Thin films of rhodamine 6G in titanium dioxide (Rh6G/TiO 2 ) and silicon dioxide (Rh6G/SiO 2 ) were synthesized using the sol−gel method. We explored two kinds of matrices as hosts for rhodamine 6G (Rh6G) at different concentrations of the dye. The pronounced effect of the dye concentration on the absorption and fluorescence spectra as well as on time-resolved fluorescence spectra was found. In particular, it was found that the aggregation of the guest dye is significantly weaker in the Rh6G/TiO 2 nanolayer. The absence of an isosbestic point in absorption spectra in a silica matrix suggests the formation of higher order aggregates, whereas the changes of absorption profile in Rh6G/TiO 2 matrix indicate the formation of dimers. Rh6G aggregates are strongly fluorescent in Rh6G/TiO 2 nanolayer, which can be seen from time-resolved and steady-state emission spectra. For Rh6G/SiO 2 nanolayers these changes are much less pronounced and concern mostly the red shift of the fluorescence maximum.
The idea of determination of local dye concentration in a nanoporous matrix is proposed based on donor− acceptor energy transfer. The method was tested for a Rhodamine 110−Rhodamine 101 system in silica and methylated silica nanolayers. Evaluation of acceptor (Rhodamine 101) local concentration was carried out by comparing the results of Monte Carlo simulation of energy transfer from donor (Rhodamine 110) to acceptor (Rhodamine 101) with the experimental data of donor fluorescence decay in which concentration was treated as a best fit parameter. The obtained values of acceptor local concentration were about 10 times higher than the mean bulk concentration. Further possible implementations of this method are discussed.
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