A strategically designed fluorescent turn-on chemodosimeter for selective detection of mercury (II) via dithioacetal deprotection reaction

Mercury (Hg²⁺) is one of the toxic heavy metals and poses severe health risks and environmental pollution. Thus, we report on the strategic design and synthesis of a new fluorescent chemodosimeter, (Z)-3-(4-(1,3-dithian-2-yl)phenyl)-2-(naphthalen-2-yl)acrylonitrile (DTNA), for detecting Hg²⁺. In the presence of Hg²⁺, DTNA exhibited an intense cyan fluorescence turn-on, showing a significant Stokes shift (150 nm), a high quantum yield (Ф_F = 0.2721), and high selectivity with low interference from other metal ions. The Hg²⁺ recognition mechanism of DTNA was demonstrated as dithioacetal deprotection through ¹H NMR titration, ESI-MS, FT-IR, and DFT calculation. In particular, test papers coated with DTNA were successfully applied for monitoring Hg²⁺, enabling on-site detection.