Detection of Fe(III) ion based on bifunctionalized silver nanoparticles: Sensitivity, selectivity and environmental safety

Functionalized silver nanoparticles (AgNPs) are widely used as optical sensors for heavy metal ions in water, due to their versatile, easy and cheap preparations and due to their peculiar physico-chemical properties. Surface functionalization plays a key role in AgNPs chemical-physical behavior as capping agents can affect sensitivity, selectivity but alsoenvironmental safety. In this framework, AgNPs are synthetised and properly functionalized using two capping agents to induce hydrophilic behavior and selectivity, respectively citrate (cit) and glutathione (GSH). The opportune choice of these capping agents induces size control and stability for AgNPs-cit-GSH in water (o = 4 +/- 0.2 nm; zeta-potential = -60 +/- 1 mV) and make available selectively detection of Fe (III) in the range 0.5-10.0 ppm. Environmental safety was also evaluated using standardized ecotoxicity assays (ecosafety) with freshwater and marine microalgae which show a low-to-negligible effects, with exception only at the highest tested concentration (10 mg/L) but only for the freshwater one.