Symposium Organizers
Yuping Bao The University of Alabama
Andrew M. Dattelbaum Los Alamos National Laboratory
Joseph B. Tracy North Carolina State University
Yadong Yin University of California-Riverside
O1: Energy Applications
Session Chairs
Tuesday PM, April 06, 2010
Room 2014 (Moscone West)
9:00 AM - **O1.1
Hybrid Colloidal Nanostructures; From Architecture to Function.
Uri Banin 1
1 Institute of Chemistry & Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem Israel
Show AbstractAn important frontier in nano-materials research concerns nanoparticles with different materials in the same nanostructure as means of increasing functionality. One particularly interesting combination of materials is that of a metal and semiconductor in the same nanoparticle where metal tips grown on a semiconductor rod can provide anchor points for electrical connections and for self assembly. We developed the growth of metal (Au) tips on the apexes of semiconductor (CdSe) rods, forming 'nano-dumbbells' (NDB's), via a simple chemical reaction. From the viewpoint of self-assembly they are equivalent to bi-functional molecules such as the di-thiols manifesting two sided chemical connectivity and the use of the tips for assembly with biomolecular linking is demonstrated. By increasing the concentration of gold in the reaction, rods with a metal tip on one side are formed. This occurs by a unique electrochemical ripening mechanism as substantiated by experimental work and model calculations. The Au-CdS system shows a similar behavior but requires different reaction conditions for Au growth. Moreover, using a light-induced reaction, highly selective one-sided growth was achieved and the competition with a thermal route for Au growth on defect sites was studied. Upon reacting Au with InAs nanoparticles a completely different behavior of diffusion of the gold into the nanoparticle was observed. Other growth modes of metal-semiconductor hybrid particles will be discussed, showing the richness of the reaction possibilities of metals and semiconductor nanoparticles. Such systems manifest a unique model for a metal-semiconductor nanoscale junction. A fundamental and intriguing problem associated with such systems is its optical and electronic properties. The electronic properties of metal-semiconductor nanojunctions were investigated by several methods including optical means, scanning tunneling spectroscopy of the gold-tipped CdSe rods and by electrostatic force microscopy. The potential use of metal-semiconductor hybrid nanoparticles as novel photocatalysts will also be discussed.
9:30 AM - O1.2
Photocatalytic Hydrogen Production With Tunable Nanorod Heterostructures.
Lilac Amirav 1 2 , Paul Alivisatos 1 2
1 Department of Chemistry, University of California at Berkeley, Berkeley, California, United States, 2 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractPhotocatalytic production of hydrogen from water using solar energy is a potentially clean and renewable source for hydrogen fuel, but there are still many materials-related obstacles to its widespread use. It is particularly difficult to find a stable semiconductor system with suitable band gap and electron affinity for visible light absorption and for driving the subsequent redox chemistry. Additional challenges facing the photocatalytic process include the quick recombination of photoinduced charge carriers, back reaction of intermediates on the catalyst surface and the back reaction of the products. With advances in size, shape, and composition control, colloidal synthesis of inorganic nanostructures is now developing toward more sophisticated construction, where multicomponent structures can be tailored in a predictable manner for a particular demand. We report herein the design of a multi-component nanoheterostructure aimed at photocatalytic production of hydrogen. Our nanoheterostructure is composed of a platinum-tipped cadmium sulfide rod with an embedded cadmium selenide seed. In such structure holes are three-dimensionally confined to the cadmium selenide, whereas the delocalized electrons are transferred to the metal tip. Consequently, the electrons are now separated from the holes over three different components, and by a tunable physical length. This enables efficient long lasting charge carriers' separation, and the formation of distinct reaction sites which are further apart, thus minimizing back reaction of intermediates. This structure was found to be highly active for hydrogen production, with an apparent quantum yield of 20% at 450 nm, was active under orange light illumination, and demonstrated improved stability.
9:45 AM - **O1.3
On the Design of High Performance Metallic Nanostructures for Electrocatalysis.
Rongyue Wang 1 2 , Caixia Xu 1 2 , Xiaohu Gu 1 , Xingbo Ge 1 , Yi Ding 1 2
1 School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong, China, 2 Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan, Shandong, China
Show AbstractExtensive studies have been devoted to the development of new catalysts for energy-saving technologies, such as fuel cells. Currently, the most common materials design strategy is based on mixing/loading Pt-based nanoparticles onto high surface catalyst supports such as carbon black. However, this method has two common problems, i.e. non-uniform dispersion and self-agglomeration of nanoparticles during catalyst processing, which will bury considerable Pt surface atoms and decrease the catalyst durability. In this presentation, we will describe a rational route to the construction of novel metallic nanostructures with designed functions at molecular level, with an ultimate goal of simultaneously fulfilling three key issues involved in the successful implementation of a practical electrocatalyst: ultra-low Pt loading, great poisoning resistance, and high stability. We will discuss the fabrication of a series of hollow and/or porous metallic nanostructures, based on a combination of processing techniques including wet-chemical synthesis, surface modification, and selective etching. These nanostructures are characterized by high surface area open porosity, excellent structure integrity and uniformity, which allow further functionalization for their implementation as highly efficient anode and cathode materials. In a particular example, we will discuss the formation and characterization of a sandwich type layer-structured nanoporous Au-Pt-Au structure. In a probe electro-catalytic reaction of formic acid oxidation, it is able to achieve over 100-fold increase in mass specific catalytic activity as compared with the commercial Pt nanoparticle catalysts, while its catalytic durability is also significantly better. In-situ spectroscopic studies show that the radically improved performance is not merely based on the increased Pt utilization, rather it is mainly achieved by changing the reaction pathways that suppresses the formation of poisoning CO-like species. Preliminary results regarding their performance in actual PEM fuel cells will also be discussed.
10:15 AM - O1.4
Silver/Gold Heterometallic Nanostructures and Their Surface Plasmon-related Behaviors.
Hyunjoon Song 1
1 Chemistry, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show Abstract Heterostructured nanocrystals containing multiple components attract much attention due to not only their multifunctional properties but also new features arising from the effective coupling of distinct domains. Metallic heterostructures are particularly interesting because optical and catalytic properties of the different components are readily hybridized due to the rapid transfer of conducting electrons. Most of the metallic heterostructures have been grown on hard templates such as anodic aluminum oxides by electrochemical deposition. There have been few reports of the synthesis of multimetallic nanostructures without hard templates, despite the fact that this approach is advantageous in terms of structural variety and controllability. Silver and gold are representative noble metals in Group 11, and have similar physical and chemical properties. Their lattice mismatch is only 0.2%, resulting in the epitaxial growth in solid states. However, the distinct electrochemical properties in silver and gold lead to interesting phenomena, such as underpotential deposition and Galvanic replacement. Using these properties, we have successfully grown silver nanorods and nanowires from gold decahedral seeds. Hierarchical gold@silver polyhedrons have also been prepared through an epitaxial seeded growth. Anisotropic hollow structures were generated by the Galvanic replacement reaction with the silver-gold-silver heterometallic nanorods. In this presentation, we demonstrate the synthesis of various silver/gold heterometallic nanostructures and their surface plasmon related behaviors by coupling of the silver and gold components.
10:30 AM - **O1.5
Shape Controlled Nanocrystals for Nanoelectronics and Energy Science.
Zhong Wang 1
1 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractTwo examples will be presented about shape control of nanocrystals. The first example is about the formation of spherical ceria nanocrystals. For chemical-mechanical planarization of advanced integrated circuits, the polyhedral shaped nanoparticles scratch the silicon wafers and increase defect concentrations. We present here an innovative approach for large-scale synthesis of single-crystal ceria nanospheres [2], which can reduce the polishing defects by 80% and increase the silica removal rate by 50%. The second example is about shape controlled Pt nano nanocrystals [3]. Platinum NCs of very unusual tetrahexahedral (THH) shape were prepared at high yield by an electrochemical treatment of Pt nanospheres supported on glassy carbon by a square-wave potential, which has a much improved catalytic properties. [1] X.D. Feng, D.C. Sayle, Z.L. Wang et al., Science, 312, 1504 (2006).[2] Na Tian, Zhi-You Zhou, Shi-Gang Sun, Yong Ding, and Zhong Lin Wang, Science, 316, 732 (2007).[4] The work presented here was also contributed by Na Tian, Zhiyou Zhou, Shigang Sun, Xiangdong Feng, Dean C. Sayle, M. Sharon Paras, Brian Santora, Anthony C. Sutorik, Thi X. T. Sayle, Yi Yang, Yong Ding, Xudong Wang, and Yie-Shein Her. [5] more details at: http://www.nanoscience.gatech.edu/zlwang/
11:30 AM - **O1.6
Multifunctional Pt-based Nanostructures for Electrocatalytic Applications.
Hong Yang 1
1 Chemical Engineering, University of Rochester, Rochester, New York, United States
Show AbstractThis presentation will cover the synthesis and electrocatalytic properties of multifunctional Pt-on-M and PtM alloy nanostructures. I will discuss several structurally diverse Pt bi- and multi-metallic nanostructures ranging from M-on-M (or nano-dendrite) to yolk-shell and hollow spheres. These structures can either be directly synthesized in solution or through post-synthesis dealloying treatments. The design of element and structure can now be guided by the requirement for a property. For instance, Pt-on-Pd heterogeneous bimetallic nanocrystals have been developed to integrate excellent activity with other different functionalities including particle stability. Noticeably, at the nanometer scale, the macroscopic miscibility gap for metals can disappear when particles are made from molecular precursors and the size is small, and thus new opportunities for a broader selection of metal elements become plausible. Using Pt-Ag as an example, I will discuss a composition-dependent shape control in nanowires and several de-alloying based post synthetic treatment for the generation of complex core-shell like structures and a high-degree of control on catalytic oxidation of organics High-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) analysis, high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) and X-ray diffraction (XRD) are among the techniques used to characterize the nanostructures.
12:00 PM - O1.7
Pd-Pt Bimetallic Nanoparticles Supported on TiO2. Characterization and Application to Photocatalysis.
Olivier Rosseler 1 2 , Sergey Pronkin 1 , Antoine Bonnefont 1 , Corinne Ulhaq-Bouillet 3 , Alain Louvet 2 , Elena Savinova 1 , Valerie Keller 1 , Nicolas Keller 1
1 CNRS, LMSPC, Strasbourg France, 2 DGA, CEB, Vert-Le-Petit France, 3 CNRS, IPCMS, Strasbourg France
Show AbstractIn catalytic applications, adsorption of the reactants is a key step. A lot of bi- or multifunctional catalytic systems are constituted of metal and oxide nanoparticles, the first adsorption step occurring generally on the metallic sites. In some cases, both adsorbing (metallic) and oxidizing (TiO2) sites are required: this is the case for carbon monoxide photocatalytic oxidation at room temperature, because TiO2 adsorbs CO very poorly. Adsorption properties of transition metals are mostly dependent on the position of the centre of their d-band [1], which also means that tuning the position of the center of the d-band by alloying metals allows to control adsorption properties of the metallic nanoparticles, or, in other word, to create a "new" metal.Coupling the catalytic properties of metal nanoparticles with the photocatalytic functions of TiO2 can lead to very interesting synergies: both the catalytic and photocatalytic functions are improved [2]. Preparation and characterization of Pt, Pd and PdPt alloys, deposited on TiO2 will be presented along with some photocatalytic results for simultaneous oxidation of a mixture of pollutants (CO + acetone) in humid atmosphere. Among all samples, only PdPt alloys proved to be very good co-catalysts, demonstrating stronger CO adsorption, very low water sensitivity, and therefore lower water deactivation compared to other monometallic (Au, Pd, Pt, ...) and bimetallic (AuPt, AgPt, NiPt, CoPt, FePt, ...) co-catalysts. Alloying Pd and Pt results in an increased electron density around Pt, enhancing the Pt 5d-CO 2π* back-donation. Therefore, CO adsorption on the alloy is stronger than on the pure metals and CO oxidation is less affected by the presence of other molecules (water, acetone) which would otherwise act as poisons. Those improved results have yet to be explained on the basis of structural, surface and electronic effects affecting the alloy adsorption properties. The structure and surface properties of the alloys have been studied by XPS, HAADF-STEM, and FTIR using CO as a probe molecule. Their electronic properties have been characterized by XPS, TPR/TPD and electrocatalysis towards CO oxidation. Some examples of applications for these metal-semiconductor composites will be given for multi-pollutant indoor air depollution. [1] E. Christoffersen, P. Liu, H. Skriver, et J.K. Norskov, “Anode Materials for Low-Temperature Fuel Cells: A Density Functional Theory Study,” Journal of Catalysis, vol. 199, 2001, pp. 123-131. [2] A.V. Vorontsov, I. Stoyanova, D. Kozlov, V. Simagina, et E.N. Savinov, “Kinetics of the Photocatalytic Oxidation of Gaseous Acetone over Platinized Titanium Dioxide,” Journal of Catalysis, vol. 189, 2000, pp. 360-369.
12:15 PM - **O1.8
Electrochemical Synthesis of Core/Shell Dendrimer-encapsulated Nanoparticles.
Richard Crooks 1 , Emily Carino 1
1 Department of Chemistry & Biochemistry, The University of Texas at Austin, Austin, Texas, United States
Show AbstractWe have previously reported a chemical approach for preparing core/shell dendrimer-encapsulated nanoparticles (DENs) in the size range of 1.5 to 2.0 nm. In this case, a core is prepared within a PAMAM dendrimer, and then the shell is added in a second step. In many cases, these materials are catalytically active. Our new results show that similar materials can be prepared by underpotential deposition of the shell onto preformed cores. Results of electrochemical, TEM, and in-situ EXAFS experiments will be discussed.
12:45 PM - O1.9
Size and Composition Controlled Synthesis of Monodispersed Core-shell Nanoparticle Catalysts.
Vismadeb Mazumder 1 , Shouheng Sun 1
1 Chemistry, Brown University, Providence, Rhode Island, United States
Show AbstractThe need to limit the use of Pt in catalysis, has promoted the search for an effective way to increase their catalytic efficiency. Construction of core-shell structures is believed to be one of the ways forward. Here we report a generalized seed-mediated synthetic approach towards the creation of a bimetallic alloy, as well as, a noble metal on a Pd core in the sub-10 nm size range. The mono-disperity of the ~5nm Pd seeds [1], was critical to the accurate construction of the shells. These surfactant coated core-shell NPs were supported on the Ketjen carbon, and were found to be readily “cleaned” by a 99% acetic acid wash. To demonstrate their usage in catalysis, these core-shell/C NPs were evaluated for the oxygen reduction reaction in both an acidic, as well as base electrolyte – reactions having direct implications in polymer electrolyte membrane fuel cells. The catalysts show no obvious activity degradation after 8000 cyclic voltammetry cycles in the oxygen saturated electrolyte. The synthesis can be extended to create other novel Pt-based nanosystems, which would have implications in myriad fields like optical sensors, hydrogen storage and detection, besides catalysis.Reference:[1] Mazumder, V.; Sun, S.; J. Am. Chem. Soc.,2009, 131, 4588.
O2: Optical Probes for Medical Applications
Session Chairs
Tuesday PM, April 06, 2010
Room 2014 (Moscone West)
2:30 PM - **O2.1
Combining Multiple Functions in Single Optically Responsive Nanoparticles for Theranostics.
Naomi Halas 1
1 ECE Dept.- MS-366, Rice University, Houston, Texas, United States
Show AbstractPlasmonic nanoparticles provide a straightforward and practical approach to the incorporation of multiple functions into the same nanoparticle. These functions can be both passive and active in nature, providing modified or enhanced optical properties, and light driven, optical actuation processes. For diagnostic imaging, enhancing multiple complementary modalities provides new methods for increasing both sensitivity and spatial resolution. Nanoshell-based nanoparticle complexes where near-IR fluorescent imaging and MRI imaging are enhanced simultaneously, to achieve this combination, will be described. Light-driven therapeutics can be photothermal in nature, for inducing hyperthermic cell death, and at lower incident light intensities can also be developed for light-triggered gene therapy. We examine the photophysical properties of light-triggered oligonucleotide release from plasmonic nanoparticles, quantifying this response in terms of releasable molecules per nanoparticle, and evaluating its efficiency in protein downregulation in living cells.
3:00 PM - **O2.2
Gold Nanocages: A Multifunctional Platform for Biomedical Applications.
Younan Xia 1
1 Biomedical Engineering, Washington University, Saint Louis, Missouri, United States
Show AbstractGold nanocages can be readily synthesized via the galvanic replacement reaction between silver nanocubes and gold chlodide in an aqueous solution. By controlling the molar ratio of silver to gold chloride, the surface plasmon peaks of gold nanocages can be continuously tuned from the blue (400 nm) to the near infrared (1200 nm). These hollow and porous gold nanostructures have extraordinarily large cross-sections for both absorption and scattering, typically more than five orders of magnitude larger than those of conventional organic dyes. Exposure of gold nanocages to a laser resulted in the effective conversion of light into heat through the photothermal effect. Gold nanocages can be easily bioconjugated with antibodies to target any specific cancer cells. This novel class of nanostructures is being developed as both a contrast agent for optical imaging in early-stage detection of cancer and a therapeutic agent for photothermal treatment of cancer, and as nanoscale capsules for targeted drug delivery.
3:30 PM - **O2.3
Cooperative Nanomaterials to Image, Sensitize, Target, and Treat Tumors.
Michael Sailor 1 , Ji-Ho Park 1 , Luo Gu 1 , Geoffrey von Malzahn 2 5 , Sangeeta Bhatia 2 5 , Erik Ruoslahti 3 4
1 Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, United States, 2 Harvard - MIT Division of Health Sciences and Technology and Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Boston, Massachusetts, United States, 5 Division of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, United States, 3 Cancer Research Center, Burnham Institute for Medical Research, La Jolla, California, United States, 4 Vascular Mapping Center, Burnham Institute for Medical Research, Santa Barbara, California, United States
Show AbstractThere is a growing need for non-toxic alternatives to II-VI and III-V semiconductors that have a chance to make it into the clinic for imaging and diagnosis of human diseases. In this presentation, we will report the synthesis and characterization of non-toxic, brightly luminescent porous silicon-based quantum dots that can circulate through the blood, lodge themselves in tumors long enough to be imaged, and then degrade into harmless by-products.Cooperative nanosystems consisting of two or more discrete nanomaterial classes will also be presented. The addition of a targeting ligand that selectively interacts with cancer cells can improve the therapeutic efficacy of a nanomaterial, although these systems have met with only limited success due to inefficient targeting. A two- component system that enhances overall targeting efficiency will be presented. The first component is gold nanorod NR) "activators" that populate the porous tumor vessels and act as photothermal antennas to specify tumor heating via remote near-infrared (NIR) laser irradiation. We find that local tumor heating accelerates the recruitment of the second component consisting of a (Lyp1) targeted nanoparticle. Mice containing xenografted MDA-MB-435 tumors that are treated with the combined therapeutic system display significant reductions in tumor volume compared with individual nanoparticles or the untargeted ombination.
4:30 PM - **O2.4
Colloidal Nanocomposites for Surface Plasmon-based Sensing.
Luis Liz-Marzan 1 , Ramon Alvarez-Puebla 1 , Isabel Pastoriza-Santos 1 , Jorge Perez-Juste 1
1 Departamento de Quimica Fíisica, Universidade de Vigo, Vigo Spain
Show AbstractMetal nanoparticles display very interesting optical properties, related to localized surface plasmon resonances (LSPR), which give rise to well-defined absorption and scattering peaks in the visible and near-IR spectral range. Such resonances can be tuned through the size and shape of the nanoparticles, but are also extremely sensitive towards dielectric changes in the near proximity of the particles surface. Therefore, metal nanoparticles have been proposed as ideal candidates for biosensing applications. Additionally, surface plasmon resonances are characterized by large electric fields at the surface, which are responsible for the so-called surface enhanced Raman scattering (SERS) effect, which has rendered Raman spectroscopy a powerful analytical technique that allows ultrasensitive chemical or biochemical analysis, since the Raman scattering cross sections can be enhanced up to 10 orders of magnitude, so that very small amounts of analyte can be detected. In this talk, recent results of our group will be presented, concerning the synthesis of gold nanoparticles with optimized morphology for LSPR biosensing, as well as their assembly within various platforms for SERS-based ultra-detection. First, a survey will be given of wet-chemistry based techniques recently developed to synthesize noble metal nanoparticles with controlled size and shape, including spheres, core-shells, rods, flat prisms and other polyhedra, which can be prepared in a wide (nano)size range. The resulting optical properties will be discussed for the various shapes and sizes, using several theoretical models, with increasing in complexity as the particles deviate from the spherical shape.The final part of the talk will be devoted to describe some recent efforts to design efficient substrates for SERS detection, including the application of a recently developed core-shell colloidal material, comprising gold nanoparticles coated with a thermally responsive poly-(N-isopropylacrylamide) (pNIPAM) microgel, which we denote Au@pNIPAM. While the gold cores provide the necessary enhancing properties, the pNIPAM shells can be swollen or collapsed as a function of temperature, which can be exploited as a means to trap molecules and get them sufficiently close to the metal core for providing the SERS signal.Additionally, we have devised and fabricated a magnetic+optical, bifunctional colloidal system that combines flexible handling and efficient SERS analytical capabilities [4]. This system comprises silica-coated magnetic γ-Fe2O3 (maghemite) cores, coated with a dense monolayer of gold nanorods presenting long-term optical stability and a high density of hot spots per area unit. The magnetic functionality allows for the use a small number of capsules that can be later concentrated under a magnetic field for SERS analysis thereby increasing the detection limits.
5:00 PM - O2.5
Nanoparticle Size Series for in vivo Imaging.
Zoran Popovic 1 , Wenhao Liu 1 , Cliff Wong 1 , Andrew Greytak 1 , Moungi Bawendi 1 , Vikash Chauhan 2 3 , Dai Fukumura 2 3 , Rakesh Jain 2 3
1 Chemistry, MIT, Cambridge, Massachusetts, United States, 2 Department of Radiation Oncology, Massachusetts General Hospital , Boston, Massachusetts, United States, 3 , Harvard Medical School, Boston, Massachusetts, United States
Show AbstractWe report construction and in vivo application of a size series of fluorescent particles spanning 10-150 nm. The particles are based on semiconductor nanocrystals, quantum dots. For the smallest sizes, 10-20 nm, we used polymer coated quantum dots; for 20-70 nm regime we used single quantum dots embedded in silica spheres, while for sizes above 100 nm silica spheres to which multiple quantum dots were electrostatically assembled were prepared. The obtained particles are pegylated, have high emission quantum yield in aqueous solutions and are non-aggregated under physiological conditions. By embedding quantum dots of distinct emission wavelengths in each domain of the size series we were able to simultaneously administer and track particles (in space and time) in vivo. The simultaneous tracking of different size particles enabled us to follow a size dependant particle distribution within the same solid tumor.
5:15 PM - **O2.6
Optical Properties of Shape-controlled Metal Nanostructures and Applications.
Jin Zhang 1 , Adam Schwartzberg 1 , Chun Li 2
1 Chemistry, UC Santa Cruz, Santa Cruz, California, United States, 2 MD Anderson Cancer Center, University of Taxes, Houston, Texas, United States
Show AbstractMetal nanomaterials have interesting properties and potential applications in various fields. We have studied the optical and structural properties of different metal nanostructures including aggregates, nanorods, and hollow nanospheres with the goal to optimize their optical properties including SERS (surface-enhanced Raman scattering) activities. We have recently demonstrated SERS from single, hollow gold nanostructures and found that exceptional sample homogeneity leads to a nearly tenfold increase in signal consistency over standard silver substrates. SERS offers a unique combination of molecular specificity and extremely high sensitivity for analytical applications. The rationally designed hollow gold nanospheres (HGNs) have turned out to be useful for cancer imaging and therapy applications through a process called photothermal ablation therapy (PTA), with performance significantly improved over conventional solid gold nanoparticles or other metal nanostructures. This has been demonstrated in both in vitro and in vivo PTA of carcinoma and melanoma cancer cells. The success is mainly due to the unique combination small size (30-50 nm), spherical shape, as well as strong, narrow, and tunable surface plasmon absorption of the HGNs.
5:45 PM - O2.7
Gold Nanorods for In Vivo Cancer SERS Detection and Photothermal Therapy.
Andrea Centrone 1 , Geoffrey Von Maltzahn 2 , Ji-Ho Park 3 , Michael J. Sailor 3 , Sangeeta N. Bhatia 2 , T. Alan Hatton 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Department of Chemistry and Biochemistry, University of California, San Diego, San Diego, California, United States
Show AbstractIn this work we show for the first time that the near-infrared plasmon resonance of gold nanorods (NRs) may be exploited to provide an integrated platform for in vivo multiplexed SERS detection and cancer photothermal heating. Particular emphasis will be given on in vivo SERS imaging and it will be shown how this technology can be integrated with photothermal cancer therapy and in situ drug delivery. By screening mixed-monolayer NRs, coated with polyethyleneglycol polymers alongside SERS active molecules, we identified three NR formulations that can be uniquely distinguished in vivo over a spectral bandwidth of only 6 nm, a spectral multiplexing density over an order of magnitude greater than semiconductor quantum dots and fluorescence. Such dense multiplexing is fundamental for in vivo applications and allows Raman scattering to be efficiently excited and detected within the near-infrared optical window, where endogenous tissue absorption coefficients are minimal. In addition to their applications in diagnosis and imaging, plasmonic materials have recently attracted attention for their potential to serve as targeted nano-antennas for selective tumor ablation. Unluckily, traditional means for delivering external energy into tumors lack selectivity over surrounding normal tissues. Plasmonic nanoantennas offer an opportunity to alter this paradigm by imparting their optical properties to tumor tissue and enabling deposition of otherwise harmless near-infrared energy into tumors. We utilized gold nanorods with peak plasmon resonance at 790nm, designed to match our SERS excitation source (785 nm) and still provide strong optical absorption at 810nm for photo-thermal heating.Given the characteristic Raman fingerprint of the molecular labels on the NRs, we named to them SERS-coded NRs. SERS-coded NRs are found to be highly stable, to be detectable down to attomolar particle concentrations, and to have low baseline cytoxicity in vitro. In vivo, they were efficiently detected following subcutaneous, intratumoral or intravenous injection and enabled remote photothermal tumor heating to ablative temperatures. Moreover, the NRs or a saline solution was injected intravenously into mice bearing two tumors on opposite flanks. Once the NRs had cleared from circulation, the right flank of each mouse was irradiated for 5 min and all tumors were measured at regular intervals. Within 10 days all the irradiated, NR-targeted tumors completely disappeared, while all other tumors continued to grow. We also combined SERS imaging and photo-thermal therapy with in situ cancer drug delivery, using SERS- coded NRs and thermo-responsive liposomes loaded with anticancer drugs. Both nanomaterials passively accumulate into the tumor tissues. The heat generated via the NRs’s surface plasmon was exploited for direct cancer destruction but also for triggering the selective release of drugs from the liposomes and increasing the therapy efficacy.
O3: Poster Session
Session Chairs
Yuping Bao
Andrew Dattelbaum
Joseph Tracy
Yadong Yin
Tuesday PM, April 06, 2010
Exhibition Hall (Moscone West)
6:00 PM - O3.10
Enhanced Laser Mark Contrast Pigments from Core-Shell Nanoparticles.
Leonard Radzilowski 1 , Jian Wang 1 , Laura Gurevich 1 , Mark Ellsworth 1
1 , Tyco Electronics Corporation, Menlo Park, California, United States
Show AbstractOur laboratory has developed a number of methods for encapsulating inorganic nanoparticles such as titanium dioxide in silsesquioxanes. In particular, two solution-based methods have been developed that deposit as much as 50% wt. silsesquioxane. In one method, a silsesquioxane shell is grown on the nanoparticle surface starting from an alkoxysilane. Titanium dioxide nanoparticles are dispersed in water with ammonium hydroxide, which creates a charged titanium dioxide surface that stabilizes the dispersion and which catalyzes the polymerization of the silane through hydrolysis and dehydrative polycondensation. In a second method a silicone polymer such as polyphenyl silsesquioxane (PPSQ) is adsorbed onto the surface of titanium dioxide nanoparticles from a toluene-water emulsion. After removing the toluene, ammonium hydroxide is added to catalyze crosslinking of PPSQ and produce an insoluble shell. Core-shell nanoparticles prepared by either of these methods are then directly formulated into coatings. With proper choice of the silsesquioxane shell, such nanoparticles are used, for example, as a pigment in a coating that yields irreversible black marks when irradiated with a laser. The degree of blackening is enhanced by the presence of the PPSQ shell compared to uncoated titanium dioxide particles.
