Photocatalytic and antibacterial properties of Au-TiO2 nanocomposite on monolayer graphene: From experiment to theory

The formation of the Au-TiO2 nanocomposite on monolayer Graphene (GTA) by sequentially depositing titanium dioxide particles and gold nanoparticles on graphene sheet was synthesized and analyzed in our work. The structural, morphological, and physicochemical properties of samples were thoroughly investigated by UV-Vis spectrophotometer, Raman spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscope, and transmission electron microscope. Photocatalytic performance of GTA, graphene (GR), TiO2, and TiO2 -graphene nanocomposite (GT) were comparatively studied for degradation of methyl orange, and it was found that GTA had highest performance among all samples. More importantly, antibacterial performance of this novel composite against Gram-positive bacteria, Gram-negative bacteria, and fungus was predominant compared to GR, TiO2, and GT. And the result of biomolecules oxidation tests suggested that antimicrobial actions were contributed by oxidation stress on both membrane and antioxidant systems. Besides, the rate of two decisive processes during photocatalytic reaction, the rate of the charge transfer (kCT) and the rate of the electron-hole recombination (kR) have been studied by Perturbation theory, Radiation theory, and Schottky barrier theory. Calculation and derivation results show that GTA possesses superior charge separation and transfer rate, which gives an explanation for the excellent oxidation properties of GTA