Synthesis of AuNPs with catalytic and antioxidant properties using the dreaded weed mimosa

The paper presents a method for the biomimetic extracellular synthesis of gold nanoparticles (AuNPs) by using the aqueous extracts of all the main parts (leaves, stem and roots) of the highly invasive terrestrial weed mimosa (Mimosa pudica). Aqueous extracts of each of these parts served as reducing as well as stabilizing agents. The effects of key variables that influenced the shape and/or size of the AuNPs – mainly metal-extract stoichiometry, temperature and pH – were studied with the help of ultraviolet–visible spectrophotometry, X-ray diffraction, energy-dispersive X-ray spectroscopy, electron microscopy and Fourier transform infrared spectroscopy. The efficacy of the AuNPs in free radical scavenging and as catalyst was witnessed. The studies thus provide a template for scaling up AuNP synthesis and utilizing it. Given the fact that M. pudica is freely available in large quantities, with no other recognized use, the present method opens up a possibility for its large-scale utilization in synthesizing AuNPs of tunable shapes and sizes in a rapid, non-polluting, energy-frugal and inexpensive manner.