth doped oxide ceramic powders for high power fiber lasers attractive for directed energy weapons applications. First, we discuss our recent research effort in developing crystal fibers for high power single frequency fiber lasers. High quality rare earth doped transparent ceramics such as Yb³⁺ or Ho³⁺ doped Lu₂O₃ have been first fabricated using high purity nano-powders synthesized in house by co-precipitation method. Single crystal fibers with diameters as small as 35mu;m, for the first time to our knowledge, have been successfully drawn using these ceramics as feed rods by the Laser Heated Pedestal Growth (LHPG) process. The optical, spectral and morphological properties of the crystal fibers are presented. In the second part of this paper, we report the synthesis of Er-doped Boehmite nano-particles (Er:AlOOH) in a high pH solution using automated titration system. These nano-particles are dispersed in a solvent and then doped in-situ into the silica soot core of the preform. The nano-particle structure is chemically engineered so that the rare-earth ion is encased in a cage of aluminum and oxygen ions to prevent ion-ion proximity and energy transfer. The preforms have been drawn into fibers with excellent optical qualities and high laser efficiencies

For this study, lead molybdate (PbMoO₄) microcrystals were prepared by the co-precipitation method and processed using a conventional hydrothermal method at 100 C for 10 min with polyvinyl alcohol (PVA) as the capping agent. These microcrystals were structurally characterized by X-ray diffraction (XRD) and micro-Raman spectroscopy, and their morphol- ogy was investigated by field-emission gun scanning electron microscopy (FEG-SEM). The optical properties were analyzed by ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns and MR spectrum indicate that the PbMoO₄ microcrystals have a scheelite-type tetragonal structure. FE-SEM images reveal that the PVA promotes the aggregation of several octahedrons and the formation of large porous stake-like PbMoO₄ microcrystals which are related to the oriented attachment growth process. Moreover, the effect of the capping agent hinders the growth of a large amount of micro-octahedrons which can be verified with by several nanocrystals on large crystals. Intense green PL emission was observed at room temperature for PbMoO₄ microcrystals which are related to structural defects at medium range and intermediary energy levels between the valence band (VB) and the conduction band (CB). Photocatalytic activity was observed for PbMoO₄ as a catalyst in the degradation of the rhodamine B (RhB) dye, achieving total degradation after 90 min under UV-light.

There has been a tremendous surge in the development of lanthanide-tetrafluoride nanocrystals over the past decade due to their wide-ranging applications, which include biomedical imaging, targeted photodynamic therapy, environmental decontamination, lighting and display technologies, solar energy capture, telecommunications, and security signatures. A major obstacle to the commercialization of these materials has been the lack of a safe, low-cost, versatile, and scalable synthetic method. This report describes the development of a one-pot ionothermal reaction that directly yields β#8209;phase upconversion phosphors from a polyol-based deep eutectic solvent (DES) at atmospheric pressure.
DESs constitute an emerging sub-class of ionic liquids, many of which are composed of renewable and recyclable components. In this work, 396 different DESs were screened, and 28 DESs were used for the preparation of nanocrystals. From these candidates, a single DES was downselected for its beneficial structure-directing effects on the particle size, crystallinity, and brightness of upconverting nanocrystalline phosphors. Specifically, ethylene glycol/choline chloride was used in a 3:1 molar ratio to prepare submicron particles of β-NaYF₄, β-NaGdF₄, and β-NaYbF₄. The particles were all in the range of 100-600 nm, depending on the particular composition. It was discovered that the use of this solvent permitted a substantial reduction in excess of fluoride ion required to direct β#8209;phase formation in the polyol-only control synthesis. Consequently, the reaction pressures were reduced to the point where lined glassware could be safely used to conduct the synthesis.
Doped phosphors, based on the β-NaYF₄ host, exhibited exceptional upconversion brightness when stimulated with a 980 nm laser source. For example, β-NaY_0.78F₄:Yb_0.2,Er_0.02 prepared in DES was more than one order of magnitude brighter than the same composition prepared in ethylene glycol. The intensity of the crystalline X-ray peaks was comparable or better using DES. Following the screening reactions, a 400 g batch of phosphor was prepared in 25 L of DES at 160°C. No special precautions were taken to protect the reaction from moisture or oxygen. The product is easily dispersed in polar solvents, including water, without further modification. It is concluded that the ionothermal synthesis method is a promising new technique for producing luminescent materials at large scales under mild conditions.

In the food packaging industry, bactericidal agents that preserve the quality and safety of food and, at the same time be harmless to the humans, are required. A very promising candidate that fulfills those two requirements are Zn- and Mg-based oxides; however, the potential synergy between these two oxides has not been evaluated in detail yet. Accordingly, the present work focuses on the polyol-mediated synthesis of zinc oxide (ZnO) nanoparticles, pure and doped with Mg species, and their corresponding structural and optical characterization. The synthesized samples were characterized via X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), ultraviolet visible (UV-vis) spectroscopy and photoluminescence (PL) techniques. The Standard Plate Count was used to assess the bactericidal properties of the nanoparticles at different concentrations. The capacity of the Zn-Mg oxides to generate single oxygen (SO) species was also evaluated. XRD information evidenced the formation of ZnO-wurtzite; no diffraction peaks corresponding to isolated Mg-phases were detected that would suggest the actual incorporation of Mg species into the host oxide lattice. The average crystallite size of the Mg-Zn oxide nanocrystals was estimated in the 6nm - 7nm range. FT-IR measurements confirmed the formation of the oxide with a clear Metal-Oxygen band centered on 536 cm^-1; other bands associated to the functional groups of polyol by product were also observed. These adsorbed species would have generated a net surface charge on the particles surface inhibiting their aggregation. A slight shift in the exciton peak of UV spectrum suggests a change in the particle size with the dopant addition. The effect of particle composition (i.e. doping level) on the corresponding generation of SO and bactericidal capacity will be presented and discussed.

The optimization of the figure of merit of thermoelectric materials requires the simultaneous control of the material&’s composition and microstructure. Assembly of nanoparticles obtained by a solution route is an attractive bulk fabrication method because size and shape of the nanoparticles can be tuned by variation of the synthesis conditions. Recently, new synthetic pathways were reported among which reducing agent assisted surfactant free processes. We report here the evaluation of this method for the synthesis of Bi₂Te_xSe_3-x alloyed nanoparticles with varying selenium concentrations. X-ray diffraction studies conducted on powder and pellet samples show that two alloyed phases are present in the sample even at low selenium content. The careful study of the position of the diffraction peaks as function of the formulation shows that this behaviour could arise from the difference in reactivity of selenium and tellurium. Moreover, the electrical conductivity of the samples is shown to increase upon selenium addition while the Seebeck coefficient is reduced. Power factor shows an optimum value around 20% selenium content with a large tolerance in composition.

Porous nanostructures find great potential and practical applications in bio-medicine, catalysis, gas storage and separation, electrode, and etc. Ordered porous nanomaterials with known pore size, which enable accurate control over the reactions happened inside the pores, are becoming one of the most popular and important research areas. Designed channels in these ordered porous nanomaterials provide selective absorption and storage for expected molecules or materials in the applications such as drug delivery, gas separation and storage, water purification and so on. And furthermore these expected molecules or materials enter and contact with the core where active reaction centers or functional materials maybe imbedded, so that only expected reactions happen, which is a hot topic in catalysis.
Metal-organic Frameworks (MOFs), composed of metal ions and one or more organic linkers, possess unique advantages over others and become one of the most interesting ordered porous materials. E.g. diverse pore size can be achieved by selecting certain length of organic linker. The hydrophilicity can be also tailored by altering the functional group on the organic linker. Most importantly, the pores are elastic, which provides controlled manner of loading and unloading of molecules or drugs though variation of pH, temperature or other external drives. Therefore, MOFs are attracting more and more attention and are widely studied in diverse research fields and applications. Especially in the biomedical applications, MOFs are considered as one of the most promising materials. Moreover, some iron and zinc based MOFs with less or no toxicity concern find improved drug loading properties with potential application to be used as drug delivery vehicles.^1-3
However, conventional synthesis always results in large sized crystals with poor size and morphology control and hinders them from biological applications. And the post-synthesis modification (PSM) for improved dispersion and bio-compatibility also remains challenging for most of the MOFs.
In this communication, we detail an improved synthesis of monodispersed sub-100 nm ZIF-90 nanoparticles. To demonstrate their potential application for biomedicine, MRI contrast agents were loaded during the synthesis. Furthermore, the as synthesized MOFs hybrids were successfully modified and conjugated with BSA to improve their dispersion and bio-compatibility.

