bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of III-V Nanocrystals by Co-reduction Reactions
Authors: Liu Zhaoping , Fang Jiye 
Published: April 2011

ABSTRACTThis 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.
Effects of Pigment Type and Dispersion on Photodegradation of Epoxy and Acrylic Urethane Films
Authors: Watson Stephanie , Forster Amanda , Tseng I-Hsiang , Sung Li-Piin , Lucas Justin , Forster Aaron 
Published: April 2011

ABSTRACTThe effects of surface treatment, particle size, and concentration of titanium dioxide (TiO2) and its dispersion on the photodegradation of two resin systems, epoxy and acrylic urethane, were examined. A suite of techniques, including laser scanning confocal microscopy (LSCM) and attenuated total reflectance -Fourier transform infrared spectroscopy (ATR-FTIR), was used to follow the degradation process of TiO2/polymer films as a function UV exposure. LSCM was used to show that both pigment dispersion and durability of the polymer matrix influenced the generation of pits/holes in pigmented polymer film. The type of pigment had a greater influence on the more durable polymer matrix, the acrylic urethane system. The epoxy system showed the greatest extent of degradation regardless of the TiO2 choice. The LCSM results were supported by the ATR-FTIR data.
Osteoblast Behaviors on Novel Self-assembled Helical Rosette Nanotubes and Hydrogel Composites for Bone Tissue Engineering
Authors: Zhang Lijie , Ramsaywack Sharwatie , Fenniri Hicham , Webster Thomas J 
Published: April 2011

ABSTRACTTo 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.
Mechanical Properties of Thermoplastic Polyolefin (TPO) /Clay Nanocomposites
Authors: Ruan Yong-Hong , Tjong Sie-Chin 
Published: April 2011

ABSTRACTThermoplastic polyolefin (TPO) contained 30 wt.% PP and 70 wt.% SEBS-g-MA, and its nanocomposites reinforced with 0.3 -1.5 wt.% organoclay (OMMT; Cloisite 30B) by a two-step melt mixing followed by injection molding. The microstructure and mechanical behavior of the TPO/OMMT nanocomposites were investigated. X-ray diffraction measurements revealed the absence of basal diffracting peak of OMMT in TPO/OMMT, suggesting formation of intercalated/exfoliated nanocomposites. Tensile tests showed that the stiffness, yield strength and tensile strength of TPO can be enhanced by adding low loading levels of OMMT. Thus, OMMT can reinforce TPO due to their large aspect ratios. Moreover, there was no reduction in the impact strength of the TPO/OMMT nanocomposites associated with the clay additions.
Temperature Dependent Sensitivity Inversion in SnO1.8:Pd Mixed Nanoparticle Layer Based CO Sensors
Authors: Aruna I. , Kruis F. E. 
Published: April 2011

ABSTRACTThis 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.
Targeted Synthesis of Nanostructured Oxide Materials
Authors: Patzke Greta Ricarda , Zhou Ying 
Published: April 2011

ABSTRACTMorphology 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.
Effect of Pore Morphology on the Electrochemical Properties of Electric Double Layer Carbon Cryogel Supercapacitors
Authors: Garcia Betzaida Batalla , Feaver Aaron M. , Champion Richard , Zhang Qifeng , Fister Tim T. , Nagle Kenneth P. , Seidler Gerald T. , Cao Guozhong 
Published: April 2011

ABSTRACTIn this study a group of resorcinol-formaldehyde carbon cryogels (CC) have been processed chemically, via catalysis and activation, to obtain varied nanostructures and pore size distributions. To understand the relation between structure and electrochemical properties the capacitor can be studied as a dielectric system composed of a porous electrode and the electrolyte (Tetraethylammonium tetrafluoroborate in propylene carbonate). Using Electrochemical impedance spectroscopy (EIS) the complex capacitance and power are used to study the behavior of the system below the relaxation frequency fo (φ = −45°). Therefore, the relaxation of the capacitor system at the low frequency range, f < fo, may be used as a measure of pore/electrolyte interaction. The approach here proposed also allows for a direct experimental characterization of the capacitance and power at low frequencies where small pores are likely to affect the diffusion dynamics of the electrolyte molecules. The results suggest a correlation between the occurrence of small micropores and that of high power losses that are related to the resistive element produced at the low frequency range. Moreover, the impact of the micropore structure upon the supercapacitor's performance is apparent in its capacitance and energy as well. In addition to the complex power and capacitance other measurements including BET Nitrogen sorption, cyclic voltammetry, galvanic cycling and X-Ray Raman Scattering were used to characterize the samples and support these results.
The Role of Polymer-particle Interactions on the Viscoelastic Properties of Polymer Nanocomposites
Authors: Sarvestani Alireza , Jabbari Esmaiel 
Published: April 2011

