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101.
Spectroscopy and Structure of Sol-Gel Systems 总被引:1,自引:0,他引:1
Sol-gel derived glasses may differ from conventional melt-quenched glasses owing to the peculiar microstructures existing at the gel state, such that, even after gel densification, some differences may remain in their composition and molecular structure.This paper discusses structural characteristics of thin film oxide gels and glasses, with a special emphasis on SiO2-TiO2 based systems, which are of particular interest for sol-gel integrated optics applications. Short range structure aspects are discussed based on infrared, X-ray photoemission and X-ray photoabsorption spectroscopies. The chemical homogeneity of sol-gel materials is evaluated, based on X-ray photoemission and nuclear magnetic resonance spectroscopies, dealing in particular with the issue of homo- vs. heterocondensation. Finally, some microstructural features of sol-gel derived films are analyzed, namely the relationship between infrared absorption and porosity and the structure of nanocrystalline sol-gel films, based on grazing incidence X-ray diffraction and micro-Raman spectroscopy. The types of structural information obtainable by each different technique are compared in detail. 相似文献
102.
Roman Pogreb Oleg Popov Vlad Lirtsman Oleg Pyshkin Alexander Kazachkov Albina Musin Gene Whyman Binyamin Finkelshtein Yuri Shmukler Dan Davidov Alexander Gladkikh Edward Bormashenko 《先进技术聚合物》2006,17(1):20-25
The work is devoted to luminescent properties of trivalent lanthanide complexes dispersed in thermoplastic host matrices. Polyethylene films and polypropylene‐rods, both doped with these complexes, were manufactured using an extrusion technique. Two kinds of dopants were used: Eu(III)‐thenoyltrifluoroacetone‐1,10‐phenanthroline complex (1) and Eu(III)‐La(III)‐1,10‐phenanthroline complex (2). Absorption, excitation, emission spectra and lifetime of luminescence were studied. The impact of the polymer matrix on the emission spectra was investigated. Emission spectra of the films were studied at room and helium temperatures. Time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) surface mapping showed that in the Eu(III)‐La(III) complex europium forms islands (clusters) with a dimension of 1 µm, whereas lanthanum was dispersed more uniformly in the polymer matrix. Dependence of emission intensity on the excitation was determined. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
103.
104.
《Electroanalysis》2003,15(13):1139-1142
Electrochemical properties of Fc‐PEM films have been studied by changing the chemical structure of the polymer chains and the content of Fc moiety in the film systematically. We have prepared a series of PEM films by a layer‐by‐layer deposition of polycations, Fc‐modified poly(allylamine) (Fc‐PAA) and poly(ethyleneimine) (Fc‐PEI), and polyanionic poly(vinyl sulfate) (PVS) on the surface of a gold electrode. The redox properties of the Fc‐PAA/PVS and Fc‐PEI/PVS films depended significantly on the content of Fc moiety in the polymer chains and on the polymer type. Fc‐ PAA and Fc‐PEI polymer chains can penetrate 3 or 4 PAA/PVS bilayers inserted between the redox polymers and electrode. The Fc‐PAA film‐modified electrode can be used for electrocatalytic oxidation of ascorbic acid. 相似文献
105.
Garth J Simpson 《Chemphyschem》2004,5(9):1301-1310
Recent observations of remarkably large chiroptical effects in second-harmonic generation (SHG) and sum-frequency generation (SFG) measurements suggest exciting possibilities for the development of new chiral-specific spectroscopies and novel chiral materials for nonlinear optics. Several fundamental studies designed to elucidate the molecular and macromolecular origins of the chiral responses are reviewed to provide a framework for development of this emerging field. In general, the chiral activity in SHG and SFG has the potential to arise from complex interactions between hosts of different competing effects. Fortunately, relatively simple electric dipole-allowed mechanisms routinely dominate the nonlinear optical chiral activities of most practical systemsexpressions can often be generated to link the. This substantial reduction in complexity allows for the development of simple models connecting the macroscopic nonlinear optical response to intuitive molecular and supramolecular properties. 相似文献
106.
IntroductionReversiblecolorchangesuponexternalorinternalstimulationshavebeenattractingmuchattentionduetotheirutilityasfunctionalmaterials .Forexample ,pho tochromismdescribesthecolorchangesinducedbypho toirradiationandcanbeusedasphoto recordingmateri als… 相似文献
107.
用恒电位电流衰减法及激光扫描光电化学显微技术研究了在于PH=12.5及13.8的模拟混凝土孔溶液中钢筋钝化化膜的生长动力学及相应的破坏过程,实验结果表明,钢筋钝化膜的生长过程存在两个主要阶段,各阶段膜厚均与生长时间存在正比对数关系,但当t<30秒和t>30秒时,膜的生长表出出不同的动力学特征,在钝化发生点蚀前,钝化膜的微区光电流一定的预兆,腐蚀抑制剂NaNO2影响膜的生长过程及膜厚,能提高钢筋的抗 相似文献
108.
B. Schoofs T. Mouganie B. A. Glowacki V. Cloet S. Hoste I. Van Driessche 《Journal of Sol-Gel Science and Technology》2007,41(2):113-122
Today, the deposition of coated conductors on a variety of substrates is often performed using a vacuum or low pressure technique.
However, obtaining uninterrupted deposition at high speed, increasing flexibility in composition and attaining independence
of geometric constraints of the substrates are areas in which vacuum techniques will need sustained development in order to
answer industrial demands. The development of the next generation of deposition methods, based on deposition under atmospheric
environment and from aqueous precursor solutions is a real challenge. This work describes the deposition of thin NdBa2Cu3O7-y layers on SrTiO3 single crystals based on a new sol-gel dip coating process using aqueous precursor solutions. Two inorganic aqueous sol-gel
routes were investigated, a metal nitrate–citric acid based and a metal acetate–triethanol amine based solution. Using detailed
thermal analysis, it is shown that adjusting the different parameters during thermal treatment can be used to control the
morphology of the films. Also special attention is given to the microstructure of the thin film because of its relevance to
the superconducting transport properties of the coated conductor system. 相似文献
109.
110.
Silica sol-gel films were prepared by dipping, starting from an acid catalyzed solution of methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS). Silver metal nanoparticles were produced in the silica layer by introducing in the sol-gel precursor solution AgNO3 or AgClO4·H2O. The silver ions were thermally reduced in air at 800°C, giving an intense yellow coating film. The silver metal particles were observed by transmission electron microscopy and X-ray diffraction. The diameter of the silver particles was found to be about 10 nm. Absorption measurements in the UV-Vis were used to evaluate the volume fraction of silver colloids embedded in the silica layer. 相似文献