The management of nuclear waste is a great challenge faced by the nuclear industry. Glass has been considered a high-level radioactive waste immobilization matrix; however, several researches have shown that crystalline ceramics are a better matrix compared to glass owing to their chemi-mechanical durability. CaTiO3(perovskite) is one of the crystalline hosts for the disposal of HLW because it can immobilize Lns (La, Gd, Ce and Sr) by forming completely solid solutions. In this study, the combustion process was applied to form a solid solution of Gd and Ce doped CaTiO3. In addition, the synthesized powders were characterized through XRD, SEM, TEM, and BET. The combustion process using the Ca and Ti-nitrates form as starting materials was proven to be a simple approach for preparing a solid solution of Lns (Gd and Ce) into a perovskite structure (ABO3) for immobilizing the radioactive elements of high-level radioactive waste.

Methods for the bulk fabrication of vanadate nanoscrolls and vanadate nanopeapods have been developed. For the nanoscrolls, a modified solvothermal synthetic approach has been applied for the rapid fabrication of V₂O_5-x nanoscrolls using vanadium pentoxide as the vanadium source and dodecylamine as the structure-directing agent. The synthesis parameters could be scaled up to produce as much as 8 grams of product per synthesis. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used to investigate the structure and morphology of the obtained nanoscrolls. With respect to the nanopeapods fabrication, two distinct synthetic strategies, solvothermal and solvent evaporation, were utilized. Reactions with silver nanoparticles led to the formation of vanadate-based nanopeapods in which silver particles are positioned inside the hollow space of the nanoscrolls. XRD and TEM were used to investigate the internal structure and the formation mechanism. Our versatile synthetic approach can also be used to encapsulate a wide variety of other nanoparticles inside the V₂O_5-x nanoscrolls. Advanced nanoarchitectures with well-designed encapsulation of distinct nanoparticles into nanoscrolls, along with controlled synthesis are very promising. They are expected to show novel properties arising from both the intrinsic behavior of the assembled nanoparticles and the interaction between the nanoparticles within the peapod assemblies

Vanadium oxides are among the centerpieces in modern semiconductor electronics and device applications. The occurrence of metal-insulator transition in the vicinity of room temperature for VO₂ makes it one of the most demanding materials for switching and FET based devices applications . Efforts are on to synthesize VO₂ on a large scale employing an easy and cost-effective technique.
VO₂ crystallizes in P2₁/C space group at room temperatures with lattice parameters a= b= c= α= β= γ=. The phase stability of different oxides is a function of temperature and oxygen partial pressure. Precise control of synthesis parameters is required in stabilizing pure phase in bulk as well as thin film form. This study focuses on the novel large scale two step synthesis of VO₂ using Solution Combustion Synthesis . This involves synthesis of product utilizing redox reaction between metal nitrate and suitable fuel. Generally the products are nanocrystalline in nature due to self propagation of the exothermic combustion reaction. First step involved the synthesis of V₂O₅ by combustion reaction between Vanadyl nitrate and urea. In the second step, the as-synthesized V₂O₅ has been reduced by a novel reduction technique to form monophasic VO₂. This involves inert atmosphere like nitrogen saturated with hydrocarbon vapors. X-ray diffraction was used to investigate the monophasic nature, lattice parameters and crystallite size. Morphology of the synthesized powders was found to be plate like and bimodal using SEM with their sizes varying between 70 nm and 2 µm. Particle size measured using SEM matched with the crystallite size measured using XRD. A four-probe electrical resistivity set up was built in-house and variation in the metal-insulator transition temperature of VO₂ was investigated using the same. This showed that the electrical resistance R followed log (R) α T over the temperature range.

Noble-metal nanocrystals are essential to applications in a variety of areas, including catalysis, electronics, and photonics. Despite the large number of reports, there still exists a gap between academic studies and industrial applications due to the lack of ability to produce the nanocrystals in large quantities while still maintaining the good uniformity and precise controls. Since the nucleation and growth of colloidal nanocrystals are highly sensitive to experimental conditions, it is impractical to scale up their production by simply increasing the reaction volume. Here we report a new and practical approach based on milliliter-sized droplet reactors to the scalable production of nanocrystals. The droplets of 0.25 mL in volume were produced as a continuous flow in a fluidic device assembled from commercially available components. As a proof of concept, we have synthesized Pd, Au, and Pd-M (M = Au, Pt, and Ag) nanocrystals with controlled sizes, shapes, compositions, and structures on a scale of 1minus;10 g per hour (e.g., 3.6 g per hour for Pd cubes of 10 nm in edge length).

Lanthanide-doped inorganic nanocrystals, so called nanophosphors, show unique optical properties such as relatively long life time, sharp peak emission, large Stokes shift compared with conventional organic dyes and quantum dots. While most nanophosphors show downshift and downconversion process, some nanophosphors show upconversion (UC) luminescence. A pair of Yb³⁺ and Er³⁺ is known as dopants for green UC luminescence. In a point of view of host crystal, fluoride materials can be good host materials due to their intrinsically low lattice phonon energy. In this study, the LiGdF₄, which was previously used as a host material for efficient quantum cutting phosphor, was adapted as a host material for UC nanophosphors.
The Yb³⁺ and Er³⁺ doubly-doped LiGdF₄ nanophosphors were synthesized via solution chemical route and they showed green UC luminescence under the irradiation of 980 nm near infrared (NIR) light. When we doped Y³⁺ into Gd³⁺ sites, particle morphology and size were changed. When there was no Y³⁺ doping, orthorhombic GdF₃ phase was formed and the synthesized nanophosphors showed rhombic plate shape. As Y³⁺ concentration increased, tetragonal LiGdF₄ phase was developed and the nanophosphors showed tetragonal bipyramidal morphology. The UC tetragonal bipyramidal nanophosphors were formed by exposure of {101} planes which are the most stable crystallographic planes. The crystal structure was analyzed with X-ray diffraction and scanning transmission electron microscopy. The Y³⁺-doped LiGdF₄:Yb,Er nanophosphors showed bright green UC luminescence peaking at 551 nm under 980 nm NIR light. The Y³⁺ doping also affected on particle size and high Y³⁺ concentration induced small size. When 60% Y³⁺ was doped into the nanophosphor, ultrasmall size of ~10 nm was obtained. These UC luminescence and ultrasmall size of the nanophosphors will be advantageous for bio-imaging applications.
In summary, bright green-emitting LiGdF₄:Yb,Er-based UC nanophosphors with single tetragonal phase were synthesized via Y³⁺ doping. The Y³⁺ doping affected phase, morphology, and size of the UC nanophosphors. The LiGdF₄:Yb,Er-based tetragonal bipyramidal UC nanophosphors showed intense green light under the excitation of 980 nm NIR light and they can be a promising agent for bio-imaging.

Bismuth (Bi) codoped Sr₄Al₁₄O₂₅:Eu,Dy long afterglow phosphors were obtained by a combustion synthesis method, and a post-annealing process in reductive graphite atmosphere. The Bi codoping molar concentrations were x = 0.0, 0.5, 3.0 and 12.0 mol% Bi₂O₃. Structural, morphological and luminescent characterizations were performed by means X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy, respectively. Photocatalytic evaluation of the powders was made by monitoring the blue methylene degradation under UV light irradiation at 365 nm. XRD analysis showed a single orthorhombic phase Sr₄Al₁₄O₂₅ even for higher Bi codoping concentrations, suggesting Bi ions are well incorporated into the host lattice. SEM micrographs show irregular micro grains with sizes in the range of 1-100 µm. Intense greenish-blue fluorescence and persistence emissions with a typical peak at lambda;= 495 nm were observed, and attributed to the 5d-4f allowed transitions of Eu²⁺. Absorption analysis indicates that the Bi codoping increases absorptions in both UV and visible, from 240 nm up to 450 nm. Degradation of methylene blue was monitored by the decrease of its 665 nm absorption peak under constant UV light (365 nm) irradiation. Complete methylene degradation is reached after 390 min by utilizing the 12.0 mol% Bi₂O₃ codoped sample. In summary, the Bi codoping enhances the photocatalytic activity whereas also inhibits the photoluminescence intensity. A detailed explanation of this effect is described as a function of the Bi induced traps within the Sr₄Al₁₄O₂₅ host lattice.

Energy storage materials often involve chemical reactionswith bulk solids. Porositywithin the solids can enhance reaction rates. The porosity can be eitherwithin or between individual particles of the material. Greater control of the size and uniformity of both types of pore should lead to enhancements of charging and discharging rates in energy storage systems. To control both particle and pore size in nanoporous palladium (Pd)-based hydrogen storage materials,we have first created uniformly sized copper particles of about 1 mu;mdiameter by the reduction of copper sulfate with ascorbic acid. In turn, these were used as reducing agents for tetrachloropalladate in the presence of a block copolymer surfactant. The copper reductant particles are geometrically self-limiting, so the resulting Pd particles are of similar size. The surfactant induces formation of 10 nm-scale pores within the particles. Some residual copper is alloyed with the Pd, reducing hydrogen storage capacity; use of a more reactive Pd salt can mitigate this. The reaction is conveniently performed in gram-scale batches.
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 DEAC04-94AL85000.

