Distance controlled and electrically driven photoluminescence quenching from quantum dot-Au complexes
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1257-O06-10
Distance controlled and electrically driven photoluminescence quenching from quantum dot-Au complexes Zhitao Kang, Jie Xu, Dinal Andreasen, Brent Wagner Georgia Tech Research Institute, Georgia Institute of Technology, 925 Dalney Street, Atlanta GA 30332-0826, U.S.A. ABSTRACT Quantum Dots (QDs) bound to gold nanoparticles have shown photoluminescence (PL) quenching dependent on distance between the two particles. The incident light from the QD couples to plasmon excitation of the metal when the frequencies of the light and the surface plasmon resonance (SPR) coincide, leading to a reduction in emitted PL in the system. The quenching effect of gold nanoparticles on QDs was used to study protein-protein interactions with the potential for drug screening applications. CdTe and CdHgTe QDs with emission wavelengths from 500~900nm were synthesized and gold nanospheres and nanorods with controlled absorption in the visible and near-infrared (NIR) wavelength regions were prepared. The PL quenching of QD-Protein-Protein-Au complexes was studied as a function of Au concentration, QD size and protein type. A quenching efficiency of up to 90% was observed. The QD-Au complexes were also studied for electric potential sensing. The surface of the QDs was negatively charged due to thiol ligands capping. By applying a positive potential on the gold or gold nanoparticle attached substrate, the local electric field between the substrate and the statically charged QDs would pull the QDs closer to the gold surface and quench the QD PL. PL quenching of QD with Au was studied as a function of electric signal and QD type. In this methodology, electric signals were effectively converted to optical signals. INTRODUCTION It is known that when a fluorophore is close to a metal surface, energy transfer from the fluorophore to the metal occurs, resulting in fluorescence quenching. Such energy transfer processes between quantum dots and gold nanoparticles or nanostructures have been demonstrated recently.1-4 This transfer efficiency is highly dependent on (a) the distance between the fluorophore molecules and the gold nanoparticle, (b) the orientation of the dipole with respect to the fluorophore-Au axis, and (c) the overlap of the molecules’ emission with the gold nanoparticle absorption spectrum.5 In this study, CdTe and CdHgTe QDs were used and the distance between QD and gold was controlled through protein-protein interaction or electrostatic attraction. The PL quenching observed from the QD-Au complexes was studied for potential biomedical applications. By using different protein-protein interactions, QDs can be bound to gold nanoparticles with controlled distances. The incident light from the QD couples to the plasmon excitation of the gold nanoparticle when the frequencies of the light and the SPR coincide, leading to a reduction in PL emission. This PL quenching of QD-Proteins-Au complexes was studied as a function of Au concentration, QD size and protein type. Another way to bring the QD and Au into proximity is through elec
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