Three-dimensional (3D) microstructures of single walled carbon nanotube (C-SWNT)/polymer nanocomposite are fabricated by the infiltration of 3D microfluidic networks. The microfluidic network was first fabricated by direct-write assembly which consists of the robotised deposition of fugitive ink filaments on an epoxy substrate to form a 3D microstructured network. After encapsulation of the deposited structure with an epoxy resin, the fugitive ink was removed by heating, resulting in a 3D network of microchannels. This microfluidic network is then infiltrated by a ultraviolet (UV) -curable polymer loaded with C-SWNTs. The C-SWNTs were produced by the UV-laser ablation method, physico-chemically purified and dispersed in a polymer matrix using ultrasonic treatment in dichloromethane. The C-SWNTs were characterized by means of high-resolution scanning electron microscopy and microRaman spectroscopy. The infiltrated nanocomposite (i.e., the C-SWNT reinforced polymer) is then cured under UV exposure and post-cured. The manufactured 3D microstructures were rectangular sandwich beams having an epoxy core and unidirectional nanocomposite fibers placed parallel to the beam axis, on both sides of the core. Flexural mechanical tests were performed on empty, pure resin and nanocomposite microfluidic beams using a dynamic mechanical analyzer. The achieved nanocomposite beams were found to show an increase of 5% in the storage modulus and more than 50% increase in the loss modulus, under 30°C compared to the pure resin beams. The nanocomposite infiltration of microfluidic networks is shown to be a promising approach to achieve 3D microstructures of reinforced nanocomposites.

This study reports a novel observation of the temperature dependent inversion in the CO sensitivity of the nanoparticle layers consisting of homogeneously mixed monodispersed Pd and SnO1.8 nanoparticles synthesized via aerosol route. Ability of sensing CO of as low as 10 ppb in dry synthetic air has been observed with decrease in nanoparticle size (to 5 nm) in the samples mixed with Pd nanoparticles, as compared to samples without Pd nanoparticles which show no sensitivity to CO in ppb levels. In contrast to the conductivity increase in SnO1.8 in response to CO exposure in the absence of Pd, the mixed nanoparticle layers exhibit decrease in conductivity. With increase in the operating temperature (523 to 673 K) reversal in the sensitivity has been observed at higher CO concentrations. The observed behavior can be understood in terms of the physiochemical and electronic processes.

Face centered cubic (FCC) single crystal silver nanoparticles(NPs) of nearly monodispersed particle size of 12nm were prepared by simple ripening multi-twined particles (MTP). The product yield was nearly 100% and growth mechanism was considered to be similar to Ostwald ripening but utilize chemical potential difference between MTP and FCC NPs. Controlling the ratio between defectless and defective particles before ripening by controlling kinetics of particle generation stage, it was possible to control the final defectless particle size from 7-18 nm maintaining almost 100% product yield.

Metallic materials widely used in orthopedic applications have much stronger mechanical properties (such as elastic modulus) than natural bone, which can weaken the newly formed bone interface due to stress-shielding. Because natural bone is under continuous physiological stresses (such as compression, tension, torsion, and/or bending), the mechanical properties of orthopedic implant materials should closely match those of living bone. This is necessary to minimize stress and strain imbalances during physiological loading conditions which will lead to implant failure. The objective of the present study was to characterize the mechanical properties of PLGA with well-dispersed nanophase titania. The dispersion of titania in PLGA was controlled by sonication and was characterized by field emission scanning electron microscopy and image analysis. For this purpose, two major stresses (compression and tension) that natural bone experiences under physiological loading conditions were characterized using an Instron Material Testing System. The results showed that nano-dispersed titania particles in PLGA increased the compressive and tensile modulus of such scaffolds compared to pure PLGA scaffolds and the more agglomerated ceramics in PLGA scaffolds. The mechanisms behind these results were also speculated. Since the predominant feature of nano-particles lies in their ultra-fine dimension, a large fraction of filler atoms can reside at the PLGA-ceramic interface which can lead to a stronger interfacial interaction, but only if the nano-particles are well dispersed at the nanometer level in the surrounding polymer matrix. As the interfacial PLGA-ceramic structure plays a critical role in determining the mechanical properties of composites, nano-composites with a great number of smaller interfaces could be expected to provide unusual properties, and the shortcomings induced by the heterogeneity of conventional (or micron) particle filled composites would also be avoided. Therefore, coupled with prior studies demonstrating greater osteoblast functions, the combination of PLGA with a strong and biocompatible well-dispersed nano-ceramic phase may provide better candidate materials for orthopedic applications.

