Metal Conjugated Semiconductor Hybrid Nanoparticle-Based Fluorescence Resonance Energy Transfer

In the present study, we demonstrate a pronounced effect on the photoluminescence (PL) quenching and shortening of decay time of CdSe quantum dots (QDs) during interaction with Au nanoparticles in a Au-BSA conjugated CdSe QD system. A systematic blue shift of the excitonic band of CdSe QDs and the red shifting of a plasmon band of Au nanoparticles are observed in a Au-BSA conjugated CdSe QDs system. Strong evidence of size dependent efficient resonance energy transfer between CdSe QDs and Au nanoparticles is observed. The PL quenching values are 60%, 40%, and 30% for 5.0 nm CdSe QDs, 5.4 nm CdSe QDs, and 5.8 nm CdSe QDs, respectively. The energy transfer efficiencies are 40.9%, 30%, and 19.2% for 5.0 nm CdSe, 5.4 nm CdSe, and 5.8 nm CdSe QDs, respectively. Using the FRET process, the measured distances (d) between the donor and acceptor are 95.3, 102.2, and 110.3 angstrom for Au-BSA conjugated 5.0 nm CdSe, Au-BSA conjugated 5.4 nm CdSe, and Au-BSA conjugated 5.8 nm CdSe QDs, respectively. These results are well matched with the structural estimated value, transmission electron microscopy data, and data from dipole approximation. Such energy transfer between QDs and Au nanoparticles provides a new paradigm for design of an optical based molecular ruler for the application in chemical sensing.