Facile preparation of zinc oxide nanorods surrounded by graphene quantum dots both synthesized via separate pyrolysis procedures for photocatalyst application

A facile pyrolysis method was employed for separate synthesis of zinc oxide nanorods (ZnO NRs) and graphene quantum dots (GQDs) and the structures were composited. The structures were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and Fourier transform infrared (FTIR) spectroscopy. The structures were optically characterized by UV-vis and photoluminescence (PL) spectrometry techniques, showing that the absorption of ZnO NRs increases in the visible region after being surrounded by GQDs. Optical bandgaps of ZnO NRs and ZnO NRs/GQDs composite were estimated as 3.2 and 2.8 eV, respectively. Based on PL analysis, it was deduced that the generated electron hole recombination rate of ZnO NRs decreases after being surrounded by GQDs. Finally, it was shown that our GQDs, despite being relatively inefficient separately, significantly enhance the photocatalytic activity of ZnO on methylene blue mainly through decreasing the e-h recombination rate of ZnO NRs.