bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Substrates on the Self-Assembling of FePt Nanocrystals
Authors: Chen Min , Nikles David E. 
Published: April 2011

ABSTRACTFe48Pt52 nanoparticles were synthesized by the simultaneous chemical reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl. As-prepared the particles were spherical with an average diameter of 3 nm and a polydispersity of less than 5%. The particles were superparamagnetic and had a fcc structure. Highly ordered self-assembled supercrystals of particles were formed in TEM grids by deposition from dispersions in hydrocarbon solvents. Nanoparticles deposited on amorphous carbon-coated and SiO2-coated Cu grids tend to assemble into small domains of hexagonal arrays. Larger domains of hexagonal arrays formed on Si3N4 membrane TEM grids. For thin multilayers, the FePt nanoparticles tends to assemble into hexagonal close-packed lattices (ABABAB stacking). For the thicker multilayers, ABCABC stacking was observed. Small angle X-ray reflectivity of the particles on a Si (100) substrate show highly ordered multiplanar structure with d-spacing of 6.2 nm. The coercivity of self-assembled FePt films strongly depended on the annealing temperature. After annealing at 700°C for 30 minutes, the particles transformed from FCC to “FCT” phase and the coercivity of film increased up to 11570 Oe. However, the particle size increased to 16 nm due to sintering.
Optical absorption spectroscopy in the metastable state SI of Na2[Fe(CN)5NO]·2H2O
Authors: Schaniel Dominik , Schefer Jürg , Delley Bernard , Imlau Mirco , Woike Theo 
Published: April 2011

ABSTRACTThe metastable state SI in single crystals of orthorhombic Na2[Fe(CN)5NO]2H2O (sodiumnitroprusside, SNP) was investigated by absorption spectroscopy. The development of the spectra with increasing population of SI was monitored and a new band in the red spectral range was assigned to SI. By comparing with density functional theory (DFT) calculations we were able to assign the band to the electronic transition 2b2→7e. In addition we found that very strong holographic light scattering influences the absorption spectra measured with light polarization along the a- or b-axis of the crystals.
Investigations of Sputtered Silver Oxide Deposits for the SUPER–RENS High Density Optical Data Storage Application
Authors: Büchel Dorothea , Mihalcea Christophe , Fukaya Toshio , Atoda Nobufumi , Tominaga Junji 
Published: April 2011

ABSTRACTThin silver oxide films used as mask layers in super-Resolution Nearfield Structure (super-RENS) disks for high density optical data storage were reactively sputter-deposited and their composition was determined by spectroscopic means. We found that the stoichiometry of the films changed with the oxygen content in the sputtering gas atmosphere. With a stepwise increase in the percentage of O2 from 0 - 100%, the corresponding layers consist of Ag, mixtures of Ag and Ag2O, Ag2O, mixtures of Ag2O and AgO and AgO. Laser activation of such oxidic phase containing deposits results in the decomposition of the material and excitation of strong local plasmons in the remaining silver clusters. This was confirmed by acquiring surface enhanced Raman spectra (SERS) of benzoic acid (BA), copper phthalocyanine (CP) and internal carbon impurities on silver oxide substrates. From this data, we conclude that the sub-wavelength resolution obtained in super-RENS disks is mediated by local surface plasmons on small silver particles forming in the mask layer.
A Study on Batch Method of Thermal Fixing for Multiplexed Holographic Recordings
Authors: Jiang Zhuqing , Meng Gang , Liu Guoqing , Tao Shiquan 
Published: April 2011

ABSTRACTWe have investigated the batch method of thermal fixing for multiplexed holograms. The batch fixing process is pictured and analyzed, for the first time to our knowledge. The batch procedure of thermal fixing includes optical erasure of electronic gratings by subsequent recordings both in the same batch and in different batches, ionic compensation during thermal fixing in one batch, smoothing of ionic gratings during thermal fixing of subsequent batches, and revealing of ionic gratings. The inter-batch optical erasure time constants of LiNbO3:Fe:Ce crystals are measured in experiment.
External Chemical Reactivity of Fullerenes and Nanotubes
Authors: Park Seongjun , Srivastava Deepak , Cho Kyeongjae 
Published: April 2011

