bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preferential Growth of Carbon Nanotubes/Nanofibers Using Lithographically Patterned Catalysts
Authors: Teo K. B. K. , Chhowalla M. , Amaratunga G. A. J. , Milne W. I. , Pirio G. , Legagneux P. , Wycisk F. , Pribat D. 
Published: April 2011

ABSTRACTIn order to utilise the full potential of carbon nanotubes/nanofibers, it is necessary to be able to synthesize well aligned nanotubes/nanofibres at desired locations on a substrate. This paper examines the preferential growth of aligned carbon nanofibres by PECVD using lithographically patterned catalysts. In the PECVD deposition process, amorphous carbon is deposited together with the nanotubes due to the plasma decomposition of the carbon feed gas, in this case, acetylene. The challenge is to uniformly nucleate nanotubes and reduce the unwanted amorphous carbon on both the patterned and unpatterned areas. An etching gas (ammonia) is thus also incorporated into the PECVD process and by appropriately balancing the acetylene to ammonia ratio, conditions are obtained where no unwanted amorphous carbon is deposited. In this paper, we demonstrate high yield, uniform, ‘clean’ and preferential growth of vertically aligned nanotubes using PECVD.
Inorganic Nanocrystals with Dendrimer Templates: Mesoscopic Model System and Route to New Nanocomposites
Authors: Gröhn Franziska , Bauer Barry J. , Amis Eric J. 
Published: April 2011

ABSTRACTWe investigate nanostructures that are formed when dendrimers act as hosts. Poly(amidoamine) (PAMAM) dendrimers can be used as templates for inorganic nanocrystals, both in aqueous solution1-3 and in a polymeric matrix4. SANS, SAXS and TEM are used to characterize the resulting hybrid structures. Different inorganic colloids like noble metal and cadmium sulfide colloids are studied1,2. With increasing dendrimer generation, we observe a transition from low molecular colloid stabilizing to an effective polymer templating in terms of a “host-guest nanoscale synthesis”. For these higher generation dendrimers, inorganic colloids are formed inside single dendrimer molecules and the size of the nanocrystal can precisely be controlled by the dendrimer generation (“fixed loading law”). Hydrophobically modified dendrimers in organic solvent represent a further, different kind of host system that we have investigated using scattering methods5.
Designing Molecular Assemblies in the Solid-State: Induced-Stacking by a Rebek Cleft
Authors: MacGillivray Leonard R. , Siebke Michelle M. 
Published: April 2011

ABSTRACTCo-crystallization of 2,7-di-tert-butyl-9,9-dimethyl-4,5-xanthenedicarboxylic acid (1), a Rebek cleft, with 1,2-trans-bis(4-pyridyl)ethylene 2 yields a four-component molecular assembly, 2(1)·2(2), that is held together by four O-H…N hydrogen bonds. The cleft organizes the bipyridine such that two molecules of 2 lie in a stacked arrangement.
Characterization of Wet-Chemically Nanostructured Stainless Steel Surfaces
Authors: Buescher R. , Jennissen H. P. , Chatzinikolaidou M. , Fischer A. 
Published: April 2011

ABSTRACTA novel surface modification process is presented, which creates a macroscopically smooth and a nanoscopically rough surface on an austenitic stainless steel. The chemical structure of the oxide layer is changed due to the acid treatment, whereas the thickness is not increased. An altered chromiumoxide content in the passive layer connected with a high bonding strength to the substrate material suggests the use of these wet chemically modified steels in biomedical applications.
Tunable Magnetic Properties in Metal Ceramic Composite Thin Films
Authors: Kumar D. , Narayan J. , Sharma A. K. , Kvit A. , Jin C. , Sankar J. 
Published: April 2011

ABSTRACTWe have developed a novel thin film processing method based upon pulsed laser deposition to process nanocrystalline magnetic materials with accurate size and interface control. Using this method, single domain nanocrystalline Fe and Ni particles in 5-10 nm size range embedded in amorphous as well as crystalline alumina have been produced. Magnetization measurements of these layered thin films as function of field and temperature were carried out using a superconducting quantum interference device magnetometer. Hysteresis below blocking temperature have been found to be consistent with the Stoner-Wohlfarth type behavior. The size of Fe and Ni nanodots measured using transmission electron microscopy and calculated using magnetic data are in excellent agreement with each other.
Silver Nanowires Eelectrodeposited from Reverse Hexagonal Liquid Crystals
Authors: Huang Limin , Wang Huanting , Wang Zhengbao , Mitra Anupam , Yan Yushan 
Published: April 2011

