On the stable homotopy of a Z₂-Moore space

Silica-germania thin films are important materials for photonic applications, but synthesis of these films is quite difficult to achieve especially with the task of obtaining a homogeneous structure. We have prepared mesoporous silica-germania films via evaporation-induced self-assembly from ethanolic solutions of Si and Ge chlorides, using a triblock copolymer as the templating agent. The mesostructure has been found to have tetragonal symmetry, and the degree of order decreased with increasing Ge content. X-ray photoelectron spectroscopy has shown that the chemical composition of the films is close to the nominal composition. Infrared analysis has revealed that the pore walls are highly condensed and residual hydroxyls are present as isolated. or hydrogen bonded silanols in short chains. UV-vis absorption and photoluminescence spectra have been correlated with the presence of photoactive oxygen-deficient Ge2+ centers which can give rise to a variation in the refractive index upon high-power density UV irradiation

Synthesis and Self-Assembly of Well-Defined Block Copolypeptides via Controlled NCA Polymerization

This article summarizes advances in the synthesis of well-defined polypeptides and block copolypeptides. Traditional methods used to polymerize α-amino acid-N-carboxyanhydrides (NCAs) are described, and limitations in the utility of these systems for the preparation of polypeptides are discussed. Improved initiators and methods that allow polypeptide synthesis with good control over chain length, chain length distribution, and chain-end functionality are also discussed. Using these methods, block and random copolypeptides of controlled dimensions (including molecular weight, sequence, composition, and molecular weight distribution) can now be prepared. The ability of well-defined block copolypeptides to assemble into supramolecular copolypeptide micelles, copolypeptide vesicles, and copolypeptide hydrogels is described. Many of these assemblies have been found to possess unique properties that are derived from the amino acid building blocks and ordered conformations of the polypeptide segments. © Springer-Verlag Berlin Heidelberg 2013

Crystallization in hybrid organic-inorganic materials through self-organization from 3-glycidoxypropyltrimethoxysilane

Hybrid organic-inorganic materials can organize into layered crystalline structures through self-organization when bridged silsesquioxanes are used in the sol-gel synthesis. Crystallization is, however, also observed in hybrid materials when 3-glycidoxypropyltrimethoxysilane is left to react in highly basic conditions; this synthesis route shows a peculiar property which is the possibility of preparing also crystalline hybrid films by controlling the sol-gel process. The crystalline films exhibit optical anisotropy and are optically transparent. In this article we briefly review the main achievements of our research group in the field. (C)2011 The Ceramic Society of Japan. All rights reserved. RI Takahashi, Masahide/C-3326-200

An alternative sol-gel route for the preparation of thin films in CeO(2)-TiO(2) binary system

Thin films of titania-ceria have been prepared via sol-gel processing by employing titanium and cerium chloride compounds in highly acidic conditions for the precursor sol. This sol-gel route allows obtaining titania-ceria and cerium titanate films, CeTi(2)O(6), after thermal treatment in air. The films exhibit a high optical transparency which is modulated by controlling the composition and the thermal treatment. The materials have been characterized by X-ray diffraction, UV-visible spectroscopy, ellipsometric spectroscopy and atomic force microscopy. The titania-ceria films show, as a function of the composition, the formation of different phases after thermal treatment in air at 800 degrees C. In particular, with the composition Ce25-Ti75 we have obtained a pure cerium titanate phase, CeTi(2)O(6), which can be formed only in a very strict range of compositions. (C) 2009 Elsevier B.V. All rights reserved

Liquid-Phase Preparation and Characterization of Zinc Oxide Nanoparticles

Zinc oxide (ZnO) nanoparticles have been prepared by a wet chemical method, from zinc acetate and LiOH ethanol-based solutions. The resulted nanoparticles were dispersed in a solvent. The effect of solvent (ethanol or butanol) and surfactant (polyethylene glycol-PEG 200) on the average size and size distribution of the nanoparticles was investigated by light scattering measurements. Smaller size was observed for ZnO nanoparticles dispersed in butanol and PEG 200. The statistical parameters of the Gaussian size distribution curves were calculated. ZnO nanoparticles have been prepared to be used as seeds on a substrate for the growth of ZnO nanowires. The morphology, surface roughness, crystalline structure, and orientation of the nanoparticles deposed on silicon substrate were characterized by atomic force microscopy and x-ray diffraction, respectively

Design of hybrid organic–inorganic materials through their structure control: The case of epoxy bearing alkoxides

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Formation of cerium titanate, CeTi(2)O(6), in sol-gel films studied by XRD and FAR infrared spectroscopy RID D-5301-2009

The process of formation of cerium titanate films as a function of annealing temperature and composition has been studied by combining X-ray diffraction analysis and far infrared spectroscopy. The films have been prepared by a sol-gel synthesis using metal chlorides as precursors; the synthesis allows obtaining cerium titanate films upon annealing in air. A brannerite type, CeTi(2)O(6), phase has been identified by X-ray diffraction and Rietveld analysis on thin films. CeTi(2)O(6) is formed upon annealing at 700 A degrees C and in a limited range of ceria-titania mixed compositions. The far infrared spectra are useful to observe the formation of crystalline phases at the beginning of the crystallization process at lower firing temperatures, when the XRD analysis is not enough sensitive

Sol-Gel Processing of Bi(2)Ti(2)O(7) and Bi(2)Ti(4)O(11) Films with Photocatalytic Activity

A new sol-gel synthesis based on chloride compounds as precursors has been used to prepare bismuth titanate (BT) films. The films have been deposited by dip-coating and fired at different temperatures in air; they remain amorphous up to 500 degrees C, and crystallize into the pyrochloric cubic phase Bi(2)Ti(2)O(7) between 600 degrees and 700 degrees C while at higher temperatures of firing the stable Bi(2)Ti(4)O(11) monoclinic phase is formed. The films have been characterized by X-ray diffraction analysis at gracing incidence, X-ray photoelectron spectroscopy, ellipsometric spectroscopy, UV-visible absorption, and atomic force microscopy. The photocatalytic properties of the films have been evaluated by exposing a methyl orange solution containing the BT films to UV light. The test has shown that the Bi(2)Ti(2)O(7) films have a higher activity in comparison with reference anatase titania films

Sol-gel reactions of 3-glycidoxypropyltrimethoxysilane in a highly basic aqueous solution

The reactions of 3-glycidoxypropyltrimethoxysilane in a highly basic aqueous solution have been studied by multinuclear magnetic resonance and light scattering techniques. The study has shown that in this peculiar chemical environment the alkoxy groups of 3-glycidoxypropyltrimethoxysilane undergo a fast hydrolysis and condensation which favor the formation of open hybrid silica cages. The silica condensation reaches 90% at a short aging time but does not go to completion even after 9 days. The highly basic conditions also slow down the opening of the epoxies which fully react only after several days of aging. The epoxy opening generates different chemical species and several reaction pathways have been observed; in particular, the formation of polyethylene oxide chains, diols, termination of the organic chain by methyl ether groups and formation of dioxane species. These reactions are slow and proceed gradually with aging; light scattering analysis has shown that clusters of dimensions lower than 20 nm are formed after two days of reactions, but their further growth is hindered by the highly basic conditions which limit full silica condensation and formation of organic chains. RI Takahashi, Masahide/C-3326-2009; Innocenzi, Plinio/D-5301-200