Preparation and Characterization of Quantum Size Zinc Oxide: A Detailed Spectroscopic Study

摘要

The synthesis of transparent colloidal suspensions of small zinc oxide particles in water, 2-propanol, and acetonitrile are reported. Quantum(Q)-size effects are observed during particle growth and qualitatively interpreted using a simple molecular orbital (MO) picture. The particles at the final stage of growth are approximately spherical in shape and consit of 2,000 to 3,000 ZnO molecules. They exhibit many of the photophysical properties of bulk zinc oxide. However, pronounced shifts in the absorption spectrum during the illumination of anoxic suspensions of ZnO reveal a distinctively different behavior of these small particles. Fluorescence spectra of the ZnO particles suggest that adsorbed electron relays are necessary to shuttle electons from the conduction band into lower laying traps. Two fluorescence maxima are observed at the final growth stage of the ZnO particles.