Green Synthesis of Ag-Cu Nanoalloys Using Opuntia ficus-indica

Bimetallic Ag/Cu nanoparticles have been obtained by green synthesis using Opuntia ficus-indica plant extract. Two synthesis methods were applied to obtain nanoparticles with core-shell and Janus morphologies by reversing the order of precursors. Transmission electronic microscopy revealed size of 10 nm and 20 nm for the core-shell and Janus nanoparticles, respectively. Other small particles with size of up to 2 nm were also observed. Absorption bands attributed to surface plasmon resonance were detected at 440 nm and 500 nm for the core-shell and Janus nanoparticles, respectively. Density functional theory predicted a breathing mode type (BMT) located at low wavenumber due to small, low-energy clusters of (AgCu) (n) with n = 2 to 9, showing a certain correlation with the experimental one (at 220 cm(-1)). The dependence of the BMT on the number of atoms constituting the cluster is also studied.