TEM and HRTEM images of ZnO QDs/graphene nanocomposite materials at different reaction times and zinc salt concentrations.(a) and (b) 5 hours, 20 mM; (c), (d) 12 hours, 50 mM. (e) Energy dispersive spectrum (EDS) analysis. The Cu peak is from the copper grid and C peak is partially from lacey carbon coat. (f) Fluorescence emission spectra of the as-prepared ZnO QDs/graphene nanocomposite samples with excitation wavelength at 254 nm, (a) 5 hours, 20 mM; (b) 12 hours, 20 mM; (c) 5 hours, 50 mM; (d) 12 hours, 50 mM, the inset is the photograph of as-prepared nanocomposite solution samples.