3 research outputs found
Enhanced Formation of Silver Nanoparticles in Ag<sup>+</sup>‑NOM-Iron(II, III) Systems and Antibacterial Activity Studies
This work reports the role of iron
redox pair (Fe<sup>3+</sup>/Fe<sup>2+</sup>) in the formation of naturally
occurring silver nanoparticles
(AgNPs) in the aquatic environment. The results showed that Fe<sup>3+</sup> or Fe<sup>2+</sup> ions in the mixtures of Ag<sup>+</sup> and natural organic matter enhanced the formation of AgNPs. The
formation of AgNPs depended on pH and types of organic matter. Increase
in pH enhanced the formation of AgNPs, and humic acids as ligands
showed higher formation of AgNPs compared to fulvic acids. The observed
results were described by considering the potentials of redox pairs
of silver and iron species and the possible species involved in reducing
silver ions to AgNPs. Dynamic light scattering and transmission electron
microscopy measurements of AgNPs revealed mostly bimodal size distribution
with decrease in size of AgNPs due to iron species in the reaction
mixture. Minimum inhibitory concentration of AgNPs needed to inhibit
the growth of various bacterial species suggested the role of surfaces
of tested Gram-positive and Gram-negative bacteria. Stability study
of AgNPs, formed in Ag<sup>+</sup>-humic acid/fulvic acids-Fe<sup>3+</sup> mixtures over a period of several months showed high stability
of the particles with significant increase in surface plasmon resonance
peak. The environmental implications of the results in terms of fate,
transport, and ecotoxicity of organic-coated AgNPs are briefly presented