Luminescence, Paramagnetic, and Electrochemical Properties of Copper Oxides-Decorated TiO2/Graphene Oxide Nanocomposites.

The properties of newly synthesized Cu2O/CuO-decorated TiO2/graphene oxide (GO) nanocomposites (NC) were analyzed aiming to obtain insight into their photocatalytic behavior and their various applications, including water remediation, self-cleaning surfaces, antibacterial materials, and electrochemical sensors. The physico-chemical methods of research were photoluminescence (PL), electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The solid samples evidenced an EPR signal that can be attributed to the oxygen-vacancy defects and copper ions in correlation with PL results. Free radicals generated before and after UV-Vis irradiation of powders and aqueous dispersions of Cu2O/CuO-decorated TiO2/GO nanocomposites were studied by EPR spectroscopy using two spin traps, DMPO (5,5-dimethyl-1-pyrroline-N-oxide) and CPH (1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine), to highlight the formation of hydroxyl and superoxide reactive oxygen species, respectively. The electrochemical characterization of the NC modified carbon-paste electrodes (CPE) was carried out by CV and DPV. As such, modified carbon-paste electrodes were prepared by mixing carbon paste with copper oxides-decorated TiO2/GO nanocomposites. We have shown that GO reduces the recombination process in TiO2 by immediate electron transfer from excited TiO2 to GO sheets. The results suggest that differences in the PL, respectively, EPR data and electrochemical behavior, are due to the different copper oxides and GO content, presenting new perspectives of materials functionalization.

Evaluation of the Photocatalytic Properties of Copper Oxides/Graphene/TiO2 Nanoparticles Composites.

Easy and cost-efficient modifications of titanium dioxide nanoparticles that improve their efficiency in the visible light domain represent a continuous and challenging research topic. In addition, the effect of graphene on the overall photocatalytic process is still debated. Consequently, herein, we prepared a series of TiO2 nanoparticle-based composites with different copper oxide mass content (1-3%) and co-doped with graphene of different oxidation degrees. Different characterization techniques were used to analyze the structural and physico-chemical properties of the obtained composites: Scanning Electron Microscopy (SEM)/Transmission Electron Microscopy (TEM)/Energy-dispersive X-ray spectroscopy (EDX) analysis, X-ray powder diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic performance was evaluated by the degradation of methylene blue under both UVA and visible light irradiation. The nanocomposites show very good photocatalytic activity independent of the presence of reduced graphene oxide, due to the Cu2O/CuO-TiO2 heterojunctions. This finding has been confirmed by the very efficient visible-light-driven degradation of amoxicillin and ciprofloxacin.