Unusual functionalization of reduced graphene oxide for excellent chemical surface-enhanced Raman scattering by coupling with ZnO

A low-cost noble metal-free substrate comprised of annealed graphene oxide (GO)/ZnO composites is prepared to demonstrate an efficient chemical surface-enhanced Raman scattering effect. A high enhancement factor of about 104, better than those reported for reduced GO (rGO)/Au and GO/Ag composites, is mainly attributed to the unusually abundant oxygen-containing groups generated on surface of rGO by coupling with ZnO nanoparticles at moderate temperature. High-resolution transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy are employed to examine the evolution of ZnO as well as reduction and functionalization of GO after different heat treatments.