Electron transfer at single CdSe/ZnS quantum dot/adsorbate interface

Electron transfer at quantum dot/molecule interface has become a subject of intense recent interest because of the application of quantum dots (QDs) in novel solar cells and because of its ability to generate multiple excitons with one absorbed photon. Ensemble averaged ultrafast spectroscopic studies show that photoinduced interfacial electron transfer (IFET) between CdS or CdSe QDs and Rhodamine B molecules exhibit multi-exponential kinetics. Fluctuation in emission intensity (blinking) and exciton lifetimes have also been observed on single QDs. To understand how the dynamic and static heterogeneity contribute to the interfacial electron transfer from and to QDs, we have studied these dynamics in single CdSe/ZnS quantum dots attached with Rhodamine B molecules. Our results showed that the fluorescence lifetime of individual QD-dye nanoassembly is shorter than that of QDs, suggesting the quenching of excitons by interfacial electron transfer. The rate of electron transfer was shown to increase with number of dyes per QD. We will discuss the static and dynamic distributions of ET rates at the single quantum dot/adsorbate interface.