ABSTRACTA molecular model is proposed for the dynamics of polymer chains in dilute polymer solutions containing well-dispersed spherical particles. In the presence of short range energetic affinity between the monomers and filler surface, the equilibrium structure of the adsorbed polymer layer is determined by a scaling theory. The viscoelastic response of the suspension is studied by a Maxwell model. It is shown that the solid-like properties of polymer nanocomposites in low frequency regimes could be attributed to the slowdown of the relaxation process of polymer chains. This process is controlled by the monomer-particle frictional interactions, density of the adsorbed polymer chains on the particles surface (controlled by monomer-particle adsorption energy), and volume fraction of the interfacial layer which can be enhanced by reduction of filler size or increasing the filler concentration.
Preparation of a Reduced Layered Tungstic Acid HxW2O7 via Acid Treatment of Bi2W2O9 in the Presence of Sn2+ Ions
Authors: Tahara Seiichi , Minato Takakazu , Kumada Nobuhiro , Hayashi Shigenobu , Sugahara Yoshiyuki 
Published: April 2011

ABSTRACTA reduced layered tungstic acid with a double-octahedral structure was prepared by acid treatment of an Aurivillius-type Bi2W2O9 in the presence of Sn2+ ions. While the color of the product formed by acid treatment with no Sn2+ ions present, H2W2O7, was yellow, a blue powder was obtained after the acid treatment in the presence of Sn2+ ions. No notable change in the morphology was observed after acid treatment. The X-ray diffraction pattern of the product acid-treated in the presence of Sn2+ ions was very similar to that of H2W2O7. Essentially all the Bi3+ ions were lost upon acid treatment, indicating the occurrence of selective leaching of bismuth oxide sheets in Bi2W2O9. A UV-visible absorption spectrum and XPS analysis demonstrated that the W6+ ions were partially reduced to W5+ ions, and the number of protons in the product was correspondingly 2.4 per [W2O7]. These results suggest the successful formation of a reduced layered tungstic acid, H2.4W2O7.
Photocatalytic Hydrogen Production from Gas-phase Methanol and Water with Nanocrystalline TiO2 Thin Films in High Vacuum
Authors: Noda Kei , Hattori Masashi , Amari Kouichi , Kobayashi Kei , Horiuchi Toshihisa , Matsushige Kazumi 
Published: April 2011

ABSTRACTPhotocatalytic 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.
Transport and Optical Characteristics of Al-rich AlO Film and its Application to a Non-volatile Memory
Authors: Nakata Shunji , Nagai Shingo , Kumeda Minoru , Kawae Takeshi , Morimoto Akiharu , Katagiri Yoshitada , Shimizu Tatsuo 
Published: April 2011

ABSTRACTWe propose the new process for fabricating Al-rich Al2O3 thin film, which is used as a charge storage layer for non-volatile Al2O3 memory. Nanoscale Al-rich thin film is deposited using RF magnetron co-sputtering by setting an Al metal plate on an Al2O3 target. Al-rich Al2O3 shows a larger conduction current in I-V characteristics and larger optical absorption than stoichiometric Al2O3 due to the increased electron trap sites. The C-V characteristics of the Al-rich Al2O3 thin film show a large hysteresis window due to the charge trapping effect in the Al-rich structure.
Photoluminescence Quantum Yields from Crystalline and Amorphous Silicon Nanoparticles
Authors: Anthony Rebecca , Kortshagen Uwe 
Published: April 2011

ABSTRACTThe optical properties of amorphous and crystalline silicon nanoparticles are studied. By tuning the power of the non-thermal plasma reactor, the structure of the particles is adjusted from amorphous to crystalline nanoparticles. The microstructure is studied using transmission electron microscopy, X-ray diffraction, and Raman vibrational spectroscopy. The photoluminescence quantum yields of crystalline nanoparticle samples are consistently higher than those of amorphous nanoparticles.
Tailoring of Structural Morphology of Silver Nanowires in Electrochemical Growth
Authors: Singh Amrita , Ghosh Arindam , Singh Amrita , Singh Amrita 
Published: April 2011

