Green synthesis of copper oxide nanoparticles from Camellia sinensis extract: Effects of calcination temperatures on...

This study explores the influence of calcination temperature on the structural, morphological, and antibacterial properties of copper oxide nanoparticles (CuO NPs) synthesized using Camellia sinensis extract. XRD confirmed the monoclinic crystal structure of the CuO NPs, while UV-Vis and FTIR analyses verified the successful formation of nanoparticles and the presence of phytochemicals from the extract. Among the samples, CuO NPs calcined at 300 °C (CT₂) exhibited superior antibacterial activity, with the highest inhibition zone of 29 mm recorded against Escherichia coli. Enhanced performance was also observed against Staphylococcus aureus, Streptococcus mutans, and Klebsiella pneumoniae. This improved efficacy is attributed to preserving key functional groups, such as CC bonds, at moderate calcination temperatures, along with favourable surface morphology and increased pore size, as confirmed by FE-SEM and BET analyses. In contrast, higher calcination temperatures led to diminished antibacterial performance, likely due to the loss of surface-active functional groups and reduced porosity. Overall, the findings emphasize the critical role of temperature control in optimizing the antibacterial potential of green-synthesized CuO NPs.