bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Computational Materials Design Facility (CMDF): A powerful framework for multi-paradigm multi-scale simulations
Authors: Buehler Markus J. , Dodson Jef , van Duin Adri C.T. , Goddard III William A. 
Published: April 2011

AbstractPredicting the properties and behavior of materials by computer simulation from a fundamental, ab initio perspective has long been a vision of computational material scientists. The key to achieving this goal is utilizing hierarchies of paradigms and scales that connect macrosystems to first principles quantum mechanics (QM). Here we describe a new software environment, the “Computational Materials Design Facility” (CMDF), capable of simulations of complex materials studies using a variety of simulation paradigms. The CMDF utilizes a Python scripting layer to integrate different computational tools to develop multi-scale simulation applications. We have integrated DFT QM methods, the first principles ReaxFF reactive force field, empirical all atom force fields (FFs), mesoscale and continuum methods. The central data structure Extended OpenBabel (XOB) plays a critical role as glue between applications. We demonstrate the usefulness of CMDF in examples that couple complex chemistry and mechanical properties during dynamical failure processes, as for example in a study of cracking of Ni under presence of O2.
High-throughput Studies on Photochemical Properties of Transition Metal-Doped SrTiO3 Epitaxial Thin Films
Authors: Ohsawa Takeo , Koinuma Hideomi , Matsumoto Yuji 
Published: April 2011

AbstractCombinatorial pulsed laser deposition approach is suitable to study complex effects such as composition, thickness and surface structure on thin film-based photocatalysis in high-throughput manner. We fabricated composition spreads and thickness gradient films of transition metal-doped SrTiO3(001) on various oxide single crystal substrates and evaluated their photocatalytic activity by the use of photoreduction of Ag+ in AgNO3 solution. We found anomalous film thickness and substrate effects on the Ag-photodeposition in the V-doped SrTiO3 epitaxial thin films grown on the Nb:SrTiO3(001) substrate.
Investigation of Antimicrobial Peptide Salts: Efficacy and Solubility in Surfactant Solutions for Latex Systems
Authors: Wicks Douglas , Rhoades Alicyn M , Williamson John S , Miriyala Bruhaspathy 
Published: April 2011

AbstractThe study and application of antimicrobial peptides is a growing niche field in the areas of pharmaceutics and medicinal chemistry. As a result, the majority of testing and development is completed under in vitro conditions. The use of synthetically derived antimicrobial peptides in applications outside the medical realm is a relatively untapped field, with the significance of interactions between antimicrobial oligopeptides and the ingredients of polymer systems being largely unknown. Water-based polymer coatings systems are attractive targets for microbial invasion because of their inherent material properties. Water-based polymer latex coatings contain a number of components which aide in stabilization and coalescence of the polymer particles, such as surfactants and polymeric cellulose-derived molecules, with several types of molecular structures existing for each. Microbes are able to flourish within the water phase of the latexes while taking sustenance from these dispersion components, resulting in a loss of properties commonly known as ‘spoilage’. This work addresses the impact of formulation variables, specifically surfactant structure, on the solution and antimicrobial behavior of a model antimicrobial oligopeptides through the use of HT absorbance measurements.
Gas Sensor Materials Based on Semiconductor Nanocrystal / Polymer Composite Films
Authors: Leach Andrew M , Potyrailo Radislav A 
Published: April 2011

AbstractHigh-throughput screening experimentation and multivariate spectral data analysis has been applied to evaluate the gas sensitivity of multi-size CdSe nanocrystals embedded in multiple polymer matrices. We have found that when CdSe nanocrystals of different size (2.8 and 5.6 nm diameter) were incorporated into polymer films, the photoluminescence (PL) response patterns upon laser excitation at 407-nm and exposure to polar and non-polar solvents were unexpectedly different. Additionally, these response patterns were dependent on the nature of polymer. We analyzed the spectral PL response from both sizes of CdSe nanocrystals using multivariate analysis tools. Results of this multivariate analysis demonstrate that a single film with different size CdSe nanocrystals serves as a selective sensor.
Macro- and Micro-Scale Probing of the Mechanical Properties of DNA-Crosslinked Gels Using Embedded Inclusions
Authors: Lin David C. , Yurke Bernard , Shreiber David I. , Chippada Uday , Jiang Xue , Watson George P. , Langrana Noshir A. 
Published: April 2011

