Thermal-Lens Study on the Distance-Dependent Energy Transfer from Rhodamine 6G to Gold Nanoparticles

A study on energy transfer from the Rhodamine 6G (donor) to gold nanoparticles (acceptor) is investigated using a laser-based dual-beam thermal-lens technique. The nanoparticles are observed to quench the intrinsic fluorescence of the dye molecule via a nonradiative energy transfer mechanism. The influence of nanoparticle concentration $(0.09,hbox {nM},hbox {to},0.24,hbox {nM})$ on the energy transfer mechanism with Rhodamine 6G $(1;upmu hbox {M})$ is investigated. Analysis of the results indicates that the energy transfer efficiency is high (more than 50 %) in the presence of nanoparticles and the efficiency is enhanced with an increase in the nanoparticle concentration. The distance between the nanoparticle and dye molecule is evaluated on the basis of the nanomaterial surface energy transfer model. The thermal-lens studies probe the nonradiative path of de-excitation of the excited molecule, and the comparison between this technique and the conventional fluorescence method in measuring the distance as well as the energy-transfer efficiency clearly indicates that the thermal-lens technique is a complementary approach to study the energy-transfer mechanism between a donor and an acceptor.