bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly Luminescent Composite Films from Core-Shell Oxide Nanocrystals
Authors: Buissette Valérie , Moreau Mélanie , Gacoin Thierry , Mercier Thierry Le , Boilot Jean-Pierre 
Published: April 2011

ABSTRACTLuminescent nanocrystals can find interesting applications for the elaboration of light emitting transparent materials. The work described here is based on the use of lanthanide doped vanadate (YVO4:Eu) and phosphate (La, Ce, Tb)PO4-0, 7H2O nanoparticles grown through aqueous colloidal synthesis, with average sizes below 10 nm. The well-dispersed colloids are transparent and respectively exhibit red and green luminescence under U.V. excitation with high luminescence yields (20 – 50 %). Improvement of luminescence properties of the nanocrystals is achieved through the elaboration of core/shell nanostructures, obtained after the growth at the surface of an amorphous silica shell or a crystalline lanthanum phosphate shell. Surface derivatization is further achieved through the controlled growth of an organically modified silica coating using a functionalized silane precursor. Concentrated sols are obtained, which are highly luminescent and well-dispersed. They can be spin-coated on various substrates, leading to perfectly transparent and highly luminescent thin films. Multi-layers films and heating treatments are performed, leading to optimized materials.
Microscopic Theory of Surface-Enhanced Raman Scattering in Noble-Metal Nanoparticles Vitaliy
Authors: Pustovit N. , Shahbazyan Tigran V. 
Published: April 2011

ABSTRACTWe study the role of a strong electron confinement on the surface-enhanced Raman scattering from molecules adsorbed on small noble-metal nanoparticles. We describe a novel enhancement mechanism which originates from the different effect that confining potential has on s-band and d-band electrons. We demonstrate that the interplay between finite-size and screening efects in the nanoparticle surface layer leads to an enhancement of the surface plasmon local field acting on a molecule located in a close proximity to the metal surface. Our calculations, based on time-dependent local density approximation, show that the additional enhancement of the Raman signal is especially strong for small nanometer-sized nanoparticles.
Layered Double Hydroxides as a Matrix for Luminescent Rare Earth Complexes
Authors: Zhuravleva Natalia G. , Eliseev Andrei A. , Lukashin Alexey V. , Kynast Ulrich , Tretyakov Yuri D. 
Published: April 2011

ABSTRACTIn the present work new luminescent materials with high quantum efficiencies based on layered double hydroxides (LDH) were obtained. Intercalation of complexes into the interlayer space of LDH doesn't affect their luminescent properties, forming non-volatile solid state material with good optical properties. The Coulomb interactions between LDH layers and complex can result in a change of complex structure in comparison with free complexes and in decreasing the number of the organic ligands per Ln atom. The energy transfer in the system was also studied.
Evolution of Porosity and Morphology in Alkylene-Bridged Polysilsesquioxane Xerogels as a Function of Gel Aging Time
Authors: Loy Douglas A. , Small James H. , DeFriend Kimberly A. , Wilson Kennard V. , Minke McKenzie , Baugher Brigitta M. , Baugher Colleen R. , Schneider Duane A. , Shea Kenneth J. 
Published: April 2011

ABSTRACTAging of silica gels before drying is known to result in significant changes in xerogel morphology, porosity and properties. In this study, the influence of aging gels on the porosity and morphology of alkylene-bridged polysilsesquioxane xerogels was examined. Gels of hexylene-, heptylene, octylene, nonylene, and decylene-bridged polysilsesquioxanes were prepared by the sol-gel polymerization of the respective bis(trimethoxysilyl)alkane monomers under acidic or basic conditions in methanol and in tetrahydrofuran. The gels were aged 3, 7, 14, 28, 35, 42, 49, and 56 days before drying to afford xerogels. The xerogels were characterized by nitrogen sorption porosimetry. Xerogels prepared in THF were non-porous. Those prepared and aged under basic conditions in methanol or tetrahydrofuran exhibited coarsening of porosity with aging time. With the exception of the hexylene-bridged gels, those prepared and aged in acidic methanol showed little change with aging. The surface area of the hexylene-bridged xerogels nearly tripled with aging times of up to several weeks, then decreased, for the gels aged for more than two weeks, to around 100 meters squared per gram.
Hybrid Materials Approach In The Design Of Electrodes And Electrolytes For Energy Storage And Conversion
Authors: Cuentas-Gallegos Karina , Lira-Cantú Mónica , Casañ-Pastor Nieves , Asensio Juan A. , Gómez-Romero Pedro 
Published: April 2011

