A Simple ZnO Nanocrystal Synthesis Illustrating Three-Dimensional Quantum Confinement

Semiconductor nanocrystals or quantum dots are attractive materials for exploring quantum confinement effects. For example, band-gap energies of these materials depend on particle size, and this dependence can be explained using simple, quantum mechanical models. We outline here an undergraduate physical chemistry laboratory involving the room-temperature synthesis and absorption spectroscopy of ZnO nanocrystals. The experimental results are compared with the predictions of a three-dimensional quantum confinement (or particle-in-a-sphere) model. The ease of synthesis and data collection, the common precursors employed, and the simple spectroscopic analysis allow facile incorporation of this experiment into essentially any undergraduate laboratory program.