Energy transfer in aqueous solutions of oppositely charged CdSe/ZnS core/shell quantum dots and in quantum dot-nanogold assemblies

We demonstrate that the nanoscale assemblies of water-solubilized, oppositely charged CdSe/ZnS core/shell quantum dots and of quantum dots and nanogold particles make it possible to develop FRET-based sensors with a donor quenching efficiency close to 100%. The cw and time-resolved photoluminescence analysis of nanoassemblies with different donor-to-acceptor ratios demonstrates a prevalence of 1:1 complexes. Experimental data perfectly fit the mathematical simulation based on long-range FRET and a static model of the assembling of the oppositely charged nanoparticles. These assemblies are stable in biological fluids, suggesting new applications.