The fabrication and evaluation of a vapour sensor based on quartz crystal microbalance coated with poly(o-anisidine) langmuir—blodgett layers

Chemical sensors based on Langmuir—Blodgett (LB) films of poly(o-anisidine) (POA) have been investigated. POA, synthesized by chemical oxidation and mixed with stearic acid, was successfully transferred onto quartz crystal microbalance (QCM) sensors using the LB film technique and used as the active sensing material. The resulting QCM sensor can selectively detect and distinguish among fatty acid vapours such as formic acid, acetic acid, propionic acid and butyric acid. The results suggest that the response of QCM sensors to fatty acids is dependent on both molecular weight and steric hindrance factors. Moreover, the sensitivity of the QCM sensors to different types of organic vapours increases linearly with the number of LB monolayers coated, with a concurrent loss of selectivity.