Controlling the Luminescence of Carboxyl-Functionalized CdSe/ZnS Core-Shell Quantum Dots in Solution by Binding with Gold Nanorods

Plasmonic nanostructures offer promising routes toward artificial control of the photoluminescence properties of various emitters. Here, we investigated the photoluminescence of carboxyl-functionalized CdSe/ZnS coreshell quantum dots (c-QDs) localized near gold nanorods (AuNRs) as a function of c-QDsAuNRs distance using the cetyltrimethylammonium bromide (CTAB) surfactant and Bovine Serum Albumin (BSA) protein layers over coating metal surface as spacer. The direct binding of negatively charged c-QDs to positively charged CTAB (34 nm thickness) caused close contact with the metal, resulting in an efficient metal-induced energy transfer (quenching). We found that quenching is modulated by the degree of spectral overlap between the photoluminescence band of c-QDs (620 nm) and longitudinal localized surface plasmon resonance (LSPR) of AuNRs (637 and 733 nm). Deposition of BSA layer over CTAB coated-AuNRs and subsequent decoration with c-QDs yielded an increase in photoluminescence signal when exciting in resonance with the transverse LSPR of AuNRs. On the basis of experimental studies using steady-state and time-resolved fluorescence measurements as well as finite-difference time-domain calculations, we report over 70% quenching efficiency for all investigated AuNRs along with a 4.6-fold in photoluminescence enhancement relative to free c-QDs (39-fold enhancement relative to c-QDs loaded AuNRs) after BSA deposition.