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International Journal of Photoenergy
Volume 2 (2000), Issue 1, Pages 47-53
http://dx.doi.org/10.1155/S1110662X00000076

Fluorescence and photostability studies of anthracene-9-carboxylic acid in different media

1Photoenergy Center, Faculty of Science, Ain Shams University, Abbassia, Cairo 11566, Egypt
2Department of Chemistry, Faculty of Science, Ain Shams University, Abbassia, Cairo 11566, Egypt

Copyright © 2000 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Electronic absorption and fluorescence spectra of anthracene-9-carboxylic acid (ANCA) were studied in different homogeneous solvents, binary protic/aprotic solvent mixtures and in heterogeneous solutions of the cationic cetyltrimethyl ammonium bromide (CTAB) micelle. Different chemical species of ANCA were identified spectroscopically in different media. The results are discussed on the basis of a mechanism that involves two equilibria: acid-base equilibrium and monomer-dimer equilibrium. These equilibria were found to be very sensitive to the nature of the medium and the concentration of ANCA.

Moreover, while it is photostable in most solvents studied, the ANCA was found to be photolabile in aqueous media of different pHs. The acid-base catalyzed photodegradation rate was studied by following up absorption and/or fluorescence intensities as a function of illumination dose. The determined rate of the photochemical degradation of ANCA depends on the nature of the medium. The first order degradation rate constant is remarkably enhanced in heterogeneous medium of CTAB. As expected, the determined activation energy is low ( 3.2 kJ. mol-1). This result favors photooxidation process. Anthraquinone was the main photodegradation product obtained via9,9-dicarboxylic head-to-head dimer of anthracene that was identified by GC-Mass technique.