6:00 PM - O3.11
Long Range Ferromagnetic Ordering in Nano Crystallite (BiFeO3)1-x (PbTiO3)x Multiferroic Systems at Room Temperature.
Kuldeep Singh 1 , Ashish Gautam 1 , K. Sen 1 , M. Singh 1
1 Physics, Himachal Pradesh University, Shimla, Himachal Pradesh, India
Show AbstractIn recent years, more attention has been paid to multiferroic materials which possess the combined properties of ferromagnetism, ferroelectric or ferroelasticity, owing to their physical mechanism and have potential application for the design of multifunctional devices. The perovskite BiFeO3 (BFO) is one of the few known magnetoelectric multiferroic materials in which ferroelectric (Tc~830oC) and antiferromagnetic (AF) (TN~370 oC) order parameters coexist up to quite high temperature. Four samples (BiFeO3)1-x (PbTiO3)x (called PFPTx) were prepared through solution combustion technique Particle size calculated using Scherrer formula lie in range 7- 8 nm. The transmission electron micrograph of BPFT0 showing spherical particles, with a narrow particle size distribution in the range 3- 12 nm.Particle size is in close agreement with that obtained from XRD. Differential scanning calorimetry (DSC) data, showing the magnetic transition temperature ( Tn = 370oC) of BPFT0 and XPS is used to identify the valence numbers of Fe ion in BPFT0. It has been known that the binding energies of Fe2+ and Fe3+ are slightly different, which can be separated from the XPS spectra. The measured Fe 2p3/2 peaks were not able to deconvolute into two peaks, corresponding to Fe2+ and Fe3+ states, which suggests that the concentration ratio between Fe2+ and Fe3+ is not comparable. The Fe 2p3/2 spectra have been fitted with a single peak. The centre of the peak was calculated to be 711.2 eV, which reflects that the valence number of Fe ion in BPFT0 ceramics is close to trivalent Fe3+. The long range ferromagnetic ordering as evident from well defined Mössbauer sextets exists at room temperature. The magnetic hyperfine splitting spectra indicate that the Neel temperature of BPFT0 nano particles is above room temperature as confirmed from DSC measurement. Mössbauer spectra of BPFT0 yield six line spectra with an isomer shift of 0.24mm/s and a hyperfine field (H) of 49.6mm/s which clearly shows the presence of Fe3+ state only; as observed from XPS. A doublet with isomer shift 0.19 mm/s and Q.S 0.51mm/s is also observed which (correspond to Fe3+) indicates the super paramagnetic behaviour of BPFT0 nano particles. Doping of Pb2+ for Bi3+ should force trivalent iron either in to tetravalent state or intermediate valence state between trivalence and tetravalence or result in the oxygen vacancies in the system. However, the observed Mössbauer spectra rules out the possibility of either intermediate valence or the tetravalence of iron. This may be due to compensation of charge by substituting Ti4+ for Fe3+. Quadrupole splitting 0.14mm/s observed for BPFT0 nano particles clearly indicates rhombohedral structure as observed from XRD. Hyperfine interaction field decreases from 49.9 T for BPFT0 to 44.2 T for BPFT2 which may be due to substitution of non-magnetic ions (Ti4+) for Fe3+.
6:00 PM - O3.13
Novel Solid Nanohybrids that Stabilize Oil/Water Emulsions and Catalyze Reactions at the Interface.
Jimmy Faria 1 2 , Min Shen 1 2 , Steven Crossley 1 2 , Daniel Resasco 1 2
1 School of Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma, United States, 2 Center for Biomass Refining, University of Oklahoma, Norman, Oklahoma, United States
Show AbstractA novel system has been developed to catalyze reactions at the oil/water interface of a biphasic liquid system. Stabilization of emulsions was accomplished through the use of nanohybrids composed of hydrophilic oxide particles and hydrophobic Carbon Nanotubes (SWNT), generated in the CoMoCAT process (1-4). These nanohybrids are inherently amphiphilic, and tend to adsorb at the interface of a biphasic water/oil liquid system. When enough energy is added to the system, these particles stabilize emulsions by suppressing the coalescence of the droplets (5). Depending on whether the particles are more hydrophilic or more hydrophobic they tend to stabilize oil-in-water or water-in-oil emulsions, respectively. The resulting emulsions are remarkably stable against coalescence and sedimentation, and can be easily separated by filtration or centrifugation, which make them suitable for applications in interfacial catalytic processes in which the catalyst can be easily recovered after reaction. The catalytic activity was provided by the deposition of transition metals onto the nanohybrids. Which allow the selective catalysis of reactions at the Oil/Water interface. The proof-of-concept of the biphasic hydrogenation and condensation catalysis was performed in three substrate classes of interest in biorefining. The first example was the hydrodeoxygenation of vanillin (4-hydroxy-3-methoxybenzaldehyde). The next one was the conversion of molecules that were exclusively soluble in the aqueous or the organic phase, like glutaraldehyde (water phase) and octanal (oil phase). Finally we explored a tandem reaction sequence in which Pd-catalyzed hydrogenation was paired with a preceding Aldol-condensation of 5-methylfurfural and acetone. The results show that with these nanohybrids is possible to perform selectively hydrodeoxygenation and condensation reactions at the water/oil interface of a biphasic system, followed by migration of the products to the oil phase. This contribution provides a proof-of-concept for a very promising catalytic system with many potential applications in the liquid phase, such as bio-oil upgrading, specialty chemicals, and pharmaceutical applications where selective reaction and separation based on water solubility are desirable.References:(1) W. E. Alvarez, B. Kitiyanan, A. Borgna, D. E. Resasco, Carbon 39, 547 (2001). (2) W. E. Alvarez et al. , Chem. Mater. 14, 1853 (2002). (3) D. E. Resasco et al. J. Nanopart. Res 4, 131 (2002).(4) D. E. Resasco, B. Kitiyanan, J. H. Harwell, W. Alvarez. U.S. Patent No. 6,333,016 (2001)(5) M. Shen, D.E. Resasco, Langmuir 25, 10843 (2009).
6:00 PM - O3.14
Multifunctional Nanoparticle Networks as Transparent Conducting Electrodes for Solar Cells.
Dennis Callahan 1 , Jeremy Munday 1 , Harry Atwater 1
1 Applied Physics, Caltech, Pasadena, California, United States
Show AbstractThere has been increased interest recently in the use of metallic nanoparticles to enhance the absorption in thin film solar cells. These studies mainly focus on the increased scattering efficiency of metallic nanoparticles in the visible region with the aim of redirecting long wavelength incident photons into guided modes within the solar cell, resulting in an increased path length. This would allow for much thinner active layers, leading to many advantages such as decreased dark current, relaxation of material quality requirements and reduction in material consumption. A previous study [1] has suggested the possibility that such nanoparticle arrays may also improve the cell’s fill factor by as much as 18%. Here, we explain this previous result by demonstrating that metallic nanoparticle arrays may also decrease the sheet resistance along the top of the solar cell, in addition to increasing the photocurrent. Thin films of various metals (Ag, Au, Cu) were deposited by thermal evaporation at 5x10-6 Torr with thicknesses varying from 2-30 nm on both GaAs and fused quartz substrates. These films were then annealed at various temperatures in 2.5 LPM of H2/N2 atmosphere to break up the metal layers into nanoparticles. Nanoparticle densities were studied ranging from sparse (~3x109 particles/cm2) to moderate (~7x1010 particles/cm2), until eventually resembling interpenetrating networks of continuous metal. 4-point probe measurements were performed on the samples to extract the effective sheet resistance of the nanoparticle-decorated surfaces. Scanning electron microscopy and atomic force microscopy were performed to determine the nanoparticle size, density and overall coverage. Identical experiments were performed on transparent fused quartz substrates to determine the transparency of the nanoparticle arrays with various surface coverage. Sheet conductance was found to increase by 10-30%, depending on initial Ag film thickness, eventually approaching that of bulk silver upon the onset of continuous metal film. A simple resistor network model is presented to explain the observed results. This study suggests the multifunctionality of metallic nanoparticle arrays for solar cell modification in that they may have the potential to simultaneously improve all relevant solar cell parameters, including short circuit current, open circuit voltage, fill factor and overall conversion efficiency. [1] Nakayama et al. Applied Physics Letters. 93, 121904 (2008).
6:00 PM - O3.15
CuInS2/Au Heterostructured Nanoparticles: Plasmonic Properties and Their Photocatalytical Applications.
Yeming Xu 1 , Quan Li 1
1 physics department, the Chinese University of Hong Kong, Hong Kong China
Show AbstractRecent demonstration of increased light absorption in a number of semiconductors as a result of scattering from noble metal nanoparticles have suggested promising application of semiconductor/Au heterojunctioned nanostructures in the field of both energy and photocatalysis. I-III-VI2 chalcopyrite compounds, in particular, nanostructured Cu(In1-xGax)(SySe1-y) are one of the most promising semiconductor candidates for photovoltaic and visible-light-driven photocatalytic applications due to their excellent optical properties—this family of material has direct band-gap and high optical absorption coefficient with desirable absorption range that matches the solar spectrum. In the present study, the heterostructured CuInS2-Au nanoparticles were synthesized with two controllable morphologies, i.e., CuInS2 nanocrystal surface decorated with multiple Au nanoparticles, and core/shell nanocrystals (Au@CuInS2). Their microstructure, electronic and optical properties were investigated in detail. In particular, the change of the Au surface plasmon (SPR) is carefully investigated using single heterstructured nanoparticles. Obvious red shift of the Au SPR energy (from ~520 nm to ~620 nm) was only observed in nanoparticles with¬ core/shell configuration. The core/shell Au@CuInS2 nanoparticles also demonstrate excellent photocatalytic response under visible light, being improved when comaring to the reported gold-loaded CuInS2 photocatalyst. This work is supported by grants from the GRF of HKSAR under project No. 414908, 414709, and CUHK Focused Investment Scheme C.
6:00 PM - O3.16
Enhanced Semiconductor Nanocrystal Conductance via Solution Phase Growth of Metal Contacts.
Mathew Sheldon 1 4 , Brandon Beberwyck 1 4 , Taleb Mokari 2 , Lin-Wang Wang 3 , Paul Alivisatos 1 4
1 Department of Chemistry, University of California, Berkeley, Berkeley, California, United States, 4 , Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractSingle nanostructure electrical measurements directly probe the fundamental limits of semiconductor device miniaturization, providing precise characterization of electronic structure resulting from quantum confinement and dimensional control. When employed to study individual colloidal semiconductor nanocrystals, the technique can also determine the ultimate transport efficiencies of these materials, essential for optimizing their performance in energy harvesting and other electronic and optoelectronic applications. Crucially, single particle experiments elucidate the semiconductor-metal interface between the nanoparticle and the device electrode, which determines the barrier physics to charge injection and thereby overall device performance. Here we show that direct solution phase growth of contact metals onto the semiconductor decreases the interface barrier, giving over 100,000 times conductivity enhancement per particle. Further, we systematically vary the contact metal and semiconductor nanoparticle to understand trends in electronic response. Our results emphasize the importance of nanoscale interface structure for robust device performance and the advantage of this contact method.
6:00 PM - O3.21
Au Nanocages: Promising Catalysts for Redox Reactions.
Jie Zeng 1 , Qiang Zhang 1 , Jingyi Chen 1 , Younan Xia 1
1 Department of Biomedical Engineering, Washington University in St Louis, St Louis, Missouri, United States
Show AbstractWe have evaluated the catalytic properties of Au-based nanostructures (including nanocages, nanoboxes, and solid nanoparticles) using a model reaction based on the reduction of p-nitrophenol by NaBH4. From the average reaction rate constants at three different temperatures, we determined the activation energy, the entropy of activation, and the pre-exponential factor for each type of Au nanostructure. The kinetic data indicates that Au-based nanocages exhibit the highest catalytic activity relative to either nanoboxes or nanoparticles. The considerable enhancement in catalytic activity for the Au nanocages can be probably attributed to the following two factors: i) the nanocage could provide a much larger surface (per particle) than a small solid nanoparticle to simultaneously accommodate both the oxidation and reduction half reactions; and ii) the ultrathin walls of the nanocage could provide a much higher activity than a big solid nanoparticle due to the size effect. In other words, the superior catalytic activity of the Au nanocages is a result of two effects -- good electrical connection and small size -- related to their ultrathin and highly porous walls. In addition, a compensation effect was observed in this catalytic system, which can be primarily interpreted by a model based on kinetic regime switching. Key words: gold nanostructures, catalysis, redox, compensation effectReferences(1) Skrabalak, S. E.; Au, L.; Li, X. D.; Xia, Y. Nat. Protoc. 2007, 2, 2182.(2) Zeng, J.; Huang, J.; Lu, W.; Wang, X.; Wang, B.; Zhang, S.; Hou, J. Adv. Mater. 2007, 19, 2172.(3) Schrinner, M.; Ballauff, M.; Talmon, Y.; Kauffmann, Y.; Thun, J.; Moller, M.; Breu, J. Science 2009, 323, 617.(4) Esumi, K.; Isono, R.; Yoshimura, T. Langmuir 2004, 20, 237.
6:00 PM - O3.22
Heat Generation in Illuminated Gold Nanoparticles on a Flat Surface.
Nan Zeng 1 , Anthony Murphy 1
1 CSIRO Materials Science and Engineering, CSIRO, Sydney, New South Wales, Australia
Show AbstractGold nanoparticles strongly absorb visible light of wavelength near520 nm through surface plasma resonance. The energy absorbed by the nanoparticles is converted to heat and thus increases the nanoparticles' temperature. Applications of this effect include modifying the shape of the nanoparticles, as well as using them as nanoscale heat sources to heat surrounding materials, such as polymers, ice, or biological cells. The aim is usually to use the heat generated to change the phase of the surrounding materials. We have previously studied heat transport problem for nanoparticles embedded in a homogeneous dielectric material, and identified the concentration of nanoparticlesas a major factor in determining the substrate temperature increase. For a porous system, where nanoparticles reside on the interface between the substrate and the voids, additional factors need to be considered. Air convection and conduction become important, as does their relation to the porosity of the system and the size of the pores.In this paper, we studied a model with gold nanoparticles adsorbed onto the surfaces of a porous polymer substrate. They are connected to the substrate through linker molecules. A flashlamp is used to irradiate the nanoparticles. The absorption efficiency of a cluster of nanoparticles is calculated using the T-matrix method. The heat transport equation is solved using the finite element method. Our results allow us to estimate the heating efficiency of gold nanoparticles in such a system.
6:00 PM - O3.23
Polycrystalline Semiconductor Nanowires: Controlling Electronic Coupling and Waveguiding.
Jianhong Zhang 1 , Andrey Lutich 1 , Christian Mauser 1 , Jessica Rodriguez-Fernandez 1 , Andrei Susha 1 2 , Markus Doeblinger 3 , A. Govorov 4 , Andrey Rogach 1 2 , Frank Jaeckel 1 , Jochen Feldmann 1
1 Department of Physics and CeNS, Ludwig-Maximilians-University Munich, Munich Germany, 2 Department of Physics and Materials ScienceDepartment of Physics and Materials Science, University of Hong Kong, Hong Kong China, 3 Department of Chemistry, Ludwig-Maximilians-University Munich, Munich Germany, 4 Department of Physics and Astronomy, Ohio University, Athens, Ohio, United States
Show AbstractPolycrystalline semiconductor nanowires prepared from colloidal semiconductor nanocrystals display an array of extraordinary optical properties. Single nanowires display optical waveguiding over distances of several micrometers rendering them promising for nanoscale optical interconnects. The photoluminescence peak wavelength of individual nanowires can be controlled thermomechanically via the distances between the nanocrystals in the wire at different temperatures [1]. Furthermore, strong anisotropic absorption, photoluminescence and Rayleigh scattering of both single nanowires and macroscopically aligned films are observed.[1] J. Zhang, A.A. Lutich, A.S. Susha, M.Döblinger, A.O. Govorov, A.L. Rogach, F. Jäckel, J. Feldmann, submitted
6:00 PM - O3.25
Design and Fabrication of Nanostructured Particles Exhibiting Enhanced Optical Functionality.
Robin Klupp Taylor 1 5 , Monica Distaso 1 5 , Volodymyr Lobaz 1 5 , Mathias Hanisch 1 5 , Huixin Bao 1 , Wolfgang Peukert 1 5 , Oleksandr Zhuromskyy 2 5 , Ulf Peschel 2 5 , Dina Ibragimova 4 5 , Andreas Hirsch 4 5 , Frantisek Seifrt 3 5 , Guenter Leugering 3 5
1 Institute of Particle Technology, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen Germany, 5 Cluster of Excellence "Engineering of Advanced Materials", Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen Germany, 2 Institute of Optics, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen Germany, 4 Institute of Organic Chemistry 2, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen Germany, 3 Insititute of Applied Mathematics, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen Germany
Show AbstractThe optical properties of small particles are key to many applications including pigments, cosmetics, optoelectronic devices, radiation control etc. In general due to the synthesis techniques available, such functional particles are usually single phase with simple or disperse morphologies. It is also known qualitatively from the literature that certain particle morphologies (spheres, rods etc.) and compositions can often lead to more favourable properties. In this paper we will summarize the work of an interdisciplinary industrial collaboration in the framework of the Cluster of Excellence “Engineering of Advanced Materials – Hierarchical Structure Formation for Functional Devices” situated at the University of Erlangen-Nuremburg, Germany. The goal of this work is to demonstrate a process chain for the design and synthesis of functional optical particles. The chain begins with 3D finite element method-based topology and shape optimization techniques. These provide suggestions for non-intuitive particle morphologies and compositions. These designs are being used as signposts for the development of real particle systems with enhanced properties. Our experimental work uses a range of colloidal techniques to synthesize nanostructured particles e.g. by “oriented attachment” assembly, sol-gel nanocoating and seeded growth. Areas of particular interest that will be introduced include particles which are designed to be transparency in one part of the optical spectrum but have strong extinction in another part as well as multifunctional magneto-optical particles. Since mathematical optimization often leads to reduced-symmetry particles, our work on the synthesis of asymmetrically coated particles (Janus particles) via modified colloidal techniques will also be presented.Product optical properties are often modified by particle-particle interactions. Hence, the use of simulation techniques such as the t-matrix method, which are being utilized to handle aggregates of the complex particles developed in this project, will be discussed.It is hoped that this paper will provide an overview of the progress of a broadly applicable strategy for the discovery and development of novel highly-functional optical particle systems.
6:00 PM - O3.26
Charge-selective Raman Scattering and Fluorescence Quenching by Metal Nanoparticle Monolayers on Semiconductor Substrates.
Karthik Bhatt 1 , Susheng Tan 1 , Kaan Kalkan 1
1 , Oklahoma State University, Stillwater, Oklahoma, United States
Show AbstractAn interesting attribute of monolayers of metal nanoparticles (NP) synthesized on semiconductor substrates is charging of NP induced by the Fermi level difference. This charging can be tapped in self-assembly, as well as selective adsorption of ions on NP, which augments the application of NP in surface plasmon resonance (SPR) sensors, surface-enhanced Raman scattering (SERS) substrates and other plasmonic devices. Although charging of NP is demonstrated in the literature by using surfactants, surfactant molecules cause signal interference. Further, surfactants form a physical barrier between analyte and metal, attenuating or completely eliminating surface-enhanced effects. In the present work, silver nanoparticles (AgNP) were synthesized on high conductivity Si wafers (p- and n-type) employing the electroless reduction of AgNO3 by Si, as well as vapor deposition. Electric force microscopy (EFM) confirms the presence of NP charge and its expected variation (charge and magnitude) with the Fermi level difference. The electric potential measured 100 nm from the NP, shows a monotonous increase with the nanoparticle size that we explain by a simple dipole approximation for the NP-semiconductor charge couple and depletion assumption for the semiconductor space charge region. Using our charged, surfactant free nanoparticles, we demonstrate charge selective Raman scattering and fluorescence quenching for ionic fluorophores (fluorescein(-), rhodamine-6G(+) and acridine orange(+)). Furthermore, we infer from atomic force microscopy (AFM) and optical absorption, that this charging phenomenon plays an important role in self-inhibiting growth of Ag nanoparticles (AgNP) during chemical reduction. In particular, the positively charged AgNP do not coalesce despite a few nm interparticle spacing. Therefore, strong electromagnetic interactions between the particles develop, resulting in well resolved hybrid plasmon modes as inferred from optical extinction. On the contrary, self-inhibition does not occur with negatively charged AgNP, resulting in the loss of surface plasmon resonance.
6:00 PM - O3.28
The Synthesis of Cu Nano Ink Using an Electrolysis Method and Application of Inkjet Printing.
Jin-min Cheon 1 , Jongryoul Kim 1 , Yong-Ho Choa 2
1 Materials Engineering, Hanyang Unv., Ansan Korea (the Republic of), 2 Chemical Engineering, Hanyang Unv., Ansan Korea (the Republic of)
Show AbstractIncreasing productivity of conductive nano-metal powder ink is recognized as a critical issue for the production of electro-magnetic devices using ink-jet printing. This paper presents a new synthesis method of Cu nano-particles mass-production using an electrolysis method. Compared with previous chemical methods, the electrolysis method makes it possible to fabricate Cu nano-particles directly from Cu plate. This can both reduce the production cost and increase productivity of Cu nano-particles. When voltage flows at Cu plate, Cu ions spring up to electrolyte and then change into Cu nano-particles by reduction agent and dispersion agent. Electrolyte containing the Cu nano-particles can be directly used as Cu conductive ink. In the electrolysis method, Cu nano-particles what having a variety size distribution are obtained by controlling voltage, dispersion agent, and reduction agent. Voltage is too high (ex. 300V), hydrolysis is rapidly occurred. In consequence, water is evaporated and electrolyte’s concentration is changed. Therefore 100~200V is suitable. Cu nano-particles are expected to form high-angle boundaries because of high surface-diffusion rate. So oxidation is critical problem of copper nano-particles. We obstruct oxidation by controlling electrolyte (ph control agent, dispersion agent, solvent, etc.). We print a pattern using inkjet printer (piezo-type single nozzle). After drying the pattern in vacuum oven at 60°C during 24hr, it is sintered in air, H2. And then the pattern is measured whether it is oxidized or not. To confirm low temperature sintering possibility for applying to flexible substrate, the pattern is sintered at 150°C, 200°C and 250°C. After that, we analyze sintering behavior by SEM image and measure resistivity of the pattern.
6:00 PM - O3.29
Dynamics of Electronic Relaxation in PbSe Quantum Dot Films.
Jesse Engel 1 2 , Matt Sheldon 1 2 , Wanli Ma 1 2 , Paul Alivisatos 1 2
1 Materials Science, UC Berkeley, Berkeley, California, United States, 2 Materials Science, Lawerence Berkeley National Lab, Berkeley, California, United States
Show AbstractFilms of colloidally synthesized quantum dots, with their size-tunable bandgaps and solution-based processing, show promise for use as electronic and optoelectronic devices such as solar cells, photodiodes, and transistors. However, charge transport through a quantum dot film is distinctly different from that through an extended crystalline solid. The films exhibit an energy landscape of localized states disordered in both their onsite energies, due to size polydispersity, and there structural periodicity, due to film packing. Hopping models have proven very effective in describing the conduction of these systems in the steady state, however much is still unknown about their dynamics. Electron localization leads to poor screening, allowing for long range coulomb interactions to play an important role. In terms of variable range hopping, this manifests itself by the creation of a “coulomb gap” in the density of states near the Fermi level due to carrier-carrier repulsion. Such systems are often referred to as coulomb glasses, as correlated electron dynamics and many-electron hopping events that arise from these interactions can lead to “glassy behavior”, such as long relaxation times due to the frustration of the minimization of configurational energy.Here, we present results on the time evolution of the resistance of PbSe quantum dot films, indicative of the relaxation of the coulomb glass. Thin film nanocrystal transistors were fabricated by evaporating patterned electrodes, with channel lengths and widths varying from 1-10um and 25-750um respectively, on n-doped Si wafers, with 100nm of dry oxidized silicon dioxide as a gate insulator. PbSe quatum dots 5 nm in diameter were colloidally synthesized and deposited on the transistor substrates via spincoating. To reduce particle spacing and increase interparticle coupling, films were then soaked in solutions of benzenedithiol in acetonitrile, to allow for ligand exchange with the native oleic acid ligands. Films were kept air-free in an argon environment for the entire course of the experiment. We observe distinctive power law decays on the order of thousands of seconds, which vary with voltage and temperature. Transient peak heights and power law decay exponents are found to increase for higher applied fields, with peak heights reaching an order of magnitude higher than the steady state at electric field values of 100kV/cm. The decay transients for increasing fields are also found to turn into growth transients (exponent > 0) for decreasing fields, leading to pinched hysteresis loops in I-V characteristics for sweep rates greater than 0.01V/s. Steady state conductance values are found to correspond to predictions for space charge limited transport with traps. Our results emphasize the correlation of the nonlinear features in the transient decay of film resistance and its equilibrium values to the dynamics of relaxation in the coulomb glass.
6:00 PM - O3.3
Synthesis and Characterization of TiO2 Nanoparticles: A Potential Adsorbent for As(III) Removal from Water/Wastewater.
Zuleyha Kocabas 1 , Yuda Yurum 1
1 Material Science and Engineering, Sabanci University, Istanbul Turkey
Show AbstractTitanium dioxide, a well-known adsorbent material, has been extensively tested in environmental applications, especially in separation technologies. In the present study, TiO2 nanoparticles were synthesized by using sol-gel method for removing arsenide (As(III)) ions from water/wastewater. Several water/titanium molar ratios were prepared in order to obtain optimum crystalline structure, morphology, and particle size of titanium dioxide nanoparticles. Two types of TiO2 minerals which were rutile and anatese were mainly synthesized at different calcination temperatures. After characterization of synthesized powders by X-ray diffraction and scanning electron microscopy (SEM), batch adsorption experiments were carried out to analyze removal capacity of the titanium nanoparticles. Residual arsenic concentrations of the solutions treated with titanium dioxide nanoparticles were measured with a Varian, Vista-Pro CCD simultaneous inductively coupled plasma ICP-OES spectrophotometer. The adsorption isotherms, kinetic and thermodynamic parameters of batch adsorption experiments were achieved. The maximum % of removal of arsenic was found ~77% at pH 3, respectively when 0.1 g rutile type TiO2 nanoparticles were used at the As0 5 ppm. Anatase type of TiO2 nanoparticles had also closer adsorption capacity which was ~63% at pH 6 with the same initial arsenic concentration. This study proposes the potential adsorbent material for water/wastewater which is contaminated with As(III) species.
6:00 PM - O3.30
Diameter Control and Theoretical Simulation of Ag-Au-Ag Heterometallic Nanowires.
Jongwook Jung 1 , Daeha Seo 1 , Hyunjoon Song 1
1 , Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractOne dimensional nanostructures have been used as basic and significant parts to fabricate nanodevices as well as an appropriate system to demonstrate quantum size and surface effects of nanomaterials. In this work, we prepared heterometallic nanowires with different thickness by a seed-mediated process using Au decahedral seeds. The thickness of the heterometallic nanowires was controlled by adjusting the size of the Au decahedral seeds, which play important roles to determine the dimension of heterometallic nanostructure. The resulting Ag-Au-Ag heterometallic nanowires have the diameters of 63 nm from small seeds (diameter : 52 nm), 86 nm for medium seeds(81 nm), and 146 nm for large seeds(143 nm), respectively. The Au and Ag segments in the Ag-Au-Ag heterometallic nanowires were analyzed by EDS, line profile, and elemental mapping. This seed-mediated process has advantaged in high yield, template-free, and relatively low reaction temperature.Optical properties of the Ag-Au-Ag heterometallic nanowires were studied to correlate with theoretical results by DDA (discrete dipole approximation) calculations. In UV-vis spectra, the peaks were significantly red-shifted when the nanowire thickness was increased. In this presentation, we demonstrated the synthesis and diameter control of Ag-Au-Ag heterometallic nanowires, and analyze their optical behaviors by DDA simulations.
6:00 PM - O3.31
Synthesis and Characterization of High Quality QDs Based on Thermal Decomposition Mechanism of Single Molecule Precursor Forming Nanoparticles.
