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Application of high performance Brillouin spectroscopy and nuclear magnetic resonance imaging on sol-gel produced organically modified silicates (ORMOSIL) indicated microseparation of organic and inorganic stages for systems with substantial polymer formation. Microstructure strongly conditioned ORMOSIL macroscopic elastic and optical properties. These properties were not affected by the sample's filmlike and monolithic character.

A study was conducted on nonlinear absorption dispersion of copper phthalocyanine tetrasulfonate in a CuPcTs/Silica xerogel composite. The ultrasound energy-based sol-gel method was employed in preparing the sample to encourage tetramethoxysilane hydrolysis. Different areas of the composite's visible spectrum exhibited saturable absorption and reverse saturable absorption.

Characterization of organic matter in four sediments in the influence area of wastewater discharges was carried out by both chemical and thermal analysis in order to assess their pollution level. Oxidisable organic carbon and organic matter were calculated by the standard methodology in laboratory. Thermogravimetry (TG), between 50 and 900° C, was simultaneously performed in oxidizing conditions on ground sediments samples after three different pretreatments. Linear regression adjust of thermal analysis results versus chemical parameters provides the better Pearson's coefficients, leading to the best coefficients for weight loss in 250-400° C temperature range versus oxidisable organic carbon and organic matter at 360°C, respectively. These results demonstrated the utility of thermoanalysis technique for the evaluation of the organic matter content of fresh sediments. [ABSTRACT FROM AUTHOR]

Aggregation effects in metallophthalocyanine/SiO2 composites play an important role in the optical properties of these materials. With the aim to decrease phthalocyanine self-association induced in aqueous solution into the network pores, alternative processing methods for trapping the organic in the matrices have been carried out. Monolithic xerogels have been obtained by three chemically different processing routes, preserving their homogeneity and transparency, even under extremely acid conditions. Micro, meso and non-porous silica xerogels have been obtained, depending on processing method. However, the organic doping highly modifies the textural features of the final composite, increasing the pore volume of composites even in more than 50%. Phthalocyanine aggregation degree has been tested by UV–VIS absorption spectroscopy and correlated to the textural parameters and pore size distribution of the composites. The effect of the textural features on molecular self-association level is evaluated. [Copyright &y& Elsevier]

The elastic properties of organically modified silicates prepared by ultrasonics aided polycondensation of Tetraethoxysilane and Polidimethylsiloxane is studied by means of high resolution Brillouin spectroscopy. Our results evidence the microseparation of the organic and inorganic phases for the systems with high content of polymer. We propose a mechanical model that qualitatively explains the observed variation of the elastic constant c11 vs molar fraction of dimethylsiloxane in these vitreous materials and develop a structural model that accounts for the observed dynamical behavior. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]