Modification of the optical characteristics of Rhodamine B dye with different concentrations using gold nanorods

The optical absorption and fluorescence of Rhodamine B dye solution with different dye concentrations, from 0.1 to 40 mu M, in the presence of gold nanorods were studied. Colloidal gold nanorods were characterized by UV-Visible spectrophotometry and Transmission Electron Microscopy. Rhodamine B dye absorbance with and without gold nanorods was shown to be approximately constant, due to the dominance of the absorbance term of longitudinal surface plasmon resonance of gold nanorods. The fluorescence peak of dye-nanorods mixture with respect to that of pure dye was blue shifted. By increasing the dye concentrations, the energy transfer efficiency between the dye-nanorod pair was increased and, as a result, the fluorescence quantum yield was decreased. The results of the spectral overlapping of the absorption and the fluorescence spectra of RhB dye solution, with and without gold nanorods, matched well with the calculated energy transfer efficiency.