Fesenko T. Laser desorption/ionization of photoactive organic molecules on the surface of mesoporous oxide sol-gel films.

The thesis concerns the investigation of laser desorption/ionization (LDI) mechanism of photoactive organic molecules on the surface of mesoporous oxide sol-gel films of various composition in comparison with LDI mechanism on the surface of standard steel target. Characteristic dependencies of mass-spectra intensities upon the duration of UV-irradiation have been obtained for dyes adsorbed on the catalytically active films. The role of dimeric associates of dyes as the initial stage of their photo-degradation has been shown. Data are presented on the methylene blue reduced forms generation in the process of photodecomposition. Some products of dyes photo-destruction were identified and it was shown that photo-catalytic activity decreased in the row TiO2 > SiO2 /TiO2 > SiO2 . It was found out that addition of Ag nanoparticles to silica films has a positive influence on the efficiency of ionization of adsorbed dye in LDI method. Observed ion yield increase correlated with target optical properties, which, in turn, depended on nanoparticles size and their density on the surface of porous film. The great potential of mesoporous films used as targets for LDI mass-spectrometry was demonstrated for dyes, flavonoids and their metal complexes.