ABSTRACTThe external chemical reactivity of graphene sheet, fullerenes and carbon nanotubes has been investigated. The total reaction energy is analyzed with several contributing terms and formulated as a function of the pyramidal angles of C atoms. We have determined the parameters for the formulae from ab initio simulation of graphene. We have applied them to predict hydrogenation energy of several nanotubes and C60, and demonstrated that the predicted total reaction energies are very close to the results of total energy pseudo-potential density functional theory calculations. This analysis can be used to predict the reaction energy and local bonding configuration of a reactant with diverse fullerenes and nanotubes within 0.1 eV accuracy.
Acoustic Microscopy and Surface Brillouin Scattering of Amorphous Carbon Pressure-Synthesized From C60
Authors: Zinin Pavel V. , Manghnani Murli. H. , Tkachev Sergey , Zhang Xinya , Lyapin Alexander G. , Brazhkin Vadim V. , Trojan Ivan A. 
Published: April 2011

ABSTRACTHere, we report successful measurements by surface Brillouin scattering (SBS) and scanning acoustic microscopy (SAM) of the elastic properties of small specimens of amorphous carbon obtained from C60 under high pressure and temperature. The superhard phases of amorphous carbon were synthesized from C60 at pressure 13 – 13.5 GPa and temperature 800–900°C. Two types of acoustic waves have been detected by SBS in superhard samples: surface Rayleigh wave and bulk longitudinal wave. The longitudinal velocity (νL) in the hardest sample is slightly lower than longitudinal wave velocity in diamond in [110] direction. Simultaneous measurements of the Rayleigh and longitudinal wave velocities make it possible to determine shear and bulk elastic moduli of the specimens. Obtained elastic properties for amorphous carbon synthesized under pressure 13.5 GPa and temperature 900°C are close to those for diamond, indicating that bonds among amorphous carbon network are diamond bonding dominated.
Raman and Eels Studies on Nanocrystalline Diamond Prepared in a Low Pressure Inductively Coupled Plasma
Authors: Okada Katsuyuki , Kimoto Koji , Komatsu Shojiro , Matsumoto Seiichiro 
Published: April 2011

ABSTRACTNanocrystalline diamonds with several hundred nm in diameter have been prepared in a 13.56 MHz low pressure inductively coupled CH4/H2 or CH4/CO/H2 plasma. The bonding structures were investigated by Raman spectroscopy and electron energy loss spectroscopy (EELS). Visible (514 nm) and UV (325, 244 nm) excited Raman spectra with CO additive exhibit peaks at ∼1150 cm-1 assigned to sp3 bonding and at 1332 cm-1 due to zone center optical phonon mode of diamond, respectively. It indicates that the UV excitations are possibly sufficient to excite the σ state of both sp2- and sp3-bonded carbon. The high resolution EELS (HREELS) spectra with CO additive show peaks at ∼1100 cm-1 assigned to C-C stretching vibration of sp3 bonding and at ∼700 cm corresponding to the bending vibration of sp3 bonding. It is qualitatively agreement with the Raman spectra. Furthermore the EELS spectrum without CO additive exhibits two peaks at 284 eV and at 292 eV corresponding to π* states and σ* states, respectively, and is similar to that of graphite rather than that of sp2-rich amorphous carbon. The EELS spectrum with CO additive, on the other hand, shows a peak at 292 eV due to σ * states and is similar to that of diamond. A slight peak appears at ∼285 eV corresponding to π* states. It consequently implies that the particles almost consist of sp3 bondings and that the small amount of sp2 bondings are considered to exist in grain boundaries. The EESL spectra are consistent with the results of Raman scattering and HREELS.
Synthesis of Vertically Aligned Carbon Nanofiber Films by RF Magnetron Sputtering
Authors: Lee K. -Y. , Fujimoto K. , Ohkura S. , Honda S. , Katayama M. , Hirao T. , Oura K. 
Published: April 2011

ABSTRACTThe aligned carbon nanofibers were synthesized on Si substrates using RF magnetron sputtering with a hot filament. The hot filament was made of tungsten wire and its temperature was up to 2000°C during the deposition. Nitrogen was used as the sputter gas at a relatively low pressure of 2×10-2 Torr. The sputtering deposition was carried out at a substrate temperature of 700°C. The nanofibers were grown vertically on the substrates. The diameters and the density of the fibers were about 30–45 nm and 109 cm-2, respectively.
Ab initio Study of Metal Atoms on SWNT Surface
Authors: Peng Shu , Cho Kyeongjae 
Published: April 2011