ABSTRACTA novel, simple and efficient procedure was developed to electrodeposit one-dimensional Ag nanowires from reverse hexagonal liquid crystalline phases by using their one-dimensional cylindrical aqueous microdomains as space-confined reactors. Using this soft-template approach, flexible Ag nanowire arrays with wire diameter of 15-30 nm, high aspect ratio over 1000, and high wire densities over 1011 wires&sol;cm2 were obtained. The Ag nanowire arrays can be easily collected by simply washing. The nanowires obtained can be used either in high-density bundle form or as single wires after dispersion by untrasonication.
Development of Quantum dot Reporters for Immunoassay Applications
Authors: Speckman D. M. , Jennings T. L. , LaLumondiere S. D. , Moss S. C. 
Published: April 2011

ABSTRACTMulti-pathogen biosensors that take advantage of sandwich immunoassay detection schemes usually rely on spatial resolution patterns of capture antibodies on a detector plate for pathogen recognition, and typically utilize fluorescent, organic dyes as optical labels to identify captured pathogens. An immunoassay-based, fiber optic detector that utilizes varying sized fluorescent semiconductor quantum dots (QDs) as the reporter labels for different antibodies would have the ability to detect multiple pathogens within a single fiber, using a single excitation source. Such a detector requires that QDs be attached to antibody proteins, such that the specificity of the antibody is maintained. We have been involved in efforts to develop a reproducible method for attaching QDs to antibodies for use in such a biosensor.We synthesized CdSe/ZnS core-shell QDs of differing size, functionalized their surfaces with several types of organic groups for water solubility, and covalently attached these functionalized QDs to rabbit anti-ovalbumin antibody protein. We also demonstrated that these labeled antibodies exhibit selective binding to ovalbumin antigen. We characterized the QDs at each step in the overall synthesis by UV-VIS absorption spectroscopy and by picosecond (psec) transient photoluminescence (TPL) spectroscopy. TPL spectroscopy measurements indicate that QD lifetime depends on the size of the QD, the intensity of their optical excitation, and whether or not they are functionalized and conjugated to antibody. We describe details of these experiments and discuss the impact of our results on our biosensor program.
Tuning the Optical Properties of Large Gold Nanoparticle Arrays
Authors: Kim Beomseok , Tripp Steven L. , Wei Alexander 
Published: April 2011

ABSTRACTGold nanoparticles in the mid-nanometer size regime can undergo self-organization into densely packed monoparticulate films at the air-water interface under appropriate passivation conditions. Films could be transferred onto hydrophilic Formvar-coated Cu grids by horizontal (Langmuir-Schaefer) deposition or by vertical retraction of immersed substrates. The latter method produced monoparticulate films with variable extinction and reflectance properties. Transmission electron microscopy revealed hexagonally close-packed arrays on the micron length scale. The extinction bands of these arrays shifted by hundreds of nanometers to near-infrared wavelengths and broadened enormously with increasing periodicity. Large particle arrays also demonstrated extremely high surface-enhanced Raman scattering (SERS), with enhancement factors greater than 107. Signal enhancements could be correlated with increasing periodicity and are in accord with earlier theoretical and experimental investigations involving nanoparticle aggregate structures.
The characterisation and reactivity of nanostructured cerium-copper-oxide composites for environmental catalysis
Authors: Adamopoulos Othon , Zhang Yu , Croft Mark , Zakharchenko Igor , Tsakalakos Thomas , Muhammed Mamoun 
Published: April 2011

ABSTRACTNanophase Ce-Cu-O powder has been synthesised via co-precipitation approach, whereas computer-assisted thermodynamic modelling was used to predict the optimum experimental criteria. The properties of Ce-Cu-O composite (10 mol% CuO) have been extensively investigated by a variety of techniques. The obtained materials show different morphology compared to other doped ceria salts, with uniform distribution of Ce and Cu throughout the powder. Detailed XRD study does not show the formation of solid solution and the composites consist of two separate metal oxides. X-ray absorption spectroscopy study shows a variation of the existence of Cu and Ce in several oxidation states. Copper oxide seems to exist evenly distributed along the surfaces and boundaries of the crystal grains of CeO2 on the nanoscale. The temperature-programmed reduction indicated that Ce-Cu-O composite has an enhanced oxygen storage capacity compared to CeO2 or pure copper oxide.
Low-Temperature Solvothermal Route to GaN Nanoparticles
Authors: Wang Jianjun , Grocholl Luke , Gillan Edward G. 
Published: April 2011

