Green synthesis of copper oxide and cobalt-doped copper oxide nanoparticles using Kalanchoe petitiana (Endahula) leaf extracts and evaluation of its antimicrobial activity

Abstract

Copper oxide nanoparticles have attracted huge attention due to their catalytic, electric, optical, photonic, and antimicrobial activity. The use of plant leaf extracts in the biosynthesis of nanostructured materials is an eco-friendly, non-toxic, and cost-effective approach. In this study, green synthesis, characterization, and evaluation of the antimicrobial activity of copper oxide and Co-doped CuO NMs were studied by using Kalanchoe petitiana leaf extracts. The CuO and Co-doped CuO NMs were successfully synthesized via a fast, convenient, cost-effective, and environmentally friendly method by biologically reducing 0.1M Cu(NO3)2.3H2O and the dopant of Co(NO3)2.6H2O solution with extract of kalanchoe petitiana under optimum condition. The formation of Copper oxide nanoparticles was primarily noticed by observing color changes. The biosynthesized CuO and Co-doped CuONMs would be characterized by using UV-Vis analysis, Fourier Transform Infrared Analysis (FTIR), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM) and cyclic voltammetry (CV). From the UV-Vis absorption spectrum, the peaks of CuO NPs and Co-doped CuO Nps were detected at 230 and 227,231 and 228 nm respectively, and with Eg of 4.87, 4.85, 4.8, and 4.82 eV respectively. FT-IR revealed the presence of carbonyl and hydroxyl groups in the synthesized nanoparticles. The XRD data showed the crystalline structure of CuO NMs and Co-doped CuO NMs with crystallite sizes of 16.398, 16.393, 16.386, and 16.379nm respectively. SEM shows some CuO NMs has a spherical shape and Co-doped CuO NMs has a mixture of spherical and rod-like shape.CV shows oxidation-reduction reaction on oxidation at 0.3 v and reduction at -0.25 v. Evaluation of its antimicrobial activity against Gram-negative bacteria E.coli and S.typhi and Gram-positive bacteria S.aureus and B.Cereus and also antifungal activity against C.albicans. They were found to have a significant effect in controlling the growth of the human pathogens with a maximum inhibition zone of 25 mm and 24mm, 20 mm, and 19mm in S.typhi, S.aureus, B.Cereus and E. coli respectively and for C.albicans 20 mm indicates for CuONMs and Co-doped CuONMs also a zone of inhibition was increased after 24 h incubation time at 37℃.