Nickel oxide decorated reduced graphene oxide synthesized using single bioreductor of Pometia pinnata leaves extract as photocatalyst in tetracycline photooxidation and antibacterial agent

Photocatalytic oxidation is one of the effective methods in pharmaceutical wastewater treatment. Among some photocatalysts, NiO-based nanocomposites with high photoactivity are recognized as stable and feasible mate-rials for this purpose. In this work, an environment-friendly approach for synthesizing of reduced graphene oxide/nickel oxide nanocomposites Nickel oxide-modifed reduced graphene oxide (NiO/rGO) prepared by green synthesis method and study on its photocatalytic activity has been performed. The green method for NiO nanoparticles (NiO NPs) was conducted by using NiCl2 with Tinosphora cordifolia stem extract under ultrasound-assisted reaction, and the obtained NPs was dispersed hydrothermally into rGO powder. Physicochemical characterization of materials including X-ray diffraction, scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy, and UV-Visible diffuse reflectance spectroscopy analyses were investigated, meanwhile, for photocatalytic activity, the removal of tetracycline over photooxidation process. The results show that NiO/rGO material provides high performance as photocatalyst with the higher band gap energy (3.28 eV) than NiO NPs (3.01 eV) along with the smaller NiO crystallite size (42 nm) in the composite than in NiO NPs (40 nm). NiO/rGO composite also shows excellent photocatalytic activity feature for tetracycline degradation as it is about 100 % tetracycline removal achieved at 30 min under both UV and visible light illumination. The rGO contribution in the photocatalytic activity is expressed by the higher turnover number (6.67) in both light sources than NiO NPs (0.55 and 0.41 under UV and visible light). NiO/rGO expresses the antibacterial activity against Staphylococcus aureus and Eschericia coli as shown by low minimum inhibitory concentrations (MIC). The MIC against S. aureus is < 0.5 mu g/mL, meanwhile the MIC against E.coli is 2 mu g/mL. Generally speaking, the green synthesized NiO/rGO which could be advantageous as functional material espe-cially as photocatalyst for pharmaceutical industrial wastewater treatment and antibacterial agent.

Automated summary

In this study, reduced graphene oxide/nickel oxide nanocomposites were synthesized using a green method and their photocatalytic activity was investigated. The results showed that the NiO/rGO composite exhibited excellent photocatalytic performance for tetracycline degradation under both UV and visible light illumination. Additionally, it also demonstrated antibacterial activity against Staphylococcus aureus and Eschericia coli.