Spectroscopic investigations of 5,10, 15,20-tetraphenyl-21H, 23H-porphine-p,p ',p '',p '''-tetrasulfonicacid in solution, microheterogenous silica and silica/titania systems and on silica surfaces

Dye doped silica and silica/titania xerogels monoliths and glasses containi ng up to 20 mass percent titania have been synthesised by using the sol-gel technique. Furthermore, TPPSA was adsorbed on Silica. Absorption and fluor escence spectroscopic measurements indicate an equilibrium between the free base TPPSA and its dicationic form in Si and Si/Ti-monoliths. During the g elation of the sols a significant change of the fluorescence lifetime of py rene was observed. Stern-Volmer Quenching of the fluorescence of pyrene by TPPSA was found in solution, xerogels and monoliths.