Krylova G. Photosensitized reduction of noble and transition metal ions in heterogenеous systems based on silica, modified with benzophenone

Objects: mesoporous SiO2 powders and films with adsorbed benzophenone molecules, colloidal solutions of nanosized metal particles, films with incorporated metal nanoparticles SiO2 / Ag, SiO2 / Au, aqueous solutions, containing Cr2O72-, Hg2+ ions. The goal of study is creation of a new photoactive material by modification of SiO2 powders' and films' surface with organic sensitizer - benzophenone, investigation of mechanisms of photosensitized reduction of noble and transition metals in the presence of this material and obtaining of stabilized noble metal nanoparticles on the surface of mesoporous SiO2 films and powders and in colloidal solutions. Methods: X-rays diffraction, adsorption-desorption isotherms, stationary fluorescent spectroscopy, laser flash-photolysis, spectrophotometry, transmission and scanning electron microscopy, chemical analysis, pH-metry. The heterogeneous photosensitizer was synthesized, which permits to shift the threshold of sensitivity of metal ions photoreduction reaction to near ultraviolet region of wavelength (365 nm) and to increase the rate of these processes. Depending on the state of benzophenone molecules (adsorbed or solubilized) the differences in the mechanism of photoreduction were revealed. On the base of study of gold and silver nanoparticles form and size dependence on laser impulse power, irradiation time, stabilizer nature the technique of particles morphology governing in the processes of photoreduction in presence of benzophenone modified silica was worked out. It was developed the photochemical method of silver and gold nanoparticles production within the pores of silica matrix modified with corresponding metal ions by irradiation in the solution of photosensitizer - benzophenone.