Water detection in organic solvents using a copolymer membrane immobilised with a fluorescent intramolecular charge transfer-type dye: effects of intramolecular hydrogen bonds
Ami Morimoto, Kei Shimizu, Naoya Suzuki, Shigeyuki Yagi, Kenji Sueyoshi, Tatsuro Endo, Hideaki Hisamoto
Abstract
= 630 nm). The fluorescence intensity of the dye-immobilised membrane decreased with increasing water content of the organic solvents. The detection ranges in tetrahydrofuran, ethanol, methanol, and dimethyl sulfoxide were approximately <40, <40, <40, and <60 vol% water, respectively. In contrast, membranes based on a quaternary pyridinium dye (without intramolecular hydrogen bonds) did not detect water in methanol and dimethyl sulfoxide, although it was more sensitive than PB1 in the narrow region of low water concentration in THF. Theoretical calculations corroborated the importance of the pyridinium betaine structure in detecting water in organic solvents, with the increase in polarity and the formation of intermolecular hydrogen bonds between PB1 and water found to induce molecular rotation and fluorescence quenching.