Effect of chitosan dissolved in different acetic acid concentration towards VOC sensing performance of quartz crystal microbalance overlay with chitosan

Abstract

Improvement in sensing layer properties of quartz crystal microbalance (QCM) sensors are crucial in developing gas sensors with high sensitivity and selectivity. In this work, we study the use of chitosan thin film as the sensing layer on a QCM sensor to identify the presence of volatile organic compounds specifically isopropyl alcohol (IPA). The effect of chitosan dissolved in different acetic acid concentrations towards QCM overlay with chitosan sensing performance were studied. Characterization work on chitosan thin film at different acetic acid concentrations (1.0, 1.5, 2.0, 2.5% (v/v)) were performed by using FTIR and FESEM. Higher acid concentration led to a higher degree of protonation which results in a more progressive solubilization of chitosan and promotes smoother film. For chitosan layer dissolved in 2% acetic acid, the highest resonance frequency shift (99.3 Hz) was observed during the adsorption of the analyte gas molecules on QCM sensors. This can be explained by the increase in chitosan solubility and protonation. This indicates that difference acid concentration in chitosan dissolution affects the sensing performance during the presence of the analyte gas.