Study of concentration-dependent quantum yield of Rhodamine 6G by gold nanoparticles using thermal-lens technique

Tailoring optical properties of the dye molecules using metal nanoparticles is a burgeoning area of research. In this work, we report our results on the studies of how the absorption and emission behavior of Rhodamine 6G dye is tailored using gold nanoparticles. Furthermore, the influence of dye concentration on these properties for a given concentration of nanoparticles in the dye-nanoparticle mixture is investigated. In addition, the difference between the concentration-dependent fluorescence quantum yield of the dye molecules is measured in the absence and presence of nanoparticles using the dual-beam thermal-lens technique. Our absorption spectral studies show additional spectral features due to nanoparticle aggregation on interaction with cationic Rhodamine 6G dye. Dye concentration-dependent steady-state fluorescence studies in the presence of nanoparticles indicate a blue shift in peak fluorescence emission wavelength. The quantum yield value measured using thermal-lens technique exhibit a non-monotonic behavior with dye concentration with substantial quenching for lower dye concentrations. The results are interpreted in terms of dye-nanoparticle interaction and the formation of dye shell around the nanoparticle.