Optimized production of antibacterial copper oxide nanoparticles in a microwave-assisted synthesis reaction using response surface methodology

Copper oxide nanoparticles (CuONPs) can be an inexpensive alternative to silver and gold nanoparticles. However, work toward the sustainable synthesis of colloidal CuONPs is limited. This work establishes a simple microwave-assisted synthesis for colloidally stabilized, antibacterial CuONPs synthesized from glucose, starch and CuCl2. Optimization using response surface methodology with central composite design enhanced the sustainability of CuONP production process. The antibacterial properties of CuONPs were tested against grampositive, gram-negative, spore-forming and methicillin-resistant bacteria. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used for elemental and morphological characterization. Bandgap, yield and production were determined by spectrophotometry and a cupric ion selective probe. CuONP formation was verified by the presence of a maximum surface plasmon resonance peak at 284 nm, as also by observing characteristic CuONP peaks by XRD, and lastly by using TEM-energy dispersive spectroscopy for elemental analysis. TEM measured the average CuONP particle diameter to be 1.36 +/- 0.6 nm, which may provide excellent antibacterial properties, owing to their small size. The CuONPs bandgap was significantly higher than bulk CuO and the reaction yield was 95 +/- 2%, thereby helping quantify the reaction system's effectiveness and efficiency at producing CuONPs. The NPs also possessed antibacterial activity against all tested species. Therefore, these CuONPs may be a cheap and sustainable alternative for broad-based antibacterial applications.