bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanoscale Measurements of Water Loss during Desiccation of Biological Cell Suspensions
Authors: Mittal S. , Devireddy R.V. 
Published: April 2011

ABSTRACTThere is an urgent need to protect and conserve the endangered species of the world. Desiccation, or the phenomenon of anhydrobiosis, offers the attractive possibility of low cost, long term storage of reproductive tissues and cells from endangered species at ambient temperatures. Biophysical optimization of anhydrobiosis procedures requires dynamic and accurate quantification of the rate of moisture loss during a prescribed desiccation protocol. Engineered microstructures can serve as a multifunctional and highly sensitive method to measure the rate of moisture loss. This study presents a novel ultrasound based (resonant) mass sensor to quantify water loss during a drying process by measuring the corresponding shift in the resonant frequency of a micromachined vibrating structure. To model the proposed ultrasound based sensor, we performed a static (stress) and dynamic (frequency change with change in imposed mass) analysis. The results suggest that by tailoring the dimension of the vibrating element appropriate sensitivity can be achieved.
Finite Element Modeling of Bone Ultrastructure as a Two-phase Composite
Authors: Oyen Michelle L. , Ko Ching-Chang 
Published: April 2011

ABSTRACTBone is a composite material with a mineral hydroxyapatite (HA) phase and an organic collagen-based phase. Each phase represents about half the material by volume. The precise arrangement of these components at the ultrastructural level is unclear but of great interest in understanding the mechanical functionality of bone. Nanoindentation tests show that the elastic modulus of bone is primarily distributed between 10 GPa and 30 GPa. In this study we examine different ultrastructural arrangements of collagen and apatite phases, to test different proposed models for bone composite ultrastructure within the same finite element modeling framework. Different configurations of the composite are considered, including (a) a compliant phase with stiff reinforcing particles, (b) a stiff phase with compliant reinforcing particles, and (c) an interpenetrating two-phase (co-continuous) composite. An elastic modulus of 100 GPa is used for the mineral phase and 100 MPa for the organic phase, with volume fraction of each phase fixed at 0.5. Stiff phase continuity (as the only continuous phase in 2D and 3D or as one of two continuous phases in 3D) gives rise to effective composite elastic modulus values of 25–35 GPa, similar to the experimental results for bone modulus. Isotropic models with compliant phase continuity only give rise to moduli around 300 MPa, far below experimental results. Anisotropy was evaluated by calculating effective moduli in parallel and transverse directions relative to the primary axes of rectangular particles. High aspect ratio, stiff particles embedded in a compliant matrix do result in a substantially stiffened composite in the direction of the particles when compared to symmetric particles. However, this configuration results in a material with an effective elastic modulus of 2 GPa along the particle direction but a transverse modulus of only 250 MPa. Decreased interparticle spacing in the direction of loading was the mechanism for stiffening parallel to the particle long axis, demonstrating an indirect effect of particle aspect ratio. Although many bone models have considered the mineral as a particle reinforcement phase, the current results suggest this arrangement would not give rise to a material with bonelike properties, particularly when transverse modulus is considered, regardless of the particle geometry. Some degree of continuity of the mineral phase is required for bone-like elastic modulus values and thus a partially to fully co-continuous ultrastructural arrangement of phases is supported.
Theoretical Study on Open-Shell Nonlinear Optical Systems
Authors: Nakano Masayoshi , Kishi Ryohei , Nakagawa Nozomi , Nitta Tomoshige , Kubo Takashi , Nakasuji Kazuhiro , Kamada Kenji , Ohta Koji , Champagne Benoît , Botek Edith , Yamada Satoru , Yamaguchi Kizashi 
Published: April 2011

ABSTRACTThe static second hyperpolarizabilities (γ) of open-shell organic nonlinear optical (NLO) systems composed of singlet diradical molecules are investigated using ab initio molecular orbital (MO) and density functional theory (DFT) methods. It is found that neutral singlet diradical systems with intermediate diradical characters tend to enhance γ as compared to those with small and large diradical characters. This suggests that the diradical character is a novel control parameter of γ for singlet diradical systems.
Strong Enhancement of the Two Photon Absorption Cross Section of Porphyrin J-Aggregates in water
Authors: Collini Elisabetta , Ferrante Camilla , Bozio Renato 
Published: April 2011

