Shell effects on hole-coupled electron transfer dynamics from CdSe/CdS quantum dots to methyl viologen

Abstract

Electron transfer (ET) dynamics from the 1Se electron state in quasi-Type II CdSe/CdS core/shell quantum dots (QDs) to adsorbed methyl viologen (MV2+) were measured using femtosecond transient absorption spectroscopy. The intrinsic ET rate kET was determined from the measured average number of ET-Active MV2+ per QD, which permits reliable comparisons of variant shell thickness and different hole states. The 1Se electron was extracted efficiently from the CdSe core, even for CdS shells up to 20 Å thick. The ET rate decayed exponentially from 1010 to 109 s-1 for increasing CdS shell thicknesses with an attenuation factor β ≈ 0.13 Å-1. We observed that compared to the ground state exciton 1Se1S..