Nano materials have a wide range of applications due to their interesting size-dependent chemical and physical
properties compared to particles of size in the range of micrometer. In this study, we studied the structural and
antimicrobial properties of cupric oxide nanoparticles (CuO NPs) that synthesized by the sol–gel method and
characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The
antimicrobial activity of CuO NPs was evaluated against gram-negative bacteria (Escherichia coli) and gram-positive
bacteria (Staphylococcus aureus) using agar-well diffusion method and minimum inhibition concentration (MIC). The
average diameter of synthesized CuO NPs was 25.8 nm with approximately round-shape particles. CuO NPs showed
excellent antimicrobial activity against both E. coli and S. aureus, but gram-positive bacteria is more sensitive to CuO
NPs than gram-negative one, where the MIC of S. aureus and E. coli were 15 and 22 µg/ml, respectively. So, CuO NPs
could be suggested as new effective agents of multidrug-resistant bacteria.