ABSTRACTNoble metal such as Ag normally exists in an fcc crystal structure. However as the size of the material is decreased to nanometer lengthscales, a structural transformation from that of its bulk state can be expected with new atomic arrangements due to competition between internal packing and minimization of surface energy. In many previous studies, it has been shown that silver nanowires (AGNWs) grown inside anodic alumina (AAO) templates by ac or dc electrochemical deposition from silver salts or complexes, adopt fcc structure and below some critical diameter ∼ 20 nm they may acquire hcp structure at low temperature. This is, however, critically dependant on the nature of confinement, as AgNWs grown inside nanotube confinement with subnanometer diameter have been reported to have fcc structure. Hence the question of the crystal structure of metal nanowires under combined influence of confinement, temperature and deposition condition remains open. In this abstract we show that the alternative crystal structures of AGNWs at room temperature can be achieved with electrochemical growth processes under specific conditions determined by the deposition parameters and nature of confinement. We fabricated AgNWs of 4H hexagonal structure with diameters 30 – 80 nm inside polycarbonate (PC) templates with a modified dc electrodeposition technique, where the nanowires were grown at deposition potentials as low as 10 mV in 2 M silver nitrate solution[1]. We call this low-potential electrodeposition (LPED) since the electrodeposition process occurs at potential much less than the standard Nernst potential (770 mV) of silver. Two types of electrodes were used – stainless steel and sputtered thin Pt film, neither of which had any influence on the crystal structure of the nanowires. EDS elemental analysis showed the nanowires to consist only of silver. Although the precise atomic dynamics during the LPED process is unclear at present, we investigated this with HRTEM (high-resolution transmission electron microscopy) characterization of nanowires grown over various deposition times, as well as electrical conductivity measurements. These experiments indicate that nanowire growth does not occur through a three-dimensional diffusion controlled process, as proposed for conventional over-potential deposition, but follow a novel instantaneous linear growth mechanism. Further experiments showed that, (a) conventional electrochemical growth at a small over-potential in a 2 mM AgNO3 solution yields nanowires with expected fcc structure inside the same PC templates, and (2) no nanowire was observed under the LPED conditions inside hard AAO templates, indicating that LPED-growth process, and hcp structure of the corresponding nanowires depend on deposition parameters, as well as nature of confinement.
Novel Synthesis of Metal Nanowhiskers: High-Temperature Glancing Angle Deposition
Authors: Suzuki Motofumi , Hamachi Kenji , Nagai Koji , Kita Ryo , Nakajima Kaoru , Kimura Kenji 
Published: April 2011

ABSTRACTWe demonstrate high temperature glancing deposition (HT-GLAD) of metals on the heated substrate. It has been found that Al, Ag, Au, Fe nano-whiskers grow on the substrate of Si, SiO2, and glass substrates. The robustness in the selection of materials suggests that the HT-GLAD is a universal method to grow nano-whiskers of various metals. We also demonstrate the selective growth of the nano-whiskers on the substrate with micro-trench patterns. The metal nano-whiskers are useful for the nano electromechanical devices and vacuum microelectronics.
Pulsed PECVD Growth of Silicon Nanowires on Various Substrates
Authors: Parlevliet David , Cornish John C. L. 
Published: April 2011

ABSTRACTSilicon nanowires with high aspect ratio were grown using PPECVD and a gold catalyst on a variety of different substrates. The morphology of the nanowires was investigated for a range of crystalline silicon, glass, metal, ITO coated and amorphous silicon coated glass substrates. Deposition of the nanowires was carried out in a parallel plate PECVD chamber modified for PPECVD using a 1kHz square wave to modulate the 13.56MHz RF signal. Samples were analyzed using either a Phillips XL20 SEM of a ZEISS 1555 VP FESEM. The average diameter of the nanowires was found to be independent of the substrate used. The silicon nanowires would grow on all of the substrates tested, however the density varied greatly. It was found that nanowires grew with higher density on the ITO coated glass substrates rather than the uncoated glass substrates. Aligned nanowire growth was observed on polished copper substrates. Of all the substrates trialed, ITO coated aluminosilicate glass proved to be the most effective substrate for the growth of silicon nanowires.
Growth of SnO2-In2O3 Hetero Nanostructures
Authors: Kwon S. Joon , Hwang In-Sung , Kim Dong-Wan , Choi Young-Jin , Park Jae-Gwan 
Published: April 2011

ABSTRACTWe present the formation of SnO2-In2O3 hetero nanostructures. Kinetically, SnO2 nanowires form prior to the heterostructure. In2O3shell was regularly distributed on the SnO2 nanowire surface, and form sheath subsequently. We theoretically explained the morphological evolution of an anisotropic heterostructure such as core-sheath structure.
Self-branching in GaN Nanowires Induced by a Novel Vapor-Liquid-Solid Mechanism
Authors: Nam Chang-Yong , Tham Douglas , Fischer John E. 
Published: April 2011

