Andryushina N. Photochemical redox processes in systems based on graphene oxide and products of its reduction

The dissertation is devoted to study of the photochemical reduction of graphene oxide (GO) in aqueous dispersions, the structure and spectral properties of GO and products of its reduction, and redox-processes in systems based on them. Aqueous dispersions of GO stabilized by sodium polyphosphate with a concentration of 0.5 g per L were prepared. Illumination of the GO colloids with UV light (310-390 nm) results in elimination of the oxygen-containing functional groups, expansion of the aromatic graphite-like areas in the basal plane of GO and lowering of the electron transition energy Ebg in the sp2-hybridized fragments. By varying the experimental conductions the Ebg can be tuned in the range of 0.5-1.9 eV. The effect of the degree of photochemical reduction of colloidal GO on its ability to stabilize graphite microparticles and multi-wall carbon nanotubes in aqueous solutions is determined. Photochemical activity of colloidal GO in initiating of the acrylamide photopolymerization in aqueous solutions under the illumination with UV and visible light (< 450 nm) is reported for the first time. Impregnation of the nanocrystalline TiO2 by colloidal GO results in a 4-fold acceleration of photocatalytic gas-phase oxidation of ethanol and benzene vapors by air oxygen as a result of enhanced separation of the photogenerated charge carriers between TiO2 and GO. The photolysis of AgCl nanoparticles stabilized in aqueous solution by GO or photoreduced graphene oxide using visible light produces nanocomposites containing silver nanoparticles with a size of 25-30 nm. The composites Ag/AgCl/GO and Ag/AgCl/RGO exhibit electrocatalytic activity in the oxidation of methanol and formaldehyde in alkaline solutions.