The effect of nanoparticle and mesoporous TiO2 additions on the electronic characteristics of reduced graphene oxide nanocomposites with zinc oxide under UV irradiation

Semiconducting nanocomposites were formed from layers of reduced graphene oxide (RGO) and ZnO and nanoparticle or mesoporous forms of TiO2 by dip-coating on fluorine-doped tin oxide (FTO) substrates. The effect of nanoparticle or mesoporous TiO2 on the electrical conductivity was compared. The crystalline phases and microstructures of the nanocomposites were investigated by XRD, DRS-UV, FTIR and FE-SEM, showing the layers to be homogeneous and of consistent thickness, with the TiO2 in the anatase form. The bandgaps and electrical conductivities of the nanocomposites, determined by Tauc plots and electrochemical impedance spectroscopy (EIS), show that under UV irradiation, the nanocomposites containing nanoparticle TiO2 have higher electrical conductivities than those containing mesoporous TiO2. A mechanism is suggested involving the formation of nano-capacitors on the surface of the ZnO layer, the pores in the mesoporous TiO2 acting as the dielectric and the conducting electrodes formed by UV irradiation of the TiO2.