Nanomolar Hg²⁺ detection via phenothiazine fluorogenic chemosensor: Applications in water analysis and intracellular...

A Knoevenagel condensation reaction paved the way for the development of the PTZ-BCN probe namely (z)-2-(1H-benzo[d]imidazole-2-yl)-3-(10-ethyl-10H-phenothiazin-3-yl) acrylonitrile. PTZ-BCN's spectral characteristics were verified through the application of IR, ¹H NMR, ¹³C NMR, and HRMS techniques. The PTZ-BCN probe showed a high selectivity and sensitivity toward Hg²⁺ ions over other interfering competing metal ions in CH₃CN: HEPES buffer (9:1, v/v) system. The addition of Hg²⁺ results in a notable redshift and fluorescence quenching of the PTZ-BCN probe. An examination of the interaction between the PTZ-BCN probe and Hg²⁺ involved recoding ¹H NMR titration spectra, HRMS, DFT analysis, and Job's plot respectively. Quantification of the lowest detectable Hg²⁺ concentration at 2.3 nM, exhibiting a correlation coefficient of R² = 0.9985. PTZ-BCN probe has proven effective in quantitatively determining the existence of Hg²⁺ in real-time water samples, test strips, solid state, and Hela living cells.