ABSTRACTStrong enhancement of the two photon absorption (TPA) cross section at 812 nm is observed for tetrakis(4-sulphonatophenyl)porphyrin diacid (H4TPPS2-) when a J-type aggregate is formed in water, in comparison to the one observed for the H4TPPS2- monomer in mixture of water, DMSO and urea. Open aperture Z-scan experiments, performed with ultra-short laser pulses, are employed to measure the TPA absorption cross section. The observed enhancement is discussed in terms of possible electronic cooperative effects in the aggregate.
Novel iridium complexes with polymer side-chains
Authors: Holder Elisabeth , Marin Veronica , Tekin Emine , Kozodaev Dmitry , Meier Michael A. R. , Lohmeijer Bas G. G. , Schubert Ulrich S. 
Published: April 2011

ABSTRACTThe focus of the presented research lies on the synthesis of novel charged iridium(III) compounds with potential applications in light-emitting electrochemical cells. The design involves iridium(III)-based materials with polymer side-chains leading to linear light-emitting polymer arrangements.To study the electro-optical properties of such light-emitting polymers conventional and combinatorial deposition methods are used. Straightforward screening approaches are introduced. The combinatorial efforts engage the processing via inkjet printing and the screening of the optical properties using plate reader technologies based on steady state UV-vis and fluorescence. Furthermore, the morphological properties are investigated using optical interferometry and atomic force microscopy (AFM). Overall it can be shown that novel materials can be deposited revealing high-quality thin films, which allow the screening of electro-optical features using combinatorial methods. Some initial local current density studies by AFM have also been performed to characterize the current injection and transport properties of the novel materials.
Size-dependence of the Linear and Nonlinear Optical Properties of GaN Nanoclusters
Authors: Pineda Andrew C. , Karna Shashi P. 
Published: April 2011

ABSTRACTIn this paper, we present the results of our first-principles quantum mechanical studies of the electronic structure, geometry, and linear and nonlinear optical (NLO) properties of tetrahedral Gam Nm (m=1, 4, 7, 17) atomic clusters. Our calculated results suggest that the linear and NLO properties both exhibit a strong dependence upon cluster size and shape (geometry). However, the size- and the geometry-dependences are more pronounced for the NLO properties than for the linear optical properties. For clusters containing equal numbers of Ga and N atoms, an open-structure with no network-forming ring has a much larger second-order NLO coefficient than a cluster with a closed ring structure.
Photoelectrochemical Behaviors of Pt/TiO2 Nanocomposite thin films Electrodes Prepared by PLD/Sputtering Combined System
Authors: Sasaki Takeshi , Nichols William T. , Yoon Jong-Won , Koshizaki Naoto 
Published: April 2011

ABSTRACTSputtering of TiO2 and pulse laser deposition (PLD) of Pt were performed simultaneously to build the nanocomposite with homogenous dispersion of Pt in TiO2 matrix. The films exhibited a pronounced decrease in the optical band gap energy with increasing Pt content indicating the formation of new energy states in the optical gap of TiO2 matrix. As-deposited nanocomposite films were amorphous and crystallized to Pt metal and rutile type of TiO2 after post-annealing at 600 °C. Pt nanoparticle size in the annealed nanocomposite films increased from 6 to 9 nm with the repetition rate of the laser. The photoelectrochemical measurements of the Pt/TiO2 nanocomposite films in aqueous 0.1 M Na2SO4 solution indicate that a dramatic increase in anodic photocurrent at 1.0 V vs. Ag/AgCl at the wavelength region of visible light occurred in annealed films. Pt nanoparticles in the matrix of TiO2 can play an important role in the optical and photoelectrochemical proprieties of Pt/TiO2 nanocomposite thin films.
From Raspberry-like to Dumbbell-like Hybrid Colloids through Surface-assisted Nucleation and Growth of Polystyrene Nodules onto Macromonomer-modified Silica Nanoparticles
Authors: Duguet Etienne , Reculusa Stéphane , Perro Adeline , Poncet-Legrand Céline , Ravaine Serge , Bourgeat-Lami Elodie , Mingotaud Christophe 
Published: April 2011

ABSTRACTColloidal particles with a controlled morphology combining both organic and inorganic parts were synthesized through a seeded emulsion polymerization process. Silica seed particles (from 50 to 150 nm in diameter) were first surface-modified by the adsorption of an oxyethylene-based macromonomer. Then, emulsion polymerization of styrene was carried out in presence of these particles, the formation of polystyrene nodules being highly favored at the silica surface in such conditions. The ratio between the number of silica seeds and the number of growing polystyrene nodules appeared to be one of the key parameters to control the morphology of the final hybrid nanoparticles. When this ratio is close to 1, original hybrid dumbbell-like nanoparticles were mainly obtained.
Novel Organosilanes for the Preparation of High Refractive Index Silicone Coatings
Authors: Chevalier Pierre M. , Ou Duan L. 
Published: April 2011

