Title : Molecularly defined chemosensors for detection, quantification, and discrimination of Zn2+ and Cd2+, Fe2+ and Hg2+ in freshwater samples
Abstract:
Our research group has been developing molecular chemosensors for metal-ion detection and remediation for over 12 years. Our previous work established effective molecular systems for the colorimetric detection of Fe²⁺ in water and the detection and removal of Hg²⁺ from aqueous and organic media. These systems use molecular receptors that specifically bind to particular metal ions. Furthermore, immobilization of these receptors on magnetic nanosupports enables efficient Hg²⁺ removal through externally applied magnetic fields.¹ This research provides a foundation for developing molecularly engineered materials that combine selective metal-ion recognition with practical environmental applications.
Building on this work, we recently developed a fully water-soluble fluorescent chemosensor based on 4′-hydrazineyl-2,2′:6′,2″-terpyridine for the selective, turn-on detection of Zn²⁺ and Cd²⁺ in aqueous media at picomolar concentrations.4 The sensor combines rapid fluorescence responses with exceptional analytical sensitivity and selectivity against 20 competing metal ions. The limits of detection (LODs) and quantification (LOQs) were 0.029 and 0.095 nM for Zn²⁺ and 0.098 and 0.328 nM for Cd²⁺, respectively, well below relevant Canadian drinking-water guidelines, including the aesthetic objective for Zn²⁺ (76.5 µM) and the maximum acceptable concentration for Cd²⁺ (62.3 nM). Importantly, the sensor enables discrimination between Zn²⁺ and Cd²⁺, addressing a persistent challenge in fluorescent metal-ion sensing.
In keeping with green chemistry principles, the sensor operates in water, supports repeated use, and offers a practical approach to reducing sensor-related material waste. We validated its performance against inductively coupled plasma mass spectrometry (ICP-MS) and demonstrated accurate quantification of metal ions in Lake Ontario water samples, with excellent recovery. The sensor can be regenerated up to 20 times using EDTA treatment and readily adapted into low-cost paper-based test strips for rapid, on-site analysis. Complementary experimental and computational investigations elucidate metal-ion coordination and its influence on the complexes’ photophysical properties.
This work establishes a promising platform for sensitive, selective, and reusable metal-ion monitoring in freshwater, combining aqueous-phase operation, resource-efficient sensor regeneration, and potential field deployment for environmental assessment.
References.
1. Egan, J. G.; Hynes, A. J.; Fruehwald, H. M.; Ebralidze, I. I.; King, S. D.; Reza, A. M. E.; Naumkin, F. Y.; Easton, E. B.; Zenkina, O. V., J. Mater. Chem. C 2019, (7), 10187 - 10195.
2. Laschuk, N. O.; Ebralidze, I. I.; Quaranta, S.; T. W. Kerr, S.; Egan, J. G.; Gillis, S.; Gaspari, F.; Latini, A.; Zenkina, O. V., Materials & Design 2016, 107, 18-25.
3. Laschuk, N. O.; Ebralidze, I. I.; Spasyuk, D.; Zenkina, O. V., Eur. J. Inorg. Chem. 2016, 2016 (22), 3530-3535.
4. Antsybora, Y. V.; Adams, C. Y.; Golus, A.; Naumkin, F. Y.; Agarwal, N. R.; Zenkina, O. V., Chem. Commun. 2026, Advances Article.
