Selective optical detection of HSO4− via hydrolysis of a simple Schiff Base

A very simple Schiff Base derived from 1-Naphthylamine and 4-(Trifluoromethy) benzaldehyde (L) was prepared as a selective colorimetric and turn-on fluorescent sensor for hydrogen sulfate. In the CH 3 CN:H 2 O (3:2, v/v) solvent system, L shows a highly selective colorimetric response to HSO 4 − ions by changing its color from yellow to colorless immediately. In addition, the weakly fluorescent receptor L shows a highly selective enhancement of fluorescence intensity at 425 nm for HSO 4 − upon excitation at 320 nm. The recognition process is proven to be hardly influenced by the other tested competitive anions. The sensing is suggested to involve a hydrolysis process promoted by HSO 4 − which has been further supported by UV–Vis, 1 H NMR and HRMS spectroscopic studies. Applicability of L to detect HSO 4 − in tap water has been demonstrated. An easy-to-prepare test strip of L has also been made for the naked-eye detection of HSO 4 − in real samples.