ABSTRACTWe report a straightforward, non-aqueous solvothermal method for the production of nanoscale gallium nitride structures. Nanoparticles with spherical and rod-like morphologies are produced via in situ gallium azide precursor synthesis and decomposition in superheated toluene or THF. The solution reaction between gallium chloride and sodium azide produces an insoluble azide precursor that is then solvothermally decomposed to GaN at temperatures below 260 °C. The resulting products are poorly crystalline but thermally stable and crystallize to hexagonal GaN upon annealing at 750 °C. Product morphologies include spherical particles (ca. 50 nm) and nanorods. Upon annealing, the nanoparticles coalesce into larger organized crystalline structures with hexagonal facets.
Investigation of Epitaxial Overgrowth on Germanium Quantum Dots
Authors: Greve David W. , Zhao Qian 
Published: April 2011

ABSTRACTWe report on the characterization of germanium quantum dots grown on silicon (001) substrates by ultra-high vacuum chemical vapor deposition (UHV/CVD). In many applications small and uniform quantum dots are required which must be overgrown by a silicon epitaxial layer. We report here on the effect of carbon predeposition from methylsilane on the dot size and uniformity. In addition, we use reciprocal space mapping to evaluate the qualityof epitaxial layers which overgrow the quantum dots. The results show some differences from previous reports on MBE-grown dots.
Processing and Magnetic Properties of Ni-Fe Alloy Dispersed Alumina Nanocomposites
Authors: Lee Jai-Sung , Oh Sung-Tag , Namkung Seok 
Published: April 2011

ABSTRACTAn optimum route to fabricate the Al2O3/Ni-Fe alloy nanocomposites with sound microstructure and magnetic propertieswas investigated. The composites were fabricated by the hot pressing of powder mixtures of Al2O3 and nano-sized Ni-Fe alloy, in which the alloy was prepared by solution-chemistry routes using Ni- and Fe-nitrate powders and a subsequent hydrogen reduction process. Microstructural observation of reduced powder mixture revealed that the Ni-Fe alloy particles of about 20 nm in size were homogeneously surrounded Al2O3, forming nanocomposite powder. The hot-pressed composite showed improved mechanical properties and magnetic response. The properties are discussed in terms of microstructural characteristics such as the distribution and size of Ni-Fe dispersion.
Resonant Tunnelling Behaviour in Multilayered Cold Cathodes Made of Nanoseeded Diamond and Nanocluster Carbon
Authors: Satyanarayana B.S. , Hiraki A. 
Published: April 2011

ABSTRACTMultilayered cold cathodes made of spin coated nanocrystalline diamond and cathodic arc process grown nanocluster carbon films, were studied. The nanocrystalline diamond was first coated on to the substrate. The nanocluster carbon films were then deposited on the seeded nanocrystalline diamond coated substrates using the cathodic arc process at room temperature. Theresultant hetrostructured microcathodes were observed to exhibit electron emission currents of 1μA/cm2 at fields as low as 1.2 V/μm. Further some of the samples seem to exhibit I-V characteristics witha negative differential resistance region at room temperature conditions. This negative differential resistance or the resonant tunneling behaviour was observed to be dependent on the nanoseeded diamond size and concentration for a given nanocluster carbon film.
Spray and Inkjet Printing of Hybrid Nanoparticle-Metal-Organic Inks for Ag and Cu Metallizations
Authors: Curtis C. J. , Schulz D. L. , Miedaner A. , Alleman J. , Rivkin T. , Perkin J. D. , Ginley D. S. 
Published: April 2011

ABSTRACTMetal-organic and hybrid metal-organic/metal nanoparticle inkswere evaluated for use in the inkjet printing of copper and silver conducting lines. Pure, smooth, dense, highly conductive coatings were produced by spray printing with (hexafluoroacetylacetonato)copper(I)-vinyltrimethylsilane Cu(hfa)·VTMS) and (hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene) (Ag(hfa)COD) metal-organic precursors on heated substrates. Good adhesion to the substrates tested, glass, Kapton tape and Si, has been achieved without use of adhesion promoters. The silver metal-organic ink has also beenused to print metal lines and patterns with a commercial inkjet printer. Hybrid inks comprised of metal nanoparticles mixed with the metal-organic complexes above have also been used to deposit Cu and Ag films by spray printing.This approach gives dense, adherent films that are much thicker than those obtained using the metal-organic inks alone. The conductivities of the silvercoatings obtained by both approaches are near that of bulk silver (2 μΩ·cm). The copper coatings had conductivities at least an order ofmagnitude less than bulk.
Imaging of gold dendrimer nanocomposites in cells
Authors: Eichman Jonathan D. , Khan Mohamed K. , Lee Inhan , Baker James R. , Lawrence Theodore S. , Sorenson Dorothy R. , Edwards Chris A. , Balogh Lajos 
Published: April 2011

