After the reaction, the synthesized sample was taken out and characterized by field emission scanning electron microscopy (FE-SEM, JSM-6500F) equipped with an energy-dispersive X-ray (EDX) spectrometer. X-ray diffraction analysis was carried out using a diffractometer (Panalytical X'pert PRO) with copper Kα line as incident radiation. Raman scattering spectra were recorded using a Jobin-Yvon T64000 Raman-scattering spectrometer at room temperature in the backscattering geometry. The 514.5 nm line of a 100 mW Ar+ laser was used for the excitation source. To study the emission properties of ZnO nanostructures, the cathodoluminescence (CL) spectra were carried out at room temperature using a temperature-controllable cathodoluminescence detector (Mono CL, Gatan) installed in the FE-SEM, which was performed at an accelerating voltage of 10 kV.