Green luminescence originates from surface defects in ZnO nanoparticles

ZnO nanoparticles were annealed in high-purity Ar, O2, and air atmosphere and were investigated by photoluminescence (PL), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Results show that the ZnO nanoparticles show emissions centered at ∼490, ∼515, and ∼520 nm after annealing in Ar, O2, and air atmosphere, respectively. The origin of the green emission was discussed.