Thiophenol amine-based Schiff base for colorimetric detection of Cu2+ and Hg2+ ions

Metal ions play a momentous role in environment and human physiology. However, heavy metal ions like Cu2+and Hg2+ are toxic for the living bodies even when present in trace amount. Thus, to detect Cu2+ and Hg2+ ions, simple spectroscopic methods (colorimetric) are used. Therefore, development of simple Schiff base probes for multi-analyte detection is favorable. In order to develop a sensor for colorimetric detection of specific ions, we explored the capability of new thiophenol amine based colorimetric sensor. Synthesis of sensor L was carried out using Single step condensation and the structure was analyzed using FT-IR, 1H NMR and HRMS, 13C NMR analysis. Sensor L is remarkably selective for the sensing of Cu2+ and Hg2+ ions over other heavy-metal ions, and also exhibits excellent color change from colorless to orange and colorless to yellow for Hg2+ and Cu2+ ions, respectively in mixed aqueous medium. Further binding stoichiometric ratio of probe with Cu2+ and Hg2+ ions was found to be 2:1, determined using Job's Plot. Limit of detection for Cu2+ and Hg2+ was observed to be 50 x 10-9 M and 18 x 10-8 M, respectively. The response time of sensor is instantaneous and its reversible nature was confirmed using EDTA titrations. For field utility, solid substrates (test strips and silica gel) were designed and tested for fast, reliable, user friendly and real time sensing of both Cu2+ and Hg2+ ions.

Automated summary

Metal ions play a significant role in the environment and human physiology, but heavy metal ions can be toxic even in trace amounts. Therefore, the development of simple Schiff base probes for multi-analyte detection is favorable. In this study, a colorimetric sensor based on thiophenol amine was synthesized and found to be highly selective for the detection of Cu2+ and Hg2+ ions, with excellent color change in mixed aqueous medium.