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A pyridine-dicarbohydrazide-based chemosensor TMC (N 2 , N 6 -bis((E)-5-chloro-2-hydroxybenzylidene)pyridine-2,6-dicarbohydrazide)showed a marked fluorescence response with Al 3+ . With analysis of Job plot and electrospray ionization (ESI)-mass spectrometry, the association of TMC to Al 3+ was determined to be a 1:1 ratio. Detection limit of TMC for Al 3+ was 1.56 μM. Especially, TMC could distinctly distinguish Al 3+ from Ga 3+ and In 3+ . TMC could suitably analyze Al 3+ in a real environment with great recovery and relative standard deviation (RSD). In addition, TMC-coated test kits can be practically used for recognition of Al 3+ . Binding process of TMC to Al 3+ was illustrated with density functional theory (DFT) calculations, NMR titration, ESI-mass, and UV-vis experiments.

A rhodanine-based fluorescent chemosensor DHM, 3-[(E)-{[4-(diethylamino)-2-hydroxyphenyl]methylidene}amino]-2-sulfanylidene-1,3-thiazolidin-4-one, has been designed and synthesized. Sensor DHM showed unique optical properties with large fluorescence change on detecting Zn 2+ . Most cations did not disturb the binding of DHM with Zn 2+ , while Co 2+ and Cu 2+ displayed fluorescence quenching and Fe 2+ , Fe 3+ , and Ni 2+ did some interference. With outcomes of Job plot and electrospray ionization (ESI)-mass data, the binding ratio of DHM to Zn 2+ was determined as a 1:1. Moreover, DHM could detect Zn 2+ with a low detection limit (1.33 μM). DHM could efficiently analyze Zn 2+ in a real environment with positive recovery and relative standard deviation (RSD) and be recyclable reliably with ethylenediaminetetraacetic acid (EDTA). DHM-doped test kits can be readily used for recognizing Zn 2+ . The binding feature of DHM to Zn 2+ was illustrated by ESI-mass, nuclear magnetic resonance (NMR) titration, and calculations.

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).