AbstractMechanical properties of a class of self-assembling hydrogels based on DNA hybridization were studied using rigid, embedded inclusions. Because inclusions can be deflected without direct contact with a manipulator (e.g., magnet) once they are embedded within the subject material, the measurement technique is well suited for monitoring instantaneous and time-varying changes in the mechanical properties of active materials as they respond to external stimuli. In gels crosslinked with complementary strands of oligonucleotides, hybridization chemistry and strand displacement mechanisms allow reversible assembly, shape change, and large changes in compliance through the application of particular strands of DNA. In earlier work using large (diameter ∼0.8 mm) magnetic beads, the scaling behavior of the global elastic modulus with crosslink density was determined. More recently, it was shown that a threefold increase in stiffness was possible by generating prestress in the DNA-crosslinked gel network. Currently, the gels are functionalized to support cell attachment and embedded with micro-fabricated nickel bars. Through the measurement of local elastic and shear moduli as well as Poisson’s ratios, cell-substrate interactions can be used as a means of evaluating the potential of DNA-crosslinked gels as active cellular engineering substrates and tissue engineering scaffolds.
Effect of Nanostructure on the Thermal Oxidation of Atomized Iron
Authors: Kumar Mohit , Rawat Naveen , Santhanam Kalathur S 
Published: April 2011

AbstractThe effect of nanostructure on the thermal oxidation of atomized iron has been investigated. Above 500°C atomized iron is oxidized in the presence of air. However, when iron is compacted with multiwalled carbon nanotubes (MWCNT) this oxidation is shifted by more than 100°C. Iron is protected by the nanostructure environment A large number of compositions of atomic ratios of iron and MWCNT have been examined in this study to understand the effect in detail. The effect of nanostructure in the thermal oxidation of iron is interpreted as due to iron atom experiencing extensive overlap and confinement effect. causing spin transfer. Based on theoretical calculations reported in the literature this confinement effect of iron is suggested to produce a transformation from 3d64s2 to an effective configuration of 3d84s0 producing spintronics effect.
Relation Between Structure and Diffusion in Nanostructured Porous Solids and in Lipid Membranes
Authors: Vasenkov Sergey , Kärger Jörg 
Published: April 2011

AbstractPulsed field gradient (PFG) NMR technique has been applied to study molecular transport in two different types of nanostructured materials, viz. in fluid catalytic cracking (FCC) catalysts and in lipid membranes. Diffusion studies have been performed for a broad range of molecular displacements covering displacements that are as small as a fraction of a micron. The effective diffusivities recorded on various length scales are used to evaluate the relevance of various transport modes in the particles of FCC catalysts for the rate of molecular exchange between catalyst particles and the surrounding atmosphere. This rate is shown to be primarily related to the diffusion in the meso- and macropores of the particles under the condition of fast molecular exchange between these pores and the zeolite crystals located in the particles. Studies of lipid membranes are focused on developing fundamental understanding of the influence of various types of domains on lateral mobility of lipids. A meaningful study of this influence requires an ability of monitoring lipid diffusion for different displacements that are smaller and larger than the domain size. First PFG NMR data along this direction are presented.
The Role Played by Strain Fields, Dislocation Arrays, and Domain Boundaries During the Catalytic Synthesis of Carbon Nanotubes
Authors: Dell'Acqua-Bellavitis Ludovico Matteo , Ballard Jake D , Vajtai Robert , Ajayan Pulickel M , Siegel Richard W 
Published: April 2011

ABSTRACTEx-situ transmission electron microscopy (TEM) was performed on catalytically-grown multi-wall carbon nanotubes (MWCNTs), leading to the identification of two types of catalyst-nanotube wall interfaces – respectively characterized by a quasi-spherical, low aspect ratio particle closer to the nanotube root and by a tapered, high aspect ratio particle farther away from it. The nanotubes exhibit two distinct types of boundaries between crystalline domains with different orientations – twist and twin boundaries in correspondence with quasi-spherical particles and tilt boundaries in correspondence with the tapered particles. TEM evidence suggests that the domain boundaries maintain a rather steady position coupled to the catalytic particles, while the carbon atoms diffuse along the nanotube axis away from the particles. From these considerations, it is possible to conclude that the relative movement of the carbon atoms with respect to the dislocation lines comprising the nanotube domain boundary located at the catalyst-wall interface is a significant mechanism for nanotube crystal growth mainly driven by surface diffusion. The results are interpreted in light of the concurrence of base- and tip- growth for the catalytic synthesis of nanotubes dominated by surface diffusion.
Growth of Silica Nanowires Catalysed by Pd Ion Implantation into Si(100)
Authors: Sekhar Parveen Kumar , Sood Dinesh Kumar , Bhansali Shekhar 
Published: April 2011

