A new and facile strategy for the one-pot fabrication of luminescent gold nanoclusters and their prospective application

A simple, novel, green, economic, environment friendly and convenient one-pot fabrication of luminescent gold nanoclusters, incorporating an aqueous extract of the peels of Allium cepa L., otherwise considered as a common household waste material, has been described. The optimal experimental conditions including concentrations of Allium cepa L. extract and different reaction temperatures have been investigated in detail. The nanoclusters were characterized by various spectroscopic techniques, such as ultra-violet spectroscopy (UV-vis), photoluminescence spectroscopy (PL), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction pattern (SAED), Fourier-transform infrared spectra (FTIR), X-ray diffraction spectroscopy (XRD) and scanning electron microscopy with energy dispersive X-ray (SEM-EDX). spectroscopic results revealed the formation of clusters with an average diameter in the range of 4-9 nm and depicted a fluorescence emission spectrum at 640 nm. Furthermore, the EDX pattern also revealed the formation of gold nanoclusters. The prepared nanoclusters were effectively utilized for the remediation of two carcinogenic and lethal textile dyes, rose bengal and methylene blue from aqueous solution. Approximately, 98.9 and 95.1% of rose bengal and methylene blue dye were degraded within 180 and 145 min using the synthesized gold nanoclusters, respectively. Additionally, the exhausted nanoclusters were regenerated and their photo catalytic capability was evaluated for three continuous rounds of cycling. The exhausted nanoclusters and the intermediates of the degradation process were respectively analysed using TEM, SAED and LC-MS techniques. The catalytic efficiency of the fabricated nanoclusters was also evaluated by conversion of 4-nitro phenol to 4-amino phenol in the presence of sodium borohydride in an aqueous medium. It was observed that about 97.3% of 4-nitro phenol was reduced within 70 min. Furthermore, the fabricated clusters were also found to inhibit the growth of a common human pathogenic bacterium, Escherichia coli. Hence, the present study has unfastened a pioneering way for synthesizing Au NCs and their applicability for the remediation of hazardous compounds and their potential as antibacterial agents.