This paper describes a co-reduction colloidal method for the synthesis of In-containing III-V nanocrystals (NCs) by using pnictogen halides (such as PCl3, AsCl3, and SbCl3) as the pnictogen-sources and superhydride (LiBH(C2H5)3) as the reducing agent. The syntheses were generally carried out in octadecene in the presence of fatty acids at ∼250 °C. The as-synthesized InP NCs were monodisperse in particle size and size distribution, whereas the InAs and InSb NCs showed relatively lower quality. The growth process of NCs was studied using InP as a model system.

The double-decker-shaped silsesquioxane (DDSQ) is a new family of silsesquioxanes consisting of a Si-O-Si case structure and functional organic side chains. The optical properties of a novel organic-inorganic hybrid polymer based on the DDSQ were studied. The double-decker-shaped poly(silsesquioxane) (DDPSQ) showed excellent transparency and thermal stability. The thermo-optic coefficient of the DDPSQ is 3 or 4 times larger than conventional polymers.

Using the Aerosol-through-Plasma (A-T-P) technique high surface area (from 100 to 203 m2/gm) bi-cationic (Ti-Al) oxide particles of a range of stoichiometries were produced that showed remarkable resistance to sintering. Specifically, we found that homogeneous nanoparticles with surface areas greater than 150 m2/gm were produced at all stoichiometries. In particular, for particles with a Ti:Al ratio of 1:3 a surface area of just over 200 m2/gm was measured using the BET method. The most significant characteristic of these particles was that their sinter resistance was far superior to that of TiAl particles produced using any other method. For example, A-T-P generated particles retained >70% of their surface area even after sintering at 1000 C for five hours. In contrast, particles made using all other methods lost virtually all of their surface area after an 800 C treatment.

Morphology control is a key challenge in the straightforward hydrothermal production of technologically relevant anisotropic oxide materials. The use of readily available ionic additives as growth modifiers is discussed and compared for molybdenum- and tungsten oxide-based systems, and it is extended upon the formation of ternary W/Mo-oxides. Generally, the one-step hydrothermal synthesis of ternary and higher oxides is an important goal, because their properties often outperform those of the binary oxides. This holds especially for the Bi2O3-MoO3-VOx (BIMOVOx) system as a rich source of new materials. We present a new solution-based approach to α-Bi2O3 nanobelts starting from commercial Bi2O3 and K2SO4 as a key step on the way to anisotropic BIMOVOx-oxides. This hydrothermal process is an illustrative example of highly selective and efficient morphology control through an inorganic additive. As mechanistic and kinetic studies are crucial for the design of complex oxide nanomaterials, the Bi2O3-K2SO4 system is compared to our previous studies on Mo-, W- and V-oxides with respect to its hydrothermal parameter window and robustness.

We report the development of oxygen sensors using polymer photonic bandgap structure and CMOS chips. These integrated sensors provide a new platform for the development of low cost, low (battery) powered, light weight, robust, fast and small sensors. We demonstrate an approach to encapsulation of chemical and biological recognition elements within the porous structures. This sensing platform is built on our recently demonstrated nanofabrication technique using holographic interferometry of a photo-activated mixture that includes a volatile solvent as well as monomers, photoinitiators, and co-initiators. Resulting structure is nanoporous polymer 1D photonic bandgap structures that has reflection grating property and can be directly integrated into optical sensor systems that we have previously developed. For optical sensor system, CMOS (Complementary Metal Oxide Semiconductor) detectors that include phototransistors, trans impedance amplifier, and other signal processing units are used. Combining CMOS chip and nano-porous polymer reflection grating, we demonstrate an oxygen sensor as a prototype by encapsulating the fluorophore (tris(4,7-diphenyl-1,10-phenathroline)ruthenium(II) using fluorescence intensity.

Nanoparticle aggregates have been found to possess unique mechanical properties. Aggregates of metal nanoparticles can be strained up to 100% before failure, and even typically brittle materials are observed to have a ductile failure mode. In this effort two materials; namely silver and silicon, were chosen to represent ductile and brittle materials, respectively. Aggregates with 2 to 6 particles were simulated using the molecular dynamics (MD) algorithm to determine the stress-strain behavior of the aggregate. Many interesting observations are made including the negligible affect of strain rate on ultimate tensile strength, and the direct relationship between Young's modulus and nanoparticle size.