ABSTRACTThe integration of electro-ionically active inorganic species in polymer matrices allows for the design of either electrode or electrolyte materials depending on the conducting or insulating properties of the polymer used. Conducting polymers can be used as the basis for a variety of hybrid electrode systems, whereas other polymers such as polybenzimidazoles have been used as electrolyte membranes by themselves or in combination with inorganic solid acids. We will discuss the general approach of hybrid design with this in mind and specifically we will describe our recent results on the use of polyoxometalate-containing hybrids in energy storage and conversion devices. In this respect we have worked in our laboratory on electrochemical supercapacitors and fuel cells but emphasis should be made on the broader potential fields of application of this type of materials.
Ligand Control of Semiconductor Nanocrystals for Efficient Carrier Injection
Authors: Murase Tomohide , Asami Harumi , Kamiya Itaru 
Published: April 2011

ABSTRACTInorganic/organic hybrid material of CdSe/ZnS core/shell nanocrystals (NCs) covered with organic ligands was prepared with ligand exchange reaction in order to facilitate carrier injection into NCs through the organic ligands. The organic ligands used in this study, 2-naphtalenethiol and bathophenanthroline, were selected as model compounds according to adjustment of highest occupied molecular orbital and lowest unoccupied molecular orbital of the ligand to valence band maximum and conduction band minimum of the CdSe NCs, respectively. The prepared hybrid NCs easily disperse in polar organic solvents such as CHCl3 and show photoluminescence only from the CdSe/ZnS core/shell NCs. Current-voltage characteristics of the ligand exchanged NCs thin films sandwiched between electrodes were investigated. It was shown that conductivity of the film was improved by the introduction of carrier injecting ligands in comparison to the ligand unexchanged trioctylphosphine oxide-capped CdSe/ZnS NC thin film.
Single-Step Microstructure Patterning in Titania-Doped Sol-Gel Glassy Thin Films with Electron Beams
Authors: Luo Xinshi , Zha Congji , Luther-Davies Barry 
Published: April 2011

ABSTRACTTo achieve a simplified microstructure patterning process, patterning in thin films with a singlestep exposure to UV-light or E-beam process for fabrication of integrated optical waveguides and components is of great interest in optics, because the complicated structure developing stage by wet chemical or plasma etching is not required. In this paper, we describe our study on the microstructure patterning in TiO2-doped hybrid glassy polymer thin films by irradiating with focused E-beam. An anhydrous sol-gel process based on hydrolysis and condensation of metal alkoxides with boric acid under non-hydrous conditions was applied to homogeneously incorporating TiO2into silica network, and transparent glassy TiO2-doped thin films with varied TiO2concentrations (up to 40 mol%) were prepared by spin coating the hybrid polymer onto fused silica substrates and silicon wafers. The TiO2-doped hybrid material showed a low OH absorption, low optical losses at the telecommunication windows (<0.40 dB/cm at 1550 nm and <0.20 dB/cm at 1310 nm respectively), good thermo-optical linearity and good thermal stability up to 200 °C. Single-step direct surface patterning in the TiO2-doped hybrid glassy films with focused electron beams irradiation showed that fine structure with resolution at submicron level can be fabricated. As the process does not need a developing (etching) process, the profiles of the lines fabricated by the E-beam direct writing showed few distortion. The high precise patterning microstructure with submicron feature sizes in the TiO2-doped hybrid glassy thin films may provide potentials for applications to the fabrication of optical gratings.
New High-Dielectric-Constant Polymer-Ceramic Composites
Authors: Arbatti Milind , Shan Xiaobing , Cheng Z.-Y. 
Published: April 2011

