The charge-transfer quenching of photoexcited TiO2 nanoparticles by hexanethiolate monolayer protected gold clusters (MPCs) with core diameters of 1.1-4.9 nm is reported. The quenching efficiency of Au MPCs was compared using Stern-Volmer plots. The quenching constants (KQ) taken from slopes of the plots reveal that KQ increases from 5.6 × 105 to 4.09 × 107 by more than 70-fold as the core diameter increases from 1.1 to 4.9 nm. The origin of the size dependence is considered. KQ was found to linearly correlate with the MPC capacitance. This suggests that the quenching process is dominantly controlled by the capacitance of the electron acceptor (Au MPC). KQ for 1.1 nm diameter Au MPC was found to be significantly smaller than that predicted by the KQ-capacitance correlation. This may reflect the size-dependent opening of an energy gap at the Fermi level for molecule-like MPCs.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry