Green synthesis of gold nanoparticles from Lawsoniainermis and its catalytic activities following the Langmuir-Hinshelwood mechanism

Abstract

The significance of green synthesised nanoparticles has gained interest in environmental safety and its manufacturing processes. The chemical methods applied for nanoparticle synthesis are expensive and utilise chemicals that are hazardous to the environment hence led to the emergence of the “greener” method. The plant-extract based synthesis of nanoparticles is a feasible alternative approach to chemical reduction techniques. This study aims to develop instant, facile, efficient, low-cost, eco-friendly green synthesis method for synthesising stable gold nanoparticles using the leaf extract of Lawsonia inermis. The phytochemicals in the leaf extract act as a reducing agent in the formation of gold nanoparticles within 45 min. The characterisation of the gold nanoparticles was performed using physicochemical techniques. Besides, the impact of different parameters like salt, pH, temperature, and storage on the stability of the gold nanoparticles has been studied. Among the three synthesised gold nanoparticles samples (X, Y, and Z), X sample showed the highest stability. The gold nanoparticles were spherical with an average size of ∼20 nm. The most stable gold nanoparticles exhibited excellent catalytic activity in the degradation of anthropogenic aromatic pollutants like 4-nitrophenol, and dyes like bromophenol blue and methyl red. Moreover, the gold nanoparticles did not show cytotoxic effect in normal human epithelial lung cell lines.