ABSTRACTA ceramic-powder polymer composite, making use of a newly developed ceramics - CaCu3Ti4O12 (CCTO) - that has a giant dielectric constant as the filler, is developed. In this work, poly(vinylidene fluoride - trifluoroethylene) [P(VDF-TrFE)] 55/45 mol% copolymer was used as matrix. It is found that the wettability between the copolymer and CCTO is poor, which makes the solution cast composites have a poor uniformity. The uniformity and thus the dielectric constant of the composites can be significantly improved by using hot-press technology to form “sandwich” structure. It is also found that the thermal annealing process can improve the dielectric constant of the composite. The experimental data show that for the flexible composites the dielectric constant at 1 kHz can reach more than 300 at room temperature and more than 700 at ∼70 °C.
Hybrid materials for Optical Limiting
Authors: Örtenblad Marcus , Parola Stephane , Chaput Frédéric , Desroches Cédric , Sigala Catherine , Létoffé Jean Marie , Miele Philippe , Baldeck Patrice L. , Eliasson Bertil , Eriksson Anders , Lopes Cesar 
Published: April 2011

ABSTRACTMaterials based on alkynyl platinum derivatives and thiacalixarenes were prepared through the sol-gel process The molecular species were grafted to the matrix (class II hybrid) in order to maximise the concentration and the stability of the final solid-state material Broadband optical limiting performance in the visible wavelength region was observed in the prepared materials Thermomechanical characterisation of the matrix is also discussed.
The Synthesis and Characterization of Energy-Conducting Polymers with Pendant Inorganic Chromophores
Authors: Alstrum-Acevedo James H. , DeSimone Joseph M. , Schauer C. K. , Papanikolas John M. 
Published: April 2011

ABSTRACTWe are interested in the synthesis, characterization, and performance evaluation of functional nanoscale materials comprised of a polymeric scaffold with appended cationic transition-metal lumiphores. We have developed a methodology to prepare, spectroscopically characterize, and evaluate a series of organic copolymers functionalized with inorganic chromophores. Preparation of these hybrid systems first involves the synthesis of a linear AB diblock copolymeric scaffold in which A is polystyrene (PS) and B is poly(p-tert-butoxycarbonyloxystyrene) (PStBOC), using Reversible Addition-Fragmentation chain-Transfer (RAFT) radical polymerization. The PStBOC block (B) was converted into poly(4-hydroxystyrene) by acid hydrolysis of the t-BOC moieties, and Ru(II) trisbipyridyl complexes were covalently appended using standard ester coupling reagents. These lumiphores were selected due to their strong absorbance in the visible spectrum, chemical/photochemical stability, useful redox properties, and long-lived excited state lifetimes. Attachment of the cationic transition-metal chromophores to block B of these linear AB diblock copolymeric arrays is expected to promote solid-state self-assembly into nanoscale structures. The metal-loaded macromolecular assemblies were characterized spectroscopically and the determination of the solid-state morphology of films of these materials was investigated using Transmission Electron Microscopy (TEM).
Interlamellar Incorporation of Charged Polymer Nanobeads into Sodium Montmorillonite
Authors: Khvan Svetlana , Lee Sang-Soo , Kim Junkyung 
Published: April 2011

ABSTRACTComplete delamination of clay in polymer matrix has been strongly prohibited due to strong adhesion of guest polymer chains between hydrophilic clay as well as degradation and desorption of organic materials in the gallery at high temperature. Incorporation of charged nanosized polystyrene beads directly into the gallery of pristine clay through exfoliation-exchange mechanism has been proposed to overcome the drawbacks.Synthesis of polymer nanobeads via emulsifier-free emulsion polymerization allowed to achieving formation of particles of appropriate particle size and surface charge density. Surface characterization, performed with XPS and ToF SIMS, has provided the results on the existence and the nature of the functional groups on the polymer particle surface, which have been found to be in a good compliance.Morphology of polymer-incorporated clay was observed from TEM, FE-SEM images. Study on mechanism of incorporation via XRD, XPS, ToF-SIMS suggested that adsorption of polymer nanobeads through cationic exchange of intergallery cation of clay for onium ion at the surface of polymer nanobead not only improves compatibility of clay with polymer matrix, but, what is essential, dramatically promotes expansion of clay gallery.
Spontaneous Formation of Ridges on Patterned Mesas and Their Role in the Evolution of Step Arrays
Authors: Chang Kee-Chul , Blakely Jack M. 
Published: April 2011

