Greenly synthesised silver-alginate nanocomposites for degrading dyes and bacteria

The environmentally friendly synthesis of silver nanoparticles (AgNPs) has been achieved employing silver nitrate and sodium alginate (SA) without using other chemicals except for sodium hydrate. In the synthesis process, SA functions as both reductive and stabilising agent. The as-synthesised AgNPs size can be controlled just changing the reactive parameters such as the concentration of silver nitrate and SA, the solution pH, the reaction temperature and time. Formation of AgNPs was observed by the colour change in the reaction medium which was further established with UV-Vis spectroscopy. The characterisation of AgNPs infers that the as-synthesised AgNPs with an average size of 8.2nm were spherical in shape and a face cubic crystal structure. The AgNPs-SA beads were easily prepared using AgNPs-SA nanocomposites due to SA crosslinking with metal ions. The catalytic efficiency of the resulting AgNPs beads is evaluated for the reduction of dyes such as 4-nitrophenol, methylene blue and reactive red in the presence of NaBH4. Antibacterial efficacy of AgNPs was analysed against gram-negative Escherichia Coli and gram-positive Staphylococcus aureus by measuring the zones of inhibition on the solid growth medium. The as-synthesised AgNPs have shown efficient inhibitory activity against the tested bacterial strains.