Fluorescence spectra of adsorbed heteroaromatic molecules at selective laser excitation

Abstract

To study heteroaromatic compounds adsorption mechanism on silica gel and aerosil surfaces and to elucidate the electron state of the adsorbed molecules, selective laser fluorescent excitation at low temperatures has been used. Emission spectra of acridine and 9-aminoacridine molecules adsorbed on silica surfaces have been studied. Electron-vibration spectral analysis of the spectrum indicates emission of acridine protonised form on the surface. Excitation and emission spectra comparison of acridine adsorbate indicates photoprotolytic reaction of acridine molecules taking place with adsorption sites - hydroxyl silica groups. The abscence of fine structure in acridine emission spectra on dehydroxylated silica surfaces under selective excitation withnesses in favour of strong electron-phonon interaction with the carrier and homogeneous spectral broadening. Concerning of 9-aminoacridine molecules adsorbed on silicas in the wide range of heat treatment, fine structure of fluorescence spectra is resolved where full set of protonised form of 9-aminoacridine vibration frequencies are present. Protonisation takes place in the ground state in the adsorption act.