ABSTRACTInteractions of metal atoms (Al, Ti) with semiconducting single walled carbon nanotube (SWNT) are investigated using first-principles pseudopotential calculations. Six different adsorption configurations for aluminum and titanium atoms are studied. Comparison of the energetics of these metal atoms on (8,0) SWNT surface shows significant differences in binding energy and diffusion barrier. These differences give an insight to explain why most of metal atoms (such as Al) form discrete particles on nanotube while continuous nanowires are obtained by using titanium in the experiment.
From Diamond to Carbon Nanotube Field Emitter
Authors: Gröning O. , Nilsson L-O. , Gröning P. , Schlapbach L. 
Published: April 2011

ABSTRACTIn this paper we review the physics and the expectations that were put into the negative electron affinity (NEA) mediated field emission of chemical vapor deposition CVD diamond films and how the emitter technology made possible by this mechanism could have challenged the classical metal micro-tip field emitter arrays. We discuss the dependency between emitter performance of micro-tip emitter arrays and feature size (size of the field enhancing tip) and due to this to the connection between emitter performance and fabrication costs.We introduce the concept of the field enhancement distribution function f(β) for a useful characterization of the field emission properties of thin film emitter and show how this distribution function can be measured by scanning anode field emission microscopy. Using f(β) measured on a thin film of randomly oriented multiwalled carbon nanotubes we show that even these kinds of low cost emitters can show a field emission performance comparable to micro-tip arrays, yet that the large spread in field enhancement values between the individual emitter prevent this performance to be fully exploited. This because the field range in which such thin film emitters can be operated is limited due to emitter disruption and triggering of vacuum arcs. Simulations show how resistor-limited emission can solve these limitations.
Three-dimensional calculation of field emission from carbon nanotubes using a transfermatrix methodology
Authors: Mayer Alexandre , Miskovsky Nicholas M. , Cutler Paul H. 
Published: April 2011

ABSTRACTWe present simulations of field emission from carbon nanotubes, using a transfer-matrix methodology. By repeating periodically a basic unit of the nanotubes in the region preceding that containing the extraction field, specific band-structure effects are included in the distribution of incident states, i.e. those entering the field region. The structures considered are the metallic (5,5) and the semiconducting (10,0) single-wall carbon nanotubes. The total-energy distributions of incident states show the gap of the (10,0) and the expected flat region for the (5,5) nanotube. The field-emitted electron energy distributions contain peaks, which are sharper for the (10,0) structure. Except for peaks associated with van Hove singularities in the distribution of incident states or with the Fermi level in the case of a metallic structure, all peaks are shifted to lower energies by the electric field.
Field Emission Site Densities of Nanostructured Carbon
Authors: Cui J B , Robertson J , Milne W I 
Published: April 2011

ABSTRACTThe field emission properties of nanostructured carbon films deposited by cathodic vacuum arc in a He atmosphere have been studied by measuring the emission currents and the emission site density. The films have an onset field of ∼3 V/μm. The emission site density is viewed on a phosphor anode and it increases rapidly with applied field. It is assumed that the emission occurs from surface regions with a range of field enhancement factors but with a constant work function. The field enhancement factor is found to have an exponential distribution.
Effects of Sulfur Concentration on the Electron Field Emission Properties of Nanocrystalline Carbon Thin Films
Authors: Gupta S. , Weiner B. R. , Weiss B. L. , Morell G. 
Published: April 2011

ABSTRACTThe electron field emission properties of sulfur-assisted nanocrystalline carbon (n-C: S) thin films grown on molybdenum substrates by hot-filament CVD technique using methane-hydrogen (CH4/H2) and hydrogen sulfide-hydrogen (H2S/H2) gas mixtures were investigated. The field emission properties of the S-assisted films are reported as a function of sulfur concentration. The incorporation of S caused structural and microstructural changes that were characterized with SEM, AFM and Raman spectroscopy (RS). The S-assisted films show smoother surfaces and smaller grains than those grown without. The lowest turn-on field measured was around 4.5 – 5.0 V/μm films grown with 500 ppm of hydrogen sulfide and at 900 °C. The electron field emission properties of S-assisted films were also compared to those grown without sulfur (i.e., intrinsic). An inverse correlation between the threshold field (Ec) and sulfur concentration was found. These finding are attributed to defect induced states within the electronic band structure.
Studies on the Interaction of Water-Soluble Fullerols with BSA and the Effects of Metallic Ions
Authors: Bingshe Xu , Xuguang Liu , Xiaoqin Yan , Jinli Qiao , Weijun Jin 
Published: April 2011