By inducing phase separation parallel to the sol-gel transition of alkoxy-derived silica systems, silica monoliths with well-defined co-continuous macropores were obtained from the systems containing anionic surfactants. We adopted three kinds of anionic surfactants which differ from each other in the length of alkyl chain (CH3(CH2)17SO3Na, CH3(CH2)15SO3Na, CH3(CH2)13SO3Na). Mesopores were also found in the silica skeletons presumably by the supramolecular templating. Characterization of the dried or heat-treated samples was carried out by a scanning electron microscope (SEM) and nitrogen adsorption measurements. Experimental results showed that due to the moderate interaction between silica oligomers and surfactants, most of the surfactants are distributed to the solvent phase which determines the macropore volume. The median size and volume of the macropores could be controlled independently by the starting composition. In the absence of any additive to enhance templating by the surfactant, the samples exhibited only amorphous mesopores.

Photocatalytic hydrogen production with gas-phase reactions in high vacuum was examined for nanocrystalline anatase-type titanium dioxide (TiO2) thin films. The hydrogen generation process on platinized TiO2 specimens was investigated using a quadrupole mass spectrometer at a real-time scale under various partial pressures of gaseous methanol and water. As a result, hydrogen generation was successfully detected under ultraviolet ray (UV) illumination even in high vacuum (∼ 10−7 Torr). And the amount of produced H2 largely depends on the temperature of TiO2 samples, probably due to different surface states of TiO2. This study suggests the possibility of new high-speed H2 production system with gas-phase photocatalytic reactions.

La0.8Sr0.2Fe0.6Ni0.4O2.9 (LSFN) and LSFN-La9.83Si4.5Fe1.5O26 (LSiF) nanocomposite were synthesized and investigated as cathode materials for intermediate temperature (IT) solid oxide fuel cells (SOFC). Phase and structure evolution with sample sintering temperature as well as their transport properties and catalytic activity in oxygen reduction were studied.

We have synthesized the dendrimer-Au hybrid nanoclusters by solution routes, and have carried out the various spectroscopic studies in order to investigate their electronic structures. From the line-shape analyses for Au 4f core-level photoemission spectra measured with hard X-ray synchrotron-radiation of Au nanoclusters with mean diameter of 2-3 nm stabilized outside the dendrimer, it is found that Au 4f core-level photoemission spectrum consists of two components. We attribute these components to interior Au atoms and surface Au atoms bonded to dendrimers. In the valence-band photoemission spectrum of these Au nanoclusters, we have observed the bandwidth narrowing of Au 5d-derived band compared to that of bulk Au crystallite. Moreover, we have observed the characteristic spectral feature in the vicinity of Fermi level due to the dynamic final-state effect in photoemission. We have also carried out the optical spectroscopic measurements of these Au nanoclusters. From these results, we discuss the electronic structures and interfacial properties of the dendrimer-Au hybrid nanoclusters.

Solutions or mixtures of aluminum halides AlX3 (X = Cl, Br, I) or aluminum halide alkoxide (ROAlX2; R= i-Pr, X = Cl, Br) are prepared in toluene, or pentamethyldiethylenetriamine (PMDETA) and treated with a slight excess of 50:50 (wt.) sodium potassium alloy (Na/K). Upon agitation, the reaction takes place slowly. The reaction appears to be limited by the deposition of insoluble products on the surface of the Na/K since sonication in an ordinary ultrasonic cleaner is necessary to bring the reaction to completion in several hours. Aluminum nanoparticles (NPs) and Na and K halides are formed, and soluble Al compounds, are also formed in some cases. Lithium powder is used instead of Na/K to reduce Al(N(SiMe3)2)3 to Al NPs. In an effort to passivate the surface of the Al particles to oxidation or hydrolysis, various agents are added either during the reaction or afterward. The products are characterized by SEM, XRD, NMR, and TEM, and the stability to water and air is evaluated.

A method from molecular dynamics simulation is developed for determining local elastic constants of an epoxy/nanotube composite. The local values of C11, C33, K12, and K13 elastic constants are calculated for an epoxy/nanotube composite as a function of radial distance from the nanotube. While the results possess a significant amount of statistical uncertainty resulting from both the numerical analysis and the molecular fluctuations during the simulation, the following observations can be made. If the size of the region around the nanotube is increased from shells of 1Å to 6Å in thickness, then the scatter in the data reduces enough to observe trends. All the elastic constants determined are at a minimum 20Å from the center of the nanotube. The C11, C33, and K12 follow similar trends as a function of radial distance from the nanotube. The K13 decreases greater distances from the nanotube and becomes negative which may be a symptom of the statistical averaging.