Due to their low fabrication costs, and uniquely tunable electronic structures and optical properties, semiconductor nanocrystal quantum dots (QDs) are among the most versatile of solution-processed materials for optoelectronic devices. Over the past several years, there have been particularly rapid advances in QD-based solar cells and light-emitting diodes, applications with immense potential impact on energy consumption, and consequently on the health of the environment, both locally and globally. Paradoxically, the most successful devices in both of these categories are based on QDs made with toxic and highly-regulated (e.g., RoHS) heavy metals, specifically lead and cadmium, respectively. Although responsible manufacturing, use and disposition of electronic products can likely minimize the environmental impact arising from their toxic (but stable) constituents, a better solution would be to find alternative materials that can offer the same performance without heavy metals.
With size- and composition-tunable band gaps spanning the ideal energy ranges for both solar energy capture and solid-state lighting, QDs based on I-III-VI semiconductors, including alloys such as CuInSe_xS_1-x (CISSe), are an intriguing candidate replacement material for use in these and other applications. This presentation will describe the synthesis and optimization of CISSe QDs, and discuss the latest developments in their incorporation into various classes of photovoltaic and light-emitting devices.

Over the last few decades the synthesis of monodisperse, size- and shape-controlled metal nanoparticles (NPs) has become one of the major goals in nanosciences.¹ Interest was shown toward these nano-sized structures since they form a class of materials with properties distinctly different from their bulk and molecular counterparts.² Consequently, metal nanoparticles found numerous applications, notably in the field of catalysis.^{3, 4}
Ever-increasing interest toward the synthesis of these nanometric species evolved the last period. The organometallic approach starting from olefinic precursors allows the synthesis of nanoparticles of uniform small size (1-3 nm) and of clean surface in mild conditions, which can be stabilized by polymers or ligands.^{5, 6}
Here in, we will present the synthesis of spherical, ultra small and monodisperse Rhodium nanoparticles synthesized from [Rh(C₃H₅)₃] precursor. The size of these NPs is controlled by a suitable quantity of different phosphines as stabilizing ligands as well as their deposition on iron core modified silica support. Characterizations in terms of morphology and surface state have been performed. The activity of these systems has been investigated as nanocatalysts in hydrogenation and hydroformylation of model alkenes and arenes showing high activity under mild conditions.
References:
1) Tuchscherer, A.; Packheiser, R.; Rüffer, T.; Schletter, H.; Hietschold, M.; Lang, H.Eur. J. Inorg. Chem. 2012, 2251
2) Moshfegh, A. Z. J. Phys. D: Appl. Phys. 2009, 42, 233001
3) Noeuml;l, S.; Léger, B.; Herbois, R.; Ponchel, A. ; Tilloy, S. ; Wenz, G.; Monflier, E. Dalton Trans. 2012, 41, 13359
4) N. Yan, C. Xiao and Y. Kou, Coord. Chem. Rev. 2010, 254, 1179.
5) Amiens, K.; Chaudret, B.; Ciuculescu-Pradines, D. ; Colliére, V. ; Fajerwerg, K. ; Fau, P. ; Kahn, M. ; Maisonnat, A. ; Soulantica ; K. ; Philippot, K. NewJ.Chem., 2013, 37,3374.
6) Philippot, K. .; Chaudret, B. C. R. Chimie, 2003, 1019-1034

Graded, hierarchically porous materials are becoming increasingly important for catalysis, separation, and energy applications due to their high mass transport properties and high surface area. Here we present the one-pot synthesis of hierarchical structures from the co-assembly of block copolymer and organic additives to form graded all-organic structures featuring macro- and mesoscopic pore sizes. Furthermore, heating up to 1100 °C under an inert environment converts the graded membranes into amorphous carbon materials. Metal nanoparticles (such as nickel and platinum) can be added into the one-pot synthesis to form well-dispersed metal nanoparticles throughout the carbon structure for potential catalytic applications.

Hollow micro-/nano-structures have recently gained tremendous interest because of their great potential in various applications such as catalysis, drug delivery, gas sensor, energy conversion and storage systems. There have been great successes on developing effective methods for the synthesis of hollow structures including hollow spheres, cubes and one-dimensional (1D) micro-/nanotubes. However, most of these reported hollow structures are relatively simple. Hollow structures with higher complexity in terms of structure and composition are anticipated to offer exciting opportunities for both fundamental studies and practical applications. As an example, multi-shelled hollow structures are shown to exhibit enhanced lithium storage and gas sensing performance compared to simple hollow structures. With this interest, researchers worldwide have recently devoted rapidly increasing efforts on the rational design and synthesis of complex hollow structures. In particular, tubular structures could be regarded as special hollow structures that might inherit the benefits from both hollow and 1D structures. Despite the great advances on complex hollow structures with isotropic architectures, it appears less developed for the fabrication of 1D complex hollow structures. Therefore, it will be highly desirable to develop a simple but general strategy to effectively synthesize novel 1D hollow structures with high complexity for different functional materials.
In this work, we have developed a template engaged effective strategy for general synthesis of complex tubular structures for various metal oxides, including binary Mn₂O₃, Co₃O₄, NiO, Fe₂O₃ and ternary CuCo₂O₄, ZnCo₂O₄, CoMn₂O₄, ZnMn₂O₄, MnCo₂O₄, NiCo₂O₄. The formation process of the novel tube-in-tube structure is proposed and could be described as: First, the carbon nanofibers (CNFs) are dispersed in ethylene glycol (EG) with different metal acetates precursors. After refluxing at an elevated temperature, a layer of metal-glycolate (MG) can be uniformly grown on the surface of the CNFs to form a CNF@MG hybrid structure. Second, the complex tube-in-tube structure can be spontaneously formed during the thermal annealing treatment of the CNF@MG composites in air because of two different actions towards opposite directions during the decomposition of carbon species. One is the contraction action originated from the oxidative degradation of the organic species included in MG and CNFs. The other one is the adhesion action induced by the gas release accompanying the combustion of the carbon species and more importantly the crystallization of metal oxide crystals forming the solid walls of tubular structures. In addition, e have also demonstrated the promising uses of these interesting tubular structures of mixed metal oxides as electrocatalysts for the oxygen reduction reaction and negative electrodes for lithium-ion batteries.

Magnetic materials with semiconducting electronic transport properties have been receiving much attention due to the promise of implement existing semiconductor technologies into spintronic counterparts. Magnetic semiconductors exhibit spin dependence in the band gaps, providing an effective means of generating spin-polarized current for spin-injection or spin filtering applications. Semiconductor type conduction with transition temperature above room temperature was reported for the bulk CuCr₂Se_xS_4-x system with the composition range 0.5 le; x le; 1.5. However, the reported magnetic semiconducting properties have not been unequivocally confirmed and their behavior at nanoscale level is yet to be investigated. This observation motivated us to synthesize the entire composition range of CuCr₂Se_xS_4-x in the form of nanocrystals and study their magnetic and electronic transport properties in order to ascertain the occurrence of ferromagnetic ordering above room temperature with semiconducting transport properties. For this purpose, we have synthesized CuCr₂Se_xS_4-x nanocrystals involving hot injection of an excess of chalcogenide containing solutions into a boiling coordinating solvent containing CuCl₂ and CrCl₃.6H₂O. Systematic changes in the lattice parameter, size, and magnetic properties of the nanocrystals are observed with composition. Dimensions of the nanocrystals measured from TEM images varied from 18 ± 3 nm to 22 ± 2.5 nm, which are in good agreement with sizes estimated from small-angle X-ray scattering measurements, but larger than sizes calculated from XRD peak broadening suggesting the polycrystalline nature of the nanocrystals. TEM-EDX elemental mapping on these nanocrystals confirmed the uniform distribution of the elements, suggesting no phase separation of the elements. Magnetization (M) as a function of applied magnetic field (H) has been measured at 5 and 300 K, in order to identify the effect of anion site substitution on the saturation magnetization and coercivity values of CuCr₂Se_xS_4-x nanocrystals. The highest magnetization measured at 5 K are 37.3 emu/g for x = 3; 33.5 emu/g for x =2; 32.2 emu/g for x = 1 and 22.5 emu/g for x = 4. The Curie temperature (T_C), estimated from Magnetization (M) as a function of temperature (T), shows a systematic increase in the transition temperature with increasing selenium content

The silver nano wires(AgNWs) have aroused excitement in materials scientists for years due to their unique electronic, optical, thermal, and catalytic properties, and their potential applications in plasmonic fibers, electronic interconnectors, transparent electrodes, cell probes, and so on. Polyol process is prevailing method because it is capable of producing high-quality silver nanowires with high yield. Polyvinyl pyrrolidone (PVP), as capping agent, has a great impact on the shape and size of the silver nano structures. The effect of chain length of PVP on synthesizing of silver nanowires has been systematic investigated. It is found that there a a critical chain length of PVP which is the side length of the AgNWs. It means that the chain length of PVP must be larger than the critical length in order to get uniform Ag NWs. Below which, only nanoparticles or short nano rods can be obtained. Surprisingly, a core-shell structure of nanowire with a polycrystal was observed when the PVP with very long chain length was employed in the processing.

