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 thiosemicarbazide-based fluorescent sensor (AFC) was developed. It was successfully applied to detect hypochlorite (ClO⁻) with fluorescence quenching in bis-tris buffer. The limit of detection of AFC for ClO⁻ was analyzed to be 58.7 μM. Importantly, AFC could be employed as an efficient and practical fluorescent sensor for ClO⁻ in water sample and zebrafish. Moreover, AFC showed a marked selectivity to ClO⁻ over varied competitive analytes with reactive oxygen species. The detection process of AFC to ClO⁻ was illustrated by UV–visible and fluorescent spectroscopy and electrospray ionization–mass spectrometry (ESI–MS).

A novel acylhydrazone-based fluorescent sensor NATB was designed and synthesized for consecutive sensing of Al³⁺ and H₂PO₄⁻. NATB displayed fluorometric sensing to Al³⁺ and could sequentially detect H₂PO₄⁻ by fluorescence quenching. The limits of detection for Al³⁺ and H₂PO₄⁻ were determined to be 0.83 and 1.7 μM, respectively. The binding ratios of NATB to Al³⁺ and NATB-Al³⁺ to H₂PO₄⁻ were found to be 1:1. The sequential recognition of Al³⁺ and H₂PO₄⁻ by NATB could be repeated consecutively. In addition, the practicality of NATB was confirmed with the application of test strips. The sensing mechanisms of Al³⁺ and H₂PO₄⁻ by NATB were investigated through fluorescence and UV–Visible spectroscopy, Job plot, ESI-MS, ¹H NMR titration, and DFT calculations.