Abstract

Aqueous extract of Kigelia africana fruits have been utilized in the syntheses of silver nanoparticles (AgNPs) and copper-silver bimetallic nanoparticles (Ag-CuNPs). The synthesized nanoparticles have been characterized using UV-vis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX), x-ray diffration (XRD) and transmission electron microscopy (TEM). The antimicrobial activities have been evaluated against both Grams-negative and Grams-positive strains of bacteria and fungus. The UV-vis and FTIR techniques revealed the formation of nanoparticles and the active components were adsorbed on the surface of the particles thereby stabilizing the nanoparticles. The SEM reveals uniform microspheres of AgNPs and anisotropic particles for AgCuNPs. TEM shows a particle size of 10 nm. The nanoparticles inhibit the growth of both Grams-negative and Grams-positive bacteria. The present nanoparticles synthesized from aqueous extract of K. africana fruits inhibits Klebsiella pneumoniae more than any of the antibiotics tested in this study. It competes very well with augmentin against Pseudomonas aeruginosa and with meropenem against Candida albicans with inhibition zones of 23 and 25 mm, respectively. The bimetallic nanoparticles have demonstrated effectiveness against Staphylococcus aureus, with maximum inhibition zone of 27 mm.

Key words: Green synthesis, bioreduction, nanoparticles, bimetallic particles, Kigelia africana, antimicrobial activities.