•A new colorimetric and ratiometric fluorescence probe for hydrogen sulfide is developed.•The use of Michael acceptor as the sensing group of H2S shows high selectivity and sensitivity.•Probe 1 for hydrogen sulfide detection is based on intramolecular charge transfer (ICT) mechanism.A new 4-hydroxy-1,8-naphthalimide-based compound (probe 1) has been designed and synthesized. The colorimetric and fluorescent properties of probe 1 towards hydrogen sulfide (H2S) were investigated in detail. The results show that the probe 1 could selectively and sensitively recognize H2S rather than other reactive sulfur species. The reaction mechanism of this probe is an intramolecular cyclization caused by the Michael addition of H2S to give 4-hydroxy-1,8-naphthalimide. The intramolecular charge transfer of 4-hydroxy-1,8-naphthalimide is significant. Probe 1 quickly responded to H2S and showed a 75-fold fluorescence enhancement in 5 min. Moreover, probe 1 could detect H2S quantitatively with a detection limit as low as 0.23 μM.

A new N-butyl-4-amino-1,8-naphthalimide-based colorimetric and ratiometric fluorescent probe for the detection of biothiols (cysteine, homocysteine, and glutathione) was designed and synthesized. The probe exhibited good selectivity and sensitivity toward biothiols over other non-thiol-bearing amino acids and common anions with significant changes in both color (from colorless to yellow) and fluorescence (from blue to yellow-green). The mechanism is based on cleavage of disulfide by thiols followed by an intramolecular cyclization to give the product, N-butyl-4-amino-1,8-naphthalimide, which showed outstanding intramolecular charge transfer (ICT). Therefore, ratiometric fluorescence signal was observed. Furthermore, the probes were successfully applied for visualizing endogenous thiols in living cells.

•A new Sciff base fluorescence probe for Hg2+is designed and synthesized.•The probe can sensitively and selectively detect Hg2+in weakly acidic and neutral pH conditions.•The probe can detect Cu2+in weakly alkaline conditions by using “masking” reagent.A new Schiff base fluorescent probe, 2-(4-(diphenylamine)benzylidene) thiosemicarbazide (DPBT), was synthesized and its sensing behavior to metal ions were studied by UV–vis and fluorescence spectra. The results show that DPBT can detect Hg2+sensitively and selectively in weakly acidic and neutral conditions, they form a complex with 2:1. The linear range was 0.095–1.14 µM and the detection limit was 0.15 nM. In weakly alkaline conditions, DPBT can interaction with Hg2+and Cu2+at the same time. We use “masking” reagent, NaBH4, to reduce Hg2+to Hg°, the detection of Cu2+were achieved. They formed 1:1 complex with the binding constant of 4×104 M−1, a good linear relationship in 0.45–3.6 µM and the detection limit of 0.17 µM. The proposed method was used to determine Hg2+and Cu2+in tap water and waste water samples.

•A new colorimetric and ratiometric fluorescence probe for H2S is developed.•The use of the diselenide bond as the sensing group of H2S shows high selectivity and sensitivity.•The probe is applied in measuring H2S in bovine plasma and bioimaging in cells.A new ratiometric fluorescence probe for hydrogen sulfide is developed. The design was based on a H2S-mediated diselenide cleavage and intramolecular cyclization to release the fluorophore. The probe showed high selectivity and sensitivity for H2S over other reactive sulfur species and was successfully applied for the detection of H2S in bovine plasma and bioimaging in live cells.