bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Search of the Molecular Triplet of C60 using Low Temperature Raman Spectroscopy.
Authors: Chambers G. , Dalton A.B. , Byrne H.J. 
Published: April 2011

ABSTRACTThe excited state properties of C60 thin films have been probed in the temperature range 77–273K using Raman spectroscopy. The change in the Raman, 2Ag mode of C60 (whose position is largely independent of temperature) was monitored as a function of the excitation intensity at 514.5nm. This mode normally positioned at 1469cm-1, was seen to shift reversibly to a lower Raman frequency with increasing laser intensity. Two excited state species have been identified. The first, at 1466cm-1 has been associated with the molecular triplet of C60. The second species at 1463cm-1, has been speculated to be an excited state co-operative involving two or more excited states in the solid and is seen to be intrinsic to solid state C60 below the phase transition.
Density Functional Based Tight Binding Study of C2 and CN Deposition On (100) Diamond Surface
Authors: Sternberg Michael , Zapol Peter , Frauenheim Thomas , Carlisle John , Gruen Dieter M. , Curtiss Larry A. 
Published: April 2011

ABSTRACTA density-functional based tight binding method was used to study elementary steps in the growth of ultrananocrystalline (UNCD) diamond. It was shown previously that C2 dimers are the dominant growth species in hydrogen-poor argon plasmas. Recent experimental evidence shows that nitrogen addition to the plasma profoundly changes the morphology of the UNCD film. CN species are believed to play a major role. Reactions of C2 and CN molecules with reconstructed diamond (100) surfaces were studied. A single CN prefers an end-on attachment to a surface atom on the unhydrided (100) surface with its C end down. It is shown how further C2 addition to the surface leads to CN-mediated diamond growth and how the CN species remain on top of the growing diamond layer.
Spontaneous Formation and Stability of GaP Cage Structures: A Theoretical Prediction of a New Fullerene
Authors: Buda Francesco , Tozzini Valentina , Fasolino Annalisa 
Published: April 2011

ABSTRACTWe report the spontaneous formation of a GaP fullerene cage in ab-initio Molecular Dynamics simulations starting from a bulk fragment. A systematic study of the geometric and electronic properties of neutral and ionized III-V (GaP, GaAs, AlAs, AIP) clusters suggests the stability of hetero-fullerenes formed by compounds with zincblend bulk structure. Our prediction is supported by several indicators: these clusters show closed electronic shells and relatively large energy gaps; the ratio between the cohesive energy per atom in the cluster and in the bulk is very close to the value found for carbon fullerenes of the same size; the clusters are thermally stable up to a temperature range of 1500–2000 K and they do not dissociate when ionized.
SWNT nucleation: Energetics of zipping—edge mechanism
Authors: Rotkin Slava V. 
Published: April 2011

AbstractA novel mechanism of SWNT nucleation is considered in oppose to an existing model. The latter model based on the formation of a hemispherical carbon bowl nucleus has no correct description within the thermodynamics and kinetics of the nucleation process. The new mechanism can explain the prevalent formation of [10,10] armchair nanotube on the base of the continuum graphene energetics.
Preparation of Carbon Nanotubes by Using Mesoporous Silica
Authors: Kawasaki Shinji , Komiyama Shingo , Ohmori Shigekazu , Yao Akifumi , Okino Fujio , Touhara Hidekazu 
Published: April 2011

ABSTRACTCarbon nanotubes were synthesized using several mesoporous silica templates with different pore sizes in order to investigate the possibility of controlling the diameter of carbon nanotubes by changing the pore size of the mesoporous silica. TEM observation confirmed that carbon nanotubes with uniform diameter can be obtained by the present method. However, it was found that it is difficult to prepare carbon nanotubes having diameter smaller than ∼20 nm by the present method even if the template with small pore size is used.
Mechanics of multi walled Carbon nanotubes probed by AFM
Authors: Decossas S. , Patrone L. , Comin F. , Chevrier J. 
Published: April 2011

