Two 8-hydroxyquinoline-based fluorescent chemosensors for ultra-fast and sensitive detection of water content in strong polar organic solvents with large Stokes shifts

Jin-Tao Wang; Ying-Ying Pei; Shang-Feng Ren; Ming-Yue Yan; Wen Luo; Bo Zhang; Qing-Feng Li

doi:10.1016/j.saa.2019.117956

Two 8-hydroxyquinoline-based fluorescent chemosensors for ultra-fast and sensitive detection of water content in strong polar organic solvents with large Stokes shifts

Spectrochim Acta A Mol Biomol Spectrosc. 2020 Mar 15:229:117956. doi: 10.1016/j.saa.2019.117956. Epub 2019 Dec 14.

Authors

Jin-Tao Wang¹, Ying-Ying Pei², Shang-Feng Ren¹, Ming-Yue Yan¹, Wen Luo¹, Bo Zhang¹, Qing-Feng Li³

Affiliations

¹ Henan Key Laboratory of Rare Earth Functional Materials, The Key Laboratory of Rare Earth Functional Materials and Applications, Zhoukou Normal University, Zhoukou 466001, Henan, PR China; International Joint Research Laboratory for Biomedical Nanomaterials of Henan, Zhoukou Normal University, Zhoukou 466001, Henan, PR China.
² Henan Key Laboratory of Rare Earth Functional Materials, The Key Laboratory of Rare Earth Functional Materials and Applications, Zhoukou Normal University, Zhoukou 466001, Henan, PR China; International Joint Research Laboratory for Biomedical Nanomaterials of Henan, Zhoukou Normal University, Zhoukou 466001, Henan, PR China. Electronic address: peiyy0329@163.com.
³ Henan Key Laboratory of Rare Earth Functional Materials, The Key Laboratory of Rare Earth Functional Materials and Applications, Zhoukou Normal University, Zhoukou 466001, Henan, PR China; International Joint Research Laboratory for Biomedical Nanomaterials of Henan, Zhoukou Normal University, Zhoukou 466001, Henan, PR China. Electronic address: liqingf335@163.com.

PMID: 31865098
DOI: 10.1016/j.saa.2019.117956

Abstract

It is of great significance to detect the moisture in organic solvents before used in water-sensitive reactions. Herein, two Schiff base quinoline derivatives, 8-hydroxyquinoline-2-carboxaldehyde thiosemicarbazone (HQCT) and 8-hydroxyquinoline-2-carboxaldehyde (pyridine-2-carbonyl)-hydrazine (HQPH), were designed and synthesized by a simple one-step reaction, and used as fluorescent chemosensors for ultra-fast and sensitive detection of water content in strong polar organic solvents. Based on excited-state intramolecular proton transfer (ESIPT) process, HQCT and HQPH exhibited strong fluorescence emissions with large Stokes shifts in dimethyl sulfoxide (DMSO) and N, N-dimethylformamide (DMF) solvents compared to other various organic solvents, and their fluorescence quenching and fluorescent color changes were obviously observed with increasing water content. The experimental results revealed that the hydroxyl groups substituted at the 8-position of HQCT and HQPH played a key role in the fluorescence emission processes. Dynamic light scattering (DLS) and ¹H NMR titration indicated that the sensing mechanism for the detection of water was based on inhibition of the ESIPT by H₂O via forming hydrogen bonds. In the range of 0.0-1.8 wt%, the fluorescence intensity of chemosensors changed as a linear function of water content. The detection limits of water in DMSO by HQCT and HQPH were as low as 0.0220 wt% and 0.0274 wt%, respectively. Moreover, HQCT and HQPH are successfully applied for the detection of moisture content in real commercial organic solvents.

Keywords: 8-Hydroxyquinoline; Fluorescent sensor; Large Stokes shift; Water detection.