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Ag and AgCu containing powdered silica fillers of polymers for medical applications have been synthesized using mechanochemical activation with a low content of solvent or dry powdered materials. The samples in the form of filled polymer films were obtained using polyurethane-urea and silica nanocomposites. The composites have been investigated by TEM, UV/Vis spectroscopy, XRD and microbiological analysis. It has been found that amorphous and nanosized structures of silver oxides and metallic Ag nanocrystallites are formed during thermal destruction of silver nitrate or ammonium complexes in silica matrix (fumed or precipitated silica). Sunlight exposure of nanocomposites contained Ag+ ions leads to the formation of Ag0 nanocrystallites. After UV irradiation, the decrease in surface plasmon resonance band intensity can be caused by the oxidation of Ag0. It is found that silica nanocomposites with the low Ag content (0.2 mmol g−1 SiO2) exhibited the highest antimicrobial activity, whereas the polymeric film with a filler content of 1 wt% exhibited the most efficient antimicrobial properties among tested polymeric composites. The observed transformations (Ag+ ↔ Ag0) of silver compounds do not suppress the biocidal activity of nanocomposites. [ABSTRACT FROM AUTHOR]

Fe2O3/SiO2 nanocomposites based on fumed silica A-300 (S(BET)=337 m2/g) with iron oxide deposits at different content were synthesized using Fe(III) acetylacetonate (Fe(acac)3) dissolved in isopropyl alcohol or carbon tetrachloride for impregnation of the nanosilica powder at different amounts of Fe(acac)3 then oxidized in air at 400-900 degrees C. Samples with Fe(acac)3 adsorbed onto nanosilica and samples with Fe2O3/SiO2 including 6-17 wt% of Fe2O3 were investigated using XRD, XPS, TG/DTA, TPD MS, FTIR, AFM, nitrogen adsorption, Mössbauer spectroscopy, and quantum chemistry methods. The structural characteristics and phase composition of Fe2O3 deposits depend on reaction conditions, solvent type, content of grafted iron oxide, and post-reaction treatments. The iron oxide deposits on A-300 (impregnated by the Fe(acac)3 solution in isopropanol) treated at 500-600 degrees C include several phases characterized by different nanoparticle size distributions; however, in the case of impregnation of A-300 by the Fe(acac)3 solution in carbon tetrachloride only alpha-Fe2O3 phase is formed in addition to amorphous Fe2O3. The Fe2O3/SiO2 materials remain loose (similar to the A-300 matrix) at the bulk density of 0.12-0.15 g/cm3 and S(BET)=265-310 m2/g.