Micelle-induced multiple performance improvement of fluorescent probes for H2S detection

In this paper, two colorimetric and turn-on fluorescent probes N-2-(2-hydroxy)-ethoxy] ethyl-4-azido-1,8-naphthalimide (SS1) and N-butyl-4-azido-1,8-naphthalimide (SS2) for selective recognition of H₂S were designed and synthesized. The probes were constructed by incorporating an azido group into the naphthalimide fluorophore as a specifical reaction group for sulfide utilizing its reducing property. Once treated with H₂S, the azido groups of the probes were converted to amino groups and the solutions’ color changed from colorless to yellow companied with a strong yellow-green fluorescence. Rapid and sensitive responses of the probes towards H₂S were achieved in the presence of cationic surfactant cetyltrimethyl ammonium bromide (CTAB): the reaction was completed within 10 min in CTAB compared to more than 4 h in buffer solution, and the detection limit decreased from 0.5 μM to 20 nM. High selectivity and good competition of both probes towards H₂S over other 11 ions and 2 reducing agents were realized in CTAB micelle. An overall linear concentration range of 0.05 μM to 1 mM was achieved with the assistance of differently charged surfactants CTAB and sodium dodecyl sulfate (SDS). The probes were applied to rapidly and sensitively detect H₂S levels in fetal bovine serum without any pretreatment of the sample.