title: Observation of individual semiconducting nanoparticle collisions by stochastic photoelectrochemical currents.
abstract: We describe a method to detect individual semiconducting nanoparticles (NPs) using the photoelectrochemical (PEC) current measured at an ultramicroelectrode (UME). We use photooxidation of MeOH by TiO2 NPs as a model system of photocatalysis in solution. NPs suspended in MeOH under constant illumination produce valence-band holes that oxidize MeOH. The electrons are collected at the UME, and the current-versus-time data show discrete current changes that are assigned to particle-by-particle interactions of the NPs with the UME. The stepwise changes in the photocurrent denote irreversible attachment of NPs to Pt UMEs (<30 μm diameter). We found that accumulation of electrons in the conduction band by the NPs is not enough to explain the stochastic PEC currents. We propose that the observed anodic steps have a PEC nature and are due to photooxidation of MeOH by the NPs at the electrode surface.
authors.affiliation: Department of Chemistry, University of Nevada, Reno, Nevada 89557, USA.
authors.forename: Ashantha
authors.initials: A
authors.lastname: Fernando
authors.forename: Suman
authors.initials: S
authors.lastname: Parajuli
authors.forename: Mario A
authors.initials: MA
authors.lastname: Alpuche-Aviles