ABSTRACTNanowires have great potential as building blocks for nanoscale electrical and optoelectronic devices. The difficulty in achieving functional and hierarchical nanowire structures poses an obstacle to realization of practical applications. While post-growth techniques such as fluidic alignment might be one solution, self-assembled structures during growth such as branches are promising for functional nanowire junction formation. In this study, we report vapor-liquid-solid (VLS) self-branching of GaN nanowires during AuPd-catalyzed chemical vapor deposition (CVD). This is distinct from branches grown by sequential catalyst seeding or vapor-solid (VS) mode. We present evidence for a VLS growth mechanism of GaN nanowires different from the well-established VLS growth of elemental wires. Here, Ga solubility in AuPd catalyst is limitless as suggested by a hypothetical pseudo-binary phase diagram, and the direct reaction between NH3 vapor and Ga in the liquid catalyst induce the nucleation and growth. The self-branching can be explained in the context of the proposed VLS scheme and migration of Ga-enriched AuPd liquid on Ga-stabilized polar surface of mother nanowires. This work is supported by DOE Grant No. DE-FG02-98ER45701.
Macroscopic 2D Design of Micro/Nano Grain Architectures by Laser Interference Metallurgy
Authors: Muecklich Frank , Gachot Carsten , Catrin Rodolphe , Schmid Ulrich , Lasagni Andrés 
Published: April 2011

ABSTRACTTailoring of micro/nano structures and surface functionalization are key goals in surface processing of materials. A new technology for a unique geometric precise 2D micro/nano design of grain architectures is presented. By means of super lateral grain growth crystalline lattice patterns such as line-, dot- and cross-like patterns were generated. The grain dimensions may be selected between a few nanometers and about 10 micrometers. The phase and grain formation was characterized by Electron Backscatter Diffraction with regard to orientation distribution and texture formation. Furthermore, dynamic aspects of this laser induced recrystallization process are studied, such as the heat transport in the films, comparing the vertical with the lateral solidification velocities by two-dimensional finite element method (FEM) simulations. Finally, the mechanical properties of the tailored thin films have been determined using nanoindentation experiments.
Effect of the Surface Nanomorphology on the Growth of Al Whiskers Formed by Glancing Angle Deposition on a High Temperature Substrate
Authors: Hamachi Kenji , Suzuki Motofumi , Nakajima Kaoru , Kimura Kenji 
Published: April 2011

ABSTRACTWe have investigated the effect of the substrate-surface morphology on the growth of Al whiskers grown by high temperature glancing angle deposition (HT-GLAD). Before the HT-GLAD of Al at 390 °C, the morphology of the substrate was systematically modified by depositing nanocolumnar SiO2 layer of thickness between 0 and 100 nm on the flat SiO2 layer. Aluminum whiskers with the width of ≈100 nm and the length ≤ μm are found on all the samples. The number of short whiskers, which can be grown from very small nuclei, depends strongly on the thickness of the SiO2 nanocolumnar layer and shows the maximum at SiO2 thickness of 20 nm. On the other hand, the number of long whiskers, which requires extraordinary amount of Al than that deposited on the side surface of the whikers, is almost independent of SiO2 thickness. These facts suggest that the surface roughness of the substrate plays an important role in the nucleation of the whiskers and that there are some transport processes of Al, which are insensitive to the surface morphology.
Nanopattern Formation by Periodic Array of Interfacial Misfit Dislocations in Bi(111)/Si(001) Heteroepitaxy
Authors: Jnawali Giriraj , Hattab H. , Bobisch C. , Bernhart A. , Zubkov E. , zu Heringdorf F.-J. Meyer , Möller R. , Krenzer B. , Horn-von Hoegen M. 
Published: April 2011

ABSTRACTDespite their large lattice mismatch of 18 %, the lattices of Bi(111) and Si(001) fit surprisingly well. A remaining compressive strain in the Bi film of 2.3 % along the direction is accommodated by the formation of a periodic array of edge-type misfit dislocations confined to the interface. The strain fields surrounding each dislocation interact with each other, producing a quasi-periodic nanopattern of grating-like periodic height undulations on the surface. The separation and the amplitude of the height undulations have been derived by spot profile analyzing LEED and STM surface height profiles. The observed undulations agree well with elasticity theory.