An indole-based fluorescent chemosensor IH-Sal was synthesized to detect Zn²⁺. IH-Sal displayed a marked fluorescence increment with Zn²⁺. The detection limit (0.41 μM) of IH-Sal for Zn²⁺ was greatly below that suggested by the World Health Organization. IH-Sal can quantify Zn²⁺ in real water samples. More significantly, IH-Sal could determine and depict the presence of Zn²⁺ in zebrafish. The detecting mechanism of IH-Sal toward Zn²⁺ was illustrated by fluorescence and UV–visible spectroscopy, DFT calculations, ¹H NMR titration and ESI mass.

A novel fluorescent turn-on chemosensor DHADC ((E)-3-((4-(diethylamino)-2-hydroxybenzylidene)amino)-2,3-dihydrothiophene-2-carboxamide) has been developed and used to detect Zn²⁺ and CN⁻. Compound DHADC displayed a notable fluorescence increase with Zn²⁺. The limit of detection (2.55 ± 0.05 μM) for zinc ion was far below the standard (76 μM) of the WHO (World Health Organization). In particular, compound DHADC could be applied to determine Zn²⁺ in real samples, and to image Zn²⁺ in both HeLa cells and zebrafish. Additionally, DHADC could detect CN⁻ through a fluorescence enhancement with little inhibition with the existence of other types of anions. The detection processes of compound DHADC for Zn²⁺ and CN⁻ were demonstrated with various analytical methods like Job plots, ¹H NMR titrations, and ESI-Mass analyses.