A variety of chemical routes exist for a wide range of nanomaterials with tunable size, shape, composition and surface chemistry. Of these materials, silicon (Si) and germanium (Ge) nanomaterials have been some of the most challenging to synthesize, due in part to the relatively high temperatures required to crystallize Si and Ge. For solution-based synthesis, one crystalline nanorods, nanowires and heterostructured nanomaterials have been made with the help of metals to catalyze their growth.
Solution-liquid-solid (SLS) growth of Si and Ge nanorods can be achieved using low melting tin (Sn) as a seed metal. For instance, Si nanorods with narrow diameters (<10 nm) and quantum-confined optical properties can be grown by the decomposition of trisilane in hot squalane (~400^oC) in the presence of tin (Sn) nanocrystals stabilized by poly-(vinylpyrrolidinone-hexadecene) (PVP-HDE copolymer). Si nanorods with photoluminescence quantum yields of 4-5% could be obtained by post-reaction surface etching with hydrofluoric acid to remove residual surface oxide, followed by thermal hydrosilylation passivation with 1-octadecene. This colloidal synthesis could be further simplified to a single reaction step by combining the molecular Sn(II) reactant, [Sn(hmds)₂], with trisilane in the reaction solution. Trisilane reduces [Sn(hmds)₂] to Sn in situ, simplifying the reaction procedure and improving repeatability by eliminating the need to use pre-synthesized seed particles. Si and Ge nanorods with various aspect ratio and Si-Ge heterostructured nanorods can be obtained with this approach.
We have also been examining silanes that are more reactive than trisilane to further lower the synthesis temperature for Si nanorods. Isotetrasilane, neopentasilane and cyclohexasilane, have all exhibited Si nanorod synthesis at lower reaction temperatures than trisilane. Cyclohexasilane is particularly interesting, enabling Si nanorod growth with Sn seeds at temperatures as low as 200^oC.
Besides [Sn(hmds)₂], other metals precursors have also been explored for single-step reactions for Si and Ge nanorod and nanowire growth. The relative rates of metal seed and Si/Ge precursor decomposition kinetics have been found to be important. The seed metal precursor must have faster decomposition kinetics than Si or Ge precursor. So far, in situ Mn, Fe, Ni, Cu, Ga, In and Bi seeded Ge nanowires and Cu, Ga, In seeded Si nanowires have been successfully grown in supercritical toluene.

The combination of conductive polymer brushes with semiconductive material such as ZnO nanocrystalline films is a perspective organic/ inorganic hybrid material for photovoltalic application. Those brushes enable vertical conducting^[1] on the level of single chains, crucial for high efficiency of the future hybrid photovoltaic systems.
The synthesis pathway of such novel hybrid material opens with fundamental understanding of the polymer brush growth on various substrate morphologies in order to fabricate dense high quality organic layer. Extended polymer chains assembled perpendicularly to metallic oxide substrate implement a direct electron pathway.^[1] This particular feature makes polymer brushes an attractive material with perspective application in organic photovoltaics.
N-isopropyloacrylamid was used as a model polymer brush to study its growth via Atom Transfer Radical Polymerization (ATRP)^[2] from initiator functionalized ZnO nanocrystalline surfaces. ZnO nanocrystalls have single crystalline nature.^[3] Nanorod metal oxide crystals grow in hexagonal shape, selectively along their c- axis during low temperature hydrothermal synthesis. These crystals can also be modified via growth promoter to form continuous film made of hexagonal plates. The influence of substrate morphology was investigated in a series of in- situ study of polymer brush growth via quartz crystal microbalance (QCM).^[4] The device enables in-situ insight of surface reactions as well as adsorbate conformational transitions. The substrates were characterized by means of grazing angle FT-IR Spectroscopy, Atomic Force Microscopy and Scanning Electron Microscopy. The experiments were held at various water- methanol solvent ratios on nanorod and continuous substrate morphologies in order to find the most suitable composition for perspective hybrid photovoltaic systems. It could be shown that even small changes in solvent composition and crystal height had a tremendous effect on quality of the obtained polymer brush films. The results helped to establish an efficient method of grafting dense high quality polymer brush layer from functionalized metal oxide surfaces for photovoltaic application.
References:
1) Szuwarzynski, M., Kowal, J., and Zapotoczny, S., J. Mater. Chem., 2012, 22. 20179.
2) Pyun, J.; Matyjaszewski, K. Macromolecules2000, 33, 217; R. Barbey et al. Chem. Rev.2009, 109, 5437.
3) Vayssieres, L., Adv. Mater. 2003, 15, 464.
4) Pomorska, A. et al. , J. Colloid Interface Sci., 2011, 362, 180.

ZnO nanorod is one of the most important one-dimensional nanostructures for optoelectronics, energy harvesting, sensing, and electronic applications. In multi-functional devices, assembly of well aligned nanorod arrays are essential for high resolution of micro-/nano-size devices. Therefore, many efforts have been made to assemble well-aligned ZnO nanorod arrays through diverse methods such as electron beam lithography, nanosphere and nanoimprint lithography, laser interference lithography using hydrothermal growth method. Even though enormous methods have been suggested for patterning ZnO nanorod arrays, none of them provides a reliable, high-throughput, and cost effective solution for large-scale fabrication of patterned nanorod arrays. To achieve selectively growth of well-aligned ZnO nanorod arrays with high reproducibility and low cost in large scale, simple technique is required without many additional steps in the fabrication process.
In this work, we demonstrate the feasible method for selectively growth of vertically aligned ZnO nanorod arrays on n-GaN layer by combining conventional photolithography, laser irradiation and hydrothermal approach. Since both ZnO and GaN have the same wurtzite crystal structure, and a low lattice misfit of about 1.9 %, ZnO nanorods grow vertically on GaN substrate. Perfectly aligned vertical ZnO nanorod arrays were then grown at pre-patterned regions via a low-temperature hydrothermal method without using a catalyst or additional seed layer. During laser lift-off (LLO) process for the removal of sapphire substrate from n-GaN layer, the energy intensity of incident laser is modulated by the pre-deposited micro-size oxide patterns on back-side of sapphire. Non-uniform distribution of the energy intensity of laser, reaching at the interface between GaN and sapphire, melts the GaN surface in non-uniform states. Relatively low intensity of laser leads to the increase of roughness at the patterned area, consisting of nano-sized GaN dots, after inductively coupled plasma (ICP) etching. Since rough surface has higher surface energy than that of flat surface, Zn²⁺ ions and OH^- ions are preferably adsorbed at the GaN nano-dots to decrease the surface energy of the GaN substrate. This feasible technique can be easily applied to the fabrication of ZnO nanorod-based sensors or optoelectronic devices requiring high order of arrays in large area with low cost.

ZnO nanostructured thin films and nanowires of have been actively investigated for gas sensing applications. Nanorods and hierarchical nanostructures appear to be particularly interesting because of their large exposed area and their fast response time. However, sensing devices based on ZnO nanorods present generally a morphology that does not take full-advantage of their characteristics. Most of the times, in fact, an uniform layer of nanorods are grown on the surface of a thin seed layer covering the entire surface of the device. With this geometry the probing current is confined mostly in the basal seed layer. In order to remove this limitation we developed a device based on long ZnO nanorod grown on a 2D array of nanocrystalline ZnO micropillars obtained by soft-lithography of a metal-loaded hydrogel. This approach produces a 2D network of electrically connencted nanorods. The synthesis of this complex nanostructure is obtained using only solution processes and it can be realized using inexpensive simple chemicals and a very simple apparatus. The geometry is such that it can be adapted to any electrode geometry without any need of lithographic alignment.

Understanding the growth process of nanomaterials in solution environment is important for better design of different structures. Oriented lateral attachment by self assembly of primary small α-MnO₂ nanorods is proposed as one of the many competing mechanisms explaining the growth process of one dimensional (1D) α-MnO₂ in solution. Until now, no consistent conclusion has been made to demonstrate the growth mechanism, which is partly due to insufficient atomic scale exploration around the growth-induced structural fingerprints in α-MnO₂.
In this paper, cryptomelane α-MnO₂ nanowires at different growing stages are synthesized via a hydrothermal reaction in aqueous solution. The α-MnO₂ nanowires grow along [001], which is also the direction for 1x1 and 2×2 tunnels. For the first time, α-MnO₂ structure featured by empty 1x1 tunnels and K⁺-supported 2×2 tunnels is clearly shown at atomic resolution under [001] TEM zone axis. The {100} planes function as the lateral surfaces of single α-MnO₂ nanowire, leading to a square shaped morphology of the nanowire. Oriented attachment mechanism is confirmed to dominate the growth of α-MnO₂ nanowires in solution via lateral attachment of primary α-MnO₂ nanorods along their common {110} surfaces. The as formed {110} interfaces are composed of complicated intergrowth of 2x3 and 2x4 tunnels sharing the same directioin as the normal 2x2 tunnels. Microtwins essential of 2×3 tunneled {110} interface is also well demonstrated.

