OPTICAL-FIBER AND QUARTZ OSCILLATOR TYPE GAS SENSORS - HUMIDITY DETECTION BY NAFION FILM WITH CRYSTAL VIOLET AND RELATED-COMPOUNDS

By using Nafion(R) film with crystal violet and malachite green, an optical-fibre and quartz oscillator type humidity sensor has been fabricated. The optical intensity, with a minimum at 615 nm in the reflection mode, decreases with relative humidity for a film with malachite green. The rise and recovery times are less than 1 min and the hysteresis is only +/- 1% RH at 50% RH. For the film with crystal violet, a similar characteristic is confirmed at 630 nm. Composite films can be used as an optical and quartz oscillator type humidity sensor, since the sorption of water induces colour and oscillating frequency changes.