Study of Photophysical Properties of Thiol-capped CdS Quantum Dots Doped with Gold Nanoparticles.

In this study, CdS quantum dots (QDs) capped with benzyl mercaptan (thiol) were prepared by microwave irradiation technique. The shape, size, morphology, and spectral properties of thiol-capped CdS QDs were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-vis absorption, and photoluminescence (PL) spectrometry. The photophysical properties of synthesized thiol-capped CdS QDs in the presence of different amounts of gold nanoparticles (AuNPs) have been investigated, exhibiting strong PL quenching. The amount of fluorescence quenching was found to be dependent on the concentration of metal nanoparticles. A Stern-Volmer kinetics model was used to analyze the observed quenching mechanism as a function of the quencher (AuNPs) concentration. The Stern-Volmer plot along with the absorption spectra of thiol-capped CdS QDs in the absence and presence of AuNPs suggest the dynamic (collision) nature of quenching and rule out the possibility of static quenching. The energy transfers from QDs to Au NPs, and hence the quenching of QDs emissions provides new insight into designing novel optical-based materials and the development of FRET-based bionanosensors and phototherapeutic applications.