Self-association of thiazine dyes i n aqueous and aqueous urea solutions

The mol ecular association of ionic dyes in s olutions due to the strongly attractive electrostatic forces is a well-known phenomenon [۱,۲]. The presenc e of aggreg ates in the dye solutio ns may influence considerably in their photo-p hysical behavior. The strength of the molecular association depends on the several factors including the dye con centration and structure, temperature, pressure, solvent a nd other factors [۳,۴]. The structu re of the aggregates has been stu died by applying excito n theory to the analysis of the absor ption spectr a [۵]. The d ye aggregation leads t o a strong coupling o f the molec ular transition dipoles, resulting in excitonic absorption band, which is cons iderably different fro m the abso rption of t he monomeric species. Thiazine d yes such as Azure A and Thionine are an important group of organic compounds which have a variety of industrial and scient ific applications [۶]. T he photo-physical prop erties of this group of dyes have been demonstrated by se veral authors [۷]. In this report, we describ e the effe cts of concentration on the spec tral data an d aggregative properti es of Azure A and Thion ine in aque ous and aqu eous urea solutions.

کلیدواژه ها:

Azure A ، Thionine ، Thiazine dy es ، Dye aggr egation ، Exciton theory