Copper oxide nanoparticles: Synthesis via chemical reduction, characterization, antibacterial activity, and possible mechanism involved

[Display omitted] •CuO NPs were synthesized via chemical reduction method using OA, SBH and TSC.•CuO NPs were synthesized at increasing concentrations of metal precursor and reducing agents.•Characterization was done using UV–vis spec, FT-IR, PSD, ZP, XRD, FE-SEM, and EDX.•Anti-bacterial activity against B. subtilis, E. coli, L. lactis, M. luteus, and P. putida was studied.•SBH synthesized CuO NPs showed highest ZOI against all the test bacteria. Copper oxide nanoparticles (CuO NPs) were synthesized via chemical reduction method using oxalic acid (OA), sodium borohydride (SBH), and tri-sodium citrate (TSC) as both reducing and stabilizing agents. The CuO NPs were synthesized at different concentrations (0.02 M, 0.04 M, 0.06 M, 0.08 M, 0.10 M, and 1.00 M) of metal precursor and reducing agent. The as-synthesized CuO NPs (18 samples) showed maximum absorbance in the range of 200 nm to 450 nm wavelength. X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the synthesis of CuO NPs. Among the CuO NPs, S-CuO NPs, showed good particle size (15.8 to 44 nm) and surface charge (42.1 to 23 mV). S-CuO NPs showed highest anti-bacterial activity (ZOI) against Bacillus subtilis (19 mm), Escherichia coli (15 mm), Lactococcus lactis (20 mm), Micrococcus luteus (14 mm), and Pseudomonas putida (21 mm) at 100 mg/L test concentration in comparison with OA and TSC synthesized CuO NPs. Therefore, as-synthesized CuO NPs has great potential to employ as effective anti-bacterial agents in medical applications as the synthesis process is faster, economical, and more importantly reliable and reproducible.