Defect states of ZnO nanoparticles: Discrimination by time-resolved photoluminescence spectroscopy

ZnO nanoparticles with different shapes and sizes were prepared by changing coordinating ligands. Hexagonal cones presented UV and green (similar to 500 nm) emissions, which originated from excitons and defects, respectively. Oxygen vacancies were found to be major defects in the hexagonal cones. Blue emission at similar to 440 nm was observed for hexagonal plates, and analyses of time-resolved photoluminescence spectra showed that two transitions were responsible for this blue emission, because transitions from Zn-i to the valence band (430 nm) and from Zn-i to V-Zn (480 nm) were distinguished by emission wavelengths and lifetimes. The visible emissions from defects were related to the roles of coordinating ligands. (C) 2010 American Institute of Physics. [doi:10.1063/1.3382915]