Yun Ku Jung 1 , Jin-Kyu Lee 1
1 Chemistry, Seoul National University, Seoul Korea (the Republic of)
Show AbstractRecently, metal dialkyldithiocarbamates have been used as a single-molecule source for the synthesis of semiconductor QDs and rare-earth metal sulfide (MS) nanoparticles. Zinc diethylthiocarbamate (Zn(DETC)2) has also been used as a single-molecule source for QD synthesis; in this method, ZnS shells are grown around the surface of CdSe QDs in a microfluidic system. We have investigated in order to understand the formation of MS nanoparticles. The major intermediates and side products were isolated under various conditions and characterized by NMR spectroscopy and LC-MS. The analysis results showed that nucleophilic attack of the metal-coordinated amine on the most electron-deficient thiocarbonyl carbon of the alkyldithiocarbamate ligands at a high temperature initiated the decomposition to generate thiourea, hydrogen sulfide, and solid MS nanoparticles. The critical role of the amine in the thermolysis method used for the synthesis of metal sulfide (MS) nanoparticles could be extended to the synthesis of metal oxide (MOx) nanoparticles as well. We have synthesis high quality semiconductor QDs based on the thermal decomposition mechanism of single molecule precursor. Compared to purified QDs, which are removed excess organic ligands such as TOPO, the synthesized high quality semiconductor QDs are air stable for long time and the PL intensity is increased about 20 times. We speculate that thermal decomposition could be extended to many interesting applications such as generation of alloy nanoparticles through consecutive thermolysis of various single molecule precursor.
6:00 PM - O3.32
Probing the Photothermal Effect of Au-based Nanocages With Surface-enhanced Raman Scattering.
Matthew Rycenga 1 , Younan Xia 1
1 Biomedical Engineering, Washington University, Saint Louis, Missouri, United States
Show AbstractMetal nanoparticles can efficiently generate heat in the presence of electromagnetic radiation. This process, known as the photothermal (PT) effect, has the potential for use in a variety of applications from cancer therapy to lithography. However, characterizing the heat generated by metal nanoparticles is difficult, and fundamental to engineering the PT effect for practical use. To this end, we demonstrate a simple approach to probe the heat generated by Au-based nanocages using surface-enhanced Raman spectroscopy (SERS). The continuous wave lasers of a Raman microscope were used to excite the nanocages for both the SERS and PT effect. Because SERS directly measures the chemical structures of molecules on a metal nanoparticle, this technique can be used to determine the temperature at a nanoparticle's surface by employing probe molecules with measurable, temperature-dependent structural changes. The trans and gauche conformations of well-ordered alkanthiolate self-assembled monolayers (SAMs) chemisorbed to the nanocages were used to determine disorder in the SAMs caused by the heat released from the PT effect. Through controlled studies and molecular dynamic simulations these SAMs were calibrated to act as a ‘thermometer’ for determining the temperature at the nanoparticle surface for different excitation wavelengths, nanoparticle LSPRs, and nanoparticle compositions. Our data confirms the PT effect is greater when the excitation wavelength matches the LSPR of the particles, demonstrates the ability of SERS to monitor the PT effect of metallic nanoparticles, and shows the Au-based nanocage PT effect can increase surface temperatures by as much as 60 degrees.
6:00 PM - O3.33
Synthesis of Au(core)/Ag(shell) Nanoparticles and Their Conversion to AuAg Alloys.
Matthew Shore 1 , Junwei Wang 1 , Aaron Johnston-Peck 1 , Joseph Tracy 1
1 Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractAu(core)/Ag(shell) and AuAg nanoparticles (NPs) with diameters of 10 nm and controlled compositions were synthesized through digestive ripening and annealing. This approach is highly general and is potentially applicable for synthesizing many kinds of core/shell and alloy NPs with novel plasmonic and catalytic properties. Au NPs stabilized by dodecylamine (DDA) were first synthesized through digestive ripening in refluxing toluene, and addition of primary amines and silver acetate under different conditions resulted in Au(core)/Ag(shell) and AuAg alloy NPs when the amine reduced Ag(I) to Ag(0). An advantage of this method is that Au NPs serve as the seeds for forming binary NPs, because growth of monodisperse Ag NPs is usually more challenging than Au. Deposition of Ag on Au requires an additional reducing species (primary amine) and cannot occur through galvanic exchange. Adding silver acetate and DDA in toluene to ripened Au NPs and further refluxing produced Au(core)/Ag(shell) NPs. The structure and composition were analyzed by transmission electron microscopy and energy-dispersive X-ray spectroscopy. Growth of the Ag shell is accompanied by a small blue shift in the surface plasmon resonance absorbance. When annealing the Au(core)/Ag(shell) NPs in oleylamine at 250 °C, they convert to AuAg alloy NPs, and their absorbance band shifts to 430-475 nm (corresponding to Au:Ag molar ratios of 1:2 to 2:1). More recently, we have found a simpler, direct approach for synthesizing AuAg alloy NPs by transferring ripened Au NPs into oleylamine, adding silver acetate and DDA, and annealing at 250 °C, which skips formation of Au(core)/Ag(shell) NPs.
6:00 PM - O3.34
Emission Inhomogeneity in InAs Quantum Dot DWELL Structures.
Alejandro Vivas 1 2 , Erick Velazquez 1 , Georgy Polupan 1 , Ingri Guerrero 2 , Ye Shcherbyna 3
1 Materials Science, National Politechnic Institute , México, D.F., Mexico, 2 Advanced Technology, National Politechnic Institute , México, D.F., Mexico, 3 KPI, National Technical University , Ukraine, Kyiv, Ukraine
Show AbstractThe photoluminescence (PL) non homogeneity and PL power dependences has been studied in InAs quantum dots (QDs) embedded in the symmetric In0.15Ga1-0.15As/GaAs quantum wells (QWs) with QDs grown at different temperatures (470-535 C). In QD structures with InAs QDs grown at 470 and 490 C the low integrated PL intensity, the high dispersion of QD sizes in ensemble and, as a result, the large value of FWHM (50-70meV), but the low dispersion of QD ensemble parameters along the line crossed the structures have been detected. In QD structures grown at high temperatures 510-535 C the high integrated PL intensity, the low dispersion of QD sizes in ensemble and, as a result, less values of FWHM, but the essential dispersion of QD ensemble parameters along the line crossed the structures have been revealed. The comparison of experimental results for the PL intensity with theoretically predicted one has shown that three reasons are responsible for the emission non homogeneity in studied QD structures: i) the high concentration of nonradiative recombination centers in the capping In0.15Ga1-0.15As layer at low QD growth temperatures (470 C), ii) the QD density and size distributions in the structure with QD grown at 490-525 C, ii) the high concentration of nonradiative recombination centers in the GaAs barrier at higher QD growth temperatures (535 C). The reasons of nonradiative center formation in DWELL structures have been discussed.
6:00 PM - O3.35
Plasmon Modulated Light Scattering from Gold Nanocrystal-decorated Hollow Mesoporous Silica Microspheres.
Manda Xiao 1 , Jianfang Wang 1
1 Physics, The Chinese University of Hong Kong, Hong Kong, Hong Kong, China
Show AbstractDielectric core-metal shell nanostructures exhibit optical properties that are different from those of both constituents. Such nanostructures not only form a platform for studying the interaction between the surface plasmon resonance of the metal coating and the resonance mode of the dielectric core, but also have many technological applications. For example, a high-Q surface plasmon whispering-gallery microcavity with a plasmon loss rate close to the theoretical limit has recently been achieved through coating a thin layer of silver on a silica microdisk resonator. Such microcavities offer possibilities for plasmonic lasing. Up to date, most of previous studies have focused on the interaction between continuous metal coatings and dielectric resonators, where the plasmon resonance of the metal shell can only be tuned in a limited range.In recent years, a wide variety of noble metal nanocrystals have been prepared. Their plasmon resonance wavelengths can be synthetically tuned over a wide spectral range by varying the chemical compositions, shapes, sizes, and the surrounding environments. We have fabricated mesoporous hollow silica microspheres coated with gold nanocrystals. The overall diameter of the microsphere, the shell thickness, and the plasmon wavelength of the gold nanocrystal can all be synthetically tailored. The interaction between the plasmon and scattering resonances was investigated by dark-field scattering spectroscopy. The scattering resonance of the hollow microsphere is observed to be preserved after the coating of the gold nanocrystals, but the light scattering is significantly enhanced in the spectral region that corresponds to the plasmon resonance of the gold nanocrystals. The enhancement can therefore be ascribed to the light concentration by the gold nanocrystals that are adsorbed on the shell of the microsphere. The enhancement is highly dependent on the plasmon wavelength of the adsorbed gold nanocrystals and can be varied readily from the visible to near-infrared region by utilizing different gold nanocrystals. A real-time study on the interaction between the plasmon and scattering resonances was further carried out by in-situ monitoring the scattering spectra of the hybrid nanostructure during the chemical etching of the adsorbed gold nanocrystals. These studies can not only help in understanding the fundamental interaction between the localized surface plasmon mode and the scattering resonance mode, but also open up possibilities for potential applications in surface enhanced spectroscopy, biosensing, as well as real-time monitoring of drug delivery processes.
6:00 PM - O3.37
Structural and Magnetic Properties of Pure and Cobalt Doped Nanocrystalline Gallium Nitride.
Vottikondala Ganesh 1 , Sundaram Suresh 1 , Krishanan Baskar 1
1 Crystal Growth Centre, Anna University, Chennai, Tamilanadu, India
Show AbstractGaN crystalline powder is a promising material for Field emission display and vacuum fluorescent display applications due to its high reliability and low electric field consumption. Transition metal doped GaN is a promising material for the field of spintronics. Several groups reported the Mn doped GaN because of their potential applications in spintronics [1-3]. Thus magnetic, optical and electronic properties of GaMnN, especially in the form of thin films have been reported widely. In the present study pure and doped gallium nitride (GaN) nanocrystals were synthesized using gallium trichloride (GaCl3), ethylene diamine tetra acetic acid (EDTA)and cobalt chloride as raw materials at a temperature of 1173K in ammonia (NH3) atmosphere. The XRD spectrum for pure GaN synthesized shows the formation of single phase wurtzite structure. No impurity phases were observed in the X-ray diffraction pattern for 5% Co doped sample. Shift in X-ray diffraction peaks towards lower angle side, it confirms that the Co atoms introduces a strain in lattice of GaN. The XRD spectrum for 10% Co doped GaN shows the presence of secondary phases. Transmission electron microscopy images were taken for pure and Co doped GaN. Hexagonal morphology was observed in pure nanocrystaline GaN samples. The average size of the particle was found to be ~20 nm for pure and Co doped GaN. The magnetic measurements were carried out for the Co (5% & 10%) doped samples both at 10K and 300K. Clear hysteresis loop in the magnetization curve suggest the presence of ferromagnetic behavior in cobalt doped GaN. Temperature dependent magnetization (M-T) measurements were also carried out for doped samples using Super Conducting Quantum Interface Device (SQUID) from 10K to 300K The results have been discussed and correlated to structural and magnetic properties of the materials. Refernces;1.Takahiko Sasaki, Saki Sonoda, Yoshiyuki Yamamoto, Ken-ichi Suga, Saburo Shimizu, Kouichi Kindo, and Hidenobu Hori J. Appl. Phys. 91, 7911 (2002)2.S. J. Pearton, C. R. Abernathy, G. T. Thaler, R. M. Frazier, D. P. Norton, F. Ren, Y. D. Park, J. Phys. Condens. Matter 16, R209 (2004).3.C. Liu, F. Yun, and H. Morkok, J. Mater. Sci.: Mater. Electron. 16, 555 (2005).
6:00 PM - O3.38
Coupling between Ferromagnetic and Superparamagnetic Nanoparticles Confined within 1D Nanotemplates.
Richard Farrell 1 , Van Le 1 , Sarah Tolbert 1
1 Chemistry & Biochemistry, UCLA, Los Angeles, California, United States
Show AbstractMagnetic and coupled magnetic nanostructures are considered to be excellent candidates for performing both logic and memory functions in future nano-electronics. In the case of magnetic nanoparticles, as they approach a critical size known as the superparamagnetic limit, the magnetic anisotropy of the individual nanoparticles becomes comparable to their thermal energies. Consequently, the magnetisation of a nanoparticle can randomly flip direction at room temperature. By organising nanoparticles into sequential arrangements of chains within defined 1-D porous channels, one can impart the host anisotropy upon the nanoparticle chains, thereby increasing their stability to spin-flipping by creating additional magnetic anisotropy through constructive dipolar coupling interactions. To this end, continuous porous anodic alumina (PAA) films grown on silicon substrates (70 -300 nm thick) with pores sizes ranging from 8-12 nm can be used as host templates for stacking and confining both soft and hard magnetic nanoparticles in vertical geometries. Both superparamagnetic face-centred cubic (soft) and face-centred tetragonal (hard) iron-platinum nanoparticles have been synthesized with various sizes ranging from 6-10 nm and their incorporation within the PAA films studied. We combine SQuID magnetometry in conjunction with high resolution microscopy techniques to examine the effect of confining hard and soft/hard linear chains of nanocrystals. Preliminary results show that the stacked 1D nanoparticle arrays display an enhancement of magnetisation reversal energy (coercive width) as a result of coupling between the nanocrystals at room temperature relative to the random ensemble of nanoparticles.
6:00 PM - O3.39
Size-dependent Kirkendall Effect During the Oxidation of Nickel Nanoparticles.
Justin Railsback 1 , Aaron Johnston-Peck 1 , Junwei Wang 1 , Joseph Tracy 1
1 Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractThe transformation of Ni nanoparticles (NPs) of different sizes (average diameters of 9 nm, 26 nm, and 96 nm) during oxidation to hollow or porous NiO through the Kirkendall effect was observed by transmission electron microscopy. Images acquired after oxidation in ambient atmosphere for different times (1-4 hours) and at different temperatures (200-500 °C) show that the nanostructures of the oxidized NPs do not significantly depend on the oxidation temperature, but oxidation proceeds much more quickly at elevated temperatures. After formation of an initial NiO shell (of thickness ~3 nm), single or multiple voids nucleate at the interface between the Ni core and the NiO shell, and the voids grow until oxidation is complete. Differences in the void formation and growth processes lead to distinctly different nanostructures for each size: The 9 nm NPs form NiO shells that are nearly radially symmetric, while there is a pronounced asymmetry in the NiO shells for 26 nm NPs. For 96 nm NPs, multiple voids form and grow, which results in porous, polycrystalline NiO NPs. The origins of this size dependence will be discussed.
6:00 PM - O3.41
Mapping Conservative and Dissipative Magnetic Response of the Ordered Arrays of Ferromagnetic Nanoparticles by Band Excitation Magnetic Force Microscopy.
Senli Guo 1 , Stephen Jesse 1 2 , Hare Krishna 3 4 , Nozomi Shirato 5 , Anup Gangopadhyay 3 4 , Ramki Kalyanaraman 5 6 7 , Sergei Kalinin 1 2
1 Center for Nanophase Materials Sciences, ORNL, Oak Ridge, Tennessee, United States, 2 Materials Science and Technology Division, ORNL, Oak Ridge, Tennessee, United States, 3 Department of Physics, Washington University in St. Louis, St. Louis, Missouri, United States, 4 Center for Materials Innovation, Washington University in St. Louis, St. Louis, Missouri, United States, 5 Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee, United States, 6 Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee, United States, 7 Sustainable Energy and Education Research Center, University of Tennessee, Knoxville, Tennessee, United States
Show AbstractThe magnetic dissipation and inter-and intra particle interactions in the ordered arrays of ferromagnetic nanoparticles are studied by band excitation magnetic force microscopy. Nanoscale patterns are formed by pulsed laser interference melting of ultrathin metal films on SiO2 substrates as a result of the competition between thermocapillary flow and dewetting. Varying the composition of immiscible Cu-Co mixtures shows significant differences in the nature of interference patterning. This effect is due to a change in the thermophysical properties which in turn modifies the thermocapillary time scale (τTC) in relation to the dewetting time (τD). By increasing Co concentration in the mixture, the τTC decreases in comparison to τD resulting in more regular patterns. The magnetization directions, domain structures and dissipation of pure Co and Cu0.5Co0.5 mixture nanoparticles have been characterized by band excitation (BE) magnetic force microscopy. In band excitation, the SPM is excited using the complex digital signal containing the frequencies in the band containing the resonance peak of the cantilever. The subsequent simple-harmonic oscillator peak allows the conservative and dissipative parts of magnetic tip-surface interactions to be deconvoluted. Complex magnetic domains relevant to particle size and the domain switching behavior have been explored. Part of this research has been conducted at ORNL’s Center for Nanophase Materials Sciences sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. DOE.
6:00 PM - O3.44
Decoration of Ag-Cu Nanoparticles on Multiwalled Carbon Nanotubes and Their Applications in Polymer Composites.
Vijaya Rangari 1 , Sanchita Dey 1 , Shaik Jeelani 1
1 Materials Science and Engineering, Tuskegee University, Tuskegee, Alabama, United States
Show AbstractAg-Cu alloy nanoparticles were synthesized in the presence and absence of CNTs using a microwave heating technique. These nanoparticles were further infused in to epoxy resin to fabricate multifunctional nanocomposites. The morphology and structure of the Ag-Cu alloy nanoparticles were analyzed by transmission electron microscopy (TEM), X-ray diffraction and X-ray energy dispersion spectroscopy (EDS). The TEM results shows that the Ag-Cu alloy particles are spherical in shape and 100nm in diameter. These alloy nanoparticles were also coated on CNTs when the Ag-Cu alloy particles were synthesized in the presence of CNTs. The polymer nanocomposites of Ag-Cu and Ag-Cu coated CNTs were prepared by reinforcing these nanoparticles in epoxy resin by ultrasound irradiation. Thermal and mechanical properties of Ag-Cu coated CNTs alloy nanoparticles infused in epoxy shows improvement in glass transition temperature, flexural strength and flexural modulus as compared with neat epoxy and Ag-Cu/epoxy.
6:00 PM - O3.45
Novel Polymethyl Methacrylate (PMMA) Nanocomposites for Optical Applications.
Kyle Gipson 1 2 , Brett Ellerbrock 1 2 , Philip Brown 1 4 , Kathryn Stevens 2 , John Ballato 1 2 , Chris Cox 3 4
1 School of Materials Science & Engineering, Clemson University, Clemson, South Carolina, United States, 2 Center for Optical Materials Science & Engineering (COMSET), Clemson University, Clemson, South Carolina, United States, 4 Center for Advanced Engineering Fibers and Films (CAEFF) , Clemson University, Clemson, South Carolina, United States, 3 Department of Mathematical Sciences, Clemson University, Clemson, South Carolina, United States
Show AbstractMany polymer optical materials are comprised of hydrocarbon amorphous polymers like polymethyl methacrylate (PMMA), which have been selected mainly due to availability, low cost and the ability to process. However, the vibrational energies of such polymers are fairly high and tend to quench many of the transitions of light emitting additives, such as rare-earths. The purpose of this work is to develop PMMA fibers containing rare-earth doped fluoride nanocrystals such that the high efficiencies of the nanoparticle can be combined with the low cost and processability of the polymer. More specifically, the rare earth dopant terbium (Tb3+) was doped into LaF3 nanoparticles and subsequently dispersed into PMMA which was melt extruded into a fiber. By partitioning the rare earth into the fluoride crystal and not the polymer, the radiative emissions are maximized and the fiber could operate as a more efficient polymer optical fiber amplifier. This presentation will discuss the melt extrusion of nanocomposite polymers for optical applications including a review the thermal properties and structural characteristics of the polymers. The information gathered from the analysis of the intrinsic bulk properties will be used as the input data for a fiber extrusion simulation model. The subsequent production and characterization of the physical and optical properties of the fibers will also be discussed.
6:00 PM - O3.46
Structure and Electrical Conductivity of TiO2 Nanoparticles-doped PANI.
Segundo Jauregui-Rosas 1 , Yolanda Ramos-Geldres 2 , Raul Zulueta-Vasquez 2 , Luis Angelats-Silva 1 , Boris Renteria 3 , Abel Gutarra-Espinoza 4 , Croswel Aguilar-Quiroz 5
1 Fisica, Universidad Nacional de Trujillo, Trujillo Peru, 2 Ingenieria, Universidad Nacional de Trujillo, Trujillo Peru, 3 Department of Materials Science and Engineering, University of Puerto Rico, Mayaguez, Puerto Rico, United States, 4 Facultad de Ciencias, Universidad Nacional de Ingeniera, Lima Peru, 5 Facultad de Ingeniería Química, Universidad Nacional de Trujillo, Trujillo Peru
Show AbstractPure and TiO2-doped polyaniline (TiO2-PANI) have been synthesized by polymerization at -10, 0 and 23°C. The effect of TiO2 nanoparticles, prepared by a simple sol-gel method, and polymerization temperature on structure and electrical conductivity of polyaniline has been studied. X-ray diffraction (XRD) indicated that pure PANI salt esmeraldine, polymerized at 0°C, presents the better crystallinty, while the nanocrystalline TiO2 shown only anatase phase, with average crystallite size of 35nm. In turn, the XTD patterns of composites shown a strong effect of TiO2 on the crystallinity of PANI, which was confirmed by FT-IR spectroscopy, and the fingerprint of PANI was clearly identified. Electrical conductivity measurements, carried out by four-point method, indicate that conductivity of composites increases from 2.55 S.cm-1 for undoped PANI to 8.36 S.cm-1 for TiO2-doped PANI (3%w/w), but decreases for higher TiO2 contents. Morphological analysis of composites by SEM will be also presented.
6:00 PM - O3.47
Fabrication of Polymer-silica Hybrid Hollow Spheres for Optimized Functionality.
Jin Young Kim 1 , Yong Seok Kim 1 , Jong Chan Won 1 , Hyun Min Jung 1
1 Advanced Materials Division, Korea Research Institute of Chemical Technology, Daejeon Korea (the Republic of)
Show AbstractFabrication of polymer hollow spheres and core-shell capsules has been considered as an important research field due to potential use in a wide range of applications. These spheres have been intensively developed to have various shapes and properties to allow them to function as nano/micro containers for controlled release, transportation, storage, and reactions of substances. To obtain functional hollow spheres, various synthetic methods have been reported and hybrid types of capsules also have been extensively developed. The major routes for fabrication are inorganic layer formation on hard and soft templates or starting with an inorganic particle template on which to form the organic layer. Although excellent control of shape and functionality is now available, for practical usage as micro-containers and reactors, there is still need for more control of structural stability and tolerance for various circumstances and processes (such as drying isolation, medium exchange, and core exchange).In this work, a simple preparation method for polymer-silica double layered capsules is described.1 These are fabricated through interfacial polymerization and successive formation of internal silica layer from pre-included precursors. This silica inner shell performs a role of internal framework to provide stability on flexible polymer capsules, which are deformable in polymer-swellable solutions. Therefore, core material exchange and complete removal of core substances, free from irreversible shape deformations, can be achieved. The hollow capsules with polymer-silica double shell, which have selective permeability depending on swelling tendency in solution, are stable for various manipulations of drying, isolation, core substances exchange, dispersion in various solvents and reactions inside capsules, to provide important characteristics for practical applications. As another advanced structure of polymer-inorganic hybrid spheres, we developed mesoporous silica shell/organic core particles, where enough free volume was fabricated between outer shell and inner core for storage of reagent. Three different type of hybrid core-shell particles were fabricated, which are polymer inner core, carbon inner core, and silica core, respectively. These particles were used for sweeping in small molecules to provide demonstration of application in separation of materials as nanometer levels.
6:00 PM - O3.48
Synthesis of Compatibilized Triacetyl Cellulose-SiO2 Nanocomposites by Surface Modification of SiO2.
Young-Jae Kim 1 , Shin-Woo Ha 1 , Jin-Kyu Lee 1
1 Chemistry, Seoul National University, Seoul Korea (the Republic of)
Show AbstractWe have successfully fabricated triacetyl cellulose (TAC) polymer-silica nanocomposite films having up to 40 wt% of incorporated silica nanoparticles by deliberately designing a surface ligand that has a structure similar to that of polymer repeating units and effectively modifying the surface of silica nanoparticles through chemical bonding. Cross-sectional TEM analysis reveals no significant aggregation in all TAC-silica nanocomposite films in. Thermal analysis results suggested that TAC-silica nanocomposites had higher Tg and Tc values as compared to pure TAC and the increase in Tg and Tc was directly proportional to the silica content. The transparency of all the nanocomposite films was over 80% in the visible range, confirming the excellent compatibility of nanoparticles with TAC.In this study, we enhance the interaction between nanoparticles and polymer matrices by modifying the surface of nanoparticles with a ligand that has a structure similar to that of polymer repeating units. It is expected that this method can be applied to other polymer systems to develop useful nanocomposites.
6:00 PM - O3.49
Anisotropic Sheets Containing Self-assembled Sunset-yellow FCF Discotic Columns.
Young-Jin Kim 1 , Seul-Ki Park 1 , So-Eun Kim 1 , SeHyun Lee 1 , Yun-Bae Kook 1 , Changwoon Nah 1 , Myung-Hoon Lee 1 , Kwang-Un Jeong 1
1 Polymer Nano Sci. & Tech., Chonbuk National University, Jeonju Korea (the Republic of)
Show AbstractAnisotropic nanofiber sheets containing self-assembled Sunset-Yellow FCF (H-SSY) discotic columns were successfully fabricated by electrospinning of a poly(vinylpyrrolidone) (PVP)/H-SSY/H2O solution exhibiting a biphase of nematic (N) and isotropic (I) phase. Macroscopically oriented nanofiber sheets were obtained by increasing rotational speed of collector than the electrospinning speed. The morphologies of the electrospun nanofibers were investigated by scanning electron microscope (SEM) and polarized optical microscope (POM). The molecular orientations and structures of H-SSY in the aligned nanofibers were also identified by POM, wide angle X-ray diffraction (WAXD) and polarized Fourier-transform infrared spectroscopy (FT IR). Based on the experimental results, it was realized that the H-SSY molecules in PVP/H-SSY nanofibers stacked together and created columns, which long axes were parallel to the axis of nanofiber. 2D WAXD results clearly that the electrospun nanofiber was not in a crystalline phase but in a glassy columnar nematic phase, which was confirmed by 2D WAXD of the annealed nanofiber. When the electrospun nanofiber was heated above Tg of PVP, H-SSY molecules migrated to the surface of nanofibers and formed nanocrystals. This means that the electrospun nanofiber below the Tg of PVP was in a metastable state.
6:00 PM - O3.5
Optimization of Light Emission from Silicon Nanocrystals Grown by PECVD.
Satoshi Ishikawa 1 , Szu-Lin Cheng 2 , Yiyang Gong 3 , Jelena Vuckovic 3 , Yoshio Nishi 3
1 Corporate Manufacturing Engineering Center, Toshiba Corporation, Yokohama, Kanagawa, Japan, 2 Department of Materials Science and Engineering, Stanford University, Stanford, California, United States, 3 Department of Electrical Engineering, Stanford University, Stanford, California, United States
Show Abstract Light emission from Si nanocrystals ( SiNCs ) embedded in Si oxide was studied in this work. SiNCs were fabricated by annealing a Si-rich oxide ( SRO ) deposited by a plasma-enhanced chemical vapor deposition ( PECVD ) system. The gas flow ratio between SiH4 and N2O of a precursor gas was changed by varying a N2O gas flow rate and the annealing temperature was varied from 800 to 1100°C. The highest PL intensity was obtained with a N2O flow rate of 125sccm, a SiH4 flow rate of 1400sccm and annealing temperature of 900°C. The PL wavelength was also controlled by N2O gas flow rate and annealing temperature, with blue shifting to the visible wavelengths for increasing N2O flow rate and decreasing annealing temperature. In addition, forming gas ( 4% H2 ) anneal for 1 hour, which is a common method to passivate Si surface, at 500°C to SiNCs was used to further enhance the emission intensity. To approach emission at shorter wavelength, the Si oxide with SiNCs / SiO2 multi layer structure ( MLS ) was also fabricated by similar methods. The SiO2 layer was used as a diffusion barrier to extra Si on vertical direction during the annealing process. Such a barrier can effectively reduce the diameter of SiNCs and shift the emission peak to shorter wavelength. A blue shift from PL was clearly observed as the thickness of Si oxide layer with SiNCs in MLS reduces.Finally, the PIN light emitting diode which consisted of n-type poly-Si / Si oxide with SiNCs / p-type poly-Si structure was also fabricated to study the electroluminescence ( EL ) of SiNCs. The current under the forward bias was about 10 times higher than under the reverse bias. The carrier injection mechanism assumed that Poole-Frenkel type conduction or hopping conduction dominates under a low electric field and Fowler-Nordheim tunneling dominates under a high electric field. EL was obtained with a forward bias voltage of around 6V and EL emission efficiency was proportional to the current density.
