Biosynthesis of Ag/Cu bimetallic nanoparticles using Ricinus communis and their antibacterial and antifungical activity

Fernando López-Ubaldo, Víctor Sánchez-Mendieta, Oscar F Olea-Mejía, Sol González-Pedroza María and Raúl A Morales Luckie

Abstract

This work demonstrates an efficient, low-cost and environmentally friendly synthetic method of Ag/Cu bimetallic nanoparticles (NPs), which allows taking advantage of renewable resources, using Ricinus Communis leaf extract as bioreducing and passivating agent. By varying the metal salt precursors of AgNO₃ and CuSO₄.5H₂O concentrations, the stable bimetallic NPs were obtained. The Ag/Cu bimetallic NPs were characterised using ultraviolet-visible absorption spectroscopy (UV–vis), Fourier-transform infrared spectroscopy (FTIR), X-ray dispersive energy spectroscopy (EDS), and scanning and transmission electron microscopy (SEM and TEM). In all cases, the particles size is less than 100 nm. The 10:90 Ag/Cu system has the best control of morphology (spheroid) and size in range of 10–25 nm ( σ = 9). Selected area electron diffraction patterns (SAED) are in concordance with JCPDF cards for silver and copper face-centered cubic (fcc) crystal structures. Microbiological susceptibility was tested by disc diffusion, minimum inhibitory concentration (MIC) and minimal lethal concentration (MLC) methods, with the following microorganism strains: Staphylococcus aureus (gram +), Escherichia coli (gram −) and Aspergillus niger (fungus). The MIC concentration for the three strains was found to range from 1.25 to 2.45 μg and the MLC allowance ranges from 2.45 to 9.81 μg.