Lipoic acid assisted microwave based synthesis of Au-Ag nanoclusters with tunable fluorescence for antimicrobial and bioimaging applications.

This study reports on the pioneering synthesis and application of monometallic lipoic acid (LA) stabilized gold nanoclusters (LA@AuNCs) and bimetallic gold-silver nanoclusters (LA@Au-AgNCs) fabricated via a novel microwave-assisted method. The synthesis process unveils a significant augmentation in the quantum yield of LA@AuAgNCs up to 7.9-fold compared to their monometallic counterparts (LA@Au NCs), showcasing the efficacy of the novel microwave-assisted fabrication methodology. The rapid synthesis facilitated by microwave heating not only ensures efficiency but also contributes to superior optical properties. Additionally, the strategic modulation of exogenous parameters, such as thermal conditions and ionic metal concentrations, was leveraged to meticulously engineer the nanocluster surface characteristics, facilitating the procurement of tunable photoluminescent emission spectra spanning from 650 to 800 nm. The applicability of the synthesized metallic nanoclusters has been rigorously evaluated, demonstrating their efficacy as a dual-functional therapeutic agent. Primarily, their antimicrobial properties are pronounced against both Gram-positive and Gram-negative bacterial strains, attributed to the ultrasmall dimensions of the synthesized nanoclusters. Also, these intrinsically fluorescent metallic nanoclusters were employed as advanced bioimaging probes for the precise labelling and visualization of bacterial cells.