Controlling the size and shape of metal nanoparticles has been a topic for materials research for the past several decades, but the quantitative analysis is still severely lacking, even though such information is very important in the design of functional nanostructures. The challenge lies in the difficulty in understanding the interactions between ligand-metal ion pairs. In this presentation, I will present our experimental data designed for understanding the mechanisms of ligand-metal ion interactions between metal precursors and common ligands used in carbon monoxide-mediated Gas Reducing Agent in Liquid Solution (GRAILS) method.^1,2,3 Singe crystal X-ray crystallography, mass spectroscopy and UV-vis spectroscopy were used to study the metal-ligand interactions. A series of metal complex species has been identified, and proved to be effective controlling factors in the synthesis of metal nanoparticles, such as Pt and Pd. The structures of metal precursors show different thermal dynamic properties during the reactions. Their chemical properties influenced the reaction pathways and the growth kinetics of the metal nanostructures, which enable us to rationally design synthetic routes for various metal nanoparticles. Density functional theory (DFT) calculations were used to understand the energetics for the formation of size and shape controlled nanostructures.^4,5 The size controllable octahedral Pt₃Ni nanoparticles, Pt nanocubes, and Pd nanoframes were synthesized. Their performance for oxygen reduction reaction (ORR) will be discussed. Our result shows that the reaction paths we have uncovered are prevalence in many synthetic systems and important to the precise control of metal nanoparticles synthesis in non-aqueous systems.
(1) Wu, J.; Gross, A.; Yang, H. Nano Lett.2011, 11, (2), 798-802.
(2) Wu, J.; Zhang, J.; Peng, Z; Yang, S; Wagner, F. T., Yang, H. J. Am. Chem. Soc., 2010, 132, 4984-4985.
(3) Wu, J.; Yang, H. Acc. Chem. Res., 2013,46, 1848-1857.
(4) Peng, Z.; You, H.; Yang, H. ACS Nano, 2010, 4, 1501-1510
(5) Yin, X.; Liu, X.; Pan, Y.-T.; Walsh, K.; Yang, H. Nano Lett.2014.

Shape-controlled synthesis of bimetallic nanostructures is of great interest because of the widespread applications enabled by such structures, especially as electrocatalysts in fuel cells. However, complicated synthetic procedures can devalue routes to such structures for practical applications. Here, the use of two capping agents in a one-pot route to Pd-Pt nanostructures provides facile manipulation of bimetallic architecture. Octopodal, highly branched, and even cubic particles are achieved depending on the specific ratio of the two structure-directing agents. Specifically, Pluronic F127 and NaBr were used with the co-reduction of Pd and Pt precursors in aqueous media. Br^- facilitated the formation of Pd-rich nanocubes from which Pt tips can emerge to yield octopodal nanostructures. The nanocubic interior is facilitated by preferential stabilization of the {100} facets of Pd by Br^-. Otherwise, dendritic nanospheres form from the aggregation of spherical metal seeds. In contrast, Pt growth is influenced by the amount of Pluronic F127. This independent manipulation of Pd and Pt in a nanosynthesis through the use of two capping agents highlights the possibility for advanced bimetallic nanostructures via one-pot co-reduction routes.

Copper nitride is a potentially interesting material for optical storage devices, high-speed integrated circuits and microscopic metal inks. The present work highlights a promising surfactant-free solution route for copper nitride nanoparticles with a diameter of around 3 nm. “Surfactant-free” synthesis does not imply truly naked nanoparticles but implies that these nanoparticles are stabilized by low molecular weight solvent molecules or by reaction byproducts. An easy one-step reaction between copper precursor and organic solvent leads to crystalline copper nitride nanoparticles within 5 minutes reaction time at temperatures as low as 110 ^oC. The present synthesis route reports the lowest synthesis temperature for copper nitride nanoparticles in solution phase.
On the basis of an analysis of the byproducts after the reaction, the mechanism for the formation of Cu₃N is proposed. The emphasis of current investigations is on assembling ultrasmall copper nitride nanoparticles into films and/or macroscopic aerogel for effective utilization of their surface properties.

Lanthanide (Ln)-based luminescent nanocrystals represent an interesting class of materials due to their up- and down-conversion (UC and DC) properties. They are currently under intense investigation due to their potential interest in various important technological fields, such as solid-state lighting, display panels, and imaging agents. Over the past two decades, the synthesis and properties of various Ln-based NCs have been reported, ranging from fluorides (LnF3, NaLnF4) to oxides (Ln2O3, LnO2) via oxyhalides (LnOX with X = Cl, F) and phosphates (LnPO4). Although potentially interesting for different technological applications, lanthanide oxide nanocrystals remain widely unexplored. Indeed, despite their simple chemical composition, the controlled synthesis of lanthanide oxide nanocrystals is still highly challenging. Additionally, the relationship between the controlled synthesis of ultra-small lanthanide oxide nanocrystals and their atomic scale structure widely influences their photoluminescence properties. As a consequence, a good understanding of such a relationship is of major interest to the design and development of innovative lanthanide-based nanophosphors. The preparation of reliable (controlled size and shape distributions) and structurally well characterized ultra-small lanthanide oxide nanocrystals is an essential prerequisite to understand size effects on their photoluminescence properties.
First we reveal that non-aqueous approaches used to synthesize ultra-small europium oxide NCs are deeply affected by ‘hidden&’ parameters which are directly related to the preparation of the reactive mixture. Indeed, side reactions and the formation of byproducts such as acetic acid and water as traces act as growth directing agents. Additionally, we discovered that the formation of ultrathin europium doped yttrium oxide nanodisks is governed by a complex self-assembly process which is unusual at high temperature.
Second, the challenging problem related to the structural characterization of ultra-small lanthanide oxide nanocrystals is addressed for the first time by coupling high resolution transmission electron microscopy (HRTEM) and x-ray atomic pair distribution function (PDF). The ultra-small thickness of the as-prepared nanocrystals apparently dictates the crystalline structure, which can no longer be described by the bulk counterpart crystal phases. The induced distortions due to the ultra-small thickness as well as the bonding of the stabilizing organic ligand are strong enough to break down the symmetry and, hence, prevent the europium oxide nanocrystals from accommodating the usual bulk crystal phases.
Finally, the unusual polymorphs discovered for pure europium oxide and europium doped yttrium oxide nanocrystals have a profound impact on the resulting crystal field with direct consequences on the photoluminescence properties.

Rare-earth (RE) doped oxysulfides RE₂O₂S are known for their luminescent properties under various excitations (X-Rays, UV, Visible, IR) and open the door to a wide range of applications. However, the underlying chemistry for the preparation of such phases is quite heavy: these phases are commonly prepared by solid state methods at high temperatures and under strictly controlled conditions that required the use of elemental sulfur or sulfur-containing gases. Innovative preparation routes appear therefore definitely welcome to broaden the panel of existing compositions, and particularly the range of solid solutions. In this work, a softer and more convenient method for the synthesis of lanthanide oxysulfides was developed. It consists in a continuous two-step molecular precursor route starting from pre-isolated dithiocarbamate lanthanide complexes. These heteroleptic ([Ln(Et₂dtc)₃(phen)], [Ln(Et₂dtc)₃(bipy)]) or homoleptic (Et₂NH₂[Ln(Et₂dtc)₄]) precursors, where Ln = La, Pr, Nd, Sm-Lu ; Et₂dtc = diethyldithiocarbamate ; phen = 1,10-phenanthroline and bipy = 2,2-bipyridine, were readily obtained for a wide range of lanthanides through a rapid and easy process starting from Ln trifluoromethanesulfonates. These complexes were then used as molecular precursors in a continuous two-step process under moderate temperatures: conversion first into the oxysulfate phase between 200°C and 600°C according to the precursor, followed by reduction at 650°C with a diluted H₂ atmosphere (H₂(5%) - Ar(95%) [1].
A large range of simple Ln₂O₂S and mixed A_(2-x)B_xO₂S was obtained by this method. In agreement with the existing literature, solid solutions were obtained throughout the composition range for the La-Gd, Gd-Y, La-Y systems. But this was also demonstrated for the La-Dy and La-Eu systems, in contradiction with previous results [2]. The La-Er system was investigated for the first time and was found to be very sensitive towards the experimental conditions because of the high oxophilicity of Er.
Ln₂O₂S (Ln = La, Gd) phases were then doped by lanthanide ions (Eu³⁺, Tb³⁺, Sm³⁺, Dy³⁺, Tm³⁺) and their luminescence properties were studied under various excitation wavelengths. The question of the carbon contamination layer was investigated in La₂O₂S:Eu³⁺. Thin films of this phase were also obtained by spin-coating. Co-doped materials Ln₂O₂S:Eu³⁺,Tb³⁺ (Ln = La, Gd) were finally prepared according to the same strategy and allowed to excite selectively the Eu³⁺ emission.
[1] N. De Crom, M. Devillers, J. Solid State Chem. 2012, 191, 195-200
[2] M. Leskela, L. Niinisto, J. Solid State Chem.,1976,19, 245-250.