ABSTRACTThe interaction of water-soluble C60 derived fullerols with bovine serum albumin (BSA) in physiological environment was studied in detail by the fluorescence method. Experiments showed that the interaction of fullerols with BAS is mainly in the manner of non-covalent hydrogen bond. Based on the measurements of fluorescence intensity, the apparent binding constant K and the binding site number n were obtained with K=4000 and n=1, and the energy transfer efficiency in the reaction is 0.63. Besides, the effects of metallic ions such as Cu2+, Fe3+ and Cr(VI) on the interaction of fullerols with BSA were investigated. It was found that the effects of the metallic ions are quite different from each other. Low concentrations of Cu2+ can promote the interactions between fullerols and BSA, while high concentrations of Fe3+ or Cr(VI) favorite the interactions between fullerols and BSA.
Effect of Crystalline Structure and Impurity Content of C60 Thin Films on the Order/Disorder Phase Transition
Authors: Katz Eugene A. , Faiman David , Shtutina Svetlana , Isakina Aleksandra P. , Yagotintsev Konstantin A. 
Published: April 2011

ABSTRACTNear the temperature of 260 K, C60 crystal is known to undergo a first order phase transition, associated with changes in molecular rotations. The present paper reports the effect of the crystalline structure and impurity content of C60 thin films on their structural behavior near this phase transition. Polycrystalline C60 films with different grain sizes and oxygen content were obtained by varying the conditions of their vacuum deposition and post-grown exposure. Temperature-resolved X-ray diffraction in the range 300 – 15 K was used to determine the lattice parameter and its changes near the phase transition temperature. Decrease in grain sizes and increase in oxygen content of the films are found to lead to a gradual reduction in the discontinuity in lattice parameter and the transition temperature.
Characterizations of HgTe nanocrystals induced by controlled precipitation in PbTe-4HgTe semiconductor alloys
Authors: Lee Manjong , Kim Choong-Un 
Published: April 2011

ABSTRACTThis paper reports the observation of HgTe precipitate formation and its subsequent evolution in a PbTe semiconductor matrix containing 4 mol. % HgTe (PbTe-4HgTe) produced by a controlled precipitation process. The controlled precipitation process is being developed as a new way to produce a large number of quality semiconductor nanocrystals more simply than the conventional methods. Characterization of the HgTe precipitates resulting from application of controlled precipitation to the PbTe-4HgTe alloy system provides evidence that this method is effective in generating nanocrystals. Transmission electron microscopy of the processed alloys reveals that HgTe precipitates are extremely small in size, maintain a coherent interface, and experience a unique shape evolution with aging.
AFM-Based Nanomechanical Properties and Storage of Dentin and Enamel
Authors: Habelitz Stefan , Balooch Mehdi , Marshall Grayson W. , Breunig Thomas M. , Marshall Sally J. 
Published: April 2011

ABSTRACTThis study evaluated the affects of 2 different solutions, e. g. deionized water and Hanks' Balanced Salt Solution (HBSS), on nanohardness and elastic modulus of dentin and enamel from human third molars at storage times of 0, 1, 7, 14 and 28 days using a modified AFM (Triboscope). The pH values of the solutions were monitored throughout the test periods. Storing the specimens in deionized water resulted in a large decrease of mechanical properties, e.g. the reduced elastic modulus of dentin decreased from 24.0 ±1.5 GPa to 21.0 ±1.6, 8.6 ±1.1 and 5.2 ±1.1 GPa for storage times of 1, 7 and 14 days, respectively. Mechanical properties of dentin and enamel dropped by more than 12% after one day and more than 50% after a week when stored in deionized water. The observed changes in mechanical response were attributed to a superficial demineralization process during storage. In contrast, storing teeth in HBSS did not significantly alter the mechanical properties of dentin or enamel over the time studied.
Surface Initiated Polymerization (SIP) on Nanoparticle Surfaces: Demonstration of First Principles and Preparation of Nanocomposite Materials
Authors: Advincula Rigoberto , Zhou Qingye , Mays Jimmy 
Published: April 2011

