The influence of pH over topography and spectroscopic properties of silica hybrid materials embedding meso-tetratolylporphyrin
- Institute of Chemistry Timisoara of Romanian Academy, M. Viteazul Avenue, No. 24, 300223 Timisoara (Romania)
- West University of Timisoara, Pestalozzi Street, No. 16, 300115 Timisoara (Romania)
- 'Politehnica' University, T. Lalescu Street, No. 2, 300223 Timisoara (Romania)
- National Institute for Research and Development in Electrochemistry and Condensed Matter, P. Andronescu Street, No. 1, 300224 Timisoara (Romania)
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.
- OSTI ID:
- 21199684
- Journal Information:
- Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 2 Vol. 44; ISSN MRBUAC; ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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