Dynamics of Electron Transfers between Electrodes and Monolayers of Nanoparticles

This paper describes measurements of the rate of electron transfers between electrodes and attached monolayers of gold nanoparticles (monolayer-protected clusters, MPCs). The Au cores have an average 1.6 nm diameter, and possess a mixed monolayer of hexanethiolate and mercaptoundecanoic acid (MUA) ligands. The nanoparticles are assembled onto Au surfaces coated with a self-assembled MUA monolayer using MUA−carboxylate−zinc ion−MUA−carboxylate bridges. The attached MPC monolayers exhibit well-defined single electron double layer charging voltammetry of the Au cores. The electron-transfer kinetics of the attached nanoparticles are estimated using cyclic voltammetric, alternating impedance, and potential step techniques. Results from these experiments are consistent with one another and yield heterogeneous electron-transfer rates in the range of 40 to 160 s -1 .