ABSTRACTUsing the AFM tip, nanotubes are caught on a raw sample then deposited on a clean surface with an absolute precision better than 500nm. A nanostructured surface made of smooth Germanium dots on flat silicon was used as deposition sample. Nanotube mechanics is probed by AFM tip induced displacement. Nanotubes are shown to be blocked by Ge dots: it is impossible to induce a controlled displacement of the nanotube over a Ge dot when it is pushed against the dot. Elastic energy due to the bending of the nanotube is at the root of that behavior.
Transformation of Active Carbon to Onion-like Fullerenes Under Electron Beam Irradiation
Authors: Xu Bingshe , Jia Husheng , Zhou Hefeng , Ichinose Hideki , Iwamoto Chihiro 
Published: April 2011

ABSTRACTThe transformation of an active carbon film with Pt nanoparticles to onion-like fullerenes has been in-situ investigated by a high-resolution transmission electron microscope. It was found that the onion-like fullerenes/metals polycrystalline film was formed under electron irradiation. The formation process was consisted of three steps: first, the flakes of onion-like fullerenes were induced by Pt nanoparticles; second, the flakes grew into a few ellipsoidal graphite shell; and third, a gradual reorganization of the formation of quasi-spheroid graphite shells and the bond of Pt particles was took place. It was a composite film of onion-like fullerenes and metal particles. It is suggested that the transformation mechanism involves an irradiation of electron and a catalytic effect of Pt nanoparticles, while any temperature rise due to electron irradiation seems to be negligibly small.
Structural Characterization of GaN Nanowires Fabricated via Direct Reaction of Ga Vapor and Ammonia
Authors: Jacobs R.N. , Salamanca-Riba L. , He M. , Harris G.L. , Zhou P. , Mohammad S. N. , Halpern J.B. 
Published: April 2011

ABSTRACTWe report structural studies of large-scale wurtzite GaN nanowires fabricated by direct reaction of Ga vapor and NH3. This recently reported growth technique [1] demonstrates processing of GaN one-dimensional structures as thin as 26 nm and up to 500 μm in length. This method is both interesting and attractive in that fabrication is carried out without the assistance of template materials as required by other methods. In this study, transmission electron microscopy (TEM) is used to characterize the nanowires, while x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS) data provide supporting structural/compositional analysis. Our structural investigation reveals the presence of thin hexagonal platelets, which we believe play a critical role in the nucleation, growth, and orientation of the wires. In particular, our findings indicate that most of the wires grow along the [2110] direction, normal to the platelet edges.
Electrochemistry in Nanostructered Inorganic Molecular Materials
Authors: Williams Mary Elizabeth , Hupp Joseph T. 
Published: April 2011

ABSTRACTWe have previously described the synthesis of a family of molecular ‘squares’ based on octahedral Re(I) coordination of difunctional bridging ligands. The size and chemical composition of the square cavity is highly tunable, and the inorganic cyclophanes are being actively studied in catalytic, separations, and sensing applications. Electrochemical techniques have been primary methods for characterization of the transport properties of thin films of the nanostructured materials. For example, cyclic voltammetry and rotating disk electrode voltammetry experiments have revealed size-selective permeation by redox probes, where the size cutoff is determined by the internal square dimensions. We have more recently begun to employ scanning electrochemical microscopy to spatially image micropatterned electrodes containing these thin film materials, simultaneously allowing us to obtain permeability data and topographical information. This paper describes data obtained by employing porphyrin-based molecular squares that feature chemically tailored cavities.
Nanocomposites by Covalent Bonding between Inorganic Nanoparticles and Polymers
Authors: Blum Yigal D. , Kambe Nobuyuki , Brent MacQueen D. , Kumar Sujeet , Chiruvolu Shiv , Chaloner-Gill Benjamin 
Published: April 2011

ABSTRACTA generic approach to chemically facilitate the interactions of nanoparticles with conventional polymers is developed to address the design and processing capability of inorganic-organic nanocomposites. This approach introduces homogeneity to the composite and can be used as a tailoring tool for microstructure architecture.Nanoparticles produced by NanoGram's technology are excellent for such nanocomposites. Their spherical shape and narrow size distribution assist in the processing of homogeneous blends. High loads of particles within a polymeric matrix can be achieved without losing homogeneity. Alternatively, the particles can be selectively attracted into desired domains.
The Facile Synthesis of Nanocrystalline Semiconductor Quantum Dots
Authors: Wong Michael S. , Stucky Galen D. 
Published: April 2011

ABSTRACTCurrent synthetic techniques to high-quality quantum dots (“QD's”) involve organometallic precursors that are hazardous and expensive and require they be rapidly injected into an extremely hot solvent to form the QD's. A new method for synthesizing high-quality CdSe QD's while circumventing these problems has been developed. Different cadmium salts were studied as Cd precursors alternative to dimethylcadmium. High-quality CdSe QD's were found possible with cadmium acetate as the Cd precursor. Changes in solvent temperature and reaction time had a systematic effect on QD particle sizes and the accompanying optical properties. These preliminary results point to a general method for producing high-quality QD's that is safer and much more versatile.
Structural, Optical and Chemical Properties of Zns and Cds Nanoparticles Obtained by an Improved Colloidal Chemistry Synthetic Route.
Authors: Lucia Curri M. , Agostiano Angela , Monica Mario Della , Leo Gabriella , Lomascolo Mauro , Alvisi Marco , Vasanelli Lorenzo 
Published: April 2011

ABSTRACTIn this work an improved synthetic route that exploits a quaternary water-in-oil microemulsion has been used to obtain nanocrystals of ZnS, CdS and their mixed compounds, - CdxZn1-xS - differing by their size and composition and having high crystalline quality, small dimensions and a quite good size distribution. The opportunity offered by the use of water-in-oil microemulsion to immobilize the nanocrystals onto solid substrate by self-assembling to obtain stable adherent layers has also been exploited.The physical and chemical properties of obtained nanocrystals and layers have been investigated by UV-vis spectroscopy, X-Ray Diffraction X-ray Photoelectron Spectroscopy and Scanning Tunneling Microscopy. The role played by the co-surfactant (pentanol) in controlling nanocrystal size and stability has been discussed.
Chemical Processing of Nanostructured Materials
Authors: Das R. N. 
Published: April 2011

ABSTRACTNanocrystalline ( particle diameter less than 50 nm) ceramic powders have been prepared by the rapid evaporation of precursor solutions containing the respective metal nitrates&sol; hydroxides, triethanolamine (TEA) and sucrose in stoichiometric amounts. Complete evaporation of the solutions yields a fluffy dried precursor mass. Heat-treatment of the precursor mass at low external temperatures (450-700 °C) resulted in the desired nanocrystalline oxides. The oxide system studied are: barium titanate (BaTiO3), lanthanum modified lead zirconate-titanate (PLZT), Nickel ferrite (NiFe2O4) and Calcium Tungstate (CaWO4).
Synthesis, Characterization and Catalytic Activity of Nanometric Complexes
Authors: Mody Kripa , Trivedi Bhavna , Pratap Arun 
Published: April 2011

ABSTRACTThe preparation and characterization of nanostructured materials and catalysts is the focus of intense study in recent years. The micro emulsion technique is one of the chemical methods known for isolation of nano-sized materials and some simple compounds such as AgCl and LiF have been prepared using this technique. However, very few attempts have been made to isolate nano-sized coordination compounds, which are known to be good catalysts.In the present paper, nano-sized complexes of Cu(II) and Ni(II) with Leucine were prepared by the reaction of metal chloride and the ligand solution in water in oil micro-emulsion medium. N-Heptane was used as oil and sodium salt of dioctyl sulfo succinate (AOT) was used as surfactant to stabilize the emulsion. The complexes were characterized by elemental analysis and spectral studies. The crystallite sizes were determined by XRD studies using single line approximation through Scherrer equation. The X- ray diffraction studies revealed that the crystallite size of the complexes prepared by micro-emulsion technique was smaller than that of the material prepared by conventional method. The difference in particle size was also observed in differential scanning calorimetric (DSC) studies, where in, the reaction peaks were observed at lower temperatures for the complexes prepared by the micro-emulsion technique. The increased surface to volume ratio is expected to give better catalytic behavior.
A ‘Building Block’ Approach To Mixed-Colloid Systems Through Electrostatic Self-Organization
Authors: Galow Trent H. , Boal Andrew K. , Rotello Vincent M. 
Published: April 2011

