Hybrid porphyrin-silica materials consisting in 5,10,15,20-tetratolyl-21H,23H-porphine, encapsulated in silica matrices were obtained by sol-gel method. The hydrolysis and condensation reactions were performed by using tetraethylorthosilicate as precursor, either in one-step acid or in two steps acid-base catalysis, assisted or not by an ultrasonic field. The porphyrin-silica hybrid materials were monitored and characterized by AFM, FT-IR, fluorescence and UV-vis spectroscopy. As a result of porphyrin entrapping into silica gels, a general phenomenon regarding hyperchromic effects of the Q bands, occurs. UV-vis study revealed that during the sol-gel process, major changes regarding porphyrin ring structure occur, especially at acidic pH, when the dicationic species of porphyrin are formed. During acid-base catalyzed method the dye molecules tend to aggregate by pi-pi and hydrophobic co-facial interactions of sandwich H-type. In acid catalyzed process, the protonation of the porphyrins prevent the formation of aggregates, due to increased electrostatic repulsion between the molecules. (C) 2008 Elsevier Ltd. All rights reserved.