ABSTRACTDendrimer nanocomposites (DNC) are hybrid nanoparticles formed by the dispersion and immobilization of guest atoms or small clusters in dendrimer matrices. They have a great potential in biomedical applications due to their controlled composition, predetermined size, shape and surface functionalities. In this work, nanocomposites of gold and poly(amidoamine) dendrimers {Au(0)n-PAMAM} have been selected to demonstrate this nanoparticle based concept. {Au(0)n-PAMAM} gold dendrimer nanocomposites with a well-defined size have been synthesized and imaged by TEM both in vitro and in vivo. Dendrimer nanocomposites have also the potential to be used as drug delivery vehicles either utilizing bioactive guests or incorporating radioactive isotopes. Radioactive dendrimer nanocomposites, e.g. {198-Au}, can be delivered to the tumor either by means of injecting the active nanoparticles directly into the tumor microvasculature or by intravenous injection. Both specific or non-specific targeting can be utilized in this process to achieve appropriate transfer.
Boundary conditions for dislocation dynamics simulations and stage 0 of BCC metals at low temperature
Authors: Tang Meijie , Kubin Ladislas P. 
Published: April 2011

ABSTRACTIn order to study the dislocation density evolution of body centered cubic (bcc) crystals at low temperature by dislocation dynamics (DD) simulations, we investigated carefully three different boundary conditions (BC) for DD, i.e., the quasi-free surface BC, the flux-balanced BC, and the periodic BC. The latter two BCs can account for the dislocation loss from the boundary of the finite simulation box. PBC can also eliminate the influence of surfaces and improve the line connectivity. We have found that the PBC provides a convenient and effective boundary condition for DD simulations and have applied it to the study of dislocation density evolution of bcc metals during stage 0 deformation at low temperature.
Concurrent Multiscale Modeling of Embedded Nanomechanics
Authors: Rudd Robert E. 
Published: April 2011

ABSTRACTWe discuss concurrent multiscale simulations of dynamic and temperature-dependent processes found in nanomechanical systems coupled to larger scale surroundings. We focus on the behavior of sub-micron Micro-Electro-Mechanical Systems (MEMS), especially micro-resonators. The coupling of length scales methodology we have developed for MEMS employs an atomistic description of small but key regions of the system, consisting of millions of atoms, coupled concurrently to a finite element model of the periphery. The result is a model that accurately describes the behavior of the mechanical components of MEMS down to the atomic scale. This paper reviews some of the general issues involved in concurrent multiscale simulation, extends the methodology to metallic systems and describes how it has been used to identify atomistic effects in sub-micron resonators.
Lattice parameter dependence versus composition in semiconductor alloys: the InGaAs case
Authors: Ferrari C. , Villaggi E. , Armani N. , Carta G. , Rossetto G. 
Published: April 2011

ABSTRACTFollowing recent works that report a non linear dependence of the lattice parameter versus composition in some semiconductor alloys the InGaAs/InP system has been investigated. The lattice parameter and the composition of InGaAs/InP lattice matched heterostructures have been independently determined by measuring the high resolution X-ray diffraction profile and the absorption of the X-ray beam diffracted from the InP substrate. In contrast with previous results that stated a linear dependence of the lattice parameter with composition, a 6% larger In content in the InGaAs/InP lattice matched alloy is found. Such result has been confirmed by the analysis of the X-ray fluorescence induced by an electron beam on the layer and on standards made of InAs and GaAs fine ground crystals. The result is in good agreement with the predictions of models based on the elasticity theory applied on a microscopic scale.
Diffusion in the Presence of Grain Boundaries: a Variable Length Scale Simulation Method
Authors: Belova Irina V , Murch Graeme E 
Published: April 2011

