A novel humidity and ammonia sensor based on nanofibers/polyaniline/polyvinyl alcohol

Abstract

An efficient sensor for monitoring humidity and ammonia gas was fabricated using nanofibers, polyaniline (PANI) and polyvinyl alcohol (PVA). The sensor was fabricated using two nanofibers, i.e. carbon nanofiber (CNF) and nano-fibrillated cellulose (NFC). The sensor film was prepared by casting of the hot aqueous PVA solution containing the nanofibers modified with polyaniline. The composites (PANI/CNF/PVA and PANI/NFC/PVA) were studied using TEM, SEM, FTIR, and BET surface area analysis. The response of the sensor was evaluated from the change in capacitance with varying humidity levels. The AC capacitance of the sensor film was measured over a relative humidity (RH) range of 30% to 100%. Compared to PANI/NFC/PVA composite, PANI/CNF/PVA composite exhibited higher sensitivity, shorter response time (41 s) and better recovery (46 s). The change of sensitivity for CNF based composite was from 290 to 6570% at 100 Hz frequency. The response of the films to ammonia was investigated over a range of 0–100 ppm at room temperature. The observed sensitivity of the film varied from 10 to 84. PANI/CNF/PVA composite was found to have much better response time (46 s) and sensitivity for ammonia sensing. This improvement in the sensing performance of CNF composite was attributed to the higher pore size and the enhanced hydrogen bonding interaction with water molecules.