Tunable electrochemistry and efficient antibacterial activity of plant-mediated copper oxide nanoparticles synthesized by <i>Annona squamosa</i> seed extract for agricultural utility

Abstract

The present report deals with the synthesis of plant-mediated copper oxide nanoparticles (pm-CuO NPs) from <i>Annona squamosa</i> aqueous seed extract for effective antibacterial activity and the further utilization of this as a platform for the electrocatalytic determination of hydrogen peroxide (H₂O₂) for applications in the agricultural domain. The structural, optical and morphological characteristics of the synthesized pm-CuO NPs were analyzed by UV-Vis, XRD, FT-IR, AFM, SEM, TEM, HR-TEM and EDX. After this, pm-CuO NPs were preliminarily investigated for antibacterial activity on Gram-positive and Gram-negative bacterial strains, and further, their activity was validated for assessing their antibacterial efficiency on the <i>Xanthomonas oryzae</i>, a plant pathogenic bacteria strain, and the obtained results showed that pm-CuO NPs have potency as an effective antibacterial agent for the treatment of the bacterial blight of rice caused by <i>X. oryzae</i> in the rice crop, which reduces the rice crop productivity. Further, pm-CuO NPs were electrophoretically deposited onto an indium-tin-oxide (ITO) glass substrate and assessed for the electro-oxidation of H₂O₂ by cyclic voltammetry (CV), and from this it was proved that pm-CuO NPs had a very high electrochemical sensitivity of 49 μA μM^-1 cm^-2 towards H₂O₂ and a low detection limit of 574 μM, with these responses obtained under optimized experimental conditions. Thus, pm-CuO NPs also provide a potential sensing platform for electrochemical studies to detect H₂O₂ produced during plant stress surroundings to properly manage crops susceptible to oxidative damage by elevated H₂O₂ levels during stress.