ABSTRACTIn this paper we introduce a Monte Carlo method for numerical analysis of the problem of tracer diffusion in the presence of isolated grain boundaries with a variable mesh in the direction perpendicular to the grain boundary plane. A number of isoconcentration contour profiles were studied. Two different expressions for the angle between the isoconcentration contours and the grain boundary were derived for the instantaneous tracer source following procedures analogous to Fisher's and Whipple's approximations for the constant tracer source. Comparison with the numerical data was made. Both these approximations overestimate the grain boundary diffusivity.
Modeling of Sol-Gel Transition with Loop Network Formation and its Implications on Mechanical Properties
Authors: Ma Hang-Shing , Prévost Jean-H. , Jullien Rémi , Scherer George W. 
Published: April 2011

ABSTRACTCertain classes of sol-gel transition have been modeled as diffusion-limited cluster-cluster aggregation (DLCA), but it produces excessive dangling branches on the resulting network that underestimates the rigidity of gels. The “dangling bond deflection” (DEF) model was developed to simulate spatial fluctuation of the dangling branches under thermal energy. Collision and sticking of two dangling branches within the same cluster turns these branches into a loop. Combination of the DLCA and DEF models creates network that possesses extensive loop structure and negligible dangling mass. The networks are substantially stiffened by the loop structure, and successfully reproduce the empirical scaling relationship between linear elastic modulus and density exhibited by real aerogels. The gel structure can be represented by the “blob-and-link” model, in which blobs refer to dense, rigid collections of particles, interconnected by tenuous links of particle chains. When the network is deformed, only these few weak links contribute to the stiffness, leaving the blobs unstrained. The gel modulus drops significantly as porosity increases because more particles reside in the blobs and fewer particles carry the strain.
A Phase Field Model for Grain Refinement in Deeply Undercooled Metallic Melts
Authors: Mullis A.M. , Cochrane R.F. 
Published: April 2011

ABSTRACTWe present the results of phase field simulations of dendritic growth into pure undercooled melts, at growth velocities up to 35 m s−1. We find that, at low growth velocities, dendrite morphologies are broadly self-similar with increasing growth velocity. However, above ≈ 15 m s−1 the initiation of side-branching moves closer to the dendrite tip with increasing growth velocity. This appears to be related to the level of kinetic undercooling at the tip. Once side- branch initiation begins to occur within 1-2 radii of the tip, profound morphological changes occur, leading to severe thinning of the dendrite trunk and ultimately repeated multiple tip- splitting. This process can be invoked to explain many of the observed features of spontaneous grain refinement in deeply undercooled metallic melts.
Molecular Modeling of the Dielectric Saturation in Proton Exchange Membranes
Authors: Paul Reginald , Paddison Stephen J. 
Published: April 2011

ABSTRACTA molecular statistical mechanical method is employed to compute the field dependant permittivity of water contained in the hydrophilic pores of hydrated proton exchange membranes. The anionic (-SO-3) groups in proximity to the pore walls generate spatially varying fields resulting in dielectric saturation, the effects of which are investigated.
Effects of Nanostructure on Bulk Mechanical Properties of Nacre - 3D Finite Element Modeling of the Segmented/Layered Biocomposite
Authors: Katti Dinesh R. , Katti Kalpana S , Tang Jingpeng , Sopp Jeffrey M. , Sarikaya Mehmet 
Published: April 2011

ABSTRACTNacre is a segmented layered composite containing both nanoscale-thick organic and sub- micrometer thick scale inorganic phases. In addition to controlling the formation of the intricate architecture, the organic plays a significant role in the mechanical properties of the biocomposite. In our previous work, three dimensional finite element models of nacre were constructed to design “brick and mortar” micro-architecture to study effects of nonlinear response of the organic component. Recently, nanomechanical properties such as hardness and elastic moduli of the individual components of nacre have been determined using nanoindentation techniques. In this work, we used these actual properties of the components to perform mesoscale finite element models to quantitatively evaluate nanoscale effects. Specifically, we studied the effect of the solid contacts between the platelets through the organic layer on bulk properties under tensile and compressive loading. In the new 3D finite element model, we also incorporated the pseudo-hexagonal platelet morphology to more accurately represent the nacre microstructure. The multiscale approach in our study involves incorporation of experimentally obtained nanoscale parameters into meso-macroscale numerical models. Our simulations imply that mineral contacts in the aragonitic platelets have marginal impact both on bulk elastic behavior of nacre and yielding. Stress concentration in contact regions were high enough for the contacts to break long before yield started in nacre. These results have important implications in the design of biomimetic segmented-layered composites for improved mechanical properties.