ABSTRACTWe have developed a highly modular electrostatically-mediated approach to colloid-colloid and polymer-colloid networks using ‘building block’ and ‘bricks and mortar’ self-assembly methodologies, respectively. The former approach involved functionalization of one type of nanoparticle building block with a primary amine and a counterpart building block with a carboxylic acid derivative. After combining these two systems, acid-base chemistry followed by immediate charge-pairing resulted in the spontaneous formation of electrostatically-bound mixed-nanoparticle constructs. The shape and size of these ensembles were controlled via variation of particle size and stoichiometries. In the ‘bricks and mortar’ approach, a functionalized polymer is combined with complementary nanoparticles to provide mixed polymer-nanoparticle networked structures. A notable feature is the inherent porosity resulting from the electrostatic assembly. The shape and size of these ensembles were controlled via variation of particle size, stoichiometries and the order in which they were added.
Bifunctional Electrocatalytic Films with Gold Nanoparticles and Metalloporphyrin: Preparation and Characterization
Authors: Yang Wenjun , Li Xiaoyuan , Yu Nai-Teng 
Published: April 2011

ABSTRACTBifunctional electrocatalytic films were prepared employing a layer-by-layer assembly approach. The cation, metalloporphyrin (MP), and the anion, potassium tetrachloroaurate (KAuCl4) were alternatively assembled on glass or indium-doped tin oxide (ITO) supports. The assembled AuCl4- ions were then converted to gold nanoparticles (Aun) under the exposure to ultraviolet light. Film growth at each adsorption step was monitored by UV-Vis absorption spectroscopy and cyclic voltammetry (CV). The formation of gold nanoparticles was characterized by UV-Vis absorption spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Bifunctional electrocatalytic activity of the film was demonstrated in the oxidative detection of nitric oxide (NO) over Aun and the reductive detection of oxygen (O2) over Co(II)P in the same CV scan.
Glass to Icosahedral Phase Transformation in Zr-based Glassy Metals
Authors: Haruyama Osami , Miyazawa Tomoaki , Saida Junji , Inoue Akihisa 
Published: April 2011

ABSTRACTElectrical properties of icosahedral phases (I-phase) that precipitated in Zr65Al7.5Cu7.5Ni10M10 (M=Ag, Pd), Zr65Al7.5Cu1.25Ni10M5 (M=Ag, Pd), Zr65Pd25Ni10 and Zr70Pd20Ni10 metallic glasses have been investigated. In-situ resistivity change with increasing temperature was measured at a heating rate of 0.67 K/s from room temperature. I-phase transformation was occurred in the supercooled liquid phase for Zr-Al-Cu-Ni-M glasses, followed by the crystallization to stable Zr2Ni- and Zr2Cu-type crystals. Ternary glasses exhibited the I-phase crystallization from the glass solid phase and subsequently the transformation of I-phase to crystal phases like Zr2Ni and Zr2Pd. The resistivity of I-phase decreased together with advancing I-phase precipitation, about 2 % compared to the resistivity of the supercooled liquid phase, for typical Zr65Al7.5Cu7.5Ni10Ag10 glass. On the other hand, Zr70Pd20Ni10 glass showed the resistivity increment of about 5 % just after completing I-phase crystallization. Low temperature conductivity of Zr65Al7.5Cu7.5Ni10Ag10 and Zr70Pd20Ni10 glasses and I-phases may be explained by the weak localization model of conduction electron in the range from about 20 K to room temperature.
Growth and Characterization of Magnetic Nanostructures on Carbon Nanotube Templates
Authors: Wu Yihong , Qiao Peiwen , Chong Towchong 
Published: April 2011

ABSTRATWe describe the growth of magnetic nanostructures on carbon nanotube templates. The nanotubes were grown by microwave plasma enhanced chemical vapour deposition. The as grown nanotubes were aligned reasonably well around the substrate normal directions. Although the nanotubes were quite straight, there were still some bent and tilt as revealed by the scanning electron microscope observations. Magnetic field has been used to re-align or re-assemble the nanotubes before they were used as the templates to grow magnetic nanostructures. Depending on whether there is a magnetic particle on the top tip of each nanotube and the density of the nanotubes, there are two different consequences of applying a magnetic field to the nanotubes. For nanotubes with magnetic particles attached to their top tips, the post-growth treatment by the magnetic field resulted in re-assembly of the nanotubes into micro-umbrella type of structures. For those without magnetic particles, however, the effect of magnetic field treatment is negligible; but after the deposition of thin magnetic layers, the field treatment made the nanotubes much straighter than what they originally were and aligned almost vertically to the substrates. The re-aligned or re-assembled nanotubes were used as the templates to grow magnetic nanostructures. It was found that most of the magnetic nanostructures exhibited characteristics similar to those of magnetic nanowires.
Pair-state formation in a nanocrystal: a theoretical perspective
Authors: Suyver J. F. , Meester R. , Meijerink A. , Kelly J. J. 
Published: April 2011