ABSTRACTSynthetic routes to high refractive index curable polyaromatics and halogenated aromatic functional silicone resins were developed. Organo silanes containing anthracenylmethyl-, naphthylmethyl- and iodobenzyl- groups were synthesized and used as precursors for the preparation of stable and soluble aryl-functional silicone resins. Alternatively the direct iodination of pre-formed aromatic-functional resins was investigated. We demonstrated the preparation of coatings with RI as high as 1.770 at 633 nm representing a significant optical enhancement as compared to traditional silicone and organic coatings.
Affinity Control of Aminopropylsiloxane-based Organic/Inorganic Hybrids for Optical Sensors
Authors: Katayama Shingo , Yamada Noriko , Awano Masanobu 
Published: April 2011

ABSTRACTThe aminopropylsiloxane-based organic/inorganic hybrid is known as a sensitive material toward NO2gas for optical sensing systems but it has the irreversible detection. The affinity of the aminopropylsiloxane-based organic/inorganic hybrid toward NO2gas was controlled by incorporating an Nb inorganic component derived from Nb(OC2H5)5into the hybrid structure. The amino groups had a strong coordination bond with hydrolyzed Nb(OC2H5)5and/or an acid-base pair with an oxoanion formed by hydrolysis of Nb(OC2H5)5. Thus, the strong solid-basicity of the aminopropylsiloxane-based organic/inorganic hybrid was weakened. The aminopropylsiloxane-based organic/inorganic hybrid containing an Nb inorganic component provided reversible sensing toward NO2gas in an optical sensing system. NO2is thought to be more weakly adsorbed because of the weakened basicity of the amino groups.
Modification and Characterization of Si-Based Nanobuilding Blocks Precursors for Hybrid Materials
Authors: Mammeri Fayna , Douja Najiba , Bonhomme Christian , Ribot François , Babonneau Florence , Dirè Sandra 
Published: April 2011

ABSTRACTNew functional nanobuilding blocks have been successfully synthesized by hydrosilylation of unsaturated alcohols with dimethylsiloxy isobutyl-POSS and further acylation with methacryloylchloride. The solvent influence on the reaction pathway has been studied, and reaction steps and final nano-objects have been characterized using multinuclear NMR and FTIR spectroscopy. The organic spacer chain length between the inorganic cage and the reactive methacrylate function has been changed in order to modify the reactivity of the final functional nanobuilding block in the polymerization process.
Evaluation of Polypyrrole Coating on Fe3O4 and Its Effect on Nanocomposite Properties
Authors: Liong S. , Harter A. W. , Moore R. L. , Rees W. S. 
Published: April 2011

ABSTRACTMagnetite (Fe3O4) nanoparticles were synthesized by chemical coprecipitation and were characterized using TEM, XRD, and VSM. XRD and TEM measurements indicate that the average particle size was approximately 10 nm. The nanoparticles were coated with polypyrrole using oxidative polymerization. TGA results show that the polypyrrole coating is 28.5wt%. TEM images indicate that the nanoparticles are bound in clusters by polypyrrole. Measurements show that nanoparticles may hinder curing of the polymer matrix, but they can be effective in producing composites with higher modulus and magnetic permeability at lower frequencies.
ORMOCER®s (Organic-Inorganic Hybrid Polymers) for Telecom Applications: Structure/Property Correlations
Authors: Kahlenberg Frank , Popall Michael 
Published: April 2011

