The interaction between semiconductor ZnSe quantum dots and graphene oxide: Ultrafast charge transfer dynamics

In this article, by connecting positively charged cysteamine-coated ZnSe quantum dots (QDs) with either negatively charged graphene oxide (GO) or reduced graphene oxide (RGO), we have assembled ZnSe-GO and ZnSe-RGO composite materials, respectively. We used time-correlated single photon counting (TCSPC) and femtosecond transient absorption (TA) to study the effects of GO/RGO on the fluorescence and carrier transport dynamics of ZnSe QDs. We confirmed that the strong excited state interaction between GO/RGO and ZnSe QDs could significantly quench the exciton fluorescence of ZnSe QDs. Picosecond ultrafast electron transfer from ZnSe QDs to GO/RGO surfaces has been found, and it can decrease the bleaching signal intensity of ZnSe QDs and accelerate the recovery of the bleaching signal as well. Moreover, we found that the energy level change caused by the GO reduction reduced the energy level difference between RGO and ZnSe QDs, which implies broader application prospects for ZnSe-RGO vs. ZnSe-GO composite.