Dramatic excitation dependence of strong and stable blue luminescence of ZnO hollow nanoparticles

Strong and stable blue luminescence was obtained from ZnO hollow nanoparticles. Significantly, dramatic excitation dependence was observed for blue emissions of ZnO (1) band-gap energy (E) is the optimal excitation energy but smaller energies are still effective; (2) there exist several fixed emitting wavelengths in blue wave band, such as 412, 439, and 458 nm. These phenomena, combined with previously reported defect levels and formation thermodynamics, point out that the initial states of corresponding transitions to blue emissions could be zinc interstitials-related defect states, which were further verified by subsequent electron paramagnetic resonance examinations. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3263712]