A Quick Responsive Chitosan‐Oxine Based Thin Film to Recognize and Remove Zn²⁺ Ions from Potable Water

Abstract

Through the functionalization of chitosan (CS) with an oxine derivative, 8-hydroxy-2-methyl-quinoline5,7-sulfonyl chloride (HQSC), a thin film was prepared (CS-HQSC). The film can recognize and adsorb Zn 2 + ions from the aqueous samples. The sensor performances were characterized by UV-Visible and fluorescence spectroscopic analysis. The weakly fluorescent thin film becomes highly fluorescent in the presence of Zn 2 + ions. The solution-phase study of the functionalized material shows a 30-fold fluorescence enhancement in the presence of Zn 2 + ions. The chelation of Zn 2 + ions with CS-HQSC could be the reason for the fluorescence enhancement. The chelation restricts the excited-state proton transfer in the quinoline ring and facilitates chelation enhanced fluorescence. The sensor showed a linear detection of Zn 2 + ions from 0.2 to 2 ppm, with the lowest detection limit of 0.08 ppm. The practical applicability studies of the sensor prove that the sensor film is quick responsive (30 seconds) and recyclable in acid solution. Also, the functionalized material CS-HQSC shows 96 % removal of Zn 2 + ions from the water samples.