ABSTRACTThe development and characterization of fluoroaryl functionalized organic-inorganic hybrid polymers for optical waveguide applications is presented. The materials are prepared from organoalkoxysilanes in a two-step process. The first step is the formation of the inorganic polysiloxane network by hydrolysis and polycondensation in order to obtain a soluble resin. This can be mixed with a photo initiator and applied onto a substrate as a photo-sensitive film. Micro patterns (waveguides with core and cladding) are then manufactured in a second step by exposure to UV-light through a mask. The polymers are characterized with respect to application in the fabrication of telecom optical waveguide devices. Thus, special attention is turned to optical losses in the telecom wavelengths at 1310 nm and 1550 nm as well as to refractive indices. During all stages of ORMOCER® preparation, structure-property correlations are deduced from presented characterization data.Various spectroscopic tools give an insight into network structures of polycondensate resins and cured hybrid polymer samples. 29Si-NMR in particular is used for the quantitative analysis of siloxane species. With the aid of molecular modeling, structural characteristics of oligomeric intermediates as determined by experiment are visualized. ORMOCER® resins with low optical losses of 0.28 dB/cm at 1310 nm and 0.42 dB/cm at 1550 nm, respectively, are prepared. Subsequent micropatterning by means of photolithography results in waveguide and other test patterns. A low optical loss of 0.51 dB/cm at 1550 nm is measured on a waveguide manufactured from a photopatternable fluoroaryl functionalized ORMOCER®.
Silica and Hybrid Silica Gels Revisited: New Insight by Solid State Nuclear Magnetic Resonance
Authors: Bonhomme Christian , Camus Lydie 
Published: April 2011

ABSTRACTThe “old” 1H→29Si CP MAS (Cross Polarization Magic Angle Spinning) experiment is revisited in the frame of silica hybrid gels and silsesquioxanes. It is proved that the analysis of the CP curves can lead to erroneous interpretation in terms of quantification. We show that this results from false assumptions concerning the dynamical CP parameters THSi (cross relaxation time constant) and T1ρH (1H relaxation time in the rotating frame). In other words, at least one parameter must be measured independently, in order to constrain the fits of the CP curves. Moreover, we demonstrate that the well-known (and universally used…) “spin bath” assumption is not always valid in the frame of 1H→29Si CP MAS NMR. This point is clearly demonstrated on model silsesquioxanes exhibiting short Si-H bonds. In this case, the transfer of magnetization (called coherent transfer) presents clearly oscillations, which can lead to the precise measurement of Si-H distances by solid state NMR! Curiously, the coherent transfer of magnetization is also demonstrated for weakly coupled spin systems, encountered in the silsesquioxane (SiO1.5CH3)8 or T units gels. In this case, a numerical simulation of the CP curves gives a deep insight in the chemical environment of the 29Si sites in terms of Si-H distances and local molecular reorientations. For weakly coupled systems, 1H-1H spin diffusion must be suppressed, in order to reveal the coherent character of the transfer: the quenching of spin diffusion is demonstrated by using a modified version of the CP MAS experiment. We introduce here the Lee-Goldburg CP MAS experiment (CPLG MAS) for that purpose. The “off resonance” 1H irradiation (at the magic angle) ensures the strong suppression of the 1H-1H homonuclear dipolar interaction and therefore the efficient quenching of spin diffusion during the CP transfer.
The use of multinuclear solid state NMR for the characterization of siloxane-oxide hybrid nanocomposites
Authors: Gervais Christel , Julián Beatriz , Cordoncillo Eloisa , Escribano Purificación , Smith Mark E. , Babonneau Florence , Sanchez Clément 
Published: April 2011

ABSTRACTThe objective of this paper is to review various solid state NMR techniques that have been, or can be used for the structural characterization of siloxane—oxide hybrid systems prepared by sol-gel process, and to discuss the type of information they provide, as well as their limitations. More precisely, this paper focuses on NMR techniques to probe and quantify the different types of oxo-bridges (M–O–M of oxide network, Si–O–Si of siloxane chains and Si–O–M siloxane–MxOy interface) in siloxane-oxide nanocomposites prepared through hydrolysis and condensation of organosilanes and M(OR)n alkoxides. In addition the influence of the functionality of the silicon alkoxides and the nature of the MxOy oxides on the extent of the Si-O-M interface will be examined.
A Novel Method for Rapid Formation of High-ordered Self-Assembled Monolayer
Authors: Fujita Yoshitaka , Nakamoto Norifumi , Takeda Hiroyuki , Hidaka Tomoya , Kimura Nobuo , Suzuki Hiroshi , Yoshimoto Noriyuki , Ogawa Satoshi 
Published: April 2011

ABSTRACTWe have discovered a novel chemisorption method using octadecyltrimethoxysilane (ODMS), titanium tetraisopropoxide (TTIP), water, and toluene [1] to form highly-ordered self-assembled monolayers (SAM) of ODMS. The SAMs were formed rapidly from the active solution even when it was kept for three months. The solution and layers were characterized by several methods. We propose a mechanism for the rapid formation of the ODMS-SAM.
Vanadium Oxide Nanotubes: New Synthesis Route and Mechanism of Formation.
Authors: Jaber Maguy , Steunou Nathalie , Azaïs Thierry , Livage Jacques 
Published: April 2011

