Hyaluronate macromolecules assist bioreduction (AuIII to Au0) and stabilization of catalytically active gold nanoparticles for azo contaminated wastewater treatment

Abstract

The opto-electrical features of gold nanoparticles (AuNPs) are being expanded broadly for high-tech applications, including electronic conductors, sensory probes, organic photovoltaics, therapeutic agents, drug delivery in medical/biological applications, and catalysts. However, the expansions of these wide applications are significantly hindered by the agglomeration tendency of colloidal AuNPs. Therefore, in obedience to the concept of eco-friendly synthesis protocol, AuNPs were synthesized via a cleaner approach and stabilized by sodium hyaluronate (SH) biopolymer instead of using any toxic agent. The optimization of synthesis parameters and controlling the properties of AuNPs were achieved by a one-variable-at-a-time technique where all reaction variables were constant. The resultant particles were mostly spherical/oval shape, highly crystalline (d-spacing = 0.204–0.233 nm), nano-range size (19.7 ± 3.3 nm) with a narrow distribution, and significantly stable The investigation also revealed that the generation and stabilization of AuNPs were mainly the result of biopolymers-to-metal cations redox-reaction and the capping by a thin layer of SH-macromolecules, respectively. Additionally, as-synthesized AuNPs exhibited catalytic activity for the azo-dye reduction with more than 99% rate of degradation within 10–30 min. The present synthesis method could be consecutively applicable for synthesizing catalytically active AuNPs to be employable in various industrial purposes, including wastewater treatment.