The prepared ZnO NRAs were characterized by field-emission
scanning electron microscope (FESEM) (Hitachi S-4700), and X-ray
diffraction (XRD) (Bede D1 System, CuKa1 radiation), respectively.
The photoluminescence measurement (Edinburgh Instruments,
FLS920) was performed at room temperature with a Xe lamp as
the light source using the excitation wavelength of 325 nm.