Selective colorimetric sensing of potentially health and environmentally hazardous heavy metal ions in aqueous solution was demonstrated using green synthesized silver nanoparticles (AgNPs) from plant extracts, by taking advantage of metal coordinating organic functional groups present in the extracts.AgNPs synthesized using fresh neem leaf extracts (NF-AgNPs) selectively detected Hg 2+ whereas sun-dried neem leaf extract based AgNPs (ND-AgNPs) were observed to selectively sense Hg 2+ and Pb 2+ at micromolar concentrations. Neem bark extract based AgNPs exhibited selective colorimetric sensing of Hg 2+ and Zn 2+ . Similarly, AgNPs synthesized from mango leaf (fresh, MF-AgNPs; sun-dried, MD-AgNPs) and green tea extracts (GT-AgNPs) showed selective colorimetric sensing of Hg 2+ and Pb 2+ ions. AgNPs obtained using pepper seed extracts exhibited Hg 2+ , Pb 2+ and Zn 2+ selective colorimetric sensor properties.Importantly these green synthesized AgNPs selectively detected the presence of hazardous metal ions in aqueous solutions across a wide range of pH values (2.0-11), which is a highly desirable attribute from the perspective of different sources of water pollution. The selective colorimetric sensing of Hg 2+ , Pb 2+ and Zn 2+ ions by green synthesized AgNPs over a wide pH range demonstrates the multi-functional utility of plant extracts in green nanotechnology and environmental sensor applications.
A method for the sensitive and selective determination of Hg2+ was developed based on the aggregation and re-aggregation of silver nanorods (SNRs) in the presence of dithiothreitol.
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