6:00 PM - O3.50
Transparent, Conductive Phase Segregated ITO/PC Composites.
Celeste Mason 1 , Rosario Gerhardt 1
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractMixtures of 50nm indium tin oxide particles and polycarbonate beads were ued to make phase segregated conducting composites. The mixtures were mechanically mixed in compositions ranging from phr = 1.0 to 0.001. Samples of each composition were heated for 25 minutes at 180°C at 20kN. Measured transmittance ranged from 5% to 68% at 400nm, 15% to 80% at 700nm, and averaged 10% to75% across the visible spectrum. Electrical percolation was found to occur at phr = 0.33.
6:00 PM - O3.51
Dielectric Studies of Segmental and Global Chain Motions in Intercalated Poly (propylene oxide) Amines/Layered Silicate Nanocomposites.
Kalliopi Vartzelis-Nikakis 1 , Sophia Kripotou 2 , K. Triantafyllidis 3 , P. Xidas 3 , Apostolos Kyritsis 1
1 Physics, National Technical University of Athens, Athens, 0, Greece, 2 Physics, National Tecnical University of Athens, Athens Greece, 3 Chemistry, Aristotelian University of Thessaloniki, Thessaloniki Greece
Show AbstractPolymer-layered silicate nanocomposites (PLSN) have, recently, attracted much attention because of significant improvement in several properties in comparison to pristine polymers. For the synthesis of PLSNs the choice of layered materials is often the smectite clays (e.g. montmorillonite, hectorite) due to their highly expansive characteristic and their rich intercalation chemistry which allows them to be chemically modified and to become compatible with the polymer precursors. Recently, a new method of preparing epoxy-clay nanocomposites has been proposed: the direct incorporation of poly (propylene oxide) amines (also used as epoxy curing agents) in the galleries of montmorillonite clays via ion-exchange. In this work we investigate the dynamics of poly (propylene oxide) amines intercalated in montmorillonite clays by means of Differential Scanning Calorimetry (DSC), Thermally Stimulated Depolarization Currents (TSDC) and broadband Dielectric Relaxation Spectroscopy (DRS) methods. The amines of interest were the commercially available α, ω-diamines known as Jeffamine D-series amines with molecular weights in the range 400 – 4000. Depending on the chain length of the diamine, different orientations of the PPO chains were adopted in the clay galleries: Low molecular weight Jeffamines (MW ~ 400) intercalate as lateral bilayer to inclined monolayer and the gallery heights are restricted to d001 basal spacing values of approximately 17 Å. For Jeffamines with MW values of 2000 and 4000 the PPO chains adopted a folded configuration within the galleries resulting in d001 values of approximately 20 – 46 Å.Our results reveal a remarkable dependence of the segmental mobility (α relaxation) of the intercalated diamines on the chain length of the polymeric chains and on the basal spacing of the organoclays which reflects differences in gallery height. Specifically, for the intercalated D400 (the shortest chain, ~ 6 repeating units) the segmental relaxation is suppressed and the molecular mobility exhibits Arrhenius temperature dependence. For the intercalated D2000 the segmental mobility is retarded whereas for the intercalated D4000 (the longest chain) the segmental mobility seems to be unaffected. The comparative study of the secondary relaxation mechanism of the diamines and of the global chain motions (although with higher uncertainty for the intercalated chains) provide valuable information with respect to the effects of a restrictive environment on chain dynamics. Acknowledgements. A.K. and S.K. acknowledge financial support of NTUA via program «PEVE 2007». K.S.T. acknowledges partial support of EU and Greek Ministry of Development via program EPAN-PENED2003.
6:00 PM - O3.52
Percolation Conduction of Mixed Nanoclusters Films for Nano-devices.
Chi Won Ahn 1 , IlSeok Kang 1
1 , NNFC, Daejon Korea (the Republic of)
Show AbstractElectrical conduction of metal nanoclusters by percolation is a very interesting area in nano-device [1]. For more functional nano-sensors consisting of multiple nanoclusters blending film, various metals, such as Cu, Ni, Sn, Ag, Au nanoclusters films were fabricated using inert-gas condensation method [2]. The percolation threshold of the films was measured. In addition, for the operation of sensors using these nanoparticle films in air, aging experiments of the percolated films, in air were carried out. While the percolation threshold was in connection not with the material species but with the area coverage of nanoparticle films, the conductive characteristics according to the aging temperature depended on the material species. The conductances of the percolated film of mixed metal nanoclusters were an approximately exponential function of temperature. Reversible and irreversible behavior of conductance of nanocluster mixture are investigated with nanoscale microstructures with electron microscope.This work was supported by the KOSEF grant funded by the Korean Ministry of Education, Science and Technology (No. R01-2009-000-20675-0).References1. A. Lassesson, M. Schulze, J. van Lith and S. A. Brown, Nanotechnology 19, 015502 (2008).2. R. Reichel, J. G. Partridge, A. D. F. Dunbar, S. A. Brown, O. Caughley, and A. Ayesh, J. Nanoparticle Res. 8, 405 (2006).
6:00 PM - O3.54
Effect of Nano Sintering Additive on the Mechanical Properties of WC-Ni Hard Metal.
GilGeun Lee 1 , KyungJu Kim 1 , KiHwan Jang 1 , ChanYoung Kim 2
1 Division of Materials Science and Engineering, Pukyong National University, Busan Korea (the Republic of), 2 , Hi-material Corporation, Jeonju Korea (the Republic of)
Show AbstractThe hard metals manufactured by the powder metallurgy process consist of a composite microstructure of hard particles dispersed in a soft binder matrix. Generally, WC, TiC, TaC, NbC and Ti(C, N) particles have been used as the dispersion material, and Co and Ni as the matrix. Hard metal based on WC-Ni has been widely used for wear-resistant machine parts because it has superior mechanical properties, such as hardness, fracture toughness and corrosion resistance, etc. The mechanical properties of the hard metals depend not only on the chemical composition but also on their microstructure. The hardness, fracture toughness and wear properties of the hard metals were significantly influenced by the size of the hard particles and the distance of the mean free path among the hard particles. Also, these mechanical properties simultaneously changed with addition of sintering additive. Generally, this has been used for increasing sinterability. However, the sintering additive also changed microstructure, because the sintering additive affects to the properties of interface between the dispersed hard particle and matrix phases. In the present study, the focus is the analysis of the nano sixed sintering additive effect on the mechanical properties of WC-Ni hade metal. The nanostructured WC-Ni hard metals were prepared by the combination of the mechanical milling and liquid phase sintering processes with addition of nano sized sintering additives, silicon and boron. The changes in the microstructure, hardness and fracture toughness with the amount of the nano sized sintering additives were analyzed using SEM, TEM, EPMA, Vickers hardness and three point bending test. The change in the mechanical properties of sintered body was discussed with the microstructure, phase and structure of the interface between the nano sized dispersed hard particle and matrix.
6:00 PM - O3.55
Effect of Porphyrin on Quantum Transport of Gold Nanoparticle Hybrid Assemblies.
Yuki Noda 1 , Tomoyuki Akutagawa 1 2 , Shin-ichiro Noro 1 2 , Takayoshi Nakamura 1 2
1 Graduate School of Environmental Science, Hokkaido University, Sapporo Japan, 2 Research Institute for Electronic Science, Hokkaido University, Sapporo Japan
Show AbstractGold nanoparticle assemblies have attracted much attention because they are expected as building blocks for a new electronic device. A number of studies have been carried out to connect gold nanoparticles using organic molecules, and the electron transport properties of the resulting network structure were evaluated. For example, saturated alkane - gold nanoparticle assemblies showed metal-insulator transitions depending on inter-nanoparticle separation. On the other hand, charge transport mechanisms of nanoparticle assemblies incorporating conjugated moleclules have not been fully understood although they would have remarkable feature arising from the contribution of molecular orbital to the electron conduction. Studies on this subject are expected to open up new applications in the field of molecular electronics.In this work, we fabricated hybrid assembly structures between gold nanoparticles and porphyrin derivatives, in which macrocyclic rings were expected to attach parallel on gold surface. The electronic transport properties in the temperature range from room temperature to 4 K were investigated using gold electrode with an electrode gap of 30 μm.Around room temperature, the conductivity of the hybrid assembly structure showed a semiconducting behavior, which followed the Arrhenius plot (EA = c.a. 15 meV) with ohmic I - V characteristics. On the other hand, the activation energies at lower temperatures were nonlinearly decreased in σ-1/T plot. Non-linear current–voltage characteristics, which corresponded to the collective quantum transport ( I ~ (V /Vth – 1)ξ ), was observed below 20 K.
6:00 PM - O3.6
Piezochromic Phenomena of 5-10nm Inorganic Powder.
Lihong Su 1
1 Departmentof applied Chemistry , Northwestern polytechnical University, Xi'an, shaanxi prov., China
Show AbstractPiezochromism describes the tendency of certain materials to change color with the application of pressure. It is particularly pronounced in polymer or some inorganic material palladium complexes etal. The main works significantly at very high pressures, usually at kbar. The author find the 5-10nm mixture oxide particle can change color at only 0.02-0.05kbar. The reported piezochromism of solid inorganic and organic materials has been investigated by examination of the phase transition phenomena. But the nanometer powder have different process, so it maybe a new kinds of piezochromism material.
6:00 PM - O3.7
Inorganic, Organic and Hybrid Sub 100 Nanometer Particles via Spray Drying.
Elizabeth Keene 3 , Debra Repko 2 , Lia Vue 1 , Cordin Arpagaus 4 , Nicholas Coppa 1
3 , Johns Hopkins University, Baltimore, Maryland, United States, 2 , Buchi Corporation, New Castle, Delaware, United States, 1 , Nanomaterials Company, Malvern, Pennsylvania, United States, 4 , Buchi Labortechnik AG, Flawil Switzerland
Show AbstractInorganic nanoparticles of technological importance including SiO2, , Fe2O3, ZnO, CeO2, TiO2 and ZrO2 were produced using a new spray drying method. The spray drying method utilized a nozzle consisting of a piezioelectricaly driven oscillating perforated membrane that delivers droplets of precise size without the use of propellants. Dried particles were collected using electrostatic precipitation. Nanoparticle size and size distribution were analyzed using real time differential mobility analysis and electron microscopic techniques including scanning transmission electron microscopy and high resolution electron microscopy. The materials produced were consistently composed of sub-100 nm particles having normal distributions about a mean between 45 and 55 nm. The technique was also applied to organic materials including trehalose and PVA and hybrid inorganic/organic materials such as PVA/Fe2O3 and Trehalose/ZrO2. Processing parameters, composition and morphology including the distribution of the organic and inorganic components in the nanoparticles will be discussed.
6:00 PM - O3.8
Preparation of MHS Nanosensor Particles and Their Potential Application for Metal Ion Sensing Device.
Chan-Yoon Jung 1 , Hae-Jung Yang 1 , Jung-Soo Kim 1 , Yong-Hyon Kim 1 , Sang-Man Koo 1
1 Chemical Engineering, Hanyang University, Seoul Korea (the Republic of)
Show AbstractMetal ions are one of major concerns in environment and public health and the determination of their concentrations is very important. The metal ion concentrations have been determined by the analytical tools such as absorption spectrometry, electrochemical methods, and fluorescence spectrometry. . However, development of simple, inexpensive, and fast responsive sensors for important metal ions is in high demand for on-site monitoring of metal ion concentrations. In our work, we have developed sensors for Zn2+, Cd2+, and Hg2+ based on prepared multi-functional hybrid silica (MHS) particles including vinyl, amine, and thiol functional groups. The sensors were prepared as follows: The MHS particles were prepared by modified sol-gel process; the amine groups of MHS particles were converted to carboxy groups and applied on the amine patterned substrate to form a self-assembled layer of MHS particles; the thiol group of the MHS particles were oxidized to SO3H by addition of H2O2 solution; and then TMPyP (α,β,γ,δ–tetrakis(1-methylpyridinium-4-yl)porphine p–toluenesulfonate) sensor molecule were bound to thus modified MHS particles by ion-pair interaction between negative (SO3H) and positive charge (TMPyP). In the presence of Zn2+, Cd2+, and Hg2+, the visible color of sensor particles is changed from orange to green due to the formation of complex between TMPyP and the metal ions. The complex with each different ion exhibits different absorption peak at nm for Zn2+, nm for Cd2+, and nm for Hg2+, repectively, enabling selective detection of each ion. A discernible color change in MHS sensor particles would be a rapid indication of the existence of heavy metal ions, while the quantitative determination of a metal ion concentration could be obtained from an absorption spectroscopy.
6:00 PM - O3.9
Hydrogen Uptake of Metal Ions Doped Multi-layer Titanate Nanostructures.
Nam-Hee Lee 1 , Hyo-Jin Oh 1 , Sun-Jae Kim 1 , Sang-Chul Jung 2
1 Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul Korea (the Republic of), 2 Department of Environmental Engineering, Sunchon National University, Sunchon Korea (the Republic of)
Show AbstractMulti-layered titanate nanostructures added with metal ions having various ionic radiuses were hydrothermally prepared in a strong basic solution. From the TEM results, the interlayer distances of metal ions added powders were changed 0.64 to 0.76 nm. The shapes of particles doped with Zr4+ and Li+ showed nano-belt and nano-plate, respectively. These results suggest that particle shape of titanates can be controlled only by adding a small amount of dopants in NaOH aqueous solutions. To minimize the effect of water molecules on obtained powders, the moisture contents were controlled by repetitive freeze drying and vacuum drying method. The hydrogen uptake of Ni2+ doped titanate was measured surprisingly more than 1.7 wt%, although that of other titanates were in the range of 0.2 - 1.5 wt%.
Symposium Organizers
Yuping Bao The University of Alabama
Andrew M. Dattelbaum Los Alamos National Laboratory
Joseph B. Tracy North Carolina State University
Yadong Yin University of California-Riverside
O4: Fundamentals for Medical Applications
Session Chairs
Wednesday AM, April 07, 2010
Room 2014 (Moscone West)
9:30 AM - **O4.1
The Workings of NCI Alliance for Nanotechnology in Cancer – From Materials and Device Development to Clinical Opportunities.
Piotr Grodzinski 1
1 , National Institute of Health, Bethesda, Maryland, United States
Show AbstractNational Cancer Institute is engaged in efforts to harness the power of nanotechnology to radically change the way we diagnose and treat cancer. Novel and multi-functional nanodevices will be capable of detecting cancer at its earliest stages, pinpointing its location within the body, delivering anticancer drugs specifically to malignant cells, and determining if these drugs are effective. Functionalized nanoparticles would deliver multiple therapeutic agents to tumor sites in order to simultaneously attack multiple points in the pathways involved in cancer. Such nano-therapeutics are expected to increase the efficacy of drugs while dramatically reducing potential side effects. In vivo biosensors would have the capability of detecting tumors and metastatic lesions that are far smaller than those detectable using current, conventional technologies. Furthermore, they will provide rapid information on whether a given therapy is working as expected.In order to further these research goals, NCI Alliance for Nanotechnology in Cancer has been formed in 2004. The Alliance pursues applied nanotechnologies for cancer detection, therapy, and prevention with an aim to achieve clinical translational stage of these technologies towards culmination of the program. The Alliance funds Centers of Cancer Nanotechnology Excellence, the development of nanotechnology platforms, and intramural Nanotechnology Characterization Laboratory (NCL). NCL provides a spectrum of data on the physical parameters and pharmacological and toxicological characteristics of clinically promising nanomaterials. The eight CCNEs – Centers of Cancer Nanotechnology Excellence represent prime research institutions in the US: Carolina Center of Cancer Nanotechnology Excellence at the University of North Carolina, Center for Cancer Nanotechnology Excellence Focused on Therapy Response at Stanford University, Center of Nanotechnology for Treatment, Understanding, and Monitoring of Cancer at the University of California, San Diego, Emory-Georgia Tech Nanotechnology Center for Personalized and Predictive Oncology at Emory University and Georgia Institute of Technology, MIT-Harvard Center of Cancer Nanotechnology Excellence at MIT and Harvard University, Nanomaterials for Cancer Diagnostics and Therapeutics at Northwestern University, Nanosystems Biology Cancer Center at California Institute of Technology, and the Siteman Center of Cancer Nanotechnology Excellence at Washington University.This presentation will describe the details behind the organization and science and technology of the Alliance.
10:00 AM - **O4.2
Multifunctional Nanoparticles, Coupled Behavior and Applications.
Xiaohu Gao 1
1 Bioengineering, University of Washington, Seattle, Washington, United States
Show AbstractNanoparticles are of considerable current interest, not only because of their unique size-dependent properties but also their dimensional similarities with biological macromolecules (e.g., nucleic acids and proteins). These similarities could allow an integration of nanotechnology and biology, leading to major advances in medical diagnostics, prognostics, and targeted therapeutics. In this talk, I present recent development of multifunctional nanostructures for multimodality imaging.
10:30 AM - O4.3
Polymeric/Inorganic Multifunctional Nanoparticles for Simultaneous Drug Delivery and Visualization.
Andrea Fornara 1 , Alberto Recalenda 1 , Jian Qin 1 , Abhilash Sugunan 1 , Fei Ye 1 , Sophie Laurent 2 , Muller Robert 2 , Jing Zou 3 , Usama Abo-Ramadan 4 , Muhammet Toprak 1 , Mamoun Muhammed 1
1 Functional Materials Division, Royal Institute of Technology, Kista Sweden, 2 NMR and Molecular Imaging Laboratory - Dep. of General, Organic & Biomed Chemistry, University of Mons-Hainaut, Mons Belgium, 3 Department of Otolaryngology, University of Tampere, Medical School, Tampere Finland, 4 Experimental MRI Laboratory, Biomedicum Helsinki, Helsinki Finland
Show AbstractNanoparticles consisting of different biocompatible materials are attracting a lot of interest in the biomedical area as useful tools for drug delivery, photo-therapy and contrast enhancement agents in MRI, fluorescence and confocal microscopy. Drug delivery systems have been designed to improve the pharmacological and therapeutic properties of drugs compared to the conventional free drugs. Nanostructured polymeric particles represent one of the most promising types of drug delivery system in relation to their small size, biocompatibility and biodegradability. Our work mainly focuses on the synthesis of nanoparticles based on biocompatible di-block copolymer poly(L,L-lactide-co-ethylene glycol) (PLLA-PEG) via nanoemulsion-evaporation method. Besides containing a hydrophobic drug (Indomethacin or dexomethasone), these polymeric nanoparticles incorporate different visualization agents such as superparamagnetic iron oxide nanoparticles (SPION) or fluorescent Quantum Dots (QDs) that are used as contrast agents for MRI and fluorescence microscopy. Gold Nanorods can also be incorporated in such nanostructures to allow simultaneous visualization and photodynamic therapy. By tailoring the synthesis parameters, it is possible to control the size of such nanoparticles to be in the range 60-200 nm and the rate of release of the drug. MRI studies were performed with different loading of SPION into the polymeric nanoparticles, showing an enhancement in T2 contrast superior to commercial contrast agents. Core-shell QDs absorption and emission spectra were recorded before and after their loading into polymeric nanoparticles. When synthesis conditions are optimized, both SPION and QDs can be loaded inside the polymeric nanoparticles containing a model drug. With these multifunctional nanoparticles, both MRI visualization and confocal fluorescence microscopy studies can be performed on the same cell culture. In-vitro cytotoxicity studies have also been performed to confirm the low cytotoxicity and enhanced biocompatibility of such nanoparticles for further in-vivo studies.
10:45 AM - O4.4
Self-assembly of Multifunctional Nanostructures for Bioseparation.
Zhenda Lu 1 , Yadong Yin 1
1 Chemistry, University of California, Riverside, Riverside, California, United States
Show AbstractBioseparation techniques allow the recovery and purification of biologically active species that are important to many biomedical applications such as cancer biomarker discovery. It has been a challenge in developing bioseparation methods that are reproducible and with high throughput and quantitative accuracy. In this presentation we report a class of novel porous nanostructured materials for the efficient separation of proteins, peptides, and DNA strands. Nanoparticles of various materials with controllable size, shape, and surface properties are self-assembled into three-dimensional clusters containing well-defined mesoscale pores. This new system shows several advantages in the selective enrichment of biomolecules. The surface property of the nanocrystal clusters can be varied to attract the target biomarkers. Additional functional ligands can also be introduced to the particle surfaces to enhance the selectivity. We also demonstrate the incorporation of fluorescent or magnetic nanocrystals into the clusters to enable additional functions such as fluorescent labeling or convenient and efficient magnetic separation.
11:30 AM - **O4.5
Complex Surfaces on Nanoparticles, Whether You Like It or Not.
Catherine Murphy 1
1 Dept of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractExciting applications for inorganic nanoparticles include biological sensing, imaging, drug delivery and photothermal therapy. In most of these processes, synthetic methods to put appropriate surface groups on the nanoparticles (cell-recognition peptides, antibodies, etc.) are a key step. However, upon exposure to aqueous buffers and the nutrient-rich broth used in cell-based experiments, components from the aqueous media are sure to adsorb to nanoparticle surfaces and perhaps overcoat nearly all the designed nanoscale features that were so painstakingly put there. Weakly-bound molecules can desorb readily from the nanoparticle surface but may be trapped there if a sufficiently strong overcoating is present. In this talk I will describe our efforts make functional plasmonic nanoparticles for biological applications, and will also describe our evolving insight into their surface chemistry in “real” environments.
12:00 PM - O4.6
Comparison Study Between Plasmon-resonant Nanorods and Superparamagnetic Iron Oxide Nanoparticles for Optical Coherence Sensing.
Amy Oldenburg 1 , Stephen Boppart 2
1 Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 2 Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractOptical coherence tomography (OCT) provides depth-resolved imaging a few millimeters into biological tissues. The ability to track nanoparticles which provide a coherent optical signal with OCT enables new studies into nanoparticle transport, molecular contrast imaging, and characterization of the micromechanical environment. In this work we will compare and contrast two promising nanoparticle platforms for OCT contrast imaging. Understanding the advantages and limitations of these nanoparticles guides future design of multifunctional nanoparticle systems.Plasmon-resonant gold nanorods (nominally 14 x 44 nm) have been employed for OCT contrast. The primary feature of the nanorods is that their aspect ratio is tuned to provide a resonant optical signal within the wavelength band of the OCT light source (nominally 750-850 nm), and their size is sufficiently small to provide a low albedo, that is, absorption dominant over scattering. In this scenario nanorods may be sensed as a modification of the typically high albedo of tissues. The use of absorbing nanorods is also known to enable hyperthermic therapy, suggesting a multifunctional imaging and therapeutic capability. Nanorods were also contrasted in spectroscopic OCT mode by tuning the resonance to the low-wavelength side of the imaging band and sensing the shift of the centroid of the backscattered light to longer wavelengths. However, contrast to nanorods in excised breast carcinoma tissues, while promising, requires improvement before it can be useful for in vivo imaging applications.Superparamangetic iron oxide nanoparticles (SPIOs), nominally 20 nm diameter, have also been employed for OCT contrast. While SPIOs do not provide a significant optical signal, we have developed a method of pulling on SPIOs during OCT imaging using magnetic gradient forces. This pulling force results in a tissue deformation that can be sensed with extremely high sensitivity (displacements <20 nm) with the OCT system. Because tissues are non-magnetic, contrast to SPIOs at levels of 27 micrograms/g, or approximately 2 nanomolars, have been demonstrated in tissue phantoms. In vivo imaging of SPIOs has been demonstrated, and methods for rejecting physiological motion artifacts have been developed. We have also found that the dynamic tissue mechanical response can elucidate its viscoelastic properties. However, the fundamental limitation to the SPIO contrast has been reached, based upon the background motion signal from diamagnetic tissues (diamagnetic repulsion effect). We suggest that further improvements may be enabled by future studies into multifunctional nanoparticles which incorporate the best features of both of these nanoparticle platforms.
12:15 PM - **O4.7
Regulating the Surface Chemistry of Nanostructured Materials With Light.
Byron Gates 1 , Amir Bahman Samsam Bakhtiari 1 , John-Christopher Boyer 1 , Dennis Hsiao 1 , Rashmika Patel 1 , Neil Branda 1
1 Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
Show AbstractThis talk will describe the ability to tune the surface chemistry of nanoparticles using light. The interaction of light with the nanoparticles can lead to a number of phenomena that can be utilized for altering the chemistry on the surfaces of nanoparticles. Absorption of light at the plasmon resonant frequencies of nanoparticles can lead to the release of energy from the surface of these materials, which can be exploited to release molecules from the surfaces of nanoparticles. In addition, light emitted from luminescent nanoparticles can alter the structure of molecules attached to the surface of the particles. This talk will examine the stabilization of nanoparticles dispersed in solution through changes in their surface chemistry. Techniques will be presented for tuning this surface chemistry to release molecules of interest and/or to change the structure of bound molecules. These results provide insight into combining light activated processes in nanoparticles with the delivery and release of molecular payloads.
12:45 PM - O4.8
Synthesis of Magnetic and Fluorescent Bifunctional Nanoparticles.
Yaolin Xu 1 , Soubantika Palchoudhury 1 , Yuping Bao 1
1 Chemical and Biological Engineering, University of Alabama, Tuscaloosa, Alabama, United States
Show AbstractMagnetic nanoparticles have significantly advanced cancer treatments through targeted drug delivery and localized therapy. Magnetic nanoparticles further make simultaneous therapy and diagnosis possible as magnetic resonant imaging (MRI) contrast agents. Unfortunately, simultaneous therapy and diagnosis of the magnetic nanoparticles are limited by the expensive MRI equipments, which are not available to common research laboratories. Currently, fluorescence imaging remains the primary choice for bio-imaging because of its high sensitivity. Here, we reported magnetic-fluorescent integrated nanoparticles using iron oxide as the magnetic component and metallic nanoclusters as the fluorescent component. Iron oxide nanoparticles were synthesized using a modified co-precipitation method by introducing a capping molecule during synthesis. Subsequently, these iron oxide nanoparticles were used as seeds for the synthesis of Ag metallic nanoclusters. Around 10 nm iron oxide nanoparticles were successfully produced, followed by attachment of fluorescent clusters with a broad emission in the range of 600 -650 nm. Detailed structural analysis and physical property characterization are on-going.This work is funded by NSF-DMR 0907204
O5: Magnetic Nanoparticles for Medical Applications
Session Chairs
Wednesday PM, April 07, 2010
Room 2014 (Moscone West)
2:30 PM - **O5.1
Synthesis and Applications of Multifunctional Magnetic Nanoparticles.
Yue Pang 1 , Bing Xu 1
1 Chemistry, Brandeis University, Waltham, Massachusetts, United States
Show AbstractMagnetic nanoparticles are well-established nanomaterials that offer controlled size, ability to be manipulated externally, and robustness for functionalization. As a result, these nanoparticles could have many applications in biomedicine as well as catalysis. Because of the potential benefits of multimodal functionality, researchers would like to design and fabricate multifunctional magnetic nanoparticles. Currently, there are two strategies to fabricate magnetic nanoparticle-based multifunctional nanostructures. The first, molecular functionalization, involves attaching antibodies, proteins, and dyes to the magnetic nanoparticles. The other method integrates the magnetic nanoparticles with other functional nanocomponents, such as quantum dots (QDs) or metallic nanoparticles. Because they can exhibit several features synergistically and deliver more than one function simultaneously, such multifunctional magnetic nanoparticles could have unique advantages in biomedical applications. In this talk, we discuss examples of the design and application of multifunctional magnetic nanoparticles. After their conjugation with proper ligands, antibodies, or proteins, the biofunctional magnetic nanoparticles exhibit highly selective binding. These results indicate that such nanoparticles could be applied to biological problems such as bacterial detection, protein purification, and toxin decorporation. The hybrid nanostructures, which combine magnetic nanoparticles with other nanocomponents, exhibit paramagnetism alongside features such as fluorescence or enhanced optical contrast. Such structures could provide a platform for enhanced medical imaging and controlled drug delivery. It is expected that the combination of unique structural characteristics and integrated functions of multicomponent magnetic nanoparticles will attract increasing research interest and could lead to new opportunities in nanomedicine and other new applications.
