Light Assisted Dimer to Monomer Transformation in Heavily Doped Rhodamine 6G−Porous Silica Hybrids

The spectral properties of postdoping prepared type I Rhodarnine 6G-silica hybrids were investigated in the case of intentionally large doping (5 x 10(-2) mol/L). Beside expected concentration quenching effects, steady state and time resolved optical spectroscopy measurements displayed the presence of different kind of aggregates, both fluorescent and nonfluorescent. As the irradiation dose on the sample increases, the emission features change: the overall emission increases, the peak of the emission is blue-shifted, and the emission decay time also increases. The modifications of the spectral properties under light excitation are interpreted in terms of dimer to monomer light assisted transformation, and a thermodynamic model based on a monomolecular kinetics is presented.