Optical humidity sensing characteristics of composite thin films of hydrolysed nafion-dye with a terminalN-phenyl group

Abstract

By using composite films of hydrolysed nafion and dyes having cyanine or triphenyl structures and with a terminal N-phenyl group, an optical humidity sensor has been fabricated. In the reflection mode, the optical intensity of the absorption peaks which depend on the used dyes decreases with relative humidity. The raising and recovery times are less than 1 min. In dry air, the alkyl amine group reacted with SO₃H of hydrolysed nafion and formed a proton additive. Sorption of water molecules induces the deprotonation of the quaternized ammonium group.