Effect of the (OH) Surface Capping on ZnO Quantum Dots

ZnO quantum dots were prepared by the reaction of Zn2+ with OH— in alcoholic solution. By annealing (150–500 °C), both the particle size and the surface conditions could be changed intentionally. The structural properties of the dots were characterized by X-ray diffraction and Raman measurements, and the optical properties by photoluminescence. For the as-prepared dots, the excitonic recombination is very weak, while it becomes dominant for the annealed samples. We present evidence that the weak excitonic transition of ZnO quantum dots is strongly correlated with the presence of the surface (OH) groups.