Silver nanoparticles based selective colorimetric sensor for Cd2+, Hg2+ and Pb2+ ions: Tuning sensitivity and selectivity using co-stabilizing agents

N-(2-hydroxybenzyl)-valine (VP) and N-(2-hydroxybenzyl)-isoleucine (ILP) organic ligands have been utilized as reducing and surface functionalizing agents in the synthesis of silver nanoparticles (AgNPs) with metal ion interacting functionality. VP and ILP metal interacting ligands functionalized AgNPs exhibited selective colorimetric sensing of toxic Cd2+, Hg2+ and Pb2+ metal ions in aqueous solution at ppm level. The colorimetric sensitivity and metal ion selectivity of VP- and ILP-AgNPs were modulated by incorporating co-stabilizing agents. Importantly, ILP functionalized AgNPs selectively detected Cd2+ ions in the polluted ground water samples also.