Comparative study on stability, antioxidant and catalytic activities of bio-stabilized colloidal gold nanoparticles using microalgae and cyanobacteria

Abstract

Vast applications of gold nanoparticles (AuNPs) in biomedical, catalytic and electronic fields has raise some concerns on the safety of AuNPs used, especially towards human and the environment. Together with the challenge to control the morphology and to produce stable AuNPs, more research has been designed to provide a simple and safer method of synthesis. Bio-stabilized colloidal AuNPs were synthesized using only gold salt, water and natural ingredients from two different groups: microalgae (chlorella) and cyanobacteria (spirulina). The stabilizers contain phytochemicals which are able to reduce and stabilize the AuNPs solution, and further provide antioxidant and catalytic properties. The biosynthesized colloidal AuNPs were characterized with UV–vis, XRD, Raman spectroscopy, and HRTEM. The antioxidant activity was determined using DPPH and hydroxyl assays. The catalytic activity was studied via 4-nitrophenol reduction. Spirulina-stabilized colloidal AuNPs showed prominent potential with average particle diameter of 14.14 nm with spherical shape. The sample also possessed higher DPPH and hydroxyl scavenging activity of 60.08 % and 58.89 % respectively and catalyzed the reduction of 4-nitrophenol faster than chlorella-stabilized colloidal AuNPs. The performance of bio-stabilized colloidal AuNPs in this study provide a promising hope of fully using natural ingredients instead of hazardous chemicals to produce safe AuNPs for its wide application.