Structural, morphological and optical studies of l-cysteine modified silver nanoparticles and its application as a probe for the selective colorimetric detection of Hg2+

•l-Cysteine capped silver nanoparticles-synthesised by chemical reduction method.•Characterised using UV/Vis spectroscopy, TEM, zeta potential, XRD and SERS.•Cysteine is bound to the Ag surface through the thiolate moiety.•Selective colorimetric detection of Hg2+ through free COO− end of adsorbate.

We report an extensive study on the evolution of a highly facile, selective colorimetric probe for Hg2+ detection using cysteine modified silver nanoparticles. The nanoparticles are stable in a basic medium and the Surface Enhanced Raman Spectrum (SERS) reveal that the cysteine is bound to the Ag surface through the thiolate moiety with the charged carboxylate group pointing outwards in a morphology that lends itself to sensor applications. In the presence of Hg2+, the absorption peak is quenched resulting in a drastic colour change. The sensor displays high selectivity to Hg2+ over other metallic ions.

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