Rapid green synthesis of reusable alginate-silver nanocomposite beads using Yerba mate (Ilex paraguariensis) for catalytic and antibacterial applications

1. Introduction

Green synthesis of NPs has gained momentum as a promising and alternative approach. The use of aqueous extracts of plants is an attractive approach as the protocol is simple, cost-effective, and does not produce any toxic wastes. Our aim was to leverage the high content of phytochemicals in fresh leaf extract of Yerba mate (Ym) to sustainably produce AgNPs and AgNc beads, and to evaluate their catalytic degradation of hazardous compounds and antibacterial efficacy.

1. Method

Sodium alginate-silver nanocomposite (SA-AgNc) beads were prepared by reduction and ionotropic crosslinking (gelation). The beads were characterized by UV-Vis absorption spectroscopy, electron microscopy, and energy dispersive X-ray spectroscopy (EDX). The catalytic potential was studied by following the degradation of organic compounds such as 2-nitrophenol, Congo red, and methylene blue. The antibacterial efficiency was tested against Escherichia coli.

1. Results

The SA-AgNc beads were close-to spherical shape with cauliflower-like morphology. The presence of pores and AgNPs on the beads were confirmed by electron microscopy and EDX mapping. Sigmoidal degradation profile reflects initial adsorption on the surface, then rapid breakdown. The beads were effective in disinfection of the bacterial solution.

1. Conclusions

SA-AgNc beads containing Ym reduced AgNPs was successfully prepared by reduction and ionotropic crosslinking with calcium ions. The catalytic and antibacterial activities of SA-AgNc were promising. In future, these types of materials hold promise in the treatment of hospital wastewater.