Core-size-dependent catalytic properties of bimetallic Au/Ag core–shell nanoparticles

Abstract

Bimetallic core–shell nanoparticles have recently emerged as a new class of functional materials because of their potential applications in catalysis, surface enhanced Raman scattering (SERS) substrate and photonics etc. Here, we have synthesized Au/Ag bimetallic core–shell nanoparticles with varying the core diameter. The red-shifting of the both plasmonic peaks of Ag and Au confirms the core–shell structure of the nanoparticles. Transmission electron microscopy (TEM) analysis, line scan EDS measurement and UV–vis study confirm the formation of core–shell nanoparticles. We have examined the catalytic activity of these core–shell nanostructures in the reaction between 4-nitrophenol (4-NP) and NaBH₄ to form 4-aminophenol (4-AP) and the efficiency of the catalytic reaction is found to be increased with increasing the core size of Au/Ag core–shell nanocrystals. The catalytic efficiency varies from 41.8 to 96.5% with varying core size from 10 to 100 nm of Au/Ag core–shell nanoparticles, and the Au₁₀₀/Ag bimetallic core–shell nanoparticle is found to be 12-fold more active than that of the pure Au nanoparticles with 100 nm diameter. Thus, the catalytic properties of the metal nanoparticles are significantly enhanced because of the Au/Ag core–shell structure, and the rate is dependent on the size of the core of the nanoparticles.