PHOTOPHYSICAL PROPERTIES OF CYANINE DYES IN SOL-GEL MATRICES

Planar and twisted cyanine dyes with different pK(a) values are examin ed concerning their protonation equilibrium in sol-gel matrices. In th e sol-gel matrix the equilibrium between the cation and the dicationic form shifts to the dication pointing to acid-base reactions of sol-ge l walls with cyanine dyes. The colorless dicationic species is not fou nd for pseudoisocyanine and in sol-gel bulks prepared with drying cont rol chemical agents (DCCA) indicating the absence of the responsible i nteraction, The fluorescence lifetimes of cyanine molecules are used t o compare the pore size and distribution in sol-gel matrices prepared with and without DCCA. J-aggregation, examined for one dye, depends st rongly on environment polarity and pore size.