Upconversion is the process that can convert a long-wavelength pump sources, typically in the infrared or near-infrared region, into a short-wavelength emission. Among various upconversion materials, lanthanide-doped NaYF₄ upconversion nanocrystals (NCs), which can efficiently emit green and red (or blue) upconversion fluorescence under 980 nm laser excitation, have attracted considerable attention due to their promising properties. For NaYF₄:Yb³⁺, Ho³⁺ or NaYF₄:Yb³⁺, Ho³⁺, Tm³⁺ NCs, the intensity ratios of green-red or blue-green-red dependent on many factors, such as dopant concentrations, particle size, and excitation power, due to the fact that the emission probability of diverse f-f transitions of Ho³⁺ and Tm³⁺ ions is sensitive to ambient conditions. Thus, it can be predicted that the green, red and blue emission would also change in different rates with the increase of the ambient temperature, and consequently lead to the change of the intensity ratios. This inspired us to design a new type of temperature-sensitive materials based on the upconversion process. In this paper, NaYF₄:Yb³⁺, Ho³⁺ upconversion nanowires have been synthesized through a facile hydrothermal method, and the effects of measuring temperature on the intensity ratios of green-red were studied in detail. It was found that the upconversion luminescence (UCL) intensity decreases in different rates for green and red emission with increasing temperature, which leads to an obviously shift in chromaticity coordinates. For easier to distinguish the change of UCL color, a triply-doped system of NaYF₄:Yb³⁺, Ho³⁺, Tm³⁺ was designed and the initial UCL color (at room temperature) was adjusted by controlling the dopant concentrations of Ho³⁺ and Tm³⁺ ions. As the temperature increases, a significant color change can be observed by the naked eye. These desirable properties make upconversion NCs promising in applications as thermosensitive materials or multicolor labels that can timely capture the changes of temperature from the UCL color.

As one of multifunctional ferroelectric materials, rare earth doped luminescent ferroelectric materials have attracted much interest in past decades for their wide applications in nonvolatile random access memory, sensors and optical-electro integration devices.^1-4 Recently, a list of results reported by several research groups around the globe on photoluminescence and the ferro-/piezoelectric properties of rare earth Er-doped series perovskite or perovskite-related ferroelectric oxides such as BaTiO₃,⁵ Bi₄Ti₃O₁₂,⁶ (Ba,Ca)(Ti,Zr)O₃,³ and SrBi₄Ti₄O₁₅,⁷ CaBi₄Ti₄O₁₅,⁸ BaBi₄Ti₄O₁₅,⁹ CaBi₂Ta₂O₉¹⁰. In these oxide materials, rare earth Er ion was used as luminous centers and strong up-conversion photoluminescence was observed. However, the emission efficiency is still low due to the low solubility of trivalent rare earth ions. Meanwhile, the ferroelectric and piezoelectric properties fade severely and even drained away when the Er concentration is high though some reports presents they can be enhanced by minor rare earth Er doping.
In this work, we will introduce the latest research route of our group, in which a perovskite-related compound with the formula of (A_0.5Er_0.5)TiO₃ (A=Na, Li, K and Rb) was introduced into series perovskite-related ferroelectric materials.^11-12 For interpreting the enhancement of electro-mechanical properties and up-conversion photoluminescence, the microscopic mechanism will be discussed from three aspects: the sensitization effect of alkali metal ions, the stabilization of crystalline phase, and the depression of physical and chemical defects. In addition, some experimental results of our recent work related to novel potential applications such as photovoltaic engineering of these multifunctional ferroelectric materials will be introduced.
References:
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12. X. Hui, D. Peng, H. Zou, J. Li, Q. Cao, Y. Li, X. Wang, X. Yao. Ceram. Int., 40, (2014)12477-12483.

SrTiO₃ pure and SrTiO₃:Eu powders were produced by pressure-assisted combustion synthesis (2.7 Megapascals) and were subsequently annealed at 1200°C. The Eu doping concentrations were 3.0, 5.0, and 7.0 a.t.%. XRD measurements indicated that undoped and Eu³⁺ doped samples presented a single cubic crystalline phase. As the Eu doping concentration increases, the crystalline lattice of the SrTiO3:Eu is expanded, since we observed a slight shift toward lower angles in the XRD peaks. According to SEM images, microparticles with sizes in the range of 0.3-0.7 µm were obtained and the size of the grains increases as the content of Eu³⁺ dopant increases. Absorption spectrum of undoped sample showed a broadband from 200-400 nm, after introducing Eu, the absorption spectra extend until 450nm. Besides, an indirect bandgap of E_g= 3.32 eV for pure SrTiO₃ was estimated from the second derivative of the absorbance spectrum. A strong red emission at 617 nm from Eu³⁺ ions was obtained by photoluminescence under excitation at 394 nm and by cathodoluminescence. All those results indicate that our red phosphors could be useful for potential applications in solid state lighting and field emission displays.

Trivalent lanthanide-ion doped upconversion nanoparticles (UCNPs) are well-known for their unique luminescent properties that enable the conversion of low-energy photons into high-energy photons by multiphoton processes. This special property enables upconversion materials to be considered as promising nano-platforms in solar cells, detection, bioimaging, and so forth. Among conventional UCNPs, the fluoride-based host material has been reported as the most efficient upconversion fluorescent material, exhibiting strong upconversion fluorescence. Considerable efforts have been devoted to multicolor tuning of lanthanide-doped fluoride-based host material nanocrystals. However, synthesizing high-efficiency UCNPs with small diameters under low-intensity laser excitation remains a notable challenge.
Chloride-based host material NCs codoped with Yb³⁺/Er³⁺ (or Yb³⁺/Tm³⁺) have attracted significant interest and have become popular choices as host materials to fabricate smaller and brighter UCNPs because of their low phonon energy. However, chloride-based host materials are hygroscopic, which leads to the limited use.
In this work, Sr/CaFCl: Yb3+,Er3+ NCs with a wide range of ions dopant concentrations were synthesized, and strong green and red upconversion fluorescence were observed under laser excitation at a wavelength of 980 nm. The influence and mechanism of ions dopant are demonstrated and discussed. The ions doped concentration has a significant influence on the phase-transfer of the host material and on the corresponding upconversion emissions, and the mechanism of which was studied. In addition, the optimized concentration represents a good balance between the occurrence of the phase transition and concentration quenching. These high-efficiency nanoparticles have potential applications in the fields of optical nanodevices and biomedicine.

The aqueous precipitation of metal cations generally forms clusters and ultrafine particles, which often rapidly grow and aggregate to minimize the extent of their interfacial area. However, such phenomena can be avoided when the electrostatic surface charge is at maximum during the formation of the nanoparticles. This suggests that the stability results from surface thermodynamics, as for micro/nano emulsions, by a lowering of the interfacial free energy. Indeed, thermodynamic stabilization of aqueous oxide nanoparticles can be achieved when formed at low interfacial energy resulting in an enhanced control of their finite size, crystal structure, surface chemistry, electronic structure and electrical properties. Such theoretical approach will be presented and illustrated with experimental results on various transition and post transition metal oxides and oxyhydroxides.

We present a versatile route for the synthesis of core-shell metal oxide nanoparticles. The surface properties of the oxide nanoparticles, decorated with monolayers of differently chained phosphonic acids (PA's) can be smoothly tuned solely by stoichiometric mixtures of the functionalization ligands during the functionalization procedure. By employing chained molecules with either hydrophobic or hydrophilic chains the surface energy of the nanoparticles was carefully modified orthogonally from fully superhydrophobic to a superhydrophilic surface. ^[1]
Metal oxide nanostructures embedded with such multifaceted surface properties are of interest to be employed as building blocks for hierarchical self-assembly nanostructure formation. By employing orthogonal surface chemistry in conjunction with reactive head groups, selective self-assembly of 0D (CeO₂, AlO_x, ITO) onto 2D nanostructures can be achieved provided a balance of sufficient attractive (Huisgen-1,3-dipolar cycloaddition) and repulsive (hydrophobic-hydrophilic) driving forces.
Moreover, superhydrophilic nanoparticles exhibited good solubility when dispersed in an aqueous solution. Thus, allowing for environmental friendly, water-based solution processing of metal oxides at neutral pH. The modified particles (Fe₂O₃, TiO₂, AlO_x, ITO) were employed for the formation of a water-processed dielectric layer in bottom-gate organic thin-film transistors (OTFT&’s).
Even more, oxide nanoparticles (Fe₂O₃, TiO₂, CeO₂, AlO_x, ITO) functionalized with ligands with polymerizable reactive headgroups (methacrylates) allow for the creation of polymer-nanoparticle composites. Embedment of nanoparticles in the polymer matrix allows for modification of the polymer properties. These approaches offer great potential in the area of nano-electronics by introducing numerous hybrid organic-inorganic materials with fine-tuned surface properties while the nanostructure core properties remain fundamentally unchanged. ^[2]
[1] Portilla, L.; Halik, M. ACS Appl. Mater. Interfaces2014, 6, 5977-5982.
[2] Pujari, S. P.; Scheres, L.; Marcelis, A. T. M.; Zuilhof, H. Angew. Chem. Int. Ed. Engl.2014, 53, 6322-6356.

