Electron Transfer and Fluorescence Quenching of Nanoparticle Assemblies

Electron transfer (ET) in aggregates of cadmium selenide (CdSe) and cadmium telluride (CdTe) nanoparticles (NPs) was studied in aqueous solution by fluorescence quenching. Both steady-state and time-resolved fluorescence measurements were used to quantify how the ET depends on the nature of the NP assemblies. The aggregation of CdSe and CdTe NPs was controlled by the electrostatic attraction of the charged functionalities placed on the NP surface coating. Electron transfer quenching was found to depend on three factors: the interparticle distance, the energetic alignment of the NP bands (hence the size of the NPs), and the direction of the electric field between the NPs, created by their surface charges.