Ag-Cu2O decorated reduced graphene oxide nanocomposite for photocatalytic water splitting, methylene blue dye degradation, electrochemical nitrite sensing, photoluminescence and selected biological applications

Pollution from textile industry and the energy crisis are becoming major issues on a worldwide scale, posing serious threats to both the environment and human health. Finding affordable, effective and sustainable technologies for pollution clean-up and energy problems is very important. In the current study, we have developed highly efficient visible light active multifunctional materials such as Cu2O, Ag–Cu2O nanoparticles (NPs) and Ag-Cu2O anchored reduced graphene oxide (Ag-Cu2O@rGO) nanocomposite. They were prepared by a simple, eco-friendly and economical green reduction methods. The as-prepared nanomaterials were subjected for the evaluation of their functional properties such as photocatalytic hydrogen evolution by water splitting, dye degradation, photoluminescence and nitrite sensing. Interestingly, Ag-Cu2O@rGO nanocomposite exhibited dramatically improved functionalities compared to its counter parts such as Cu2O and Ag-Cu2O. Photocatalytic hydrogen evolution rates of Cu2O, Ag-Cu2O and Ag-Cu2O@rGO composite were found to be 121, 333 and 1218 μmolg−1 h−1 respectively. Hydrogen generation capacity of Ag-Cu2O@rGO composite was found to be 10 times higher than Cu2O nanoparticles. Similarly, Ag-Cu2O@rGO composite showed superior photocatalytic dye degradation activity by degrading completely in 60 min compared to Cu2O and Ag-Cu2O counterparts through swift degradation of methylene blue dye. The composite also exhibited remarkable and sustained stability and functionality up to 6 successive catalytic cycles of photodegradation. Luminescence studies indicate prominent emission peaks at 243 and 359 nm in Cu2O NPs due to a near-band-edge emission and a green emission band at 506 nm probably due to ionised oxygen vacancies. The composite material exhibited reduction in photoluminescence intensity compared to the Cu2O and Ag-Cu2O NPs. The CIE graphs demonstrate that Cu2O, Ag-Cu2O and Ag-Cu2O@rGO NPs emit precisely in the blue region which merits their use in LEDs. Further, the developed Ag-Cu2O@rGO composite exhibited an improved nitrite sensing with a LOD of 19.8 μM when fabricated as an electrode material. Additionally, all the synthesised materials were analysed for biological activities such as antioxidant, direct haemolytic, anticoagulant, antiplatelet and antibacterial activities. Consequently, this study exemplifies a simple, economical and eco-friendly method for the preparation of Ag-Cu2O@rGO nanocomposite having promising multifunctional properties.