Sequentially reduced biogenic silver-gold nanoparticles with enhanced antimicrobial potential over silver and gold monometallic nanoparticles

Bimetallic nanoparticles have emerged up as advanced nanomaterials due to the synergism between two metallic nanoparticles in core-shell or alloy arrangement. Moreover, bioinspired synthesis of nanoparticles is an evergreen approach of nanobiosciences. In this experiment, we have fabricated silver, gold and silver (core) gold (shell) bimetallic nanoparticles using leaf extract of Catharanthus roseus Linn. by sequential reduction technique. The sequentially reduced silver-gold nanoparticles in core-shell arrangement were detected by shift in the surface plasmon resonance of nanoparticles from 423 nm to 526 nm with the aid of UV-Visible spectrophotometer. Nanoparticle tracking analysis confirmed the mean particle size for all the nanoparticles within the range 11 to 65 nm. X-Ray diffraction analysis revealed Bragg’s reflections denoting face cubic centered crystalline nature of all the synthesized nanoparticles. Transmission electron microscopy showed that silver and silvergold nanoparticles are quite polydispersed and spherical in shape while anisotropic Au nanoparticles were also observed. These phytofabricated Ag-Au nanoparticles have been evaluated with enhanced antibacterial and anticandidal potential over their monometallic counterparts with particular reference to some pathogenic bacteria and Candida sp. The maximum lethality of bimetallic nanoparticles was observed for Escherichia coli followed by Pseudomonas aeruginosa, while Candida parapsilosis was found to be the least susceptible organism for the silver-gold nanoparticles. Copyright © 2015 VBRI press.