In the fast developing field of nanoscience, nanoparticles and the development of new routes to their synthesis play an important role. Reduction in the crystal size to only a few nanometers greatly modulates the electronic, optical and magnetic characteristics of the nanocrystals. The properties of the nanoparticles are strongly dependent on their size, shape, composition, surface chemistry and the crystallinity. Therefore, development of new synthesis approaches providing full control over those parameters in a broad nanoscale size range is of significant interest in the nanoparticle research. We have extended the scope of the available metal oxide nanoparticles by introducing a novel non-aqueous protocol based on tert-butanol as a reaction medium. The crystalline metal oxide nanoparticles are formed already in solution by a chemical reaction with the solvent, without the need for a further high temperature treatment unavoidably leading to an irreversible particle agglomeration. The particles prepared in this way are dispersible in different solvents without additional stabilizing agents. Moreover, tert-butanol can be easily removed from the particle surface leaving an electrically “clean” interface, which is important for interfacial redox processes. Using this approach we have obtained crystalline dispersible nanoparticles of titania,^[1,2] electrically conducting Nb-doped titania,^[3] lithium titanate spinel^[4] and nickel oxide,^[5] whose size can be varied from ultra-small (3 nm) to relatively large (15 nm) and can be further tuned by a post-synthesis temperature treatment. The obtained nanoparticles demonstrate excellent properties in applications involving interfacial charge transfer and bulk charge transport processes such as dye-sensitized solar cells, batteries, and catalysis. Currently we are working on the extension of our successful tert-butanol strategy for the fabrication of nanoparticles of other functional metal oxides and mixed oxides.
[1] J. M. Szeifert, J. M. Feckl, D. Fattakhova-Rohlfing, Y. Liu, V. Kalousek, J. Rathousky, T. Bein, J. Am. Chem.Soc. 2010, 132(36), 12605-12611.
[2] J. M. Feckl, A. Haynes, T. Bein, D. Fattakhova-Rohlfing. New J. Chem. 2014, 38, 1996#8209;2001
[3] Y. Liu, , J. M. Szeifert, J. M. Feckl, B. Mandlmeier, J. Rathousky, O. Hayden, D. Fattakhova-Rohlfing, T. Bein, ACS Nano 2010, 4(9), 5373-5381.
[4] J. M. Feckl, K. Fominykh, M. Döblinger, D. Fattakhova-Rohlfing, T. Bein, Angew. Chem. Int. Ed. 2012, 51, 7459-7463.
[5] K. Fominykh, J. M. Feckl, J. Sicklinger, M. Döblinger, S. Böcklein, T. Bein, D. Fattakhova-Rohlfing. Adv. Funct. Mater. 2014, 24 (21), 3123

Zirconia (ZrO₂) can adopt three different crystalline phases, i.e. monoclinic, tetragonal and cubic. It is used in numerous applications depending on its crystalline phase, e.g. cubic ZrO₂ is applied in oxygen sensors, tetragonal ZrO₂ is used as high performance transformation-toughened ceramics and can catalyze ethanol formation from syngas, while monoclinic ZrO₂ will catalyze isobutanol formation from syngas and is important for gate dielectrics and bioactive coatings. The cubic and tetragonal phase are not stable at room temperature, but they can be stabilized by reducing the crystallite size of ZrO₂ below 30 nm.¹
The autoclave synthesis of metal oxide nanoparticles (NPs) through the benzyl alcohol route is readily described in literature.² In this work, we used the same benzyl alcohol route but via a microwave-assisted solvothermal treatment. Here, the same result - cubic ZrO₂ NPs - is obtained as in the conventional method. However, the microwave treatment makes it possible to reduce the reaction time from 2 days in the autoclave to 4 hours in the microwave.
Furthermore, we demonstrate the possibility to use this microwave-assisted solvothermal treatment to synthesize both pure monoclinic or pure cubic ZrO₂ NPs by solely changing the precursor. We used GC-MS analysis on the reaction mixtures to proof that the change in crystal structure rises from a difference in reaction mechanism induced by the release of a strong acid during synthesis.
The as-synthesized ZrO₂ NPs (cubic or monoclinic) are small in size (3 - 10 nm), yet aggregated and thus showing a low dispersibility. Aggregrate-free NPs are generated through surface-functionalization of the NPs with long chain ligands, providing stabilization in apolar solvents via steric hindrance. Solution ¹H NMR was used to study the details of this post-modification step and the surface chemistry of the resulting aggregate-free NPs. This led to the conclusion that not only a different crystal structure yet also a different surface chemistry is obtained depending on the used precursor.
1 R.C. Garvie, Journal of Physical Chemistry, (1978), 82, 218-224
2 M. Niederberger, G. Garnweitner, N. Pinna et al., Progress in Solid State Chemistry, (2005), 33, 59-70

Tailoring the size of magnetic particles at the nanometer scale has led to the emergence of new magnetic properties, of great interest in various research topics including magnetic recording. One of the main challenges for the synthesis of such granular materials is the design of organized structures with enhanced tunable physical properties. Particularly, the thermal stability of the nanomaterials magnetization is critical for magnetic recording.
Several recent experimental studies have indicated that exchange coupled ferromagnetic (FM) and antiferromagnetic (AFM) nanostructures exhibit an improved thermal stability of the magnetization and all the features of exchange bias (EB).
Besides, in the case of core-shell FM-AFM exchange-biased nanoparticles (NPs), dipolar interactions may be of great importance and have to be considered. Despite an impressive number of works on exchange-biased systems, few of them deal with the interplay between EB and dipolar interactions. To study the relationships between EB and dipolar interaction, we propose to tune the NP-NP distance by growing polymer brushes on the surface of these nanoparticles.
We prepared, by the polyol process, highly crystallized nanoparticles (NPs) consisting in a Fe_3-xO₄ core perfectly epitaxied to a polycrystalline CoO shell. We choose to use the grafting from technique to grow poly(methyl methacrylate) (PMMA) chains directly on the surface of the nanoparticles. First, a brominated initiator was anchored to the particle surface. Then, radical polymerization (ATRP) was performed to grow PMMA brushes of controlled lengths.
At low temperature, it appears that increasing the average distance between the NPs increases the coercive field HC and is decreasing the hysteresis loop shift, i.e. EB. These results emphasize the relationships between the dipolar interaction and the hysteresis loop shift in the magnetic NPs presenting EB properties.

The design of low-cost, highly efficient and recyclable systems is crucial for the development of multifunctional nanomaterials. Herein, we report on a new and facile approach to fabricate iron oxide@carbon (IO@C) nanochains through the hydrothermal carbonization of glucose in the presence of wüstite (FeO) precursor nanoparticles. By using the non-magnetic FeO precursor nanoparticles that can slowly oxidize into the magnetic magnetite (Fe₃O₄) crystal phase under hydrothermal conditions, we are able to control the magnetic dipolar interactions in the system, thereby guiding the self-assembly of well-defined and short-length IO@C nanochains that are highly dispersible in water. The fabricated IO@C nanochains readily interact with bacterial cells causing membrane disruption, which leads to a significant loss in Escherichia coli cell viability within short incubation times at minimal dosage. In addition, the resulting IO@C nanochains are magnetic and can be readily removed with an external magnet and recycled as antibacterial agents that demonstrate high efficacy even after five treatment cycles.

