Size-Dependent Electron Injection from Excited CdSe Quantum Dots into TiO₂ Nanoparticles

Abstract

Electron injection from excited CdSe quantum dots into TiO 2 nanoparticles can be easily modulated by controlling the particle size. Femtosecond transient absorption studies indicate that the rate constant for electron transfer from the thermalized s-state of CdSe quantum dots increases with decreasing particle size. The energy difference between the conduction bands of the two semiconductor systems acts as a driving force for the electron transfer in the normal Marcus region. An increase in the interparticle electron transfer rate constant by 3 orders of magnitude (from ∼10 7 to 10 10 s -1 ) has been achieved by decreasing the CdSe particle diameter from 7.5 to 2.4 nm.