Photoelectrochemistry in Aqueous Media at Polyacrylate-Capped Q-CdS Assembled in Polyelectrolyte Matrix on Electrode Surfaces

Abstract

The photoelectrochemical behavior in aqueous media of multilayered films of polyacrylate-capped quantum (Q)-CdS nanoparticles, nm, assembled in poly(diallyldimethylammonium chloride) on electrode surfaces is reported. Charge transport was feasible, likely via charge hopping between the Q-particles through the embedding matrix. Either anodic or cathodic photocurrents were generated at the films, depending on the applied electrode potential, which is attributed to the quantized properties of the nanoparticles. The potential at which the photocurrent reversed in direction from anodic to cathodic shifted by −66 mV per pH unit, in the same direction and similar magnitude as the shift in the flatband potential reported for the bulk material. This shift is partly attributed to an increase in the reducing power of the quantum dot electron with increasing pH, as indicated from photocurrent-voltage plots acquired in the presence of methyl viologen. Anodic photocurrents increased with increasing particle loading up to four bilayers, while cathodic photocurrents increased up to eight bilayers. Photogenerated carrier losses as films thicken, and differences in the density of the e and h trap sites, are believed to cause the observed photocurrent dependence on the number of bilayers. © 2003 The Electrochemical Society. All rights reserved.