Iron oxide nanoparticles (IONPs) have become ubiquitous in a wide variety of research fields, including everything from catalysis, environmental remediation, and, perhaps most importantly, biomedical applications. The majority of applied research on IONPs concerns spherical or quasi-spherical particles. This is necessarily so, since most of these syntheses - aqueous or otherwise - result in spherical particles. There exist a number of methods for changing and controlling the shape of IONPs. Examples include the synthesis of nano-sized cubes, rods, and octahedral particles. The vast majority of these are modifications of thermal decomposition methods. These typically require high temperatures (> 200 °C) and harsh organic solvents, and furthermore require additional ligand exchange reactions in order to disperse the particles in aqueous media (a necessary step for biological or medical applications). This is important because differences in overall morphology can have significant effects on both the physical and chemical properties of IONPs. As such, a low temperature, aqueous method for synthesizing non-spherical IONPs is highly desirable. Herein we describe such a synthesis, through the addition of lyotropic liquid crystals (LLCs) to the well-known Massart method.[1] Adding surfactants (e.g. Triton X series),[2] which can form various LLC phases in water, to the co-precipitation of aqueous iron salts under basic conditions allows for the formation of octahedral and brick-like IONPs. These particles can be easily coated in hydrophilic silane ligands, allowing for their stable dispersal in aqueous media and thus investigations into properties relevant to biomedical applications. They show potential for applications in hyperthermia, MRI contrast, and drug delivery. Most interestingly these particles demonstrate differential cell uptake. That is, they enter into and pass through different types of cells at different rates in a manner not seen in spherical IONPs with identical surface ligands.[3] These results show that changes to IONP shape can have a profound effect on their physical properties, and an aqueous synthesis provides a means to exploit these properties in novel ways.[4]
[1] Massart R. Magnetics, IEEE Transactions on. 1981;17(2):1247-1248
[2] Yathindranath V, Ganesh V, Worden M, Inokuchi M, Hegmann T. RSC Adv. 2013(24):9210-9213
[3] A) Sun Z, Yathindranath V, Worden M, et al. Int J Nanomed. 2012;8:961-970, B) Sun Z, Worden M, Wroczynskyj Y, et al. Int J Nanomedicine. 2014;9:3013-26
[4] Worden M, Bruckman M, Kim M, Kikkawa J, Hegmann T. in prep.

A general route to produce ferrite nanoparticles in triethylene glycol (TREG), using the polyol (thermal, microwave) methodologies has been described recently in our laboratories. Due to its high boiling point TREG acts as solvent and also as a capping ligand of the nanoparticles, stabilizing them in polar solvents. Nanoparticles have been characterized by several common physical laboratory techniques: HRTEM, IR , X-Ray Powder Diffraction (XRPD), magnetometry via Superconducting Quantum Interference Device (SQUID). With these techniques, the final size, shape, composition, crystal structure and magnetic behaviour have been studied, showing the high quality of crystals generated. In addition, we demonstrated the high efficiency of one-pot methodologies that have been optimized to synthesize different families of nanoparticles such as Ru, CeO₂, ZrO₂, Y₂O₃ and BaZrO₃. All of these nanoparticles will be stabilized in highly ionic environments and used for the preparation of nanocomposite ceramic layers. In the case of magnetite (Fe₃O₄) appropriate tuning of the size and shape of nanoparticles gives an added value as they can exhibit shape dependent phenomena and the subsequent use of them as building blocks for the fabrication of nanodevices is a matter of significant interest. An easy shape-controlled synthesis of magnetite nanoparticles by modifying the 1,3-substituents of propanedionate chain of the iron (III) precursor without changes on the additive or synthetic route is presented. It is shown the effect brought about by the presence of fluorine either in the organic ligand of the precursor or in the media; in this case formation of FeF₂ nanocrystals is observed.
The formation of FeF₂ opened a new line of synthesis of nanoparticles and, in particular synthesis of RE (Y, Ga ) fluoride nanoparticles has been started. We present here our last results on the formation of YF₃ and GdF₃ nanoparticles as the starting point of a study in water media so as to know their potential antibacterial and antibiofilm applications.
The research leading to these results has received funding from EU-FP7 NMP-LA-2012-280432 EUROTAPES project

Single crystalline {100} dominant BaTiO₃ nanocubes have been synthesized as typical nanoblocks by the hydrothermal method using aqueous sources of Ba and Ti, and organic additives. TEM and HRTEM images indicated that the 15 nm-sized single crystals had a uniform cubic shape with sharp edges and high lattice coherence and without any voids and defects. The size was stepwise tunable in the range of several tens nanometers such as 15 nm, 20 nm and 30 nm by tuning the composition of the staring materials. During the growth, step and terrace structures were clearly observed on the {100} surfaces and the height of the each step and terrace was found to be identical to one unit cell. By precise analysis of the nanoblocks using HR-TEM, it was found that the anisotropy of the shape appeared when the size increased. The 20 nm- and 30 nm-sized nanoblocks contained 20 vol% and 50 vol% of nanocuboids, respectively. In addititon, the anisotropic ratios of Lc/La (Lc: long length, La: short length) changed with the size. The characteristic behaviors were considered to be associated with the crystal phase of the nanoblocks. The as-grown and preheat-treated nanoblocks were characterized by DSC method. The nanoblocks exhibited endothermic peaks in the range of 223K to 423K on heating, which were considered to be associated with the phase transitions. The size and shape dependences of the transition behaviors will be discussed.
The BaTiO₃ nanoblocks were easily dispersed in non-polar solvents such as toluene and the derivatives. Based on the highly dispersing properties and the volatility of solvents, the nanoblocks with small size and shape distribution were able to develop orderly structures on various kinds of substrates according to the capillary force assisted self-assembly mechanism during the evaporation of solvents. Therefore, the BaTiO₃ nanoblocks are considered to be a kind of cutting-edge material for deep understanding of ferroelectric science in nanometer scale and also development of next generation devices as well as innovative processing instead of conventional ceramic or thin film processing.
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).

Nano-crystals (20-30 nm) of LiNb_xTa_1-xO₃ (where x = 0, 0.25, 0.5, 0.75, 1) embedded in borate based glass matrix were obtained by subjecting the melt-quenched glasses (of the compositions Li₂O-2B₂O₃- 0.5((1-y)Ta₂O₅-yNb₂O₅), where y = 0, 0.25, 0.5, 0.75, 1) to isothermal heat-treatment at various temperatures (530-560^oC/3h). X-ray diffraction (XRD) and Selected Area Electron Diffraction (SAED) confirmed the desired phase formation. The crystallite size and volume fraction of crystallization (determined from Transmission Electron Microscopy and XRD) increased with the heat-treatment temperature. Raman spectroscopy was employed to unravel the structural units present in the system and also to confirm the formation of solid solution of LiNb_xTa_1-xO₃ in the glass matrix. Scanning Electron Microscopy showed distinguished microstructures that changed with composition (x). These glass nanocrystal composites exhibited intense second harmonic signals (532 nm), as comparable to that of KDP single crystal, when exposed to an Nd-YAG laser (1064 nm). Broad Maker-Fringes were obtained on rotating the sample about its vertical axis. Their non-linear hyperpolarizabilities were determined using Hyper-Rayleigh Scattering technique as a function of composition.

Non-precious metal nanoparticle catalysts are a growing research focus for the catalysis community as the demand and subsequent cost of precious metals continues to increase. In the field of electrochemical fuel conversion, platinum group metal (PGM) nanoparticle and nanostructured catalysts have been widely studied for acidic electrooxidation, and the use of non-PGMs is limited due to acid dissolution of the metals. However, when an alkaline electrolyte is used instead, non-PGMs become viable replacements for PGM catalysts. In particular, nickel-based catalysts are a primary choice for PGM substitution, but few nickel-based nanoparticle catalysts thus far have shown equivalent catalytic performance to PGM nanoparticle catalysts. Lessons learned from multi-metallic PGM nanoparticle catalyst development suggest that control of nanostructure and metal-metal atomic arrangement during nanoparticle synthesis can allow enhancement in catalytic performance.
In our research, we have developed an aqueous solution-based synthesis technique for the synthesis of unique bimetallic iron-nickel nanoparticles that show a 10-fold increase in the current density (mA/cm²) produced during electrooxidation of methanol or ethanol, as compared to a nickel-only nanoparticle catalyst. Iron-nickel nanoparticles resulted in a current density of 125 mA/cm² (at 0.8 V vs. Ag/AgCl), whereas nickel-only nanoparticles resulted in a current density of 1.3 mA/cm² during methanol oxidation. Surface and crystal phase characterization of the iron-nickel nanoparticles suggests that the specific stabilizers used and specific parameters controlled during solution synthesis cause the formation of significantly disordered nano-scale structure as well as changes in the surface metal and metal-oxide species detected. In addition, electron microscopy images show nanoparticles that are atypical compared to PGM nanoparticle catalysts (i.e., > 50 nm in diameter, heterogeneous morphologies, possible core-shell and hollow structures). Despite a nominal two-step synthesis approach to form core-shell (iron-nickel) nanoparticles, elemental analysis suggests iron-nickel-oxygen atomic ratios that vary across the diameter of the nanoparticles, as opposed to a clear separation between core and shell metals. Detailed structural analysis of these iron-nickel nanoparticles and initial work to vary the synthesis procedure suggest that the disordered crystalline structure, the surface composition, and the unique atomic arrangement of iron, nickel, and oxygen in the nanoparticles may all contribute to the observed increase in electrocatalytic activity of the catalyst. As a result, understanding and optimization of the solution synthesis parameters is critical to further development of these, and similar, non-PGM nanoparticle catalysts. Details of the solution-based synthesis procedure will be discussed, as well as results from nanoparticle characterization and catalytic performance testing.