Victor Yanishpolskii

Behaviour of pure water and water mixture with benzene or chloroform adsorbed onto ordered mesoporous silicas

Structural characteristics of synthesized ordered mesoporous silicas MCM-41, MCM-48 and SBA-15 were studied using XRD, nitrogen adsorption and FTIR methods. Pure water and mixtures with water/benzene and water/chloroform-d adsorbed onto silicas were studied by 1H NMR spectroscopy with layer-by-layer freezing-out of bulk and interfacial liquids. Concentrated aqueous suspensions of MCM-48 and SBA-15 were studied by thermally stimulated depolarization current (TSDC) method. Benzene and chloroform-d can displace a portion of water to broad pores from the pore walls and from narrower pores, especially in the case of a large excess of an organic solvent. This process is accompanied by diminution of both interaction energy of water with an adsorbent surface and freezing temperature depression of adsorbed water. The effect of nonpolar benzene on pore water is much stronger than that of weakly polar chloroform-d. Modifications of the Gibbs-Thomson relation to describe the freezing point depression of mixtures of immiscible liquids confined in pores allow us to determine distribution functions of sizes of structures with unfrozen pore water and benzene.

The Reduction of Gold Nanoparticles in the Surface Layer of Modified Silica

Silicas with deposited hydridepolysiloxane layers were used for the in situ preparation of gold nanoparticles by the reduction of metal ions from a solution of chloroauric acid. The metal-containing silicas obtained were characterized by X-ray powder diffraction, transmission electron microscopy, and UV, IR, and laser correlation spectroscopy.

Synthesis and Application of Metal-Containing Silicas

Gold nanoparticles were obtained by in situ reduction with silicon hydride groups grafted to the silochrom C-120 and aerosil A-300 silica surface. Such gold-containing silicas have been applied for hydrogen oxidation.

Potentialities of silane-modified silicas to regulate palladium nanoparticles sizes

A promising approach to control palladium nanoparticle sizes by application of silane modified silicas was suggested. The combination of reductive properties of silicon hydride groups and hydrophobic properties of alkylsilyl groups which act as agglomeration limiters for metal nanoparticles gives an opportunity to synthesize uniformly distributed particles with a specified size. Silicas modified with triethoxysilane (TES) and diisopropylchlorosilane (DIPCS), as well as, the combination of hexamethyldisilazane (HMDS) and triethoxysilane were applied for formation of such bifunctional matrices. Properties of the silane-modified silica samples and changes occurred during the formation of palladium nanoparticles were studied by IR spectroscopy. Thermal stability of surface chemical compounds was investigated by thermogravimetric analysis (TGA); low-temperature nitrogen adsorption was used to study structural properties of the applied materials. With the use of transmission electron microscopy (TEM) the dependence of palladium nanoparticle size on the nature of support surface layer was found.

ADSORPTION PROPERTIES OF FUNCTIONAL SILICAS TOWARDS SOME TOXIC METAL IONS IN WATER SOLUTIONS

bound complexing phenolic-type analytical reagents 8-hydroxyquinoline, 1-(2-pyridylazo)-2-naphthol, 4-(2-pyridylazo)resorcinol have been studied. Structures of the surface complexes of toxic metals with grafted analytical reagents were determined using IR, ESR and electronic diffuse reflectance spectroscopies. Possibility of simultaneous determination of micro amounts of heavy metals was demonstrated using the x-ray fluorescence analysis of modified adsorbents after absorption of metal ions from their multicomponent mixtures in natural and artificial water solutions. Silica gel with adsorbed polyionene (1,4-MePh) was shown to have high adsorption properties towards some metal-containing anions, in particular MoO4, WO4 and Cr2O7 in water solutions. Adsorption isotherms of these metal-containing anions on initial silica gel and silica-supported polyionene were investigated.

Template Syntheses of Porous Silica Adsorbents with Spherical Particle Morphologies

The peculiarities of template syntheses of ordered porous silicas with spherical particle morphologies were investigated in alkaline and acidic media. The silicas obtained were characterized by nitrogen adsorption/desorption measurements, X-ray diffraction, scanning and transmission electron microscopies. Mesoporous silica matrices with high specific surface areas (450–1200 m2/g), an ordered pore structure and a spherical particle granulation of ca. 0.5 μm size were synthesized in alcohol/ammonia media. In acidic media, silica spheres with an average diameter of ca. 10 μm, a slightly ordered pore structure and a lower specific surface area (600 m2/g) were obtained.

Nanoporous Silica Matrices and Their Application in Synthesis of Nanostructures

The effect of the presence of I-4 Me-Ph ionene in the supramolecular template (cetyltrimethylammonium bromide) on formation of porous structure of silicas was studied. We also studied the peculiarities of template synthesis of mesoporous silicas inside of large pores of silica gel. Mesoporous silicas with chemically modified surface were applied in synthesis of metallic nanostructures. Porous silicas with grafted layer of hydridepolysiloxane were used for in situ preparation of supported nanoparticles of gold and silver by reduction of metal ions from chloroauric acid and silver nitrate solutions, respectively. Nitrogen adsorption–desorption, X-ray powder diffraction analysis, scanning and transmission electron microscopies, IR-, UV–visible, and laser correlation spectroscopies were applied for characterization of adsorbents and nanostructures obtained.

Morphology Control of Ordered Porous Silica Adsorbents

Peculiarities of template synthesis of ordered porous silicas with spherical morphology of particles were investigated in alkaline and acidic media. Obtained silicas were characterized by nitrogen adsorption—desorption measurements, x-ray diffraction, scanning and transmission electronic microscopies.