Homogeneously-Alloyed Gold–Silver Nanoparticles as per Feeding Moles

Abstract

Wet-chemical methods involving the coreduction of HAuCl4 and AgNO3 have been proven particularly suitable for producing stable Au–Ag alloy NPs with controllable structure–property relationship. However, very poor-solubility of AgCl in aqueous medium and intrinsically different surface energies of Au and Ag remained detrimental-factors in synthesizing so-called “alloy” NPs above the solubility-product of AgCl. Here, we report a robust coreduction procedure for producing citrate-stabilized “homogeneously alloyed” Au–Ag NPs of average size sub-10 nm at room-temperature upon simultaneously overcoming the detrimental factors by a simple reagent NH4OH. The alloy NPs revealed a high-degree of crystallinity, composition-tunable surface plasmon resonance (SPR) behavior, controlled-catalysis, biocompatibility, surface enhance Raman scattering (SERS) activity and high-chemical stability. The alloy NPs could withstand corrosive chemical environment and be easily transferred from aqueous medium to various organic media. Fusion of NPs under high-energy electron-beam suggested an inertial coalescence. Our method may lead to the developments of metallic and bimetallic alloy NPs in the fulfillment of various applications in the future.