Zinc-8-hydroxyquinoline intercalated in calcium bentonite: A promising DO sensor

Zn(II) and 8-hydroxyquinoline were made to react in an in situ solid−solid reaction in the interlayer space of Ca-bentonite from Thailand, resulting in [Zn(8-hydroxyquinoline)2]2+, the well known –Znq2. X-ray diffraction patterns showed that the interlayer space of the bentonite increased from 1.56 to 1.67 nm on going from Zn(II)-bentonite to Znq2-bentonite, which confirmed the intercalation of Znq2 in bentonite. The intercalated Znq2-bentonite compound was mixed with a solution of polystyrene in toluene and coated as a film on a polystyrene sheet. The fluorescence intensity of Znq2-bentonite film was measured in the presence of dissolved oxygen (DO). It was found that the fluorescence intensity of the film decreased as dissolved oxygen increased, which is a promising result for developing an optical dissolved oxygen sensor (DO sensor). The fluorescence quenching by oxygen followed the Stern–Volmer plot.