Green synthesis of silver nanoparticles by coral vine and assessment of their properties

Aqueous extracts of all parts (leaves, stem and roots) of the invasive terrestrial plant coral vine (Antigonon leptopus; Polygonaceae) were used to synthesise silver nanoparticles (AgNPs) in a rapid and single-step process at ambient temperature and pressure. The effect of several key variables that influenced the shape and/or size of the AgNPs was studied – including metal–extract stoichiometry, temperature, interaction time, stirring and pH – on the basis of ultraviolet-visible spectrophotometry, scanning electron microscopy, transmission electron microscopy, dynamic light scattering and X-ray diffraction. The study has yielded a template with which processes for synthesising AgNPs of desired shapes and sizes can be developed using A. leptopus as the bioagent. Besides being simple, non-polluting, inexpensive and non-hazardous, the template makes available a means with which it may become possible to utilise the weed A. leptopus on a large scale, thereby opening an avenue to reducing the ecological degradation that it causes. The synthesised AgNPs showed potential to scavenge free radicals and also had catalytic activity.