FLUORESCENCE EFFECTS IN RAMAN-SPECTROSCOP Y OF TITANIUM-DIOXIDE - INFLUENCE OF TEMPERING AND ADSORPTION

The fluorescence in the region of 3000 cm(-1) which occurred in connec tion with Raman investigations of TiO2 (rutile and anatase) and Pt/TiO 2 (anatase) using NIR excitation was studied in dependence on the calc ination conditions (temperature and oxygen partial pressure) and on hy drogen adsorption. An increase of the amount of oxygen vacancies under reducing calcination conditions led to an increase of the fluorescenc e. Hydrogen application to platinum-containing samples at room tempera ture led to a marked decrease of the fluorescence. The origin of this effect is an electronic interaction of the hydrogen spilt-over species with titania. The fluorescence is correlated with a photoionization o f the singly ionized oxygen vacancy.