To date, although traditional autografts and allografts have been standard methods to treat bone fractures and defects, the formation of biocompatible and injectable scaffolds to induce new bone growth is still a promising method to repair bone defects considering their minimally invasive and osteoinductive features. In this study, a novel bone tissue engineering scaffold based on the self-assembled properties of helical rosette nanotubes (HRNs) and biocompatible hydrogels (specifically, poly(2-hydroxyethyl methacrylate)-pHEMA) was designed to fill bone fractures and repair bone defects. HRNs are a new class of organic nanotubes with a hollow core 11 Å in diameter, which originate from the self-assembly of DNA base pair building blocks (guanine-cytosine) in aqueous solutions. Since HRNs can significantly change their aggregation state and become more viscous based on heating or when added to serum free medium at body temperature, HRNs may provide an exciting therapy to heal bone fractures as injectable bone substitutes. In addition, biocompatible hydrogels were used in conjunction with HRNs in this study to strengthen the bone substitutes and also to serve as a potential drug releasing carrier to stimulate new bone growth at such fracture sites. Two types of HRNs, one with a lysine side chain and the other conjugated to 1% and 10% RGD (arginine-glycine-aspartic acid) peptides on HRNs, were prepared and dispersed into hydrogels. Due to their nanometric features and the helical architecture of HRNs which biomimic collagen, results showed that these HRN hydrogel composites can significantly improve osteoblast adhesion compared to hydrogel controls. Furthermore, 0.01 mg/ml HRNs with RGD embedded in and coated on hydrogels can also enhance osteoblast attachment compared to 0.01 mg/ml HRNs with lysine side chains embedded in and coated on hydrogels. Results showed an increasing trend of osteoblast adhesion on these scaffolds with more RGD groups (10%) on HRNs. In this manner, nanostructured HRN hydrogel composites provide a promising alternative to repair bone defects considering the flexibility in the design of HRNs and their exceptional cytocompatibilty properties.

An approach has been presented in the current work to fabricate and characterize nanocomposite systems for optimizing electrical and thermal properties without sacrificing mechanical properties. An epoxy matrix based nanocomposite system has been processed with different volume fractions of carbon nanotubes. The purpose was to tailor macroscale properties to meet competing performance requirements in microelectronics industy. The nanofiller consisted of comparatively low cost XD grade carbon nanotubes (XD-CNTs) that are optimized for electrical properties. This system was compared with another system consisting of single wall carbon nanotubes (SW-CNTs) as nano-reinforcements in epoxy matrix. The electrical percolation threshold (about seven orders of magnitude increase in electrical conductivity) measured by dielectric spectroscopy was found to be at lower loading weight fraction of SWCNTs (0.015 weight %) as compared to XD-CNTs (0.0225 weight %). However, the electrical conductivity after percolation was higher for XD-CNTs reinforced epoxy with respect to SW-CNTs filled nanocomposites. The governing mechanisms for this phenomenon were investigated using transmission optical microscope. The enhancement in thermal conductivity, measured using differential scanning calorimetry, was found to be moderate at lower weight loadings corresponding to electrical percolation. However, a 90% improvement in thermal conductivity was observed for 0.3 weight percent of XD-CNTs. Dynamic mechanical analysis was performed to measure the storage and loss modulus along with the glass transition temperature. No significant change in modulus values and glass transition temperature was measured for nanocomposites varied filler contents with respect to neat matrix.

Multiphase epoxy-nanocomposites based on multi-wall carbon nanotubes (MWCNT) and inorganic nanoparticles (TiO2) were produced. The rheological, electrical and thermo-mechanical properties were investigated in order to reveal informations about the interparticle interactions between the different types of nanoparticles. TEM-investigations reveal altered microstructures for the multiphase nanocomposites (MWCNT plus TiO2). TiO2 causes changes in the state of dispersion of MWCNT which can lead to an increase of the rheological parameters (e.g. G'). Due to changes in the formation of the percolated MWCNT network during curing, the electrical conductivity is decreased if the concentration of the non-conductive fillers exceeds a critical value. Additional synergistic effects could be found for the glass transition temperature. The presence of nanoparticles leads to a chemical inactivation of reactive groups of the matrix. Thus, the generated interphase between matrix and nanoparticles exhibits a lower curing degree which results in lower thermo-mechanical properties. For the multiphase systems the glass transition temperature is decreased less, due to an inactivation of the surface of the different types of nanoparticles by a self assembly which leads to a higher curing degree of the interphase.

PtRu bimetallic nanoparticles supported on carbon nanoparticle (PtRu/C) catalysts were synthesized with radiation irradiation. The samples were structural analyzed by techniques of X-ray absorption fine structure (XAFS), transmission electron microscope (TEM) and X-ray diffraction (XRD). The results indicated that PtRu/C catalysts which prepared by an electron beam irradiation had more homogeneous atomic arrangement than that prepared by a gamma-ray irradiation. We found a clear correlation between the atomic structure and the catalytic activity of PtRu/C catalysts. These results supported the bi-functional mechanism.