Brownian motion induced dynamic near-field interaction between quantum dots and plasmonic nanoparticles in aqueous medium

Metal-enhanced fluorescence has been studied over the past three decades in order to improve fluorescence sensing and imaging techniques in microfluidics and medical diagnostics. However, most of previous studies were performed while precisely maintaining the distance between fluorophore and plasmonic nanoparticles. In the present study, we investigate the enhanced fluorescence from quantum dots (QDs) that are mixed with plasmonic nanoparticles, such as gold nanoshell (GNS), in the aqueous medium without confining the interparticle distance. Although the near-field interaction could not occur based on the estimated interparticle distance according to particle concentrations, the experimental results indicate that the QD fluorescence can be greatly enhanced. A Monte Carlo simulation revealed that there exists considerable probability that QDs can reach the near-field region of GNS due to the thermally induced Brownian motion.