Sustainable preparation of AuAg alloy@AgBr Janus nanoparticles via dissipative self-assembly for photocatalysis

Abstract

We report a facile synthesis of cetyltrimethylammonium bromide (CTAB) templated AuAg alloy@AgBr Janus-nanoparticles (JNPs) using a non-conventional top-down approach with precise control over symmetry breaking. The addition of AgNO₃ to a micellar solution of CTAB results in micelle-stabilized AgBr colloids having excess Ag⁺ at the interstitial sites of AgBr. AgBr colloids undergo weak self-assembly supported by inter-micellar interactions. The interfacial disturbance of self-assembled colloids via electrostatic adsorption of AuCl₄⁻ or Au(OH)₄⁻ at the micelle–AgBr interface downsizes the colloids. This is followed by the growth of the AuAg phase onto AgBr resulting in AuAg alloy@AgBr JNPs via different reduction pathways (photoreduction or chemical reduction) in the presence of ascorbic acid. The prepared JNPs act as efficient visible light photocatalysts for the degradation of aqueous rhodamine B. Interestingly, the trapping of holes favors the photocatalytic efficiency. Furthermore, the JNPs have shown proficiency in inhibiting the growth of both Gram-positive and Gram-negative bacteria as compared to the commercial antibiotic kanamycin, with a very low MIC value of ∼35 μg ml⁻¹. In this way, a new single-pot strategy for the controlled preparation of photo-catalytically active and antimicrobial AuAg alloy@AgBr JNPs governed by dissipative self-assembly is reported for the first time.