ABSTRACTSelective synthesis of silica nanowires on silicon wafers catalyzed by Pd ion implantation is reported.Nanoclusters of palladium silicide acts as seeds for nucleation of wires following a Vapor-Liquid-Solid (VLS) growth model. The consumption of silicide towards nanowire growth is confirmed through Rutherford Backscattering Spectrometry (RBS).The influence of growth time, implantation dose and heating temperature on the structure and morphology of the wires is investigated. Optimization of the these tunable parameters would be needed to facilitate controlled and directed bottom-up growth of silica nanowires.Such selective synthesis may enable a large number of applications in wide areas of future technologies such as localization of light, low dimensional waveguides for functional microphotonics, scanning near field optical microscopy (SNOM), optical interconnects, sacrificial templates, optical transmission antennae and biosensors.
Sprayed Carbon Nanotube Thin Films as Hydrogen Sensors
Authors: Sayago Isabel , Terrado Eva , Aleixandre Manuel , Horrillo Maria del Carmen , Lozano Jesus , Fernandez Maria Jesus , Lafuente Esperanza , Maser Wolfgang K , Gutierrez Javier , Martinez Maria Teresa , Benito Ana M , Munoz Edgar 
Published: April 2011

ABSTRACTWe report a novel, simple, and inexpensive method for preparing efficient carbon nanotube-based hydrogen sensors. Sensor devices were fabricated by simply spraying single-walled carbon nanotube (SWNT) dispersions on alumina substrates. Pd-functionalization of the employed SWNTs enabled increasing the device sensitivity to hydrogen. The effect of aging, thermal processing, and the employed carrier gases on the sensor performance is here described. The fabricated thin film sensors exhibited good sensitivity to hydrogen at room temperature in reversible and reproducible detection processes.
Atomic and Electronic Structures of Pt Supported on Graphene
Authors: Okazaki-Maeda Kazuyuki , Morikawa Yoshitada , Tanaka Shingo , Kohyama Masanori 
Published: April 2011

ABSTRACTWe examined atomic and electronic structures of Pt supported on graphene, using the first-principles calculations based on the density functional theory (DFT). First, we examined the interaction between graphene and a Pt(111) monolayer. The stable distance between graphene and the Pt-monolayer is 3.48Å and the adhesive energy is 0.09 eV/atom. The density of states (DOS) for the Pt(111)/graphene system is the same with the sum of respective DOS's of the graphene sheet and the Pt monolayer. These results indicate that the interaction between graphene and a Pt(111) monolayer is very weak. Second, we examined the interaction between graphene and a Pt atom. The Pt-C bond length is 2.31Å and the adsorption energy is 2.82 eV/adatom, which means the stronger interaction. Finally, we examined the interaction between graphene and a Pt cluster consisting of ten atoms. The distance between graphene and the bottom layer of the cluster is about 2.7Å, which is shorter than that between graphene and the Pt(111) monolayer. This shows that the interaction between the Pt10 cluster and graphene is stronger than the Pt-monolayer/graphene interaction. The center atom in the hexagonal bottom layer of the Pt cluster has the nearest distance with graphene of about 2.5Å. If there is a defect on graphene, the center atom of the hexagonal bottom layer strongly interacts with that.
Nanoparticle SnO2 films as gas sensitive membranes
Authors: Schumacher B. , Szabó Dorothee Vinga , Schlabach Sabine , Ochs Rolf , Müeller Harald , Bruns Michael 
Published: April 2011

