The microemulsion method for preparing ZnO nanocrystallites was reported.Through measuring ZnO microcrystllite ESR spectra, we found that at room temperature it has a significant ESR signal and its intensity descends with the increase of annealed temperature. This result is in contrast with that of bulk ZnO which is a diamagnetic material and no ESR signal. Finally it was found and verified that on the surfaces of ZnO nanocrystallites there are a lot of oxygen vacancies and defects which trap electrons and form paramagnetic centers to provide the observed ESR signal.
It is found that the SnO2 nanometer particle modified by chemical methods on its surface with a layer of steric acid molecules has a significant red shift of optical absorption band edge and clear photoluminescence at room temperature, which is in contrast with that of bulk SnO2 and naked SnO2 nanometer particles. It is concluded that these results are related to the dielectric confinement effects on the SnO2 nanometer particles surfaces.