ABSTRACTThe synthesis of vanadium oxide nanotubes containing phosphorus (VPOx-NT) is described. A mixture of V2O5.nH2O gels, phosphoric acid and hexadecylamine was heated under hydrothermal conditions at 180°C for 7 days. The VPOx nanotubes were characterized by X-ray diffraction, scanning and transmission electron microscopy, 51V and 31P solid state NMR. In-situ experiments were performed in order to get a better understanding of the mechanism of these nanotubes formation.
Macrocellular Silica Monoliths Hierarchically Textured: Mesostructured Si-HIPE Materials
Authors: Carn F. , Colin A. , Backov R. 
Published: April 2011

ABSTRACTInterface between sol-gel process and soft matter appears recently as a very nice tool to generate new materials with complex textures or/and structures extended at various length scales. In this general context, hierarchical inorganic porous monoliths have been prepared using a double templates procedure, namely concentrated emulsion as a macroscopic pattern and mesoscopic micellar templates. The texture of those monoliths can vary dramatically playing either with the oil volume fraction, synthetic pH conditions or the emulsification process. These materials show interconnected macroporosity associated to vermicular-type mesostructuration with an average mesoporosity of 800 m2/g associated to bulk density as low as 0.08 g cm-3 which is comparable to values obtained for silica aerogel.
Molybdenum and Tungsten Oxide Nanowires Prepared by Electrospinning
Authors: Sawicka Katarzyna M. , Karadge Mallikarjun , Gouma Pelagia-Irene 
Published: April 2011

ABSTRACTTungsten oxide (WO3) and molybdenum oxide (MoO3) nanowires were synthesized through utilizing sol gel and electrospinning methods. Mixtures of metal oxide sol gel and polyvinylpyrrolidone (PVP) in ethanol solution were electrospun and resulted in metal oxide composite nanofiber mats. Precise annealing process removed all organic material, and pure metal oxide single crystal nanowires remained. Both the as-spun nanocomposite mats and the heat-treated nanofiborous materials were characterized using Scanning and Transmission Electron Microscopes. The average diameter of the nanofibers was concluded to be proportional to the flow rate used and inversely proportional to the metal oxide concentration in the solution.
Hierarchical Macro-Mesoporous Silica Monolith
Authors: Amatani Tomohiko , Nakanishi Kazuki , Hirao Kazuyuki , Kodaira Tetsuya 
Published: April 2011

ABSTRACTMonolithic pure silica gels with hierarchical macro-mesoporous structure have been synthesized via spontaneous sol-gel process from silicon alkoxide using a structure-directing agent and a micelle-swelling agent. Monolithic body with well-defined co-continuous macropores is a result of concurrent phase separation and sol-gel transition induced by the polymerization reaction, whereas the mesopores are templated by the cooperative self-assembly of inorganic species, a structure-directing agent and a micelle-swelling agent. The following removal of surfactants by heat-treatment gives silica gels with hierarchical and fully accessible pores in discrete size ranges of micrometers and nanometers. The highly ordered 2D-hexagonal arrays of mesopores have been confirmed by X-ray diffraction measurements and FE-SEM observations. Furthermore, by further additions of the micelle-swelling agent, the mesostructural transition from well-ordered 2D-hexagonal arrays to mesostructured cellular foams (MCF) have been induced accompanied by minor modifications of the micrometer-range structure.
Dichroism of Thin Films Containing Aligned Ag Nanoparticles Prepared by Multi-Source Dynamic Oblique Deposition.
Authors: Maekita Wataru , Suzuki Motofumi , Kishimoto Kazuaki , Nakajima Kaoru , Kimura Kenji 
Published: April 2011

ABSTRACTWe have demonstrated the direct formation of elongated Ag particles with a quasi-parallel major axis on SiO2 template layer by using dynamic oblique deposition (DOD). The peculiar nanomorphology of the particles and template is physically self-organized owing to the self-shadowing in the oblique vacuum deposition. The resulting films exhibit anisotropic optical absorption due to plasma resonance sensitive to the shape of the Ag particles on the template. Since our method can be applied to any combination of thin film materials, it is useful for enabling the plasmon-mediated optical phenomena and to apply them for the development of various photonic devices such as thin film polarizers.