Highly sensitive electrochemical sensors employing chemical probe with electron-deficient benzothiadiazole groups for mercury (II) ions detection

• A novel chemical probe of TBB was designed and synthesized for Hg 2+ detection. • TBB showed high selectivity and anti-interference ability for interacting with Hg 2+. • TBB@3D-rGO-based electrochemical sensor showed high sensitivity for Hg 2+ detection. • Selective chemical probe was innovatively applied to electrochemical sensing material. The development of an ultrasensitive electrochemical sensing interface is crucial for precise detection of mercury ions (Hg 2+ ) in water, due to its bioconcentration and persistence present a significant threat to human health and ecosystems. Herein, a selective chemical probe for Hg 2+ was designed and synthesized by incorporating an electron-deficient benzothiadiazole (BTD) group into a triphenylamine-based 2-(benzylideneamino)benzenethiol (TPA-BT) compound, obtaining a novel TPA-BTD-BT (TBB) probe. TBB exhibited impressive selectivity and resistance to interference from other substances during Hg 2+ detection, as predicted through UV–vis, fluorescence spectrometry, and theoretical calculation. The lone pair electrons of nitrogen and sulfur atoms in the TBB molecule facilitated specific recognition of Hg 2+ through coordination. Leveraging the high sensitivity of electrochemical techniques, TBB was noncovalently functionalized with electrochemically reduced three-dimensional graphene oxide (3D-rGO) to fabricate a novel interfacial material for electrochemical sensors. The TBB@3D-rGO/GCE sensor was developed by modifying the TBB@3D-rGO nanocomposite onto the surface of a glassy carbon electrode (GCE). The strong coordination ability of TBB and the exceptional electrochemical properties of 3D-rGO provided the sensor with high sensitivity, selectivity, low detection limit (8.6 nM), wide linear concentration range (0.01–4.0 μM), and excellent reproducibility, making it suitable for the accurate detection of Hg 2+ in aqueous solutions.