3:00 PM - O5.2
Multifunctional Magnetic Nanoparticle – Polymer Composites.
Raju Ramanujan 1 , S. Purushotham 1 , S. Kayal 1 , V. Nguyen 1
1 , Nanyang Tech Univ, Singapore Singapore
Show AbstractNovel and unique devices and systems can be developed from multifunctional magnetic nanoparticle - polymer composites. Magnetic oxide (core)-thermoresponsive polymer (shell) composite nanoparticles (CNP) were studied for multimodal cancer therapy, i.e., magnetic drug targeting followed by simultaneous chemotherapy and hyperthermia. Doxorubicin loaded CNP with Fe3O4 core and thermoresponsive poly-n-isopropylacrylamide polymer shell were synthesized. The CNP exhibit on/off switching behavior and excellent in-vitro hyperthermia with simultaneous drug release. In vivo targeting of CNP to hepatocellular carcinoma in a buffalo rat model was also studied by MRI diagnostics and histology, modeling studies of drug targeting and tumor heating were also performed. Our work shows that drug loaded CNP have excellent potential for cancer treatment by combined drug targeting, hyperthermia and controlled drug release. Combined actuating and sensing responsive morphing transducers have also been developed using magnetic particle-polymer composites. External magnetic fields resulted in several actuation modes, including a novel coiling mode, actuation performance is better than that of mammalian skeletal muscles. Actuation can also be sensed by electrical feedback, resulting in versatile soft transducer devices.
3:15 PM - O5.3
Confinement of Iron(III) and Gadolinium(III) Complexes onto Gold Nanoparticles for Magnetic Applications.
Eddy Dumas 1 , Caroline Cannizzo 2 , Loick Moriggi 3 , Frederic Dumur 4 , Lothar Helm 3 , Cedric Mayer 1
1 Chemistry, Institut Lavoisier de Versailles, Versailles France, 2 Universite d'Evry-Val-D'essone, Laboratoire analyse et modelisation pour la biologie et l'environnement, Evry France, 3 Ecole polytechnique federale de Lausanne, Institut des sciences et ingenieurie chimique, Lausanne Switzerland, 4 Universite Aix-Marseille III, Laboratoire de chimie Provence, Marseille France
Show AbstractThe functionalization of metal nanoparticles by metal complexes is an attractive approach to design multifunctional nano-objects. It is possible to combine or even induce a synergy between the various physico-chemical properties of the two components of these nanocomposites, namely the metal nanoparticle and the coordination complex. For example, we recently grafted ruthenium complexes onto the surface of gold and silver nanoparticles using fully conjugated linkers to control the electronic transfer between the metal nanoparticle and the ruthenium centers.1 We recently extended this work to other coordination complexes such as iron(III) complexes derived from Schiff base ligands2 and gadolinium(III) chelates. In the case of iron complexes, preliminary results will be presented.3 The aim is to study the effect of the confinement of the complexes onto the surface of the nanoparticle on the magnetic properties (spin crossover) of the iron(III) complexes. In the case of gadolinium complexes, gadolinium chelates already studied as potential magnetic resonance (MRI) imaging agents have been successfully grafted onto the surface of gold nanoparticles.4 The aim is not only to confine a large number of gadolinium chelates around metal nanoparticles but also to increase the relaxation enhancement induced by a single paramagnetic Gd(III) ion. The idea is to build rigid systems that minimize internal degrees of freedom to take full advantage of the slow rotational motion expected for such nanocomposites.1.(a) C. R. Mayer, E. Dumas, F. Sécheresse, Chem. Commun. 2005, 345. (b) Cédric R. Mayer, Eddy Dumas, Aude Michel, Francis Sécheresse, Chem. Commun. 2006, 4183. (c) C. R. Mayer, E. Dumas, F. Miomandre, R. Méallet-Renault, F. Warmont, J. Vigneron, R. Pansu, A. Etcheberry, F. Sécheresse, New J. Chem. 2006, 30, 1628. (d) C. R. Mayer, E. Dumas, F. Sécheresse, J. Colloid Interface Sci. 2008, 328, 452.2.J. Jullien, G. Juhász, P. Mialane, E. Dumas, C. R. Mayer, J. Marrot, E. Rivière, E. L. Bominaar, E. Münck, F. Sécheresse, Inorg. Chem. 2006, 45, 6922.3.C. R. Mayer, G. Cucchiaro, J. Jullien, F. Dumur, J. Marrot, E. Dumas, F. Sécheresse, Eur. J. Inorg. Chem. 2008, 3614.4.L. Moriggi, C. Cannizzo, E. Dumas, C. R. Mayer, A. Ulianov, L. Helm, J. Am. Chem. Soc. 2009, 131, 10828.
3:30 PM - O5.4
Impact of Genetic Modifications on the Magnetic and Electronic Structure of Nanoparticles Particles Synthesized by Magnetotactic Bacteria.
Marco Liberati 1 , Dorothee Murat 2 , Arash Komeili 2 , Elke Arenholz 1
1 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Department of Plant and Microbial Biology, UC Berkeley, Berkeley, California, United States
Show AbstractTo optimize magnetic nanoparticles (MNP) for applications such as cancer therapy and drug delivery, the ability to tailor their size, morphology, surface chemistry as well as their magnetic and electronic properties is of critical importance. Moreover, the appropriate functionalization of their surface to ensure biocompatibility with the human body is necessary.Magnetotactic bacteria (MTB) represent a promising approach for the synthesis of MNP for biomedical applications. Once placed in iron rich and oxygen poor environments [3,4,5], they synthesize single crystals of magnetite (i.e. Fe3O4) which form of linear chains within the bacteria. Compared to chemically engineered MNP, the magnetosomes single crystals display numerous advantages:1) narrow size distribution and uniform morphologies2) typical sizes (10-130 nm) not easily achievable through chemical synthesis3) superparamagnetic properties 4) genetic control with access to morphologies inaccessible with chemically methods5) lower toxicity compared to some artificial MNP6) enveloped naturally by a biological membrane that can be specifically functionalizedTo controll and tune the particle properties through genetic modifications of the MTB is expected to be possible [5] but needs to be confirmed through the detailed characterization of their magnetic, structural and electronic properties. We have employed X-ray absorption (XA) spectroscopy and X-ray magnetic circular dichroism (XMCD) to determine the magnetic and electronic state of MNP synthesized by different genetic modifications of the Magnetospirillum magneticum strain AMB-1. The XA data are indicative of Fe ions in Fe2+ and Fe3+ in octahedral and tetrahedral sites as well as metallic Fe. In all samples a Fe XMCD was observed at ambient temperatures in external fields of 0.2 T. From a detailed analysis of the spectral shape of the XMCD signal we conclude that the pure strain AMB-1 forms Fe3O4 single crystals [6], while the genetically modified strain forms MNP with Fe in different states of oxidation. Our results indicate that the characteristics of MNP produced by magnetotactic bacteria can be tuned through genetic modification of bacteria and that soft x-ray absorption spectroscopies provide valuable information about the resulting MNP.The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. References:1. O. Salata, J. Nanobiot. 2, 1 (2004)2. C. Sun et al., Adv, Drug Deliv. Rev. 60, 1252 (2008)3. D. Faivre and D. Schuler, Chem. Rev. 108, 4875 (2008)4. C. Lang and D. Schuler, J. Phys. Cond. Matter. 18, S2815 (2006)5. A. Komeili, Annu. Rev. Biochem. 76, 351 (2007)6. S. Staniland et al., Nat. Nanotech. 3, 158 (2008)
4:15 PM - **O5.5
Designed Fabrication of Multifunctional Nanostructured Materials Based on Uniform Nanocrystals for Biomedical Applications.
Taeghwan Hyeon 1 , Ji Eun Lee 1 , Nohyun Lee 1 , Taeho Kim 1
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractBy combining different functional nanostructured materials, versatile multifunctional nanomedical platforms have been fabricated for multimodal imaging, and simultaneous diagnosis and therapy. We developed several multifunctional nanosystems by combining uniform oxide nanocrystals and mesoporous silica materials. We synthesized discrete and monodisperse mesoporous silica nanoparticles consisted of single Fe3O4 nanocrystal core and mesoporous silica shell, and the core/shell nanoparticles were used as in vivo MR and fluorescence imaging agents, along with a drug delivery vehicle. Highly versatile nanocomposite nanoparticles were synthesized by decorating surface of mesoporous dye-doped silica nanoparticles with multiple monodisperse magnetite nanocrystals, and the nanocomposite nanoparticles showed remarkable enhancement of MR signal due to the synergistic magnetism and in vivo passive targeting and accumulation of the nanoparticles at the tumor site was confirmed by both T2 MR and fluorescence imaging. We designed and fabricated magnetically recyclable protein separation system by combining ferrimagnetic magnetite cores and NiO nanoparticles decorated onto the mesoporous silica shell. The exposed NiO nanoparticles provide for the selective adsorption of the His-tagged protein from the mixture protein solution, as well as cell lysate, and the magnetic core allows the particles to be separated from the solution by applying an external magnetic field and the binding properties of His-tagged protein were maintained during several recycling steps. Hollow nanostructures have attracted tremendous attention from researchers in various disciplines because their high surface to volume ratio and large pore volume are highly desirable for many technological applications including drug delivery system. We used a wrap-bake-peel process, which involves silica coating, heat treatment, and finally the removal of the silica layer, to transform spindle shaped akagenite to hollow magnetite nanoparticles. The synthesized water-dispersible magnetite nanocapsules were successfully employed not only as a drug delivery vehicle, but also as a T2 MRI contrast agent.
4:45 PM - O5.6
Supercritical Fluid Assisted Sol-gel Synthesis of Magnetic Silica Nanospheres as Enhanced T2 Contrast Agent for MRI.
Anna Roig 1 , Elena Taboada 1 , Elisenda Rodriguez 2
1 , Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Bellaterra Spain, 2 , Institut d’Investigacions Biomèdiques de Barcelona (IIBM-CSIC) , Barcelona Spain
Show AbstractA large number of biomedical applications make use of magnetic nanoparticles, some examples are: magnetic resonance imaging, controlled drug delivery, tissue repair, detoxification of biological fluids, immunoassays and biological targeting or separation. We have developed a useful method for the synthesis of magnetic silica nanospheres and we have evaluated the material as contrast agents for MRI. Fabrication of the magnetic silica nanospheres was done in a straight forward one-pot method combining sol-gel chemistry and supercritical fluid technology [1]. Briefly, pre-formed iron oxide superparamagnetic nanoparticles stabilized in hexane (7 nm in diameter) are dispersed in a sol containing a silicon alkoxide, water and acetone as the solvent. The precursor solution is introduced in an autoclave and pressurized with compressed CO2. Then, pressure and temperature are raised over the supercritical conditions of the CO2/acetone mixture allowing the silicon alkoxide to hydrolyze and condensate forming the silica shell. The composite gel nanoparticles get dried as the solvent is extracted at supercritical conditions. The resulting nanospheres present a narrow particle size distribution and each nanosphere consists of a magnetic core of several non-contacting γ-Fe2O3 nanoparticles, surrounded by a microporous silica shell. The nanospheres are superparamagnetic at RT presenting an enhanced magnetization compared to the initial preformed iron oxide nanoparticles. Their size can be tuned by controlling the reaction conditions. Some advantages of the method are short reaction times as compared to non-supercritical sol-gel procedures, purity of the product since the final material is a dry powder, free of precursors and solvents, and potentiality to be scaled up. Moreover, the silica shell could be further functionalized with targeting directing agents or it could be used to carry a therapeutic pay load.Cytotoxicity and evaluation of the composite nanospheres as contrast agents for MRI will also be reported. Remarkably, the composite nanospheres show high transversal relaxivity values (130 – 326 s-1mMFe-1 at 20 MHz, 37 oC). [1] Taboada et al., Advanced Functional Material, 19, 14 (2009) 2319.
5:00 PM - **O5.7
Porous Hollow Fe3O4 Nanoparticles for Targeted Delivery and Controlled Release of Cisplatin.
Shouheng Sun 1 , Kai Cheng 1
1 Department of Chemistry, Brown University, Providence, Rhode Island, United States
Show AbstractWe report a new approach to cisplatin storage and release using porous hollow nanoparticles(PHNPs) of Fe3O4. We prepared the PHNPs by controlled oxidation of Fe NPs at 250C followed by acid etching. The opening pores (∼2-4 nm) facilitated the cisplatin diffusion into the cavity of the hollow structure. The porous shell was stable in neutral or basic physiological conditions, and cisplatin escape from the cavity through the same pores was a diffusion-controlled slow process with t(1/2) = 16 h. However, in low pH (<6) conditions, the pores were subject to acidic etching, resulting in wider pore gaps and faster release of cisplatin with t(1/2)< 4 h. Once coupled with Herceptin to the surface, the cisplatin-loaded hollow NPs could target to breast cancer SK-BR-3 cells with IC50 reaching 2.9 μM, much lower than 6.8 μM needed for free cisplatin. Our model experiments indicate that the low pH-responsive PHNPs of Fe3O4 can be exploited as a cisplatin delivery vehicle for target-specific therapeutic applications.
5:30 PM - O5.8
Tuning the Loading Level of Superparamagnetic Nanoparticles in Silica and Polymer Matrix.
Vikash Malik 1 , Herve Dietsch 1 , Peter Schurtenberger 1
1 Adolphe Merkle Institute, University of Fribourg, Marly Switzerland
Show AbstractManipulation of physical and chemical properties of magnetic nanoparticles system require high degree of precision and greater control over the synthesis conditions. Magnetic hybrid nanoparticle system have shown tremendous possibilities as far as their use in biology, medicines and magnetic separation are concerned. We are working on single domain magnetite nanoparticles which shows superparamagnetic behaviour at room temperature. These nanoparticles have limited applications because their surface modification is not well developed. However, coating of a silica layer can overcome this problem and allows one to modify the surface by silane coupling chemistry which can further provide binding sites for the drugs and polymers. Magnetic response of this hybrid system can be varied simply by changing the amount of magnetite nanoparticles. Therefore loading level of magnetite in a silica matrix can be finely tuned in order to have a hybrid nanosystem with desired magnetic properties. PS-b-PAA_magnetite hybrid nanoparticles were also synthesized and subsequently used to make janus nanoparticles system which have movable magnetite component. The hybrid nanoparticles thus synthesized were studied with dynamic light scattering in order to investigate their colloidal stability. TEM and SQUIDS were used for size and magnetic properties measurement respectively.
5:45 PM - O5.9
Uniform Mesoporous Dye-doped Silica Nanoparticles Decorated with Multiple Magnetite Nanocrystals for Simultaneous Enhanced MRI, Fluorescence Imaging and Drug Delivery.
Ji Eun Lee 1 , Nohyun Lee 1 , Jaeyun Kim 1 , Hyoungsu Kim 2 , Woo Kyung Moon 2 , Taeghwan Hyeon 1
1 , Seoul National University, Seoul Korea (the Republic of), 2 , Seoul National University Hospital, Seoul Korea (the Republic of)
Show AbstractCombining different nanostructured materials have enabled the development of multifunctional nanomedical platforms for multimodal imaging or simultaneous diagnosis and therapy. We synthesized highly versatile nanocomposite nanoparticles by decorating surface of mesoporous dye-doped silica nanoparticles with multiple magnetite nanocrystals. The PEG-stabilized nanoparticles were very stable in aqueous solution and did not affect cell viability or proliferation. Superparamagnetic property of the magnetite nanocrystals enabled the nanoparticles to be used as a contrast agent in T2 magnetic resonance (MR) imaging, and dye molecule in the silica framework imparted optical imaging modality. Integrating a multitude of magnetite nanocrystals on the silica surface resulted in remarkable enhancement of MR signal due to the synergistic magnetism. Anticancer drug, doxorubicin, could be loaded in the pores and induced efficient cell death. Furthermore, in vivo passive targeting and accumulation of the nanoparticles at the tumor site was confirmed by both T2 MR and fluorescence imaging. The composite nanoparticles were extremely versatile and have great potential as probes in MRI and fluorescence imaging as well as drug delivery carriers.
O6: Poster Session
Session Chairs
Yuping Bao
Andrew Dattelbaum
Joseph Tracy
Yadong Yin
Thursday AM, April 08, 2010
Salon Level (Marriott)
9:00 PM - O6.1
Development of Green Route for Nano Tin Drug Vehicles: Characterization, Antimicrobial Screening and in vitro Release Studies.
Athar Hashmi 1 , Nazia Khan 1
1 chemistry, jamia millia islamia, New Delhi, New Delhi, India
Show AbstractThe synthesized tin oxide nanoparticles have been deposited on soyabean oil based polymeric matrix, which was prepared through an environment- friendly microwave assisted technique. The newly developed nanocomposites were studied for some of the useful physico-chemical properties, making use of XRD, FTIR, SEM, etc. and optical methods. XRD studies showed incorporation of the peaks compared from standard values, indicating presence of tin oxide in nanoparticles form in the polymer matrix. FTIR study shows presence of the Sn–O–Sn vibrational peak and characteristic vibrational peaks of polyester amide. Study of SEM micrograph revealed a network of polymeric particles with the SnO2 nanoparticles adsorbed over it. The in vitro release studies carried out using solutions of different pH values also showed substantial and positive results. Preliminary drug assessment was carried out through antimicrobial screening for various strains of bacterial and fungal species and the developed nanocomposites were found to be fairly active against them. These microbial active systems may be rapidly and conformally coated onto a wide range of substrates without regard to size, shape, or chemical composition, and as such they may find use in a host of new applications in drug delivery as well as the related fields of tissue engineering, medical diagnostics, and chemical detection. Keywords: tin oxide nanoparticles, microwave assisted, soyabean oil, antimicrobial, adsorbed, drug delivery.
9:00 PM - O6.10
Distance Controlled and Electrically Driven Photoluminescence Quench From Quantum Dot-Au Complexes.
Zhitao Kang 1 , Jie Xu 1 , Dinal Andreason 1 , Brent Wagner 1
1 Georgia Tech Research Insititute, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractQuantum Dots (QDs) bound to gold nanoparticles have shown photoluminescence (PL) quenching dependent on distance between the two particles. The incident light from the QD couples to plasmon excitation of the metal when the frequencies of the light and the surface plasmon resonance (SPR) coincide, leading to a reduction in emitted PL in the system. The quenching effect of gold nanoparticle to QD was used to study the protein-protein interaction. CdTe and HgTe QDs with emission wavelengths from 500~900nm were synthesized and gold nanospheres and nanorods with controlled absorption in the visible and near-infrared (NIR) were prepared. PL quenching of QD-Protein-Protein-Au complexes was studied as a function of QD size, protein type and Au concentration for drug screening application. Quenching efficiency up to 90% was observed. The QD-Au complexes were also studied for electric signal sensing. The surface of the QDs was negative charged due to thiol ligands passivation. By applying a positive potential on the gold or gold nanoparticles attached substrate, the local electrical field between the substrate and the statically charged QDs would pull the QDs closer to the gold surface and quench the QD photoluminescence. In this methodology, electric signals were effectively converted to PL quenching which could then be measured with a photo detector. PL quenching of QD with Au was studied as a function of electric signal, QD type and concentration. The PL quenching of gold coupled NIR-emitting QD by a voltage over controlled distance is promising for applications such as neural signal recording. This methodology can potentially establish a novel wireless neural interface system with a minimal number of implanted components while promoting a high throughput of neural signals from multiple recording sites.
9:00 PM - O6.11
Simple, Controllable, and Scalable Synthesis of Dispersible Superparamagnetic Nanoclusters.
Jinmyung Cha 1 , Jin-Kyu Lee 1
1 Chemistry, Seoul National University, Seoul Korea (the Republic of)
Show AbstractFor the last 20 years, magnetic nanocrystals have been prepared by various synthetic methods, including coprecipitation, hydrothermal method, and thermal decomposition of organometallic compounds. The development of magnetic nanocrystals with high magnetic response is of great importance because magnetic nanocrystals synthesized by these approaches had a low magnetization, which limits to their applications, where high magnetic field responsiveness is demanded. Recently, the convenient synthesis of superparamagnetic nanoclusters by reduction of iron(III) chloride with in ethylene glycol as the reductant and solvent in present of sodium acetate was reported, but experimental investigation of the formation of nanoclusters are not clear. We studied systematically and quantitatively the formation of superparamagnetic nanoclusters obtained from the solution-phase partially reduction of iron(III) ion via the “hydrothermal polyol” process. Indeed, experimental data show that resultant nanoclusters are formed by a reaction involving the following step: 1) dissolution of the precursor; 2) phase transition and reduction by polyol of the dissolved species; and 3) nucleation and growth of the nanoclusters from the solution. Moreover, the formation of an intermediate phase is clearly observed by analytical tools such as TEM, XRD and FT-IR. By refluxing at atmospheric pressure, unlike the conventional autoclave method, we could enhance the dispersibility of nanoclusters by controlling the size smaller than 100 nm in a large-scale synthesis of few grams. The size of the nanoclusters can be precisely controlled by simply varying the amount of sodium acetate and water. The simple, controllable, and scalable synthesis of superparamagnetic nanoclusters may have a significant impact on practical applications such as magnetic separation, magnetic resonance imaging and drug delivery. The as-prepared superparamagnetic nanoclusters with high saturation magnetization value are ideal candidates for high-efficient T2 contrast agent. The synthetic process of superparamagnetic nanoclusters and various applications will be discussed, where high magnetic response is very critical.
9:00 PM - O6.12
The Preparation of Nanocrystalline Magnetic Quantum Dot Complexes (nMAG-QDs) for Biomedical Applications.
Minjung Cho 1 , Huiguang Zhu 1 , Vicki Colvin 1
1 Chemistry, Rice University, Houston, Texas, United States
Show AbstractWe describe an approach for making nanocrystalline magnetic quantum dot complexes which directs the nucleation and growth of semiconductor nanocrystals (quantum dots, QDs) onto preformed iron oxide nanocrystals (nMAG). The resulting complexes, referred to here as nMAG-QDs, consist of quantum dots, quantum rods, and core/shell QDs attached to a larger magnetic core material. An interesting feature of the materials is that the QD islands grow so as to maximize their distance from one another: samples with two QD/core have material at opposite poles for example. The size-dependent optical and magnetic properties of each component are retained in the nanocomposite assemblies. The CdSe QDs can be formed of varying size and subsequently tunable emission; after passivation with a ZnS shell their quantum yields can be increased. Because of their association with the iron oxide, these highly fluorescence materials can be concentrated via external handheld magnets. High resolution transmission electron microscopy (TEM) reveals that the quantum dots form directly on the iron oxide surface in these complexes. This heterogeneous nucleation process occurs most efficiently under conditions which promote quantum dot growth (e.g. high temperature and surfactant) while minimizing homogeneous nucleation of QD. As a result, well-defined nMAG-QDs complexes form in high yield only within a specific range of temperatures, injection speeds, and surfactant composition. These complexes possess optical and medical properties useful in a range of biomedical applications including specific cell sorting and separation, multiplexed detection of antigens, and multi-modal MRI imaging.
9:00 PM - O6.13
Magnetic Beads Prepared by Ink-jet Technique Using Ferrite Nanoparticles and Biodegradable Polymer.
Keishi Fuse 1 , Kazunori Nakagawa 1 , Hajime Wagata 1 , Masaru Tada 2 , Takashi Nakagawa 3 , Masanori Abe 2 , Ken-ichi Katsumata 1 , Kiyoshi Okada 1 , Nobuhiro Matsushita 1
1 materials and structures laboratory, Tokyo Institute of Techhnology, Yokohama Japan, 2 , Tokyo Institute of Techhnology, Yokohama Japan, 3 , Osaka University, Oosakafu Japan
Show AbstractRecently, magnetic beads, in which magnetite nanoparticles dispersed in matrix material attract much attention due to their potential applications in biotechnology such as bio-screening, drug deliver and hyperthermia application.In this study, we synthesized the ferrite alginate beads designed for magnetic hyperthermia which enables the cancer treatment only in specific portion of body attaining high quality of life. The ferrite nanoparticles are dispersed in alginate gel matrix, which is one of the most extensively used biopolymers since it is abundant, low in cost and biocompatible. The diameter of beads 50−60 μm is large enough not to flow out to the capillary blood vessel 3−10 μm in diameter.The sodium alginate aqueous solution containing ferrite nanoparticles with different average diameter (6-40 nm) were dropped into a calcium chloride aqueous solution through ink-jet nozzle 60 μm in diameter. Since Alginates become rigid and dense gel quickly in the presence of calcium ions, the droplet ejected from nozzle can keep its size and shape even after alighting on the solution. Temperature rise ΔT of these beads fixed in agar was measured by applying AC magnetic field of 112 Oe and 120 kHz.The ΔT from room temperature became 8 K after 10 min for the ferrite alginate beads containing ferrite particles 13.5 nm in diameter. This result suggested that the ferrite alginate beads can be heated up to 317 K(44°C) enough high for the cancer treatment.
9:00 PM - O6.14
Rotational Motion and Magnetically Controlled Drug Release of Spin Vortex Microdisks.
Dong-Hyun Kim 1 , Pavel Karavayev 1 2 , Elena Rozhkova 3 , Valentyn Novosad 1
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 , Pennsylvania State University, University Park, Pennsylvania, United States, 3 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractRecently, a rotational and vibration motion of novel magnetic disks by vortices shifting under very low frequency (~10s Hz) alternating magnetic field that can be used for inducing cancer cell apoptosis was reported [1]. The oscillating motion and fast reaction of the disks shaped soft magnetic core emerges various useful possibilities in terms of cancer treatment. Surface of the fabricated Au-coated 50nm thin, 1 micron magnetic disks were further modified with biocompatible chitosan polymer for improved water dispersibility and anti-cancer drug loading capacity using ionic crosslinker tripolyphosphate (TPP). The magneto-mechanical response of the microdisk aqueous solution was probed using the laser transmittance experiments as a function of the ac magnetic field frequency and amplitude. The magnetic field-driven doxorubicin (DOX) drug release showed 3-5 folds increase when compared to the spontaneous diffusion-based release with no magnetic field applied. The suspended DOX loaded chitosan magnetic disks in a solution is subjected to hydrodynamic forces by external magnetic driving forces and liquid drag force. The effective hydrodynamic forces therefore can be controlled by changing the magnetic field characteristics. The described nanoplatform could be of interest for targeted, on-demand drug therapy for biomedical applications. [1] D.-H. Kim, E. A. Rozhkova, I. V. Ulasov, S. D. Bader, T. Rajh, M. S. Lesniak and V. Novosad, Nature Materials, in press (2009).* Work at Argonne and the Center for Nanoscale Materials and Electron Microscopy Center is supported by the U.S. Department of Energy Office of Science, Basic Energy Sciences under Contract No. DE-AC02-06CH11357. Technical support from the Nanofabrication and NanoBio Interfaces group at the CNM is gratefully acknowledged.
9:00 PM - O6.15
Synthesis of Multifunctional Superparamagnetic Iron Oxide Nanoparticle/Organic Hybrid for Medical Applications.
Koichiro Hayashi 1 , Makoto Moriya 1 , Wataru Sakamoto 1 , Toshinobu Yogo 1
1 EcoTopia Science Institute, Nagoya University, Nagoya University, Nagoya, Aichi, Japan
Show AbstractFunctional inorganic nanoparticle/organic hybrid materials have attracted attentions because of their beneficial properties of each phase. Magnetic nanoparticle/organic hybrid materials have various applications, such as recording media, printing agent, ferrofluid, magnetic resonance imaging, hyperthermia. The authors reported the chemoselective synthesis of folic acid (FA)-functionalized magnetite nanoparticles via click chemistry for magnetic hyperthermia [1]. This paper describes the synthesis of β-cyclodextrin (β-CD) and folic acid (FA)-functionalized superparamagnetic nanoparticles (SPIONs) through the hydrolysis and functionalization of iron-organic compound. The immobilization of β-CD and FA on spinel iron oxide nanoparticles, which are Fe3O4 or γ-Fe2O3, was confirmed by FTIR and XRD. The product also had a mean size of 7.5 nm and a prolonged stability in water. The magnetic properties of the hybrids were analyzed by VSM and SQUID. The BH curve of the FA-CD-SPIONs showed no remanence at room temperature. The saturation magnetization of product was 51 emu g−1 and the magnetic profile revealed that the product was superparamagnetic. The product generated heat by applying an AC magnetic and the specific absorption rate (SAR) value in water is 574 W g−1 at 1 MHz and 100 Oe. Furthermore, the induction heating simultaneously triggers the release of drug from the cavity of β-CD. Tamoxifen citrate (TMX) loaded on the FA-CD-SPIONs was released by heat generated through on-off switching of a 230 kHz AC magnetic field and 100 Oe. Thus, the product can be a novel device having the ability to perform drug delivery and hyperthermia simultaneously. The FA-CD-SPIONs are expected for the future application in multifunctional nanomedicine with hyperthermia, drug delivery, and MRI.1.K. Hayashi, M. Moriya, W. Sakamoto and T. Yogo, Chem. Mater., 21, [7] 1318 (2009).
