Phenothiazine-Indole Acetonitrile Based Ratiometric Chemosensor for S

The detection of sulfide ions in environmental and biological systems has garnered significant interest, but finding probes that combine rapid response with high selectivity remains difficult. Despite progress, the quest for efficient sulfide detection methods is still ongoing. This article introduces the synthesis and development of the ratiometric fluorescent probe PTZ-ICN, utilizing the phenothiazine framework to address the challenge of selective detection. The PTZ-ICN probe's structural integrity and spectral properties were confirmed via FT-IR, ¹H-NMR, ¹³C-NMR, and HRMS analyses. PTZ-ICN exhibits remarkable selectivity and sensitivity towards sulfide ions (S²⁻), even in the presence of competing anions, within a DMSO: HEPES buffer system (9:1, v/v). The interaction between the PTZ-ICN probe and sulfide ions was thoroughly analyzed using Job's plot, HRMS, ¹H-NMR titration, and DFT analysis. The PTZ-ICN probe successfully quantified sulfide ions with a detection limit as low as 11.63 nM, demonstrating a strong linear correlation (R² = 0.99941). Moreover, PTZ-ICN has shown great utility in real-time scenarios, including the detection of sulfide ions in water samples, test strips, solid-state platforms, and living A549 cells. This study emphasizes PTZ-ICN's significant promise for real-world applications in environmental monitoring and bioimaging, establishing it as a valuable probe for reliable sulfide detection across diverse environments.