Research PaperMercaptobenzoheterocyclic compounds functionalized silver nanoparticle, an ultrasensitive colorimetric probe for Hg(II) detection in water with picomolar precision: A correlation between sensitivity and binding affinity

- A correlation between sensitivity and binding affinity of mercaptobenzoheterocyclic ligands towards Hg2+ and enlightens the mechanism of label-free nanoparticle based mercury sensing..
- These functionalized silver nanoparticles shows excellent sensing capability towards Hg(II) providing a LOD of 1.8 ppt /9.2 pM (MBO capped), 9.2 ppt/46 pm (MBI capped) and 18.4 ppt/92 pm (MBT capped) towards Hg2+ ion with excellent discrimination against other heavy metals.
- To the best of our knowledge, this is the only report that divulges a definitive correlation between sensitivity and binding affinity of mercaptobenzoheterocyclic ligands towards Hg2+ sensing. The detection limit can be pushed to 1.8 ppt using UV-Vis spectroscopy which is competitive with many of the existing protocols developed for Hg(II) sensing.
- Our convenient method can be directly used to detect Hg(II) ions in real water matrices that contains complicated organic and inorganic interferents.
- Our Sensing system can also perform in the physiological pH =7.4 and makes it lucrative alternative for the biological samples.

Toxic heavy metal ions, specially Hg(II) pose lethal threat to the environment and human beings. To this end, there is a strong need to establish a simple, inexpensive method for the detection of Hg(II) ions with high selectivity and sensitivity in aqueous medium. Herein, we report an ultra-sensitive colorimetric detection of Hg(II) ions following a simple protocol by synthesizing silver nanoparticles functionalized with mercaptobenzoheterocyclic compounds (viz. mercaptobenzooxazole (MBO), mercaptobenzoimidazole (MBI) and mercaptobenzothiazole (MBT). These nanoparticles are found to show a limit of detection (LOD) of 1.8 ppt (9.2 pM), 9.2 ppt (46 pM) and 18.4 ppt (92 pM) for MBO, MBI and MBT respectively). In addition, the binding affinity trend of the mercaptobenzoheterocyclic ligands seems to be in tune with the observed sensitivity trait of Hg2+ sensing.

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