Hyaluronate macromolecules assist bioreduction (Au-III to Au-0) and stabilization of catalytically active gold nanoparticles for azo contaminated wastewater treatment

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. (C) 2021 The Authors. Published by Elsevier B.V.