Thiazole-derived pyrazin-2-carbohydrazide chemosensors: Colorimetric & photoluminescent detection of silver ions for theoretical, environmental, and cell imaging

In this work, a simple and versatile chemosensor receptor TZPYZ was synthesized through the combination of thiazole with pyrazine-2-carbohydrazide, resulting in a confirmed chemical structure via various analytical techniques including FT-IR, ¹H, and ¹³C Nuclear Magnetic Resonance Spectroscopy, as well as High-Resolution Mass Spectroscopy analysis. TZPYZ exhibits specific colorimetric and photoluminescent responses to Ag⁺ ions in a solvent solution consisting of DMSO and H₂O (7:3, v/v). Upon addition of Ag⁺ ions, noticeable changes in absorption spectra occur, resulting in a visible color change from pale yellow to blue. Additionally, an enhanced emission intensity with wavelength at 523 nm, when excited at 410 nm. Notably, TZPYZ demonstrated exceptional selectivity for Ag⁺ ions over other metal cations, achieving a detection limit (LOD) of 10.6 × 10⁻⁹ M and 6.74 × 10⁻⁹ M and using the UV–visible & photoluminescent titration method. Interference studies indicated minimal disruption from other metal ions on emission at 523 nm, highlighting TZPYZ discerning capability for Ag⁺ ions. With a binding affinity of 3.622 × 10⁻¹¹ M⁻¹, TZPYZ proved effective in detecting Ag⁺ ions across various water samples, showcasing its practical utility. The mechanism of interaction between TZPYZ and Ag⁺ ions was investigated using various experimental techniques, including Job’s plot, Benesi-Hildebrand investigations, ¹H NMR, and HRMS analysis. Test strips coated with TZPYZ showed selective detection of Ag⁺ ions, indicating its potential for on-site applications. Furthermore, DFT computations provided insights into the structural and electronic properties of TZPYZ and its complex with Ag⁺ ions, further elucidating the binding mechanism and stability of the complex. In addition, TZPYZ demonstrated compatibility with biological systems, as fluorescence imaging tests on MCF-7 breast cancer cells confirmed both its non-cytotoxic nature and its proficiency in detecting intracellular silver ions. Based on these findings, TZPYZ is highlighted as a highly sensitive and selective chemosensor for Ag⁺ ions, with promising applications in environmental analysis and bioimaging.