In Fig. 2a, XRD pattern of ZnO/GO shows wurtzite ZnO. The
absence of the typical diffraction peaks of GO stacking layers might
be attributed to the fact that the regular stacking of GO layers is
destroyed by introducing ZnO into the sheets of GO. In the UV–vis
spectrum of ZnO/GO (Fig. 2b), the increase of the absorptive intensity and the red-shift of the band edge and appearance of a
shoulder-peak at about 425 nm are observed, suggesting an
increase of surface charge due to the presence of GO, the narrow
of band gap energy and an effective electronic coupling between
ZnO nanoparticles and GO sheets [13].