Long-Range Electronic Communication between Metal Nanoparticles and Electrode Surfaces Separated by Polyelectrolyte Multilayer Films

Abstract

The dynamics of electron transfer across Au electrodes modified by ultrathin polyelectrolyte multilayers (PEM) and a diluted monolayer of Au nanoparticle was investigated as a function of the film thickness. Au electrodes were sequentially modified by a self-assembled monolayer of 11-mercaptoundecanoic acid (MUA), followed by alternate adsorption of poly-l-lysine (PLL) and poly-l-glutamic acid (PGA) layers. Submonolayer coverage of citrate stabilized 19.2 ± 2.1 nm Au nanoparticles was achieved by electrostatic adsorption on PLL terminated surfaces. In the absence of nanoparticles, cyclic voltammetry and electrochemical impedance spectroscopy of the hexacyanoferrate redox probe showed that the charge-transfer resistance is independent of the number of adsorbed polyelectrolyte layers. These results revealed that the redox species can penetrate the PEM film and the electrochemical responses are controlled by the electron tunneling across the initial monolayer of MUA. The phenomenological charge-transfer resi...