AbstractMesa structures fabricated on Si(111) surfaces have been found experimentally to develop step arrays with large spacing of the order of a micron or more after annealing at temperatures where sublimation becomes important. Ridges around the edges initially develop during annealing and form barriers to step motion before eventually breaking down. This produces an array of steps of the same sign with a few wide terraces. Computer simulations using one dimensional Burton, Cabrera and Frank (BCF) theory including attachment-detachment rates and step-step repulsion for this configuration show that the terraces evolve under different dynamics depending on the terrace widths. For large terrace widths, sublimation dominates the step dynamics and the Ehrlich-Schwoebel effect is negligible. Sinusoidal terrace width distributions result in this case. The experimentally measured step distribution has such a sinusoidal shape suggesting that the step dynamics is sublimation dominated on the mesas after ridge breakdown.
Photo Etching of Polyimide Thin Film by TiO2 Micro Wire Prepared Using Phase Separation-Selective Leaching Method
Authors: Sone Y. , Nishio K. , Yasumori A. 
Published: April 2011

ABSTRACTTiO2 photocatalysts have a strong oxidation ability for organic compounds under UV irradiation. The surfaces of polyimide and polymethyl methacrylate (PMMA) were photocatalytically machined using a porous TiO2 wire prepared by phase separation and selective leaching with elongation. After UV irradiation, these surfaces were decomposed along the length of the TiO2 wire. Such surface decomposition depended on the irradiation angle of UV light and irradiation time. The machining rate of PMMA was higher than that of the polyimide.
Topography Evolution of Si (001) Substrate Fabricated by Ar+ Ion Beam Sputter Etching
Authors: Kim Hyung Seok , Suh Ju Hyung , Park Chan Gyung 
Published: April 2011

ABSTRACTSelf-formed nanopatterns on Si (001) substrates fabricated by ion beam sputter etching were investigated by atomic force microscopy (AFM). The ion beam sputtering was performed with an Ar+ ion beam produced from a Kaufman type ion gun. In order to fabricate the periodic nanoscale patterns on Si surface, the effects of sputter parameters such as ion energy, flux, incident angle and etching time on surface morphology was investigated. As a result, nanometer scale ripples and 3-dimensioal nanodots were formed uniformly after ion beam sputtering. The surface morphology of Si was significantly dependent on incident angle and ion beam flux.
Fabrication of High Aspect Ratio Nanoscale Pit Using Carbon Nanotube Probe
Authors: Arima Norikazu , Matsumuro Akihito 
Published: April 2011

ABSTRACTWe developed a method to fabricate nanoscale pits having high aspect ratio, using a scanning tunneling microscope with an attached carbon nanotube (CNT) probe. CNT probes used in this study were synthesized by the pulling method. The nanostructures were produced in Au thin film in an ambient pressure and room temperature. The results of our experiment show that a threshold value exists for the fabrication of the pits between 1 V and 2 V. The depth and diameter of the pit increased with the increase in the bias voltage and tunnel current, respectively. Consequently, a bias voltage of 3 V and tunnel current of 4 nA were found to be the optimum conditions for a high aspect ratio nanoscale pit fabrication. In changing the fabrication time at the optimum conditions, the depth of the pit increased with the increase in the fabrication time, with little change in the diameter of the pit. This demonstrates that CNT probes can be useful for fabricating nanoscale structures.
Controlled growth of nanowires using annealing and pulsed laser deposition
Authors: Park Hyun D. , Hogan Timothy P. 
Published: April 2011

ABSTRACTA new nanowire growth technique using annealing and pulsed laser deposition is described. The technique demonstrates the control in the precise nanowire growth temperature thereby yielding higher quality nanowires than obtained from simple annealing alone. InSb substrate and gold target were used to demonstrate the new technique. The results from the variation of gold deposits from 2.5 mins to 40 mins at the fixed growth temperature of 510 °C are discussed.
Nanopatterning of GaAs(110) vicinal surfaces by hydrogen-assisted MBE
Authors: Crespillo M. L. , Sacedón J. L. , Joyce B. A. , Tejedor P. 
Published: April 2011

ABSTRACTThe effect of atomic hydrogen on the growth mode and surface morphology of GaAs(110) thin films grown by molecular beam epitaxy (H-MBE) has been studied for different kinetic regimes using atomic force microscopy (AFM). Growth in the Ga supply-limited regime after H-assisted oxide removal leads to the formation of multi-atomic step arrays by step bunching with a very uniform terrace size distribution in the 80 nm range. Growth under As-deficient conditions after H-assisted oxide removal induces a rapid self-organization of the GaAs(110) surface into a ridge pattern along the <001> tilt direction, which is broken down into a 3D mound morphology when H is also present during growth. A chacteristic nanofacetting of the surface with very straight <1–10> -type steps is observed at high temperatures regardless of atomic hydrogen being used during oxide desorption and/or epitaxial growth.
Photocatalysis of Columnar TiO2 Thin Films
Authors: Suzuki Motofumi , Kishimoto Kazuaki , Maekita Wataru , Nakajima Kaoru , Kimura Kenji 
Published: April 2011

ABSTRACTPhotocatalysis of oblique columnar TiO2 thin films has been investigated as a function of thickness using photobleaching of methylene blue (MB). The degradation rate of MB depends on the thickness of the films, although no significant differences in the columnar morphology, crystallinity and optical absorption are found. The relation between the degradation rate and the thickness is well described by a simple model, in which the degradation rate at a certain depth is proportional to the intensity of ultra violet (UV) light. The photocatalytic active thickness is estimated at approximately 200 nm. Thus the interior surface of the oblique columnar TiO2 thin films works well as photocatalyst.
IN SITU Tem Study of Electron Beam Stimulated Organization of Three-Dimensional Void Superlattice in Caf2
Authors: Ding T. H. , Zhu S. , Wang L. M. 
Published: April 2011

ABSTRACTCaF2 is widely adopted as deep-UV window material and thin film optical coating. It has been known that ordered defect superlattices may form in electron irradiated CaF2.[1] However, the nature of the defects on the superlattice point (i.e., Ca colloids or voids) has not been certain and the self-organization mechanism has not been fully understood. In this study, single crystal CaF2 were irradiated under 200 keV electron beam at room temperature with in situ TEM observation of the dynamic process of defect ordering. The superlattice reached steady state after an electron dose of 1×1021e-/cm2 with void radius about 5 nm. Videos recorded during the in-situ observation reveal the dynamic self-organization process of the void superlattice. Coalescence was prevalent at the initial stages. Migration and preferential growth were dominant at the final stages of the superlattice formation. At a dose higher than 3×1021 e-/cm2 the superlattice structure was destroyed. These critical doses of void superlattice formation and deformation seem to be independent of dose rate. The anisotropic diffusivity of the migrating “molecules” may explain the superlattice formation.
Laser and particle beam irradiation effects in amorphous metals
Authors: Sorescu Monica 
Published: April 2011

ABSTRACTIn view of the potential use of amorphous magnets as radiation-resistant materials, we performed a comparative study between laser and particle beam induced effects in amorphous alloy systems. We irradiated Fe81B13.5 Si3.5C2, Fe40Ni38Mo4B18, Fe66Co18B15Si1 and Fe72.6Cr22Al4.8Si0.3Y0.3 with pulsed laser radiation as well as with high (W=7 MeV) and low energy (W=30 and 50 keV) electrons and with 2.8 MeV alpha particles. The irradiation effects in these systems were investigated using several complementary techniques: transmission and conversion electron Mössbauer spectroscopy, magnetometry and electron microscopy. We were able to deduce details of the mechanism of magnetic texture formation and of the amorphous-to-crystalline phase transformations in the studied amorphous alloys.
Microstructure Development in High-Temperature Mo-Si-B Alloys
Authors: Sakidja R. , Perepezko J. H. 
Published: April 2011

ABSTRACTMo-Si-B alloys are considered as potential high temperature structural materials due to their high melting points (above 2000°C) and excellent oxidation resistance attributed to their self-healing characteristics over an extended temperature range. In the current study, the effect of alloying additions to achieve lower weight density and microstructure stability has been examined. The critical factor to the alloying additions appears to be the stability of the high melting ternary-based T2 borosilicide phase.