Aggregation States of Rhodamine 6G in Mesostructured Silica Films

Mesostructured films are an ideal material for incorporation of fluorescent dyes; controlling the doping process is, however, a critical step because the dyes will be constrained in a complex chemical environment. We have incorporated rhodamine 6G, a well-known fluorescent dye, in silica mesostructured 2d-hexagonal films at different concentrations. We have used dense silica films as reference material to compare the effect of incorporation of rhodamine 6G in mesostructured and dense materials. We have also prepared mesostructured films at different surfactant concentrations to compare the surfactant effect on dye aggregation state. The dye-doped films have been characterized by UV-vis absorption spectroscopy and emission and excitation fluorescence spectroscopy. At high dye concentrations, nonfluorescent sandwich H-type dimers are formed, but in mesostructured films the amount of this type of aggregates is reduced and the formation of fluorescent J-type dimers is favored. The presence of the surfactant within the mesopores gives rise to fluorescent dimers (J-type) at the expense of the nonfluorescent sandwich H-type.