ABSTRACTThe Karlsruhe Microwave Plasma Process (KMPP), a versatile gas-phase process is applied to produce SnO2 and core shell SnO2/SiO2 nanoparticles which are, respectively, deposited in-situ on preheated Si-Substrates. These substrates are already equipped with an electrode microarray. The proof of sensor concept shows, that mechanically stable, nanoscaled and nanogranular gas sensing layers can be produced.In a first step synthesis and deposition parameters of SnO2 are elaborated, and gas-sensitivity tests are performed. Additionally, annealing experiments are done. The morphology and struc-ture of nanoparticles is characterized by X-ray diffraction and TEM-methods. The layers are in-vestigated by SEM techniques and by XPS. The sensitivity of the nanogranular layer is deter-mined in comparison with a standard microarray equipped with sputtered layers. Particles crys-tallize in the tetragonal cassiterite structure. It is found that a precursor concentration of 3×10−6mol/l leads to particles with crystallite size in the region of 2nm, whereas a concentration of 5.5×10−4mol/l results in approximately 5nm particles. With the precursor concentration, columnar porous layers of 200nm thickness are obtained after a deposition time of 1min. This thickness is comparable to the one of sputtered layers. First sensor tests show 10 times higher sensitivity to isopropanol, compared to the standard array. The time of response is equivalent. The grain growth observed for bare and core/shell nanoparticles at 300°C is marginal.
Position Controlled Growth in Carbon Nanotubes Catalyzed by an Iron Nano-dot Array
Authors: Fujita Jun-ichi , Mukawa Takahito , Okada Satoshi , Kobayashi Ryota , Ishida Masahiko , Ichihashi Toshinari , Ochiai Yukinori , Matsui Shinji 
Published: April 2011

ABSTRACTWe report a successful demonstration of a position control technique for carbon nanotube growth catalyzed by an iron nano-dot array, which was fabricated by using electron beam induced chemical vapor deposition (EB-CVD). Point irradiation of an electron beam with ferrocene source gas produced an amorphous carbon dot containing iron atoms that were uniformly dispersed into each dot, and its position could be precisely controlled. Vacuum annealing of the ferrocene based dots induced segregation of iron nano-particles, whose size was almost proportional to the beam irradiation time. After removing the carbon residue, an ethanol CVD process carried out at 800°C under 40 mmHg of ethanol vapor induced carbon nanotube growth from the dots. Many grown nanotubes were very thin, being 0.7 to 1.8 nm in diameter. These diameters were much less than that of the bottom iron particles.
Reactions of Methyl Iodide and Halopropanes with Na0 Treated and Untreated NaX and NaY Zeolites
Authors: Kanyi Charles W. , Yan Ka King , Kowenje Chrispin O , Kanyi Charles Wairagu 
Published: April 2011

ABSTRACTProducts formed from reactions of methyl iodide, 1-chloropropane, 1-iodopropane and 1-bromopropane with Na0 treated and untreated NaX and NaY zeolites were studied using solid state 13C NMR and IR spectroscopy. At room temperature, methyl iodide dissociates to form framework methoxy in untreated NaX with no reaction observed in untreated NaY. Upon Na0 treatment, both NaX and NaY reacts with methyl iodide to form framework methoxy, methane and ethane. Longer carbon chain 1-iodo, bromo and chloropropane were also studied. 1-iodopropane undergoes dehalogenation to form framework propoxy while 1-chloropropane and 1-bromopropane undergoes dehalogenation/ dehydrohalogenation to form framework propoxy and propene.
N2 Detection by the Carbon nanotubes Mat and Bundle
Authors: Huang Chien-Sheng , Huang Bohr-Ran , Jang Yung-Huang , Tsai Meng-Shian , Ya Jiun-You , Jian Jia-An 
Published: April 2011

ABSTRACTCarbon nanotubes (CNTs) were synthesized by thermal chemical vapor deposition (thermal CVD) on n-type Si (100) at 700 ° under C2H2 gas flow ratio of 30 sccm. Fe catalysts were pre-deposited by RF sputtering system with RF power 150 W. Two kinds of as-grown CNTs were used to detect N2: the vertically oriented carbon nanotubes (CNTs) mat and horizontally oriented CNTs bundle. Two-terminal electrical measurements were performed at room temperature of 25 °. The electrical resistance of CNTs mat or bundle was found to increase when exposed to N2 environment, and to return back after the N2 pumping, respectively. However, the CNTs bundle had better sensitivity and possessed faster response and recovery time. This could be ascribed to that the CNTs bundle, with more effective grooves on the surface, provided more lower binding-force sites to absorb N2 molecules than the CNTs mat dose, which prominently had interstitial sites.
Epitaxial Growth of Strontium Bismuth Tantalate/Niobate on Buffered Magnesium Oxide Substrates
Authors: Thomas George H. , Morrell Jonathan S. , Aytug Tolga , Xue Ziling B. , Beach David B. 
Published: April 2011

