Search

Reversible electrochemical injection of discrete numbers of electrons into sterically stabilized silicon nanocrystals (NCs) (∼2 to 4 nanomaters in diameter) was observed by differential pulse voltammetry (DPV) in N,N′-dimethylformamide and acetonitrile. The electrochemical gap between the onset of electron injection and hole injection—related to the highest occupied and lowest unoccupied molecular orbitals—grew with decreasing nanocrystal size, and the DPV peak potentials above the onset for electron injection roughly correspond to expected Coulomb blockade or quantized double-layer charging energies. Electron transfer reactions between positively and negatively charged nanocrystals (or between charged nanocrystals and molecular redox-active coreactants) occurred that led to electron and hole annihilation, producing visible light. The electrogenerated chemiluminescence spectra exhibited a peak maximum at 640 nanometers, a significant red shift from the photoluminescence maximum (420 nanometers) of the same silicon NC solution. These results demonstrate that the chemical stability of silicon NCs could enable their use as radox-active macromoleculer species with the combined optical and charging properties of semiconductor quantum dots. [ABSTRACT FROM AUTHOR]

The article investigates electron transfer kinetics between a solution redox mediator and the nanocrystal core using a monolayer of alkanethiolate protected gold nanocrystals and reports the first quantitative estimate for the rate of electron transfer at the nanocrystal/solution interface. The rate of electron transfer was found to be depended on the redox couple used, which shows the importance of molecule specific properties such as the effect of their relative hydrophilicities.