Room temperature green synthesis and time resolved kinetics of formation of xanthan gum stabilised silver nanoparticles with catalytic and antibacterial potential

Well-defined and stable, spherical silver nanoparticles (AgNPs) were synthesized at room temperature by a green approach using xanthan gum (XG) as a reducing and stabilizing agent. The effect of various concentrations of silver nitrate on the formation kinetics of AgNPs at 23 °C and pH 10 was studied. The nanoparticles formation with XG as a reducing agent followed a first-order reaction kinetics. The denaturation of XG from a helix to a random polymer coil was achieved at 23 °C and pH 10. Renaturation of XG was not observed at room temperature, and the nanoparticles were stable against aggregation during prolonged storage of more than 8 months. The formation of AgNPs was studied using UV-Vis absorption spectroscopy, and a strong surface plasmon resonance peak centred around 407–413 nm confirmed the presence of nanoparticles. The optical bandgap of the nanoparticles was estimated to be in the range of 2.46 to 2.55 eV. Transmission electron microscope (TEM) images showed spherical and non-agglomerated nanoparticles of 10–22 nm size range. The Fourier-transform infra-red spectroscopy (FTIR) revealed the presence of an organic layer (due to XG) on the surface of the nanoparticles. The nanoparticles were highly effective in the degradation of a model organic pollutant, 2-nitrophenol, exhibiting 80% degradation within 10 min, with a pseudo-first-order rate constant of 0.211 min− 1. The AgNPs showed size-dependent favourable antibacterial potential against Staphylococcus aureus and Salmonella typhimurium.