Discriminative ion detection of Hg and Cu and selective recognition of PO ions: Real time monitoring in food and water samples and molecular keypad lock integration.

A series of sensors, designated S3R1-S3R4, were designed and synthesized for the detection of PO ions and toxic metals, specifically Hg and Cu ions. The colorimetric detection of PO ions using these sensors exhibited a distinct visual color transition from yellow to purple in organo-aqueous media. The intrinsic cavity-like structure in the thiosemicarbazide-based derivative S3R4 significantly enhances the binding affinity for Hg and Cu ions in organic media. Utilizing UV-visible spectroscopic techniques and electrochemical investigations, the binding constants, stoichiometric ratios, limits of detection (LOD), and the electrochemical properties of the sensor-ion complexes were comprehensively characterized alongside their stability. Density Functional Theory (DFT) validation studies elucidated the binding mechanisms involved in the ion detection process. The LOD for PO with S3R1 was determined to be 0.28 ppm, while the LODs for Hg and Cu with S3R4 were found to be 0.15 ppm and 0.15 ppm, respectively. The significant binding constants and detection limits underscore the potential of S3R1-S3R4 as real-time sensors for detecting PO, Cu, and Hg ions in environmental applications. Furthermore, the integration of molecular keypad locks and logic gate constructions highlights the applicability of these sensors in molecular communication systems.