Sensitive and robust colorimetric assay of Hg2+ and S2- in aqueous solution directed by 5-sulfosalicylic acid-stabilized silver nanoparticles for wide range application in real samples

In this paper, a colorimetric sensor, based on 5-sulfosalicylic acid stabilized silver nanoparticles has been designed and synthesized. It exhibited excellent selectivity, rapid response in recognition, and swift sensitivity toward sulfide and mercuric ion in aqueous solution. The synthesized nanoparticles not only identify mercuric or sulfide ion through sharp and selective colorimetric responses in aqueous medium, also detect the ions in the presence of high salt concentration. The mechanistic approach is based on amalgam formation via a redox reaction path and electrostatic interaction inducing aggregate formation for mercuric and sulfide ion, respectively. The colorimetric sensing mechanismis vividly confirmed through various experiments like HR-TEM, DLS, zeta Potential, UV-vis, FT-IR and H-1 NMR spectroscopic studies. Color deflection for this colorimetric detection is well observed by open eyes within 30 s. The proposed sensing strategy was specific in determining toxic Hg2+ and S2- ion within WHO's standard range. The calculated detection limit was found 4 +/- 0.25 nM for S2- ion and 14 +/- 0.42 nM for the Hg2+ ion. This method is very much interference free from closely associated competitive ions and fruitfully demonstrated prospective outlooks for the onsite practical applications.