9:00 PM - O6.16
Synthesis of Organic Materials Suitable for Environmental Applications.
Jhinuk Gupta 1 , Narahari Mahanta 1 , Wei Jun Tan 1 , Suresh Valiyaveettil 1
1 Chemistry, National University of Singapore, Singapore Singapore
Show AbstractThe environmental impact of nanotoxicity is becoming more and more profound with the ever increasing use of nanotechnology in day-to-day life. It is found that, nanoparticles of gold, silver, carbon nanotubes, fullerene and many more show considerable toxicity to living system up on prolonged exposure at high concentration and accumulation. Water is the most effective carrier of nanomaterials from environment to biological systems. Hence, water, being maximum susceptible for pollution, needs to be purified thoroughly before recycling. In this project, we have designed and synthesized a few organic oligomers and polymers to remove gold and silver nanoparticles from aqueous medium. The synthesized compounds are incorporated to the electrospun nanofiber matrix with diameter ranging from 300 to 600 nm. The nanofiber membrane offers high surface area with active functionality on nanoscale which helps to increase the filtration efficiency. The fluorescence property of the target compounds is used as the probe to monitor the process.
9:00 PM - O6.17
Temperature Sensitive Hydration and Interactive Core-shell Nanomagnetic Micelles.
Dong-Hyun Kim 1 , Elena Rozhkova 2 , David Gosztola 2 , Valentyn Novosad 1
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractTemperature sensitive conformational changes by hydration and dehydration of poly(N-isopropylacrylamide-co-acrylamide)-b-polycaprolactone (P(NIPAAm-co-AAm)-b-PCL) block copolymer comprising 11nm Fe3O4 nanoparticles loaded micelles in aqueous solution were investigated. Phase transition temperature by the collapse/aggregation of a thermoresponsive P(NIPAAm-co-AAm) part in the amphiphilic block copolymer was tailored by adjusting amount of hydrophilic AAm [1]. After the micelle structure formation, temperature dependent hydration states of the respective core and shell were investigated by confocal Raman spectroscopy and hydrodynamic size measurements in aqueous solution. The hydration state of core-shell in the micelle was demonstrated by recording the integrated intensity ratio of C-H stretching vibration of the polymer and O-H stretching vibration of water molecules in the Raman spectras. The dehydration of the outer shell around phase transition temperature of 42-45 °C and the hydration of the PCL core at 45-50 °C were observed. The hydration states at each temperature ranges induce temperature dependent hydrodynamic size/volume changes of the micelles. The temperature dependent interaction of outer brush shell and core of the magnetic micelles in the hydrodynamic condition resulted in controlled amount of drug release at hyperthermia temperature range. The extended drug release controllability of the temperature sensitive magnetic micelles could be of interest for development of multifunctional hyperthermia and chemotherapy anti-cancer nanoplatforms.[1] D.-H. Kim, E. A. Rozhkova, T. Rajh, S. D. Bader, and V. Novosad, IEEE Trans. Magn. 45(10), 4821-4824, (2009)* Work at Argonne and the Center for Nanoscale Materials and Electron Microscopy Center is supported by the U.S. Department of Energy Office of Science, Basic Energy Sciences under Contract No. DE-AC02-06CH11357. Technical support from the Nanophotonics and NanoBio Interfaces group at the CNM is gratefully acknowledged.
9:00 PM - O6.18
Multifunctional DNA-based Nanocarriers for Efficient Drug Delivery.
Young Hoon Roh 1 , Jong Bum Lee 1 , Pichamon Kiatwuthinon 1 , Mark Hartman 1 , Bojeong Kim 1 , Dan Luo 1
1 Biological Environmental Engineering, cornell university, Ithaca, New York, United States
Show AbstractLiposomes, an important class of drug delivery vectors, are usually made of layers of phospholipids. Here, we report the synthesis of novel, DNA-based amphiphiles consisting of DNA building blocks and lipids and their self-assembly into various types of nanostructures. (DNAsomes) The morphologies and properties of these nanostructures can be easily controlled by selecting the DNA building blocks and the number of lipid chains tethered onto the branches of the DNA building blocks: a core/shell shaped vesicular structure of DNA-lipid amphiphiles. Interestingly, the sizes of the vesicles were manipulated with various size ranges approximately from 5µm to 100 nm. It is expected that DNA-lipid amphiphiles and DNAsomes will become new tools for designing and synthesizing novel, drug delivery materials and for tracking self-assembling processes.
9:00 PM - O6.2
Nanoparticle-based Multifunctional Substrates for Controlling Integrin-mediated Cell Adhesion.
Parimal Bapat 1 , Rebecca Kraft 1 , Marco Bottino 1 , Renato Camata 1
1 Physics, University of Alabama in Birmingham, Birmingham, Alabama, United States
Show AbstractCell adhesion is mediated by the integrin family of transmembrane glycoproteins. Over two dozen different integrins are known to be expressed in humans and contribute to the specific binding of cells to proteins of the extracellular matrix (ECM). Understanding how the ECM microenvironment affects integrin function is a major goal of regenerative medicine and tissue engineering. Recent studies of cell behavior show that integrin function is affected by the topographical features, dissolution behavior and distribution of RGD peptides on a surface. We have created nanoparticle-based multifunctional substrates that may help elucidate the mechanisms through which these chemical and nanotopographical features cooperate in determining cell behavior. The substrates comprise hydroxyapatite (HA) nanoparticles of well defined size, crystallinity, and inter-particle spacing on atomically flat SiO2 layers with the following functionalities: (1) Tunable nanoparticle diameter for modulation of substrate nanotopography; (2) Adjustable particle crystallinity for controlled rate of release of ionic species; (3) Variable inter-particle spacing for specified density of anchoring points for biomolecule functionalization. In our synthesis, an HA target is ablated in a tube furnace reactor at 800-900oC in 720 Torr of flowing Ar/H2O using a KrF excimer laser. The nanoparticle aerosol formed by laser ablation passes through an ionization zone and the charged particles are sorted according to size using a differential mobility analyzer. Size-selected nanoparticles are deposited by gas-phase electrophoresis on SiO2, leading to a surface of bioactive HA nanoislands on an otherwise nonfouling surface. Atomic force microscopy shows that this method can create uniformly dispersed nanoparticle deposits with size tunable in the 3–100 nm range and size dispersion of ~15%. X-ray diffraction (XRD) on calibration substrates indicate that the HA nanoparticles can be tailored to the desired level of crystallinity, as well as to other calcium phosphate phases such as tricalcium phosphate and amorphous HA. For example, XRD on samples obtained at 950oC show that the nanoparticle phase changes from HA to tricalcium phosphate as the laser fluence varies from 1.7 to 5.4 J/cm2. Post-deposition annealing of HA-nanoparticle substrates at 800oC enables further control of particle crystallinity, yielding tunable ionic release. These substrates can be further functionalized by the adsorption of peptides to the HA nanoislands. This is particularly the case for RGD peptides conjugated to polyacidic aminoacid domains, which have high affinity for HA surfaces. Because of their spatial specificity, these substrates may allow direct observation of controlled peptide adsorption as well as enable multivariate studies to decouple the effect of nanotopography, ionic products, and biochemical motifs on cell adhesion and motility, with relevance for applications in bone tissue engineering and regeneration.
9:00 PM - O6.3
Preparation, Characterization and in vitro Bioactivity Evaluation of Bioactive Glass Nonoparticles.
Abeer El-Kady 1 , Ashraf Ali 1 , Bothaina Abd El-Hady 1
1 Biomaterials, National Research Center, Cairo, south cairo, Egypt
Show AbstractBioactive glasses were used extensively as an orthopedic and dental grafting material. Reducing the particle size of materials to nanosize was shown to improve their biological properties. Therefore, the main objective of the present study was to engineer bioactive glass nanoparticles (BGN) using an alkali-mediated sol–gel method. Characterization of bioactive glass nanoparticles was carried out using transmission electron microscopy (TEM), x-ray florescence (XRF), Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction analysis (XRD), thermogravimetric analyses (TGA), and differential thermal analysis (DTA). TEM micrograph showed that the bioactive glass nanoparticles were less than 100 nm in diameter. The results of XRF showed that the composition of the obtained glass nanoparticles were almost consistent with the designed one, which indicated that the glass composition was not affected by the rapid gelation during synthesis. Thermal analysis showed that all the organic and inorganic precursor decomposed completely before 700, Therefore, this temperature was chosen for the stabilization of the glass powder. XRD confirmed the amorphous nature of glass after stabilization. The FT-IR spectra of the sol-gel prepared bioactive glass nanoparticles showed bands located in the range of 1000-1200 cm-1 that correspond to Si–O–Si asymmetric stretching vibration, whereas the bands seen in the range of 725-800 cm-1 are attributed to the Si–O–Si symmetric stretching vibration. In addition, bands located in the range of 450-480 cm-1 were ascribed to the Si–O–Si bending mode. In vitro bioactivity evaluation was carried out in simulated body fluid. The formation of a hydroxycarbonate apatite layer on the glass surface was confirmed by thin film X-ray diffraction analysis (TF-XRD), and scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDXA), demonstrated the potential application of bioactive glass nanoparticles in bone engineering.
9:00 PM - O6.4
Synthesis of Fe3O4/ZnO Core-shell Nanoparticles and Their Applications in Photodynamic Therapy.
Juan Beltran 2 , Surinder Singh 1 , Maharaj Tomar 2 , Oscar Perales 1 , Sandra Pena 3 , Luis Rivera 3
2 Department of Physics , University of Puerto Rico , Mayagüez, Puerto Rico, United States, 1 Engineering Science & Materials, University of Puerto Rico - Mayagüez Campus, Mayagüez, Puerto Rico, United States, 3 Department of Chemistry, University of Puerto Rico , Mayagüez, Puerto Rico, United States
Show AbstractRecently, the use of nanoparticles as carriers of photosensitizer (PS) molecules for photodynamic therapy (PDT) has attracted much interest in the core-shell structured nanoparticles. Herein, we used a simple aqueous solution method to synthesize ZnO@Fe3O4 core-shell nanoparticles. X-ray diffraction (XRD) analyses showed the presence of well defined reflection planes corresponding to both Fe3O4 and ZnO suggesting the formation of core-shell structure. The particle size has been calculated from X-ray diffraction and confirmed with transmission electron microscopy (TEM) measurements. Vibrating sample magnetometer (VSM) analyses showed that these nanoparticles retained the typical superparamagnetic behavior of core with no coercivity and remanence at room temperature. X-ray photoelectron spectroscopy analyses revealed the presence of Zn1/2 and Zn3/2 species on the surface. Photoluminescence measurements showed excitonic emission of ZnO co-existing with a weak and broad defect- related green emission at room temperature. The generation of singlet oxygen was monitored with the photooxidation of diphenyl-1,3-isobenzofuran with different light sources, followed by absorption spectroscopy at 410 nm. The results on the quantum yield of this core-shell nanoparticles and their capability to generate reactive singlet oxygen 1O2, will be presented.
9:00 PM - O6.6
Responsive Nanocobs With Tunable SERS Intensity.
Maneesh Gupta 1 , Srikanth Singamaneni 1 , Sehoon Chang 1 , Lawrence Drummy 2 , Ray Gunawidjaja 1 , Rajesh Naik 2 , Vladimir Tsukruk 1
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio, United States
Show AbstractHybrid organic–inoragnic nanostructures are a critical platform for the design of nanomaterials for chemical and biosensing. It is well known that the plasmon absorption (resonance condition) and the electromagnetic coupling between metal nanoparticles can be tuned by external ambient, shape, dimensions, inter-particle distance, and orientation. Optical responses such as Raman scattering, and absorbance serve as a signature for specific chemical groups and can be used for specific sensing of analyte molecules. Raman scattering, which is quantized vibration signature of a molecule can be enhanced when the molecule is subjected to enhanced electromagnetic field in the vicinity of plasmonic nanostructures. Of special interest is the coupling of plasmon resonances in adjacent metal nanostructures separated by nanoscale gaps, which can dramatically enhance Raman scattering leading to extremely sensitive analyte detection.In this work, we demonstrate the pH responsive surface enhanced Raman scattering (SERS) properties of silver nanowires functionalized with gold nanoparticles (called nanocobs henceforth) using a polyacrylic acid (PAA) linker. The pH responsive nature of the polymer (PAA) linker is employed to vary the distance of separation between the gold nanoparticles and the silver nanowire. The PAA conformation is sensitive to the pH of the surrounding solution. At neutral pH the PAA takes on an extended conformation, which collapses at lower pH. High resolution transmission electron microscopy (HRTEM) revealed that the thickness of the PAA layer in collapsed (2.3 nm) and extended state (8 nm). The tunable separation distance between the two plasmonic structures (Au NP and Ag wire) resulted in different degrees of electromagnetic coupling, resulting in a 100% reversible change in the SERS intensity of reporter (rhodamine B) molecules. The large and reversible changes in the optical properties of the pH responsive nanocobs demonstrated here can find applications in chemical and biological sensing and bioimaging.
9:00 PM - O6.7
Superparamagnetic and Fluorescent Nanoparticles Containing Iron Oxide Nanoparticles and Semiconductor Quantum Dots.
Numpon Insin 1 , Jongnam Park 1 , Wenhao Liu 1 , Zoran Popovic 1 , Moungi Bawendi 1
1 Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractTwo different nanoparticle systems with superparamagnetic and fluorescent properties were synthesized. The first system comprises silica-coated iron oxide magnetic nanoparticles (MPs) encapsulated with CdSe/CdZnS quantum dots (QDs)-containing silica shell on their surfaces. These nanoparticles were formed using two separated steps: reversed microemulsion for the formation of silica shell on the MPs followed by electrostatic-driven decoration of QDs into the silica surface of MPs. In the second system, conjugation of MPs and QDs was achieved by use of functional PEGylated polymer surfactants on the MPs and QDs surfaces. These nanoparticles were characterized using TEM, SEM, optical microscopy, Scanning Transmission Electron Microscopy (STEM), and SQUID magnetometry. These superparamagnetic, tunably fluorescent, and photo-stable particles can be useful for applications that required biocompatible and functionalizable surfaces.
9:00 PM - O6.8
Synthesis and Characterization of Core (Au,Ag)-shell (LDH) Nanoparticles.
W. Noh 1 , Colton Rearick 1 , A. Hyla 1 , M. Kamboj 1 , A. Ramachandran 2 , S. Dey 1
1 School of Mechanical, Aerospace, Chemical, and Materials Engineering, Arizona State University, Tempe, Arizona, United States, 2 School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona, United States
Show AbstractCurrently, in the field of medicine, there is convincing evidence that promising physiological, clinical, and diagnostic effects are observed in the presence of colloidal particles (~10 nm) in vivo of noble metals such as silver (Ag) and gold (Au). Additionally, biodegradable layered double hydroxides (LDH), which belong to a class of inorganic ceramics, are being evaluated as a potential drug/gene delivery platform based on nano-sized geometries called nanovectors. A Core (metal)-Shell (LDH) structure, with the latter hybridized with bioactive agents, may be designed to have a high scattering cross-section for optical imaging, but could also be tailored for chemotherapy or hyperthermic treatments. In addition, these hybrid nanostructures may be conjugated with ligands to target specific diseased cells, thus minimizing the damage to the surrounding healthy tissue. These multifunctional characteristics are typical of theranostics that are capable of simultaneous therapy and imaging. This poster demonstrates the synthesis and characterization of spherical Core (metal)-Shell (LDH) nanoparticles by a constant pH method and use of surfactants to ensure uniform size distribution and particles that are free of agglomeration. The physio-chemical characteristics of LDH, as well as LDH-coated Ag and Au nanoparticles were evaluated by using X-ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, Inductively Coupled Plasma Emission Spectrometry, and Dynamic Light Scattering. The experimental data demonstrates the strong potential of these nanostructures as theranostic materials.
9:00 PM - O6.9
Erodible Nanogels for Targeted Therapeutics.
Michael Smith 1 , Erin Dickerson 2 , William Blackburn 1 , Antoinette South 1 , Jeffrey Gaulding 1 , John McDonald 2 , Louis Lyon 1
1 Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractNanogels are a promising class of drug delivery vehicles for cancer therapy. By concentrating macromolecular therapeutic agents within the interior of targeted nanogels, we have shown the delivery of those macromolecules in a cell-specific fashion. This delivery system has potential to overcome several of the pharmaceutical deficiencies of modern anticancer agents (e.g. toxicity, lack of bioavailability, instability in biological media). Specifically, nanogels with a core/shell morphology were shown to effectively deliver small interfering RNA molecules (siRNA) to ovarian cancer cells. Whereas the core compartment was used for drug entrapment and fluorescence imaging, peptide ligands were conjugated to the nanogel shell to enable receptor-mediated uptake. These studies have illustrated that nanogels are promising vehicles for siRNA delivery, effectively entrapping, protecting, and delivering functional siRNA to the intracellular space of malignant cells. Those results have motivated the investigation of advanced architectures for in vivo applications. For example, we have designed a new degradable nanogel species that undergoes bulk erosion under physiologic conditions (pH = 7.4, 37 °C). To monitor particle degradation, we have developed an on-line separation (asymmetrical flow FFF) and multiangle light scattering method to detect changes in nanogel mass and topology as a function of both temperature and pH. Using these techniques, we revealed an enabling new drug delivery vehicle, which erodes under conditions and on timescales that are relevant for many drug delivery applications.
Symposium Organizers
Yuping Bao The University of Alabama
Andrew M. Dattelbaum Los Alamos National Laboratory
Joseph B. Tracy North Carolina State University
Yadong Yin University of California-Riverside
O7: Medical Applications
Session Chairs
Thursday AM, April 08, 2010
Room 2014 (Moscone West)
9:15 AM - **O7.1
Theranostic Magnetic Nanoparticle Systems for Biomedicine.
Kannan Krishnan 1
1 , University of Washington, Seattle, Washington, United States
Show AbstractTwo of the principal challenges in biomedical nanoscience and personalized medicine are: a) the detection of disease at the earliest possible time prior to its ability to cause damage (diagnostics and imaging) and b) delivering treatment at the right place, at the right time whilst minimizing unnecessary exposure (targeted therapy with a triggered release). The former is dominated by optical methods, emerging “life on a chip” systems and the versatile magnetic resonance imaging technology. The latter remains an ongoing challenge. In this context, we have been developing multifunction platforms for therapy, diagnostics and imaging (hence, theranostic) based on biocompatible, magnetic nanoparticles and core-shell structures with coupled properties. Our work encompasses innovations in synthesis and functionalization, advanced characterization, a wide-range of magnetic measurements and modeling to tailor their behavior for high moment or high frequency applications and carrying out cytotoxicity and biocompatibility studies. Currently, in vitro (magnetic separation and diagnostic relaxometry), in vivo (hyperthermia treatment of cancer, triggered drug delivery) and imaging (contrast enhancement in MRI and the development of a novel magnetic particle imaging technology to compete with MRI) applications are all being pursued. I will present details and summarize our current work in these areas highlighting the fundamental principles behind our research in the context of emerging technological and clinical opportunities. This work was supported by grants NSF/DMR 0203069, 0501421 & 0315460, NIH/NINDS and NIH/ISD.
9:45 AM - **O7.2
Multifunctional Nanoparticles for Targeted Imaging and Therapy of Cancer.
Yong Eun Koo Lee 1 , Raoul Kopelman 1
1 , University of Michigan, Ann Arbor, Michigan, United States
Show AbstractThe decade old idea of making biocompatible multifunctional nanoparticles, combining therapy, imaging and targeting, was aimed from the start at cancer. This presentation will emphasize targeted theranostic nanoparticles, where “theranostic” literally means combining therapy and diagnostics, but more generally may mean a combination of imaging/visualization with therapy/surgery. Specific examples will cover (1) imaging (MRI, CT, ultrasound and optical methods), (2) therapy (chemo, photodynamic, radiation) and (3) guided surgery (using intra-operative imaging and therapy). Progress on brain and on head and neck cancer will be reported.
10:15 AM - O7.3
Development of a Multifunctionalized SERS-active Nanoprobe System for Enhanced Cellular Delivery and Nuclear Targeting in Single Cells, and Demonstration of Treatment Delivery/Activation in Cancer Cells.
Molly Gregas 1 2 , Jonathan Scaffidi 1 2 , Benoit Lauly 1 2 , Tuan Vo-Dinh 1 2 3
1 Biomedical Engineering, Duke University, Durham, North Carolina, United States, 2 Fitzpatrick Institute for Photonics, Duke University, Durham, North Carolina, United States, 3 Chemistry, Duke University, Durham, North Carolina, United States
Show AbstractWe describe the development and application of a multi-functionalized cellular nanoprobe and biodelivery platform combining a nuclear targeting peptide (NTP) for improved cellular uptake and intracellular targeting with p-mercaptobenzoic acid (pMBA) as a surface-enhanced Raman scattering (SERS) reporter for tracking and imaging. The nuclear targeting peptide, an HIV-1 protein-derived TAT sequence, has been previously shown to aid entry of cargo through the cell membrane via normal cellular processes, and furthermore, to localize small cargo to the nucleus of the cell. In this work, two-dimensional SERS mapping was used to track the spatial and temporal progress of nanoparticle uptake in PC-3 human prostate cancer cells and to characterize localization at various time points, demonstrating the potential for an intracellularly-targeted multiplexed nanobiosensing system with excellent sensitivity and specificity. Noble metal nanoparticles co-functionalized with the TAT peptide showed greatly enhanced cellular uptake over the control nanoparticles lacking the targeting moiety. The ability to detect and monitor nanoprobe trafficking using SERS spectroscopy offers an improved alternative over previous tracking and detection methods such as light microscopy and fluorescence methods. We also show demonstration of in vitro cellular activity of a drug cargo delivered via the multifunctional nanoprobe system. Significant reductions in gross cell density were observed for PC-3 cancer cell cultures treated with an apoptosis-inducing drug tethered to the nanoparticle surface and activated within the cells after uptake and localization. The development of a multifunctional nanoprobe system for intracellular delivery has potential clinical applications in early detection and selective treatment of disease in affected cells.
10:30 AM - **O7.4
Multifunctional Nanocarriers for Imaging Angiogenesis and Tumor Vasculature.
Ravi Bellamkonda 1 , Ananth Annapragada 3 , Estathios Karathanasis 2
1 Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, United States, 3 School of Health Information Sciences, University of Texas at Houston, Houston, Texas, United States, 2 Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States
Show AbstractLiposomal nanocarriers afford the design of several features appropriate for enabling personalized medicine. Here, we report the design of 100nm scale liposomal nanocarriers that possess the following features - they have long circulation times, can carry multiple payloads including iodine contrast agents and chemotherapeutics, are capable of peptide and receptor mediated targeting, and can be engineered for triggered release of their payloads.Specifically, high resolution blood pool imaging that enables simultaneous visualization of arterial and venous trees in with CT is described. Also, the ability of nanoscale contrast agent to quantitatively probe the permeability of tumor blood vessels, permitted prediction of systemically administered chemotherapeutics dosing to tumors, and this in turned determined efficacy. This is the first demonstration, to our knowledge, of a nanoscale agent predicting the responsiveness of individual tumors to a systemically administered chemotherapeutics.
11:30 AM - **O7.5
Design and Development of Integrated Multi-functional Fluorescent Superparamagnetic Fe3O4 Nano Spheres for Medical Diagnosis and Treatment.
Donglu Shi 1 7 , Hoon Sung Cho 1 , Chris Huth 1 , Feng Wang 1 , Wei Wang 1 , Hong Xu 2 , Hongchen Gu 2 , Giovanni Pauletti 3 , Zhongyun Dong 4 , Jie Lian 5 , Guokui Liu 6 , Lumin Wang 8 , Peng Zhao 7 , Rodney Ewing 8
1 Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, United States, 7 The Institute for Advanced Materials and Nano Biomedicine, Tongji University, Shanghai China, 2 Med - X Institute, Shanghai Jiao Tong University, Shanghai China, 3 College of Pharmacy, University of Cincinnati, Cincinnati, Ohio, United States, 4 College of Medicine, University of Cincinnati, Cincinnati, Ohio, United States, 5 Mechanical, Aerospace & Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 6 Chemistry Division, Argonne National Laboratory, Argonne, Illinois, United States, 8 Geological Sciences, Nuclear Engineering & Radiological Sciences, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractIn this presentation, we report the design of a new nanostructure that ideally satisfies the important biomedical requirements in cancer diagnosis and treatment. Quantum dots (QDs) were conjugated on magnetic nano spheres (MNS) of polystyrene-Fe3O4 composites. Surface-associated QDs on these MNS exhibited intense visible emissions using fluorescent spectroscopy and successfully facilitated in vivo soft tissue imaging in mice. Furthermore, application of an alternating electromagnetic field effectively induced heating of the MNS into temperature ranges suitable for therapeutic hyperthermia. The magnetic nano spheres were incorporated with PLGA for paclitaxel delivery through an emulsion technique. The drug loading efficiency of PLGA-coated MNS and their cytotoxicity on PC-3MM2 human prostate cells were investigated. MNS were also functionalized with antibodies to target a prostate-specific membrane antigen (PSMA). To determine primary antibody binding to LNCaP cells, we performed immunocytochemical studies. Experimental results on MNS surface structure development, in vivo imaging, cell targeting, and hyperthermia will be presented. Future requirements, aims, and trends in the development of multi functional nano particles, particularly with intelligent functionalities for fundamental studies, are also given in this presentation.
12:00 PM - O7.6
Silicon Quantum Dots Functionalized for siRNA Delivery.
Stefanie Klein 1 , Carola Kryschi 1
1 Dept. Chemistry and Pharmacy, Physical Chemistry I, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen Germany
Show AbstractIn this contribution, we present a novel class of transfection tools that are based on biocompatible, water-soluble, green luminescent silicon quantum dots (SiQDs). Our research objective was to temporarily down-regulate via RNAi the P-glycoprotein expression of the multidrug resistant gene 1 (MDR1, symbol approved by the HUGO Gene Nomenclature: ABCB1) in a human colon carcinoma cell line (Caco-2) as representing an in-vitro cell model for the enterocytes of the gastro-intestinal tract. P-glycoprotein often invalidates cancer chemotherapy because of its overproduction in tumor cells giving rise to multidrug resistance. 2-vinylpyridine terminated (2-vipy) SiQDs dispersed in aqueous solutions were shown to form complexes with ABCB1 siRNA and to act as shuttle for siRNA delivery into Caco-2 cells. The internalization of 2-vipySiQDs by Caco-2 cells as observed by transmission electron microscopy and confocal laser scanning microscopy imaging studies occurs via endocytosis. Experiments employing agarose gel electrophoresis revealed positive charging of 2-vipySiQDs in aqueous solutions and the 2-vipySiQD-siRNA complexes are formed through electrostatic interactions. The release of siRNA in the cytosol with subsequently RNAi induced down-regulation of the P-glycoprotein translation was substantiated to take place by determining a reduced ABCB1 mRNA level in transfected Caco-2 cells using real-time PCR. Additional evidence for successful ABCB1 gene silencing was obtained by measuring a significant decrease of the P-glycoprotein transporter efficiency for the fluorescent substrate Rhodamine 123 (Rh123). Both, transcellular transport study and real-time PCR analysis were performed with 2-vipySiQD-siRNA complexes and Lipofectamine 2000 as reference transfection tool for ABCB1 siRNA. 2-vipySiQDs pose only negligible effect on both viability and apoptosis of Caco-2 cells as demonstrated by MTT and TUNEL-assays.
12:15 PM - **O7.7
Multifunctional Mesoporous Silica, Carbon, and Polymer Nanoparticles for Intracellular Delivery of Drugs, Genes, and Proteins.
