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The mesoporous silica particles were prepared by the sol–gel method in one-step synthesis, in acidic conditions, from tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES), varying the mole ratio of the silica precursors. Nitric acid was used as catalyst at room temperature and hexadecyltrimethyl ammonium bromide (CTAB) as structure directing agent. Optical properties, porosity and microstructure of the materials in function of the MTES/TEOS ratio were evaluated using infrared spectroscopy, nitrogen adsorption and small angle X-ray scattering. All materials showed the ordered pore structure and the high specific surfaces, making them suitable as the drug delivery systems. Drug loading and release tests using ketoprofen were performed to assess their performance for drug delivery applications. The amount of the methylated precursor used in the synthesis had little effect on the drug loading capacity, but had a strong influence on the initial rate of the drug release.

Magnetic iron oxide-silica shell nanocomposites (IONP@SiO2) have been prepared in a two-step procedure. IONPs were obtained by coprecipitation of iron salts, and coated by silica in sol-gel method under sonication. Two IONP/silica ratios and two drying methods, heating in oven and supercritical CO2 drying, were used. The samples were analyzed using X-ray diffraction (XRD), infrared spectroscopy, magnetic measurements, small-angle neutron scattering (SANS), nitrogen sorption, and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis (EDX). The iron oxide silica nanocomposites obtained via supercritical drying exhibited higher values of the specific surface area and of saturation magnetization compared to the samples synthesized with the same iron oxide content but obtained after drying at 60 °C. Pd(II) adsorption experiments were performed on the materials prepared by supercritical drying. The maximum adsorption capacity 6.5 mg/g showed that the materials can be used as good and cheap adsorbent for palladium ions from aquatic environment. [ABSTRACT FROM AUTHOR]

Hematite/silica nanocomposite (α-Fe2O3/SiO2) was synthesized by sol-gel method at room temperature followed by thermal treatment through calcination at the temperature of 500o C selected based on thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) results. The crystalline phases of α-Fe2O3 and SiO2 were characterized by the correlation of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) results. The composite average particle size values ranged between 10 and 22 nm were estimated through XRD and transmission electron microscopy (TEM). The composite exhibited a high capacity to remove humic acids (HA) from water, through the sorption and VIS irradiation-assisted photocatalysis processes. The heterogeneous structure of the composite was found by corroborating Brunauer-Emmett-Teller (BET) results with the HA sorption physical mechanism determined by Dubinin-Radushkevich isotherm model. A synergic effect regarding visible irradiation-assisted photocatalysis process using α-Fe2O3/SiO2 was manifested for HA removal by comparison with the sorption and photolysis under VIS irradiation, which suggested a great potential for developing of a new nature-based inspired unitary processes for advanced treatment water for drinking purpose. [ABSTRACT FROM AUTHOR]

Spherical silica xerogels were synthesized by Stöber route using tetra-ethyl-orthosilicate (TEOS) in order to obtain good properties for opto-electronic and catalytic applications. The reactants mole ratio was n TEOS: H2O: ETOH: NH3 (where n = 0.098 - 0.26: 0.45: 0.789: 0.06). To study these properties, we know from literature, that nanoparticles under 100 nm show unique electrical, mechanical and optical properties. We have choosen the optimum sample, with the smaller surface area and particles size of 91 nm. To improve the optical properties, this sample was further doped with 0.1% Ce3+. The obtained xerogel was thermally treated at 300, 600 and 900 °C. The changes in properties were put in evidence by morpho-textural (N2 adsorption-desorption isotherms and SEM images) and optical measurements (FT-IR, Fluorescence and Raman spectra's). [ABSTRACT FROM AUTHOR]