Effective ROS generation and morphological effect of copper oxide nanoparticles as catalysts

In this work, the successful synthesis of spherical (sCuONPs) and rod-like (CuONRs) copper oxide nanoparticles was reported. Several microscopic and spectroscopic techniques were used to confirm the different morphologies (spherical and rod-like) and also different diameter sizes. Copper metal within nanomaterials had different oxidation states (Cu0, Cu+, and Cu2+) as was confirmed by X-ray photoelectron spectroscopy (XPS). The optical properties of the synthesized nanoparticles were investigated, and their reactive oxygen radical species (ROS) generation was confirmed using UV–vis spectroscopy. Copper oxide nanoparticles catalytically converted H2O2 to form ROS (HO●−, HOO●−, or O2●−). ROS generation was confirmed using UV–vis spectroscopy and 1,3-diphenylbenzofuran (DPBF, as a radical quencher) and also using electron paramagnetic resonance (EPR) spectroscopy and 2,2,6,6-tetramethylpiperidine (TEMP) as a spin trap. UV–vis spectroscopy was further used to monitor a blue color development when copper oxide nanoparticles were mixed with 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2). The color changes were confirmed by UV–vis spectra with absorption maxima at 370 nm and 652 nm and naked eye for blue color development. Oxidase enzymes produce hydrogen peroxide as by-product and this property was used for the detection of biological analytes. Glucose and glucose oxidase (GOx) enzyme were used as model bioanalytical system. Copper oxide nanorods were successfully synthesized and characterized their surface properties using various techniques. The nanoparticles exhibited excellent catalytic properties towards converting hydrogen peroxide to reactive oxygen radical species (ROS). The catalytic properties were confirmed using UV–vis (DPBF, radical scavenger) and EPR spectroscopy (TEMP, spin trap). The radicals could oxidize TMB to blue products visible to the naked eye as further proof of ROS generation.