Victor Lin 1 2
1 Department of Chemistry, Iowa State University, Ames, Iowa, United States, 2 , U.S. Department of Energy Ames Laboratory, Ames, Iowa, United States
Show AbstractWe have synthesized a series of multi-functionalized, mesoporous silica, carbon and polymer nanoparticle materials, i.e., MSN, MCN, and MPN, respectively. These mesoporous nanoparticle materials were designed as stimuli-responsive intracellular controlled release delivery systems. Several pharmaceutical drugs, genes, proteins, and imaging agents were encapsulated inside these nanoparticles by capping the openings of the mesopores with various chemically removable caps, such as nanoparticles (surface-derivatized semiconductor nanocrystals, superparamagnetic iron oxide and gold), proteins and dendrimers, to block the molecules of interest from leaching out. We studied the stimuli-responsive release profiles of these mesoporous nanoparticle-based delivery systems by using various non-cytotoxic chemicals and photo-irradiation as release triggers. Furthermore, the gene transfection efficacy, uptake mechanism, and biocompatibility of the capped-mesoporous nanoparticle systems with animal and plant cells and tissues have been investigated. For example, a MSN material with a large average pore diameter (5.4 nm) has been designed to serve as a transmembrane, controlled release carrier for a membrane impermeable protein (cytochrome c). The enzymatic activity of the MSN-released protein was quantitatively analyzed and compared with that of the native cytochrome c in physiological buffer solutions. We found that the enzymes released from the MSNs are still functional and highly active. We discovered that the cytochrome c encapsulated MSNs could be internalized by live human cervical cancer cells (HeLa) and the protein could be released into the cytoplasm. Furthermore, we successfully delivered both gene and its chemical inducer into cell wall containing plant cells/tissues and triggered gene expression under controlled-released conditions. We envision that these mesoporous nanoparticles can serve as a universal transmembrane vehicle for many biotechnological applications including therapeutics and metabolic manipulation of cells.
12:45 PM - O7.8
Multivalent Biomimetic Glyconanoparticle Platforms as QCM Amplifiers for Lectin-carbohydrate Interactions.
Mihail Barboiu 1
1 , Institut Europeen des Membranes, Montpellier France
Show AbstractThe Lectin-Carbohydrate interaction was investigated by combining the quartz crystal microbalance technique with signal amplifying biomimetic nanoparticle platforms. A small library of glyconanoparticles was prepared and the affinity of theses particles for immobilised lectin layers was then evaluated using the A100 Quartz crystal Microbalance system from Attana AB. Large responses were observed as a result of surface recognition by nanoparticles displaying the appropriate molecular functionality. Large affinity enhancements were also in evidence due to the biomimetic nature of the glyconanoparticle assemblies showing evidence of the multivalent cluster glycoside effect. A. Cazacu, A. van der Lee, T.M. Fyles, M. Barboiu, J. Am. Chem. Soc. 2006, 128(29), 9541-9548. C. Arnal-Herault, M. Michau, M. Barboiu, Angew. Chem. Int. Ed. 2007, 46, 8409-8413. C. Arnal-Hérault, M. Barboiu, A. Pasc, M. Michau, A. van der Lee, Chem. Eur. J. 2007, 13, 6792C. Arnal-Herault, A. Pasc-Banu, M. Barboiu Angew. Chem. Int. Ed. 2007, 46, 4268-4272.
O8: Multifunctional Polymers
Session Chairs
Michael Bockstaller
Jeffrey Pyun
Thursday PM, April 08, 2010
Room 2014 (Moscone West)
2:30 PM - **O8.1
Polymer Functional Ferromagnetic Nanoparticles: Novel Dipolar Building Blocks for Mesoscopic Assemblies and Semiconductor Nanowires.
Jeffrey Pyun 1 2
1 Chemistry, University of Arizona, Tucson, Arizona, United States, 2 Chemical & Biological Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractWe describe our efforts to develop the synthesis, functionalization and utilization of polymer functional dipolar nanoparticles to create responsive colloidal assemblies and heterostructured semiconductor nanowires. Synthetic methods to prepare ferromagnetic polymer coated cobalt nanoparticles on gram-scale with tunable control of particle size will be discussed. We will also discuss our development of Colloidal Polymerization, where dipolar nanoparticles as used as “colloidal monomers” to prepare cobalt oxide and heterostructured nanowires. Synthesis, characterization and evaluation of potential applications of these materials for biotechnology and energy will be discussed.
3:00 PM - O8.2
Multifunctional Magneto-polymer Composite PRINT® Particles.
Janine Nunes 1 , Kevin Herlihy 1 , Lamar Mair 2 , Richard Superfine 2 3 , Joseph DeSimone 1 4
1 Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 2 Curriculum of Applied Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 3 Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 4 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractThere is great interest in processes that can efficiently generate uniform multi-functional magnetic nanometer-sized particles for a range of applications in both life and materials science. The Particle Replication in Nonwetting Templates (PRINT®) process is an imprint lithography process that has been successfully applied to the fabrication of such multifunctional particles. Here, the PRINT process has been used to fabricate uniform size and shape specific cross-linked poly(ethylene glycol) particles loaded with superparamagnetic iron oxide, magnetite, nanoparticles. The PRINT particle dimensions ranged from 80 nm to 10 μm, with geometries such as nano-worms and micro-boomerangs. These hybrid magneto-polymer particles can be fabricated with the magnetite nanoparticles randomly dispersed within the polymer particle or aligned and oriented in any desired direction prior to curing the particle matrix, thus locking in the magnetite orientation. Using this method, particles containing up to 50 wt.% magnetite were able to be fabricated. Superconducting Quantum Interference Device (SQUID) magnetometry confirmed the superparamagnetic nature of these magneto-polymer composite PRINT particles. Aqueous suspensions of these particles were monitored in the presence of stationary and rotating external magnetic fields. The orientation of the magnetite chains within the particles determined the orientation and motion of the composite particles when manipulated by an external field. Furthermore, the orientation of the composite particles adopted during chaining in a stationary magnetic field was also influenced by the magnetite chain orientation within the particle matrix. Additional functionality was imparted by the anisotropic surface functionalization of platinum to one face of the PRINT composite particles. In hydrogen peroxide solution these multi-functional particles behaved as self-propelled micromotors that were capable of being steered remotely. Particle tracking was used to analyze the particle motion.
3:15 PM - O8.3
Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/Cellulose Nanowhiskers (CNW) Composites Near Mechanical Percolation Threshold.
Elena Ten 1 3 , Long Jiang 1 , Michael Wolcott 1 2
1 Composite Materals and Enginnering Center, Washington State University, Pullman, Washington, United States, 3 Materials Science Program, Washington State University, Pullman, Washington, United States, 2 Civil & Environmental Engineering, Washington State University, Pullman, Washington, United States
Show AbstractStudy of thermal, viscoelastic and dialectic properties of nanocomposites near their mechanical percolation threshold is of great importance in order to understand the influence of nanoparticles on the polymer properties. In this study, CNW suspension (in water) was produced by sulfuric acid hydrolysis and dialysis in deionized water. CNW was transferred from water into DMF by solvent exchange method. PHBV/CNW composite films with various CNW concentrations (0-4.6 wt%) were prepared by solution casting using N,N-dimethylformide (DMF) as a solvent. From both bulge and tensile test results the CNW loading of ca. 2 wt% was determined as mechanical percolation threshold. Compared to neat PHBV, the Young’s modulus and tensile strength for 2wt% CNW increased by 74% (from bulge test) and 39% (from tensile test) respectively. The same value for percolation threshold was calculated based on the CNW aspect ratio determined from AFM and TEM studies. DSC and polarized optical microscopy (POM) study showed that CNW was an effective nucleating agent for PHBV. Moreover, at CNW concentrations higher than 2wt%, decreased melting temperature of the composites demonstrated reduced lamellar thickness and less refined crystalline structure due to the CNW induced crystallization. DMA results showed a gradual increase in storage modulus for the composites with CNW up to 2.8wt% and a sudden decrease at higher concentrations, indicating that higher concentrations led to CNW agglomeration. The same trend was discovered for real permittivity at 2.3 wt% CNW over a wide spectrum of frequencies (0.01-10^6 Hz), confirming poorer dispersion and possible voids formation from solvent evaporation at higher CNW concentrations. Moreover, dielectric loss was found to be more frequency dependent at concentrations higher than 2wt% indicating significant structural changes in nanocomposites.
3:30 PM - O8.4
Multifunctional Polymeric Nanocomposites of Silver Nanoparticles in Ferroelectric Fluorinated Polymers.
Tonino Greco 1 , Michael Wegener 1
1 Functional Materials and Devices, Fraunhofer Institute for Applied Polymer Research, Potsdam Germany
Show AbstractComposites consisting of metal nanoparticles dispersed in a polymeric matrix are of great interest for basic research as well as for different kind of applications e. g. in electronics and opto-electronics. Preparation procedures of embedding different kind of nanoparticles into various polymer matrices have been developed recently. Among the developed composites those with noble metal particles play an important role. These metal particles are the origin of surface plasmon polariton oscillations which occur when light interacts with the conducting electrons. Theoretically the absorption bandwidth of the composites can be tuned within a broad spectral range from the near ultraviolet to the infrared wavelengths. In order to obtain multifunctional nanocomposites ferroelectric polymers can be chosen as matrix materials. Fluorinated polymers such as polyvinylidene fluoride (PVDF) and its copolymer with trifluoroethylene (P(VDF-TrFE)) show a ferroelectric polarization accompanied with piezo- and pyroelectric properties. In both polymers metal particles could be embedded as shown recently. Thus, metal-PVDF and metal-P(VDF-TrFE) nanocomposites are potential candidates for photo-electric applications such as infrared photodetectors and optimized pyroelectric sensors.Here, we demonstrate the synthesis of silver (Ag) nanoparticles, the preparation of thin composite films and the evaluation of their optical and electrical properties. The synthesis of nanoparticles is carried out in situ in the solid polymer matrix whereby no more synthesis in solution is required in order to stabilize and isolate the colloids and to prevent agglomeration of the nanoparticles. Composite films are prepared by mixing the solved matrix polymer PVDF or its copolymer P(VDF-TrFE) with the silver precursor solution, evaporating the solvent thermally and performing an UV-irradiation in order to decompose the silver precursors and to form silver nanoparticles. Finally, Ag-P(VDF-TrFE) and Ag-PVDF nanocomposites with silver weight contents up to 30% are prepared and characterized.Significant surface plasmon oscillations are found while the oscillation strengths depend on the amount of silver in the composite. Based on the effective particle size in composites with different silver mass fractions, the light absorption has a broad bandwidth covering the UV, visible and infrared spectral range. In addition, it will be demonstrated that an electrical poling procedure causes a dipolar polarization of ferroelectric nature in the matrix polymers. Therefore, in a certain range the Ag-P(VDF-TrFE) nanocomposites show beside the adjustable optical absorption also significant piezo- and pyroelectric properties.
4:15 PM - **O8.5
Why Structure Matters – Controlling the Properties of Nanoparticle Hybrid Materials.
Jihoon Choi 1 , Hongchen Dong 2 , Krzysztof Matyjaszewski 2 , Michael Bockstaller 1
1 Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 2 Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Show AbstractThe grafting of polymers to nanoparticle surfaces is ubiquitously being used as a means to facilitate the dispersion of particles fillers within polymer matrices or to control the interaction potential of individual particles and their assemblies. Conceptually polymer-grafted nanoparticles (PGNP) represent an intermediate state between nanoparticles and polymers – the first being characterized by size-dependent physical properties and interactions that typically involve short-range hard sphere and/or long-range electrostatic potentials, the latter by ductility and processability that result from chain entanglement. The complementary physical properties of the distinct constituents render polymer-grafted nanocrystals intriguing materials systems in which property characteristics can be tuned over a wide range from hard particulate to soft polymer-type. Yet, up to date only little is known about the effect of polymer grafting density and molecular weight on particle interactions and the static and dynamic attributes of materials comprised of PGNPs. This presentation will review our recent research efforts on the synthesis and structure-property relations of polymer-functionalized particle fillers and particle-filled materials. In a first part the application of novel controlled radical polymerization techniques to facilitate precise control of polymer molecular weight, grafting density and polydispersity will be presented. Subsequently, the effect of filler particle architecture on the morphological and physical properties of polymer-grafted nanoparticles and their assemblies will be discussed. In particular, it will be demonstrated that tailoring of polymer grafts can reduce the scattering cross section of particle fillers by several orders of magnitude. The ability to tune the structural as well as mechanical properties of PGNP thin films by meticulous control of both, polymer grafting density as well as molecular weight, will be discussed.
4:45 PM - O8.6
Nanoscale Ionic Materials for Controllable Fluidic and Thermal Properties.
Sung A Kim 1 , Lynden Archer 1
1 Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States
Show AbstractSolar thermal energy systems capture solar energy in the form of heat. The simplest approaches directly utilize the harvested thermal energy to supply hot water or space heating. More complicated systems transform the captured heat to electricity. In both systems, a heat transfer fluid is required to convey the thermal energy from the solar collectors to the storage media, where heat exchange occurs. Molten nitrate salts and mineral oil are the most commonly used heat transfer/storage fluids because of their relatively high heat capacities and high-temperature stabilities. This talk introduces two new classes of organic/inorganic hybrid materials, which show good promise as heat transfer and storage fluids for solar thermal capture. Termed Nanoscale Ionic Materials (NIMs), these materials are synthesized by densely tethering an organic telomer/oligomer (short polymer) to the surface of nanoparticles. NIMs are unique among hybrids because they spontaneously form particle-laden fluids in the absence of a suspending liquid. We show that if the NIMs core is a metal oxide nanostructure and its corona is a poly(ethylene glycol) (PEG) derivative, heat capacity, thermal stability, and viscosity can be facilely manipulated through selection of the core particle size and corona polymer molecular weight and grafting density. At one end of the spectrum are polymer-rich NIMs, which manifest high heats of melting (ΔHm ≈ 170 J/g, compared with ΔHm ≈ 187 J/g for the attached PEG) and display simple fluid-like properties at temperatures above the melting transition. At the opposite extreme are particle-rich materials with high thermal conductivities which exhibit soft glassy flow characteristics. We show that crowding and the consequent reduction of conformational freedom of the tethered corona polymer chains profoundly affects the melting transition and thereby the heat transfer and storage properties of the materials. We also present results for the second family of “raspberry” Au-NIMs in which PEG corona chains tethered to a central metal oxide nanoparticle are end-functionalized with a constellation of smaller Au nanoparticles. By controlling the size of the Au particles, a spectrum of melting behaviors can be engineered into these Au-NIMs. Using a combination of thermal scanning (TGA/DSC), imaging (TEM), and scattering (WAXS) techniques we investigate how the structure of both materials influences their thermal and fluid-flow properties.
5:00 PM - **O8.7
Highly Aligned Carbon Nanotube/Polymer Nanocomposites.
Xuemei Sun 1 , Tao Chen 1 , Sanqing Huang 1 , Fangjing Cai 1 , Xuli Chen 1 , Zhibin Yang 1 , Li Li 1 , Huisheng Peng 1
1 Advanced Materials Laboratory and Macromolecular Science Department, Fudan University, Shanghai China
Show AbstractThe excellent mechanical, electrical, and thermal properties of carbon nanotubes make them good candidates as nanofillers in the fabrication of multifunctional polymer nanocomposites. However, there are still many technical challenges to fabricate such nanocomposites. One of the big technical barriers is the random dispersion of nanotubes in the polymer matrix, which results in very low electrical conductivity and mechanical strength of nanocomposite. To address this issue, we have developed several novel approaches to fabricate highly aligned nanotube/polymer nanocomposites in forms of arrays, films, and fibers. The above nanocomposites show much improved conductivities and strengths (e.g., see JACS 2008) as expected and unique sensing properties as unexpected (e.g., see Nature Nanotechnology 2009). These nanocomposites are proved promising for a wide variety of applications such as optoelectronic devices and structural materials.
5:30 PM - O8.8
Polymer Silica Nanocomposites: Influence of the Nanoparticles Dispersion and of the Polymer Chains Conformation on the Macroscopic Properties of the Materials.
Jacques Jestin 1 , Chloe Chevigny 1 , Nicolas Jouault 1 , Francois Boue 1
1 , Laboratoire Léon Brillouin CEA/CNRS, Gif/Yvette France
Show AbstractWe are interested in nanocomposites formed by inclusion of silica nanoparticles in a polymer matrix, following different ways of tuning the dispersion to finally correlate the structure of the particles and the chains conformation with the macroscopic mechanical properties of the materials. The first processing way (mixing colloidal silica with polystyrene (PS)) allowed us to control the filler connectivity inside the polymer matrix: using a combination of scattering (SAXS) and microscopy (TEM), we show that the particles organize as non connected finite size fractal aggregates at low silica concentration, which percolate as a connected filler network when the silica concentration increases[1]. The conformation of the chains, which can be measured with neutron scattering (SANS) using the Zero Average Contrast method, is not modified by the filler whatever the silica concentration. For small deformations of the material, the evolution of the elastic modulus depends directly on the local filler connectivity: it diverges at the percolation threshold. For high deformations, the presence of the filler does not modify the deformation of the chains and the elastic modulus remains constant as a function of the deformation rate due to non affine reorganization of the filler network. The second tuning way (polymer-grafted silica particles mixed with matrix chains[2]) permits to control the local dispersion of the particles inside the matrix with the mass ratio between the grafted PS chains and the free chains: when the grafted chains are smaller than the free chains, the particles organize as dense aggregates and when both chains are similar, the particles are well dispersed in the matrix. Using a specific neutron contrast variation method, we show that these dispersion states can be respectively related to a dry or wet conformation of the grafted corona. In addition, the elastic modulus of the material depends also on these conformations as it can be related to the interdiffusion between the grafted and the free chains.[1]N. Jouault, P. Vallat, F. Dalmas, S. Said, J. Jestin, F. Boué, Macromolecules, 42 (6), 2031-2040, 2009[2]C. Chevigny, D. Gigmes, D. Bertin, J. Jestin, F. Boué, Soft Matter, 5 (19), 3741-3753, 2009
5:45 PM - O8.9
Electron Microscopy (TEM) and X-ray Spectromicroscopy (STXM) of PP/MMT/PP-g-MA and PP/MMT/SEBS Nanocomposites.
Zulima Martin 1 2 3 , Ignacio Jimenez 3 , M. Angeles Gomez 3
1 Chemistry, McMaster University, Hamilton, Ontario, Canada, 2 , Advanced Light Source-LBL, Berkeley, California, United States, 3 Polymer Physics and Engineering, Polymer Sci.&Tech. Institute - CSIC, Madrid Spain
Show AbstractNanocomposites of commodity polymers like polypropylene (PP) with nanoparticles of layered silicates like montmorillonite (MMT) lead to a great improvement of the polymer properties such as thermal stability and mechanical performance with very low filler contests, because the high surface area of these nanometric particles increases the interfacial interactions between matrix and clay. However, an efficient dispersion of the particles and their interfacial interaction with the polymer matrix requires the incorporation of additives containing polar and non-polar parts. In this work we have considered the addition of polypropylene-graft maleic anhydride (PP-g-MA) with a content of 5 and 15%, used as a polar compatibilizer, and of poly(styrene-b-ethylene butylene-b-styrene) (SEBS) with a content of 15%.We present a combined study by x-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission x-ray microscopy (STXM) of the formation of nanocomposites of isotactic polypropylene (PP) with 5 wt % of organically modified montmorillonite (C20A) by melt processing, providing a complete picture of the intercalation and exfoliation processes taking place. X-ray diffraction (XRD) and microscopy reveals a complex morphology, with partial intercalation/exfoliation. A better understanding of the mechanism of compatibilization and a deeper characterization of the structure and morphology of the nanocomposite were achieved using scanning transmission X-ray microscopy (STXM) has been used. Based on the different x-ray absorption of each component, STXM spectromicroscopy performs chemical mapping at nanometric scale providing direct visual and compositional chemical information of the presence of the different polymer components at the polymer silicate interfaces and details on the intercalation mechanism.
Symposium Organizers
Yuping Bao The University of Alabama
Andrew M. Dattelbaum Los Alamos National Laboratory
Joseph B. Tracy North Carolina State University
Yadong Yin University of California-Riverside
O9: Multifunctional Oxides
Session Chairs
Andrew Dattelbaum
Huisheng Peng
Friday AM, April 09, 2010
Room 2014 (Moscone West)
9:30 AM - **O9.1
Synthesis and Characterization of Nanocomposite Films.
H. Yang 1 , G. Zou 1 , H. Luo 1 , H. Wang 2 , Z. Bi 2 , P. Zerrer 3 , A. Fouchet 3 , M. Blamire 3 , J. MacManus-Driscoll 3 , E. Bauer 1 , T. McCleskey 1 , A. Burrell 1 , Quanxi Jia 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 , Texas A&M University, College Station, Texas, United States, 3 , University of Cambridge, Cambridge United Kingdom
Show AbstractNanocomposite films hold great promise for improved or novel functionalities. In order to achieve practical applications, one needs to create ordered structures, to achieve different combinations of materials, and to control strain coupling between different phases. In this presentation, we show metal-oxide/metal-oxide and carbide/carbon nanotube nanocomposite systems that exhibit improved functionalities. In detail, self-assembled (BiFeO3)0.5:(Sm2O3)0.5 nanocomposite films were deposited on (001) SrTiO3 and Nb-doped SrTiO3 substrates by pulsed laser deposition. Composites of superconducting NbC with oriented carbon nanotubes (CNTs) were synthesized by a polymer-assisted deposition. Both the structural and the transport properties of the composites will be discussed in this presentation.
10:00 AM - O9.2
Highly Visible-light-active TiO2-based Composite Photocatalyst.
Diana Oliveira 1 , Qiao Zhang 1 , Ilkeun Lee 1 , Francisco Zaera 1 , Yadong Yin 1
1 Chemistry, University of California, Riverside, Riverside, California, United States
Show AbstractIn this presentation, we discuss the synthesis and application of TiO2-based photocatalyst with enhanced visible light response and high stability. To utilize visible light more efficiently in photocatalytic reactions, non-metal doping and metal-sensitization are combined to control the optical properties of TiO2. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance UV-Vis spectra were used to characterize the as-obtained photocatalyst. The non-metal doping was confirmed by XPS. Photocatalytic activities of the as-obtained samples were evaluated by Rhodamine B (RhB) degradation under visible light or direct sunshine irradiation. By optimizing the synthetic condition, highly visible-light-active TiO2-based photocatalyst can be fabricated in a cost-effective and high-throughput way.
10:15 AM - O9.3
Single-pot Synthesis of Surfactant-capped Platinized TiO2 Nanoparticles for Use as a Visible Light Hydrogen Evolution Catalyst.
Derek Johnson 1 , Megan Lazorski 1 , Hongfei Jia 2 , C. Elliott 1 , Amy Prieto 1
1 Chemistry, Colorado State University, Fort Collins, Colorado, United States, 2 Materials Research, Toyota Research Institute of North America, Ann Arbor, Michigan, United States
Show AbstractIn an attempt to convert solar energy into storable chemical energy, donor-chromophore (DC) and donor-chromophore-acceptors (DCA) are being used to sensitize the surface of platinized TiO2 for hydrogen production. Numerous investigators have pursued various DC and DCA combinations with the most common non-porphyrin chromophore containing Ru, and to a lesser extent Pt. This effort is justified as the use of DC and DCA sensitizers on platinized TiO2 allows for the photogeneration of hydrogen gas from aqueous solutions using visible light. In contrast, most transition metal oxides used for photocatalytic water splitting require radiation sources with wavelengths in the UV. The pursuit, however, to improve the platinized semiconductor nanoparticle has been conducted with a lot less vigor. Significant obstacles need to be overcome in order for this energy conversion option to be viable.The fact that TiO2 is typically platinized post synthesis by a photoinduced reduction of a platinum-based acid or salt has two repercussions when considering the viability of this process. First, because a surfactant is not used, the initial nanoparticle sized is large, c.a. 100 nm; resulting in an undesirably low surface-to-volume ratio. If a surfactant were used to control particle growth, it would subsequently be destroyed during the photoinduced platinization reaction. Second, the nanoparticles agglomerate and do not suspend well in solution because a surfactant is not initially bound to the platinized TiO2 surface. This makes binding the DC or DCA to the surface of the particle much more difficult and results in low yields. To overcome these obstacles, a new one-pot reaction which yields surfactant-capped 5 nm platinized TiO2 nanoparticles has been developed. An electrochemical evaluation of these nanoparticles to determine hydrogen evolution efficiency was conducted. These results are compared to surfactant-capped, non-platinized 5 nm TiO2 particles as well as 80 nm platinized and non-platinized TiO2 and SrTiO3 nanoparticles. In addition to the electrochemical analysis, high-resolution transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (HRTEM-EDX) and X-ray photoelectron spectroscopy (XPS) data are presented to further characterize the nanoparticles.
10:30 AM - O9.4
Active Nanostructures at Interfaces for Photocatalytic Reactors and Low-power Consumption Sensors.
James Gole 1 2 , Serdar Ozdemir 1 , James Corno 1 , William Laminack 1
1 School of Physics, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractActive nanostructures are being introduced to phase matched porous silicon (PS) nano/microfilters and nano/micropores to form a platform for low power consumption highly selective sensors and microreactors. Visible light absorbing, anatase TiO2-xNx photocatalysts have been formed in seconds at room temperature at the nanoscale via the direct nitration of anatase TiO2 nanocolloids. Tunability throughout the visible is found to depend upon the degree of nanoparticles agglomeration and upon the ready ability to seed these nanoparticles with metal (metal ions) including Pt, Pd, Cu, Co, Ni, and Fe. Co metal ion seeding also leads to unique efficient room temperature phase transformations, including that of anatase to rutile TiO2, where normally much higher temperatures are required. Further, the seeding with high spin magnetic transition metal ions (Co, Ni) of a properly nitridated TiO2 nanocolloid allows for the enhancement the Raman and infrared spectra of the nitridated titania surface in excess of 10-fold, providing a means to analyze for minor contaminants and intermediates. Evidence for nitrogen fixation is found in Fe treated systems. The visible light absorbing photocatalyts readily photodegrade methylene blue and gaseous ethylene. They can be transformed from liquids to gels and, in addition, can be placed on the surfaces of PS-based sensor and microreactor based configurations to produce an improved photocatalyst induced solar based sensor response and to break down larger polyatomics into their constituents on PS microfilters both for photocatalytic transformation and for sensing. These highly efficient nitridation processes at the nanoscale are now being extended to the conversion of additional catalytic oxides and molecular sieves including faujasite. Here, the conversion from acidic to base-site pores may provide an efficient route to the transformation of CO2 and H2O to carbon organic fuels.
10:45 AM - O9.5
Multifunctional Composite Nanostructures Through Surface-protected Etching.
Yadong Yin 1
1 Chemistry, University of California, Riverside, Riverside, California, United States
Show AbstractIn this presentation, I would like to discuss our recent process in the synthesis and application of multifunctional nanostructures. A “surface-protected etching” process has been developed to directly produce porous colloidal silica particles without the need of additional templates. The “surface-protected etching” process involves coating of oxide surfaces with a layer of polymeric ligands and subsequent preferential etching of material from the interior of the particles using an appropriate etching agent. The protection by the polymer allows the oxide particles to retain their original size, while selective etching at the interior produces porous structures and eventually hollow spheres. Nanocrystals of various compositions can be incorporated in the porous silica to produce hybrid nanostructures with magnetic, plasmonic, and fluorescent properties. By incorporating the “surface-protected etching” strategy, we have also developed an “encapsulation and etching” method that may provide a solution to the important challenges in improving the stability, recyclability, and catalytic selectivity of metal nanocatalysts.
11:30 AM - O9.6
Surface Functionalization of ZnO Nanorods With Phosphonic Acid Derivatives of Fullerene-C60.