ABSTRACTTo investigate the grafting of polymer chains onto nanoparticles (metal, semi-conductor, inorganic, etc) and nanostructured (patterned) surfaces, we have investigated anionic surface initiated polymerization (SIP) on a variety of surfaces. Understanding the surface chemistry issues involved is critical for future applications and protocols. SIP of polystyrene from Silicate and clay nanoparticles surfaces have been made by the living anionic polymerization method with 1,1-diphenylethylene (DPE) initiation sites attached to nanoparticle surfaces using chlorosilane and amino functional groups. Model studies were initially done on flat Si-wafer surface and recently with Au surfaces. For the nanoparticles, the grafted polymers were cleaved and characterized by FTIR, NMR, AFM, TGA and SEC. Polymers grafted from nanoparticle surfaces show higher polydispersity and lower molecular weight than those formed in solution. We observed that diffusion of the monomer, stability of the initiator attachment to the surface, and aggregation of the particles controls the properties of the grafted polymers on particle surfaces. On the other hand, the use of the anionic polymerization method on surfaces allows the possibility of combining a variety of polymers (organic) with various nanoparticle and surfaces (inorganic) for the preparation of hybrid nanocomposite materials.
Sub-10 nm Gold Nanoarrays for Tethering Single Molecules
Authors: Chan Vanessa Z-H. , Codd Sarah L. , van der Helm Mark J. , Spatz Joachim P. , Röcker Carlheinz , Ulrichs Nienhaus G. , Levi Stefano , van Veggel Frank C. J. M. , Reinhoudt David N. , Möller Martin 
Published: April 2011

ABSTRACTNanometer sized gold patterns were produced with controlled spacings using the combination of a top-down (e-beam lithography) and a bottom-up (macromolecular chemistry) technique. Sub-10 nm nanoparticle arrays on silicon consisting of gold nano particles separated by micro meter spacings were fabricated with this approach. Using electron beam lithography, templates comprising of 150 nm to 1 μm sized trenches, holes and aperiodic patterns were made in an electron-beam resist. Block copolymer micelles were then patterned into this template by spincoating. The micelles acted as positioners for a nanometer sized gold precursor that is sequestered within its core. Subsequent removal of the resist layer left an array of Au loaded organic micelles ordered according to the pattern of the template. Exposure of this substrate to a hydrogen plasma removed the organic block copolymer and resulted in an array of sub-10 nm gold nanoparticles/nanoclusters with micron separations. The gold was then used as an anchor point for the tethering of functional molecules in order to localize fluorescent molecules.
Study of Catalytic Methane Oxidation Over Pd Supported on Nanocrystalline CeO2: Effects of Calcination and Pd Loading
Authors: Oh Seung H. , Everett Michael L. , Hoflund Gar B. , Seydel Johannes , Hahn Horst W. 
Published: April 2011

ABSTRACTThe catalytic oxidation of methane was studied over palladium supported on nanocrystalline ceria. Three palladium weight loadings (1, 5, and 10 wt%) were tested after calcining at 500 °C, at 280 °C and after no calcination at all. For the 5 and 10 wt% loadings, the 280 °C-calcined and non-calcined catalysts exhibit enhanced activity after several heating and cooling cycles. Calcining these same catalysts at 500 °C results in a systematic decline in activity. For all pretreatments the 1 wt% Pd catalyst exhibits decreasing activity. For the 5 and 10 wt% Pd loadings, the non-calcined catalysts are more active than the 280 °C-calcined catalysts, which are more active than the 500 °C-calcined catalysts. For the 1 wt% Pd catalyst, the opposite is true. The catalyst activity improves as the Pd loading is increased.
Charge-influenced structural properties of electrically connected platinum nanoparticles
Authors: Viswanath R. N. , Weissmüller J. , Würschum R. , Gleiter H. 
Published: April 2011

ABSTRACTWe present results of a study motivated by the recent suggestion that the properties of nanocrystalline materials with a large surface-to-volume ratio can be tuned by inducing spacecharge regions at interfaces by means of an applied voltage. As an example, we investigate the reversible variation of the lattice constant of platinum nanoparticles immersed in an aqueous 1M KOH electrolyte as a function of applied potential. It is found that a reversible volumetric strain of up to 1.2 % can be induced, corresponding to pressures of up to 3.2 GPa. We present the experimental set-ups for in-situ X-ray diffraction with an electrochemical cell. The variation of the space charge at the metal-electrolyte interface results in a variation of the surface stress f as a function of the applied potential, which is not an electrocapillary effect.