Structural characterisation of green-synthesised CuO nanoparticles from different precursor sources and their antibacterial activity

Abstract The green synthesis approach, employing eco-friendly methods, offers a sustainable and environmentally benign alternative to conventional synthesis routes by minimising toxic by-products and energy consumption. This study presents the green synthesis, structural characterization, and antibacterial evaluation of copper oxide (CuO) nanoparticles, denoted as CuO(1), CuO(2), and CuO(3), synthesised using copper nitrate (Cu(NO 3 ) 2 ), copper acetate (Cu(CH 3 COO) 2 ), and copper sulfate (CuSO 4 ), respectively. Structural characterisation showed that the choice of precursor salt significantly influenced the crystallite size, lattice parameters, and porosity of the resulting nanoparticles. CuO(3) exhibited the largest crystallite size (76.73 nm) and the lowest surface area (0.0120 m 2 g −1 ), while CuO(1) had the smallest crystallite size (35.78 nm) and the highest surface area (0.0258 m 2 g −1 ). All samples showed spherical morphology as confirmed by microscopic analysis. The synthesised CuO(1), CuO(2), and CuO(3) nanoparticles exhibited antibacterial activity against Staphylococcus aureus, Streptococcus pyogenes , Escherichia coli, and Pseudomonas aeruginosa with MIC values ranging from 0.031 to 0.25, 0.062 to 0.50, and 0.062 to 0.50 mg ml −1 , respectively. These results highlight the potential of precursor-dependent tuning of CuO nanoparticles for enhanced antibacterial applications using green synthesis strategies.