Photoluminescence of zinc oxide mesostructured films doped with Rhodamine 6G

The photoluminescence of thin films doped with fluorescent dyes, such as rhodamine 6G (Rh6G), is strongly dependent on their concentration and aggregation states. We have doped ZnO dense and mesostructured thin films with different concentrations of Rh6G. The films have been prepared via sol-gel using a block copolymer as template to obtain the mesostructured samples. Rh6G at high concentrations aggregates preferentially as not-fluorescent H-dimers in the dense samples and fluorescent J-dimers in the mesostructured films. The dense ZnO coatings show a shift of the typical excitation because of the formation of H-dimers. On the contrary, the mesostructured films exhibit an intense emission, typical of the Rh6G monomer, with a small contribution of the J-dimers. The optical response of the films has been characterized by UV–vis and steady state fluorescence spectroscopy. Controlling the aggregation states of the dyes within a fluorescent matrix has shown to be an important strategy for tuning the emission.