ABSTRACTSimulations of dopant pair-state distributions are presented for zincblende nanocrystals with different radii and for different dopant fractions. The probability of finding at least one pair-state and the concentration of pair-states were calculated on the basis of a statistical average of 105simulations per crystal size and dopant concentration. The distribution of nanocrystal lattice positions over the surface and the bulk of the crystal is computed. A mathematical description of the distributions, valid in any crystal lattice, is discussed. This removes the need for further simulations.
Depth Selective Mössbauer Spectroscopy as a Bridge between Surface and Small Particle Phenomena in Magnetic Materials
Authors: Stahl B. , Ghafari M. , Hahn H. , Kamzin A. , Hanzel D. 
Published: April 2011

ABSTRACTA most feasible tool in characterizing magnetic properties is Mössbauer spectroscopy. By a combination with electron spectroscopy, the depth profile of the Mössbauer excitation is experimentally accessible [Liljequist01, Stahl97]. Depth selective Mössbauer studies in the vicinity of the Néel temperatures of an antiferromagnetic FeBO3 single crystal and a α-FeOOH thin film and of the Morin transition in an β-Fe2O3 single crystal are presented. Especially in FeBO3, the divergence of both, the spatial correlation between atomic moments and the autocorrelation of the local moment, could be observed in the critical region.
A molecular dynamics investigation on grain disappearance at a triple junction in polycrystalline silicon
Authors: Satta Alessandra , Colombo Luciano , Cleri Fabrizio 
Published: April 2011

ABSTRACTTopological changes in microstructure are strictly related to the microscopic evolution of triple junctions (TJ). The three-sided grain disappearance, usually called T2 process, is here investigated via 3D-atomistic modeling. In particular the stability of a three-sided grain insertion in a triple junction in silicon is studied within the framework of Molecular Dynamics simulations. The Stillinger-Weber interatomic potential is adopted and constant-traction border conditions are considered to ensure a proper embedding of the atomistic region in a virtually infinite bulk continuum. Dealing with the T2-event, the critical radius below which the three- sided inner grain become unstable is evaluated to be three to four times the lattice constant of silicon. Moreover, we show that the instability sets in through the amorphization of the central shrinking grain.
Computer Simulation of Hydride Precipitation in Bi-crystalline Zirconium
Authors: Ma X.Q. , Shi S.Q. , Woo C.H. , Chen L.Q. 
Published: April 2011

ABSTRACTγ-hydride precipitation and growth in a zirconium bi-crystal were simulated using a phase field kinetic model. The temporal evolution of the spatially dependent field variables is determined by numerically solving the time-dependent Ginzburg-Landau equations for the structural variables and the Cahn-Hilliard diffusion equation for the concentration variable. The morphology evolution of γ-hydride with and without external load was simulated. It is demonstrated that nucleation density of the hydride at the grain boundary increases as compared to the bulk and favorable hydride precipitation at the grain boundary become weaker when an external load is applied.
In-plane Thermal and Electronic Transport in Quantum Dot Superlattice
Authors: Khitun A. , Liu J.L. , Wang K.L. , Chen G. 
Published: April 2011

ABSTRACTWe present a theoretical model in order to describe both thermal and electronic in-plane transports in quantum dot superlattice. The model takes into account the modifications of electron and phonon transport due to the space confinement caused by the mismatch in electronic and thermal properties between dot and host materials. The developed model provides the analysis of the in-plane superlattice electronic and thermal properties versus quantum dot size and their arrangement. Numerical calculations were carried out for a structure that consists of multiple layers of Si with regimented germanium quantum dots. The simulation results of the lattice thermal conductivity are in a good agreement with experimental data.