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

Abstract 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 Hg 2+ sensing.