Silver nanoparticle induced enhancement and quenching of fluorescence of thiol-capped CdS quantum dot

This work deals with the investigation on the photophysical properties of benzyl mercaptan (thiol) capped CdS quantum dot (QDs) in N, N-dimethylformamide (DMF) solution. The effect of silver nanoparticles (AgNPs) on the photophysical properties of thiol-capped CdS QDs has also been studied for different concentrations of AgNPs. Both nanoparticles were characterized with Transmission Electron Microscopy (TEM). From the photophysical measurements, we have observed AgNPs induced enhancement and quenching of fluorescence from thiol-capped CdS QDs in DMF solution depending upon the concentration of AgNPs. At relatively lower concentrations of AgNPs, the QDs fluorescence was found to increase with the increase in nanoparticles (NPs) concentration up to a critical value of concentration. On the other hand, quenching of thiol-capped CdS QDs fluorescence was observed at higher concentrations of AgNPs. The enhancement of QDs fluorescence was explained by the surface plasmon resonance induced enhancement of fluorescence. The observed quenching of QDs fluorescence was explained by the excitation energy transfer from QDs to AgNPs. The nature of quenching was analyzed by using the Stern-Volmer equation. The straight-line Stern-Volmer plot suggests that the quenching is dynamic in nature. The absorption spectra of thiol-capped CdS QDs in the presence and absence of AgNPs also suggest the dynamic nature of quenching and rules out the possibility of static quenching. This type of quenching is useful in preparing OLEDs with pure emission from the dopant and can also be useful as detector of metal nanoparticles. [Graphics] .