AbstractEpitaxial films of strontium bismuth tantalate (SrBi2Ta2O9, SBT) and strontium bismuth niobate (SrBi2Nb2O9, SBN) were grown using solution deposition techniques on magnesium oxide (MgO) substrates buffered with a 100 nm layer of lanthanum manganate (LaMnO3, LMO). Film structure and texture analyses were carried out using x-ray diffraction. Theta-2theta diffraction patterns were consistent with a c-axis aligned structure for both the buffer layer and the solution deposited films. Theta-2 theta scans revealed (001)SBT, SBN //(001) LMO epitaxial relationships between the solution deposited films and the buffer layer. A pole figure about the SBT, SBN (115) reflection indicated a single in-plane epitaxy. Film quality was assessed using ω and φ scans. Nuclear Magnetic Resonance (13C) was used to characterized the methoxy-ethoxide solutions used for the deposition of the SBN and SBT films.
Surface Photovoltage Spectroscopy for the Investigation of Perovskite Oxide Interfaces
Authors: Beyreuther Elke , Grafström Stefan , Thiele Christian , Dörr Kathrin , Eng Lukas M. 
Published: April 2011

AbstractIn the present study, we comparatively investigate the distribution of electronic interface states of three different perovskite oxide interfaces, formed by epitaxial thin films of La0.7Sr0.3MnO3 (LSMO), La0.7Ca0.3MnO3 (LCMO), and La0.7Ce0.3MnO3 (LCeMO) on SrTiO3(100) substrates, in the as-prepared state as well as after an annealing procedure. We find that annealing significantly reduces the number and density of interface trap states. Two different experimental realizations of the surface photovoltage spectroscopy (SPS) technique were employed: an approach based on X-ray photoelectron spectroscopy (XPS), as well as a capacitive method. The advantages and limitations of both methods are critically discussed.
Laser-Patterned Blue-Green SiC LED
Authors: Bet Sachin Madhukar , Quick Nathaniel R , Kar Aravinda 
Published: April 2011

AbstractLaser direct writing and doping has already been successfully demonstrated for fabrication of PIN diodes, Ohmic and Schottky contacts and other optical structures in silicon carbide (SiC). Although SiC is an indirect bandgap semiconductor a SiC green light emitting diode (LED) has been recently shown to perform better than a GaN green LED. This observation is primarily due to 1) a simple device structure in SiC as opposed to the multilayered structure in GaN and other high bandgap semiconductor compounds and 2) high thermal conductivity. This initial phase focuses on the fabrication of reference SiC LED's to baseline this novel laser direct writing and doping process.6H:SiC (n-type) wafer samples were used for fabrication of LED's. A Nd:YAG laser (1064nm wavelength) was used in continuous wave mode as well as pulsed mode for doping. Doping process iterations were carried out to obtain a uniform doped layer. Two different techniques were employed for patterning: 1) top doping where the incident laser beam assists in doping on the top surface and 2) bottom doping where the bottom surface is doped using the same top incident laser beam. Different structures were synthesized using these two doping techniques. P-type dopants such as boron (in powder form) and aluminum (metalorganic compound tri-methyl aluminum) and n-type dopant (pure nitrogen gas) were used. The doped structures were characterized for I-V characteristics, C-V characteristics and electroluminescence.Electroluminescence (EL) spectrum of the doped samples showed the output in the range of blue to blue green for different samples and the different doped structures. The feasibility of wavelength tuning using nanostructure patterning has also been explored.
Pr-O-N Dielectrics for MIS Stacks on Silicon and Silicon Carbide Surfaces
Authors: Henkel Karsten , Torche Mohamed , Sohal Rakesh , Schwiertz Carola , Hoffmann Patrick , Schmeißer Dieter 
Published: April 2011

AbstractWe combine high-k dielectrics with wide band gap semiconductors for new possibilities for high frequency and high power applications. We investigate the dielectric properties of Praseodymium based oxides and silicates by preparing MIS structures consisting of metal layer (M), PrOx (praseodymium oxide) as a high-k insulating layer (I), and silicon (Si) or silicon carbide (SiC) as semiconductor substrates (S). Our approach consists both, electrical measurements and spectroscopic characterization to analyze properties of the various interfaces within the stacks.For the electrical measurements we produce PrOx layers in the thickness range of 10nm to 240nm. We use capacitance-voltage analysis and determine permittivity values of 8 to 20 depending on physical thickness resulting in an equivalent oxide thickness (EOT) down to 5nm. These data are consistent with the formation of a Pr-silicate between Si and PrOx.In order to prevent interface reactions and to improve the band alignment an interfacial layer is introduced into the stack between the semiconductor and the high-k material. We find aluminum oxynitride (AlON) as a suitable layer which reduces the interface state density to a mean value of 5E11cm2/Vs and the leakage current (1V above flat band) below 1E-5A/cm2.