Rhodamine fluorescent dimers adsorbed on the porous surface of silica gels

Rhodamine 6G (R6G)-doped silica gels were prepared through the sol-gel process using dye concentrations ranging from 4.00 x 10(-6) to 6.40 x 10(-4) M. The adsorption of the R6G on the porous surface of the silica gels determined the formation of R6G fluorescent J-dimers as concentration increased, in concordance with the behavior reported for other xanthene molecules as rhodamine B (RB) and rhodamine 110 (R110) also doped in silica gels. The photophysical study of the R6G fluorescent dimers doped in silica gels was done through the recording of the excitation and emission fluorescence spectra as well as the measurement of the lifetime values. The exciton theory was used for the elucidation of the adsorption angle (theta), the angle between the monomer units (alpha), and the separation distance between the molecules (R) of the R6G fluorescent dimers. The angle between the monomer units (alpha) and the separation distance between the molecules (R) were also determined for RE and R110 fluorescent dimers doped in silica gels.