Michael Voigt 1 , Martin Klaumuenzer 1 , Alexander Ebel 2 , Andreas Hirsch 2 , Wolfgang Peukert 1
1 , Institute of Particle Technology, Erlangen Germany, 2 , Institut für Organische Chemie LS II, Erlangen Germany
Show AbstractThe main objective of our project is to produce ZnO nanoparticle films with high charge carrier mobility and long term stability for applications in printable electronics. The main idea is to optimize the electrical properties by engineering of the particle/particle and the particle/insulator interfaces. This approach is essential because the charge transport in nanoparticular electronic devices is known to be dominated by the interfaces. In particular, complex organic molecules are used to modify the nanoparticle surfaces and to build up hybrid structures of high hierarchy and functionality. In order to achieve this, we applied different methods for the surface functionalization of ZnO nanorods with photo- and electroactive molecules. ZnO nanorods were used because of their strong tendency for self-alignment. The photo- and electroactive molecules used in our study consist of three basic functionalities: (1) electro-/photoactive group (fullerene-C60), (2) alkyl chain (-CH2)n- of variable length n, and (3) the phosphonic acid group –PO(OH)2 as the anchor group. The C60 is separated from the particle surface by the alkyl chain and the anchor. The length of the alkyl chain was varied from n = 3 to n = 18 in order to study the electronic interaction between the C60 and the ZnO as a function of the distance. The ZnO nanorods were functionalized in chloroform by the different phosphonic acid derivatives. For the successful functionalization it is mandatory to avoid traces of methanol which are assumed to block the –PO(OH)2 anchor groups. Evidence for the successful functionalization is given by the results from optical spectroscopy (UVVis absorption, photoluminescence (PL), FTIR) and high resolution transmission electron microscopy (HRTEM). As can be seen by HRTEM, the ZnO nanorods are coated by a homogeneous amorphous film with a thickness that corresponds to the length of the phosphonic acid derivatives. For the successful functionalization it is mandatory to avoid traces of methanol which are assumed to block the –PO(OH)2 anchor groups. In the UVVis and the PL spectra a significant blue shift of the excitonic peak of ZnO (near-bandgap) is observed with the decrease of the alkyl chain length. The blue shift is up to 20 meV and up to 50 meV in the UVVis and PL, respectively. In addition, the yellow defect PL of ZnO is quenched by the surface functionalization. The results mentioned above indicate that there is an electronic interaction between the C60 and the ZnO, which is explained by band-banding effects.
11:45 AM - O9.7
Nanospheres of Silica With An ε-Fe2O3 Single Crystal Nucleus.
Anna Roig 1 , Elena Taboada 1 , Marti Gich 1
1 , Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Bellaterra Spain
Show AbstractEpsilon iron-oxide is a metastable ferric oxide which has been previously stabilized as a pure nanophase in the form of nanoparticles, nanowires or nanorods. The majority of systems investigated up to now have been: composite powders of ε-Fe2O3 nanoparticles in a silica matrix or non-supported aggregates of epsilon particles or nanowires. The challenge is to produce ε-Fe2O3 in a more controlled manner and with a variety of shapes to facilitate its integration in devices and thus its technological use. The interest of ε-Fe2O3 is owed to its rich magnetic phase diagram and magnetoelectric properties not found in other simple ferric oxides. In addition, an appealing potential application has recently been reported in the use of ε-Fe2O3 as electromagnetic wave absorber in the millimetre range [1]. The potential of this material has not been fully exploited due to the difficulties encountered, initially obtaining the material as a pure phase, and lately in producing it in a useful shape.We will report on a novel route to produce single crystals of ε-Fe2O3 (average size 37 nm) wrapped in a silica shell [2]. Formation of ε-Fe2O3/silica nanospheres (average size 160 nm) was achieved by controlled recrystallization of maghemite particles (γ-Fe2O3) confined in silica via calcination in air. Phase transition was monitored by X-ray diffraction, magnetometry and transmission electron microscopy. Core-shell nanocomposite particles can be dispersed as a colloidal suspension in several polar liquids enlarging the processability spectrum of the material and thus facilitating the use of ε-Fe2O3 in technological applications.[1] S. Ohkoshi et al. Angew. Chem. Int. Ed. 2007, 46, 8392.[2] E. Taboada et al. ACS Nano Publication Date(Web):Oct 13,2009 doi: 10.1021/nn901022s
12:00 PM - O9.8
Core-shell Multi-functionalized Colloidal Mesoporous Silica Nanoparticles.
Thomas Bein 1 , Valentina Cauda 1 , Axel Schlossbauer 1 , Johann Kecht 1 , Andreas Zuerner 1
1 Chemistry, University of Munich (LMU), Munich Germany
Show AbstractThe selective functionalization of the inner and outer surface of colloidal mesoporous silica (CMS) nanoparticles with different trialkoxy-silanes was achieved following a newly developed delayed co-condensation approach. Complementary CMS nanoparticles were prepared, with two different functional groups located either on the outer shell or in the inner core of the particle. The localization of the functional groups was achieved by different techniques including zeta-potential and fluorescence spectroscopy with FITC-(fluorescein isothiocyanate) labelled CMS featuring aminopropyl functional groups on the periphery or the internal pore surface of the particles. It could be shown that fluorescence quenching with gold nanoparticles only occurs when the FITC is positioned on the outer surface of the CMS nanoparticles. Our approach thus offers the opportunity to synthesize, in a novel one-pot synthesis strategy, various bi-functional mesoporous nanoparticles with controlled localization of different functional groups. We will discuss the potential of these systems for controlling cell functions.
12:15 PM - O9.9
Formation Mechanism of Noble Metal Nanoparticles in Reactively Sputtered TiO2 Films.
John Okumu 1 2 , Dominik Koehl 1 , Alexander Sprafke 1 , Gero von Plessen 1 , Matthias Wuttig 1
1 Institute of Physics (IA), RWTH Aachen, Aachen Germany, 2 Physics, Kenyatta University , Nairobi Kenya
Show AbstractRecently a simple approach has been developed to prepare Ag nanoparticles in a TiO2 matrix [1, 2]. In this scheme, silver nanoparticles are formed in a TiO2 matrix first by sputtering a thin silver film sandwiched by TiO2 layers followed by an annealing process. The resulting Ag nanoparticles show multicolor photochromism and have also been studied for their effect on the photocatalytic behavior of TiO2 host matrix. To determine the formation mechanism of noble metal nanoparticles in the TiO2 matrix, we have compared the behavior of Ag with two similar noble metals, gold and copper. The formation of metal nanoparticles in the TiO2 matrix is investigated by a combination of techniques including x-ray diffraction, x-ray reflectance and optical spectroscopy. Despite the similarity of the three noble metals, no nanoparticles are formed for Cu and Au as confirmed by optical absorption studies. This is in striking contrast to the behavior observed for Ag. The difference can be explained by a three step process, which involves oxidation of the metal, dissociation of the metal oxide upon annealing and metal aggregation to form nanoparticles.
12:30 PM - O9.10
Multi-component Nanoparticles for Near-infrared Fluorescence and Magnetic Resonance Imaging.
Andrew Dattelbaum 1 , Folami Ladipo 2 1 , Jun Gao 1 , Joshua Hanson 1 , Peter Goodwin 1 , Rebecca Martin 1 , Raea Hicks 1 , Dana Dattelbaum 1 , Rashi Iyer 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Department of Chemistry, University of Kentucky, Lexington, Kentucky, United States
Show AbstractWe will discuss the preparation of versatile silica-based nanoparticles that may be used for both far-red-to-near infrared fluorescence and magnetic resonance imaging in biological systems. Ruthenium polypyridyl complexes have been encapsulated in water soluble silica nanoparticles, which are known to be useful for fluorescence imaging studies inside of cells. The ruthenium complexes are photostable and have tunable ligand environments that can be used to optimize emission signals towards the near-infrared where most biological materials have minimal absorption or emission signals. Using ruthenium complexes with far-red to near-infrared emission encapsulated in silica nanoparticles, the confocal imaging of cells stained with Giemsa, a dye used for chromosome and other identification procedures, has been demonstrated. Further, we will describe the preparation of paramagnetic gadolinium oxide nanoparticles with a water-soluble ruthenium dye-doped silica shell that allows for both magnetic resonance imaging combined with fluorescence-based imaging near the tissue transparent window region.
12:45 PM - O9.11
Dry Autogenic Reactions for Synthesizing Anode Materials for Lithium-ion Batteries.
Vilas Pol 1 , Sun-Ho Kang 1 , Michael Thackeray 1
1 Electrochemical Energy Storage Department, Chemical Sciences and Engineering Division,, Argonne National Lab., Argonne, Illinois, United States
Show AbstractA solvent-less, single step process has been developed for fabricating a variety of anode and cathode materials for lithium-ion batteries. The technique has particular merit for producing carbon- and carbon-coated materials from organic- and organometallic precursors, respectively. In this presentation, we will report on the synthesis of carbon-coated titania (TiO2-C) and spherical carbon particles, and on their structural, morphological and electrochemical properties when used as anode materials in lithium cells.The secondary, micron sized TiO2-C particles, prepared from a titanium alkoxide precursor, are comprised of an agglomerate of primary TiO2 nanoparticles, approximately 20-30 nm in diameter, each of which is uniformly coated and interconnected by a 2-3 nm carbon layer. By contrast, the decomposition of a single polymer precursor in the autogenic reactor results in amorphous C spheres approximately 3 microns in diameter. The materials were evaluated in lithium half cells and in full cells with lithium-rich, high-capacity 0.5Li2MnO30.5LiNi0.44Co0.25Mn0.31O2 cathodes developed at Argonne. ACKNOWLEDGEMENTS This work was supported by the U.S. Department of Energy, Office of Vehicle Technologies (EERE). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357
O10: Coupled Behaviors and Other Multifunctional Nanoparticle Systems
Session Chairs
Friday PM, April 09, 2010
Room 2014 (Moscone West)
2:30 PM - O10.1
Collective Properties of 3D Self-assembled Nanoparticle Superlattices.
Paul Podsiadlo 1 , Xiaohua Wu 1 , Galyna Krylova 1 , Byeongdu Lee 2 , Paul Ashby 3 , Tijana Rajh 1 , Vitali Prakapenka 2 , Jeffrey Guest 1 , Matthew Pelton 1 , Dmitri Talapin 4 , Elena Shevchenko 1
1 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 2 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States, 3 Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 4 Chemistry Department, University of Chicago, Chicago, Illinois, United States
Show AbstractNanoparticles (NPs) and their assemblies have attracted interest from many branches of science and industry, because, in general, physics at the small scale is very different when compared to bulk materials. Furthermore, controlled assembly of different nanomaterials into superstructures is an attractive route to designing systems possessing novel physical and chemical properties. In such systems one can expect unique properties originating from collective interactions between the constituents. As such, design of new materials which combine properties of different components and potentially collectively generate novel properties motivates the researchers to search for different approaches that will allow formation of these “metamaterials”.Here, we present our results from characterization of collective properties in self-assembled, periodic NP superstructures. We discuss synthesis of highly monodisperse NPs and their self-assembly into ordered 3D superlattices. We also show results from control of superlattice nucleation, growth, and interdot spacing. In particular, we show that the interparticle distance can be controlled via post-assembly thermal annealing, giving a new method for controlling electronic coupling. Furthermore, we present the first experimental results from evaluation of mechanical properties of 3D supercrystals using nanoindentation technique. The results of this work show critical role of 3D organization, the composition of stabilizing ligands, as well as strong cohesion of the organic matrix with polymer-like properties. Lastly, we will discuss results from optical and electronic studies on 3D assemblies of semiconductor NPs, i.e. CdSe and PbS. We found anomalous optical properties in the CdSe superlattices and several orders of magnitude enhanced electronic transport in the PbS superlattices in comparison to disordered films.
2:45 PM - O10.2
Colloidal Semiconductor/Magnetic Nanocrystal Heterostructures.
P. Davide Cozzoli 1 2
1 Scuola Superiore ISUFI- Distretto Tecnologico, Università di Lecce, Lecce Italy, 2 National Nanotechnology Laboratory (NNL), CNR-INFM, Lecce Italy
Show AbstractThe recognition of the unique properties of nanoscale matter has stimulated efforts towards fabrication of nanomaterials in a controlled and systematic manner [1-2]. Colloidal routes have opened access to a variety of finely size- and shape-tailored nanocrystals upon regulation of thermodynamically and kinetically driven growth processes in liquid media. Further challenges are now being imposed on nanochemistry research in the pursuit of advanced prototypes of nanocrystal heterostructures (HNCs) that incorporate multiple sections of distinct materials into individually processable multifunctional nano-objects [1-3].Here, we review our recent progress in seeded-growth nonhydrolytic approaches to various types of elaborate HNCs that comprise semiconductor and magnetic portions interconnected together through small interfaces. HNCs based on crystal-phase-controlled TiO2 nanorods decorated at selected sites with either iron oxide, Pt, Ag [4] or Co [5], asymmetrically Co-tipped CdSe@CdS core@shell nanorods [6], Co- or Ag-functionalized γ-Fe2O3 tetrapods [7] as well as CoPt3-Au [8] and FePt-Fe3O4 hetero-dimers [9], respectively, will be discussed. The structural and magneto-optical properties as well as the potential technological advantages offered by such multifunctional HNCs will be highlighted. Overall, our results will illustrate how facet-dependent chemical reactivity, lattice strain at the relevant junction regions and surface-interface energy balance interplay at the nanoscale, dictating the HNC topologies ultimately achievable. Guiding criteria for the rational design of colloidal nanoheterostructures with higher architectural sophistication and increased functionality will be given.[1] P. D. Cozzoli et al. Chem. Soc. Rev. 2006, 35, 1195.[2] "Advanced Wet-Chemical Synthetic Approaches to Inorganic Nanostructures", P.D. Cozzoli Ed.; Transworld Research Network Kerala (India) 2008, pp. 407-453 (ISBN: 978-81-7895-361-8)[3] M. Casavola et al. Eur. J. Inorg. Chem. 2008, (6), 837.[4] (a) R. Buonsanti et al. J. Am. Chem. Soc. 2006, 128, 16953. (b) R. Buonsanti et al. J. Am. Chem. Soc. 2008, 130, 11223. (c) R. Buonsanti et al. Phys. Chem. Chem. Phys. 2009, 11, 3680 (d) Buonsanti et al. submitted[5] M. Casavola et al. Nano Lett. 2007, 7, 1386.[6] S. Deka et al. J. Am. Chem. Soc. 2009, 131, 12817[7] (a) P. D. Cozzoli et al. Nano Lett. 2006, 6, 1966. (b) Petkov, V. et al. J. Am. Chem. Soc. 2009, 131, 14264. (c) M. Casavola et al. Nano Lett. 2009, 9, 366 (d) M. Casavola et al., in preparation[8] T. Pellegrino et al. J. Am. Chem. Soc. 2006, 128, 6690.[9] A. Figuerola et al. J. Am. Chem. Soc. 2008, 130, 1477.
3:00 PM - **O10.3
Tuning the Electronic, Magnetic, and Catalytic Properties of Boron-doped Carbons With Transition-metal Adsorbates.
Wei An 1 , Christoffer Turner 1
1 Chemical and Biological Engineering, The University of Alabama, Tuscaloosa, Alabama, United States
Show AbstractCarbon nanotubes (CNTs) have demonstrated remarkable versatility and wide applicability in emerging technologies, such as components in field-effect transistors, optoelectronics, spintronic devices, and sensors. The ultimate performance of these devices often hinges on the underlying material properties and our ability to synthesize complex structures at small length scales. While the experimental synthesis of devices on the nanometer length-scale can present major technical challenges and can be very costly, computational investigations can help provide benchmarks and targets for experimental synthesis. Ultimately, this synergism is expected to accelerate the discovery process.
Here, we explore the range of magnetic, electronic, and catalytic properties that may emerge from newly-proposed inorganic composite materials, which are based on combining transition-metal (TM) adsorbates with boron-doped carbon nanotubes (B-CNTs). Depending on the pairing between a specific TM adsorbate and a specific B-CNT adsorbent, we predict that a wide range of fundamental material properties may be achieved. We have modeled eleven different transition metals, and we have adsorbed these metals on several different B-CNT models (with varying chirality), in order to achieve different magnetic moments, conductivity, and band structures. Critical to the stability of these structures, we find that the boron-doped CNTs provide significantly enhanced binding with the TM adsorbates (as compared to prisitine CNTs). In effect, this allows the B-CNTs to serve as templates for the growth of TM adsorbates, and in many cases, we predict that monatomic TM strings can be templated along the axis of the B-CNTs. Thus, TM monatomic string can be stabilized and manipulated, once attached to B-CNTs, which may allow them to be more easily integrated into a functioning device. Our most recent calculations involve predictions of the magnetic properties of TM-alloy monatomic strings adsorbed on B-CNTs. By changing the composition of the alloy, the easy axis of the composite material can oscillate between the magnetization directions parallel to and perpendicular to the tube axis. Ultimately, the TM-alloy strings anchored on a B-CNT substrate could still possess magnetic anisotropy with a sizable magnetic anisotropy energy.
3:30 PM - O10.4
Multifunctional Carbon Nanotube/Metal Nanoparticle Composite Membranes.
Susanna Back 1 2 , Andrey Voevodin 1 , Ilia Ivanov 3 , Steven Patton 1 4 , Richard Vaia 1 , Michael Jespersen 1 5
1 , Air Force Research Laboratory, Wright Patterson AFB, Ohio, United States, 2 , Universal Technology Corporation, Dayton, Ohio, United States, 3 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 4 , University of Dayton Research Institute, Dayton, Ohio, United States, 5 , National Research Council, Washington , District of Columbia, United States
Show AbstractMuch research has been conducted to exploit the excellent properties of carbon nanotubes (CNTs) and nanoparticles (NPs). However, little efforts were done to investigate CNT/NP composite materials, which themselves represent a novel class of materials. The combination of CNT and metallic NP technologies is expected to give a CNT/NP composite with enhanced thermal, electrical, and optical properties. A series of multifunctional CNT/Au-NP composite membranes were synthesized where the chemical functionality and physical properties were varied. In-situ measurements were taken on a micro/nanocontact apparatus to measure the contact force, stiffness, strain, and electrical resistance of CNT/NP membranes. Four point probe, differential 3-omega, and 2-color pump probe methods were also used for electrical and thermal conductivity measurements on CNT/NP membranes. The correlation of thermal, electrical, and optical properties is of particular importance to CNTs where thermal transport modes are coupled to low energy optical (electronic) transitions. Thermal, electrical, and optical data as well as potential correlations will be discussed.
3:45 PM - O10.5
Using Multifunctional Nanoparticles to Modify the Properties of Carbon Nanotube Networks for Electronic Applications.
Melburne LeMieux 1 , Ajay Virkar 1 , Zhenan Bao 1
1 Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractThe ultimate goal of this work is to further enable carbon nanotube technologies including nanotube based diagnostic sensors, electronic devices (including transistors, displays, touch screens, e-paper, and solar cells), and composite materials. Transparent electrodes are a central component in many of these aforementioned electronic devices. We have developed approaches for the directed solution assembly of carbon nanotube networks with tunable density, alignment, and chirality, all of which effect overall conductivity. The primary issue concerning nanotubes films for electronic applications to date is inferior conductivity, which is mainly hampered by high resistance at nanotube/nanotube junctions. We address this issue by using a hybrid nanotube film. These films are composed of carbon nanotubes and novel organic nanoparticles. The purpose of the nanoparticle material is bi-functional. Firstly, it can be selectively assembled at nanotube junctions greatly increasing conductivity by reducing contact resistance. Secondly, it can dope semiconducting nanotubes, which also increases film conductivity. Using these nanotube/nanoparticle hybrid films, we are able to fabricate a material suitable for ITO replacement by resolving these issues with the conductivity in pristine nanotube films. This nanoscale hybrid approach should be a universal approach to the bottom-up assembly of nanomaterials in general. Furthermore, because the assembly is from solution, we have been able to integrate these hybrid films on flexible plastic surfaces. We will also discuss processing and morphology and how it relates to conductivity and electronic properties of this material. Importantly, the ultimate properties of the resulting hybrid films is directly coupled to the chemistry and size of the multifunctional nanoparticles, which we have characterized.
4:30 PM - **O10.6
Spin Torque Transfer Switching of Magnetic Nanopillars With a Scanning Probe Tip.
Sara Majetich 1 , James Bain 1 , Eric Evarts 1
1 , Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Show AbstractMagnetic tunnel junctions have been studied extensively for their magnetoresistance and potential uses in magnetic logic and data storage devices, but little is known about how their performance will scale with size. Here we examined the electronic behavior of nanopillars of different sizes that were fabricated from magnetic tunnel junctions (MTJs) provided by Everspin Technologies, Inc. The thin films had a resistance area product of 5 microOhm-cm2, independent of the pillar size, indicating that there was not significant damage duing patterning. The parallel or antiparallel state of the MTJ nanopillar was determined by resistance measurements. Unlike in most previous studies, these measurements used conducting atomic force microscopy to contact pillars individually. The tip need not have a ferromagnetic coating, but it was sputtered with an extra layer of Pt in order to handle the high current density needed for spin torque switching. The results of magnetic field induced switching are compared with those of current-induced switching.
5:00 PM - O10.7
Gold and Silver Nanocomposites Based on Metallic Nanoparticles and Ru(II) Coordination Complexes: Design, Optical and Electrochemical Properties.
Eddy Dumas 1 , Frederic Dumur 2 , Audrey Guerlin 1 , Fabien Miomandre 3 , Cedric Mayer 1
1 University of Versailles, Institut Lavoisier de Versailles, UMR-CNRS 8180, Versailles France, 2 Universty Aix-Marseille , Laboratoire Chimie Provence, UMR-CNRS 6264, Marseille France, 3 ENS Cachan, Laboratoire PPSM, UMR-CNRS 8531, Cachan France
Show AbstractThe richness of the optical, magnetic and electronic properties of ruthenium(II) coordination complexes make these molecular objects ideal candidates1 for the formation of multifunctional composite nanomaterials with a gold or a silver core. The organization of these molecular units at the surface of gold or silver nanoparticles will allow the combination of the chemical, electronic and optical properties of the gold or silver nanometric object with the ones of the molecular metallic complex. We will describe the design of nanocomposites formed by the grafting of polypyridyl metallic complexes, onto the surface of metallic nanoparticles through fully conjugated linkers. The aim of this project is to control the electronic transfer between the grafted metallic complexes and the nanoparticle.2 This project will open perspectives for a variety of applications such as in optoelectronic or biology.1.(a) F. Dumur, C. R. Mayer, K. Hoang-Thi, I. Ledoux-Rak, F. Miomandre, G. Clavier, E. Dumas, R. Méallet-Renault, M. Frigoli, J. Zyss, F. Sécheresse, Inorg. Chem., 2009, 48, 8120. (b) C. R. Mayer, F. Dumur, F. Miomandre, E. Dumas, T. Devic, C. Fosse, and F. Sécheresse, New J. Chem., 2007, 1806.2.(a) C. R. Mayer, E. Dumas, F. Sécheresse, Chem. Commun., 2005, 345-347. (b) C. R. Mayer, E. Dumas, F. Miomandre, R. Méallet-Renault, F. Warmont, J. Vigneron, R. Pansu, A. Etcheberry, F. Sécheresse, New. J. Chem, 2006, 30, 1628. (c) C. R. Mayer, E. Dumas, A. Michel, F. Sécheresse, Chem. Commun., 2006, 40, 4183. (d) C. R. Mayer, E. Dumas, F. Sécheresse, J. Coll. Interf. Scienc., 2008, 328, 452.
5:15 PM - O10.8
Shape Controlled Synthesis of Composite Pt-Au NPs.
Chao Wang 1 2 , Vojislav Stamenkovic 1 , Shouheng Sun 2
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Chemistry, Brown University, Providence, Rhode Island, United States
Show AbstractHeterogeneous nanoparticles (NPs) containing multiple components have attracted increasing interest owing to their great potential for optical, magnetic, catalytic and particularly multifunctional biological applications. Despite the recent advances in preparation of various types of heterogeneous NPs, synthesis of heterogeneous NPs with shape control remains challenging today. Here we report the synthesis of Pt-Au NPs by overgrowing Au on Pt. The shape control was achieved by finely tuning the size and shape of seeds, or the polarity of solvent. Theoretical modelling reveals that these NP morphologies are respectively energy-favorable under the rational designed chemical environments. In addition, enhanced catalytic activity has been demonstrated on the composite NPs for methanol oxidation. Our findings could help rule out the factors governing the epitaxial growth of nanocrystals and guide the development of shape-controlled synthesis of heterogeneous nanomaterials.
5:30 PM - O10.9
Combinatorial Discovery and Optimization of Rare Earth-doped Nanocrystals.
Emory Chan 1 , Gang Han 1 , Bruce Cohen 1 , Delia Milliron 1
1 Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractRare earth-doped nanocrystals can exhibit strong upconversion luminescence in the visible region of the spectrum when excited with near-infrared laser excitation. This anti-Stokes emission has been utilized for biological, telecommunications, and display applications. The efficiency of such upconversion processes is dependent on the alignment of the energy levels of the single or multiple dopant ions, as well as material of the surrounding matrix. Optimizing parameters such as dopant identities, dopant concentrations, matrix choice, and the matrix crystal phase can be tedious. Searching for new upconverting materials is typically performed by trial and error, and most of the known upconversion transitions are optimized for a handful of common laser lines. The availability of inexpensive diode lasers and the rise of applications that require non-traditional excitation wavelengths have increased demand for novel upconverting materials with tunable excitation and emission energies.We describe the high-throughput discovery and optimization of rare earth-doped nanocrystals that exhibit a tunable upconversion luminescence. To perform combinatorial screening of a library of dopants, we used an automated platform capable of synthesizing high quality NaYF4 nanocrystals and characterizing their optical and structural properties in parallel. Previously, we demonstrated that this automated synthesis robot could control the reaction parameters of semiconductor nanocrystal synthesis with exquisite precision. Here, we use this Workstation for Automated Nanocrystal Discovery & Analysis (WANDA) to test numerous combinations of dopants in order to identify targets that exhibit upconversion luminescence at novel excitation and emission wavelengths. We use secondary screening to tune dopant concentration and reaction conditions in order to optimize the upconversion efficiency and to select for preferred radiative transitions. Finally, we demonstrate that we can optimize crystal structure and upconversion efficiency by tuning the surfactant concentration during synthesis. This combinatorial approach will be useful for mapping the parameter space for doped upconversion materials and for tuning upconversion excitation and emission wavelengths for specific applications.
5:45 PM - O10.10
Magnetization Dynamics of Co/Pt Core-shell Nanoparticles Studied With Femtosecond Laser Pulses.
Hasan Kesserwan 1 , Jae Young Ahn 2 , Jung-tak Jang 3 , Jinwoo Cheon 3 , Valerie Halte 1 , Tae Hee Kim 2 , Jean-Yves Bigot 1
1 Institut de Physique et Chimie des Matériaux de Strasbourg, CNRS, University of Strasbourg, Strasbourg France, 2 Department of Physics, Ewha Womans University, Seoul Korea (the Republic of), 3 Department of Chemistry, Yonsei University, Seoul Korea (the Republic of)
Show AbstractImproving further the density and speed of magnetic memories beyond a few Terabit/inch2 and a few Gigahertz is challenging. New approaches are therefore necessary for understanding the fundamental mechanisms underlying the change and control of the magnetization. In particular it is essential to investigate the dynamical behavior of close packed nanomagnets near the super-paramagnetic limit using ultrafast laser techniques to understand the mechanisms responsible for the temporal evolution of the magnetization. In the present work, we study assemblies of Co/Pt ferromagnetic nanoparticles performing time resolved magneto-optical Kerr (MOKE) measurements with femtosecond laser pulses. We are able to distinguish between several steps : 1) the initial demagnetization and the spin thermalization, following the absorption of light which occurs within 200 fs; 2) the equilibrium between the spins and the lattice temperatures within ~1.5 ps; 3) the precession and damping of the macro-spin around the effective field. The experiments have been performed with pellets made with spherical particles, 4 nm cobalt core and 2 nm platinum shell, separated by an average distance of 4 nm. The laser configuration is a typical pump-probe set up with 150 fs pulses (pump : 400 nm and probe : 800 nm) obtained from a 5 kHz amplified titanium laser system. The time resolved MOKE allows us investigating the magnetization dynamics of the nanostructures with an accuracy of 100 fs and up to one nanosecond. By comparison with isolated cobalt nanoparticles implanted in a dielectric matrix, our results show that the platinum shell favors the heating of the cobalt core which remains demagnetized for longer times. In addition the dynamics of the precession is much better contrasted than for isolated cobalt nanoparticles. A detailed analysis of the phase of the precession reveals an anisotropy which can be removed by slightly heating the nanoparticles assembly (thermal annealing at 450 K). We attribute this anisotropy effect to the dipolar interaction between particles which changes dynamically after excitation with the femtosecond pulses. The detailed magnetization dynamics will be discussed as a function of the laser intensity as well as the modulus and the angle (with respect to the sample plane) of the external applied static magnetic field.