The influence of exfoliated graphite on sensing properties of chitosan / PVA based ammonia sensors

Abstract

Chitosan was used as a sensing material for gas sensing applications. In order to nurture the chitosan properties as a sensing material, chitosan (CS) was blended with polyvinyl alcohol (PVA) and filled with exfoliated graphite (EG). The chitosan films, CS/PVA films and CS/PVA/EG films were characterized to study the effect of EG on microstructure and electrical properties of the composites films. The films casting method has been used to characterize the composite films. The characterization analysis was done using Ultra Violet-Visible (UV-VIS), Four Point Probe (Conductivity testing), X-Ray Diffraction (XRD), Fourier Electron Scanning Electron Microscopy (FESEM) and Fourier Transform Infrared Spectroscopy (FTIR). Chitosan with concentration 1.75 (w/v) % was blended with polyvinyl alcohol (PVA) with concentration 5.00 (v/v) % of ratio 95:5 ml and filled with exfoliated graphite (EG). The results showed that the addition of EG with concentration of 0.8 (w/v) % gives the highest conductivity value of CS/PVA/EG films. The CS/PVA/EG films sensor was deposited on the gold pattern electrode by using electrochemical deposition technique to fabricate the sensor for the ammonia detection. The best electrochemical deposition time and deposition voltage in this study were 6 minutes and 2.5 voltage to fabricate the films sensor. The optimum sensing properties were obtained with CS concentration of 1.75 (w/v) %, CS/PVA ratio of 95:5 ml with PVA concentration of 5.00 (v/v) % and EG concentration of 0.8 (w/v) % upon exposure to wet air. This parameter of CS films sensor and CS/PVA/EG films sensor was used to fabricate the films sensor to test upon exposure of ammonia gas. The CS film sensor and CS/PVA/EG film sensors were exposed to ammonia with different concentration i.e. 10 ppm, 20 ppm, 30 ppm, 40 ppm and 50 ppm to examine the sensing properties of the CS film sensor and CS/PVA/EG film sensors.