Polyaniline–TiO2 nano-composite-based trimethylamine QCM sensor and its thermal behavior studies

Inorganic/organic composites are very attractive due to synergetic behavior and a wide range of potential use. A polyaniline–TiO2 nano-composite, obtained by combination of chemical polymerization and a sol–gel method, was deposited on the electrode of quartz crystal to implement a quartz crystal microbalance (QCM) chemical sensor. The morphology of the composite film was studied by scanning electron microscopy (SEM) measurements. The coated quartz crystal and a non-coated quartz crystal were mounted in a sealed chamber, and their frequency difference was monitored. When analyte vapor was injected into the chamber, gas absorption decreased the frequency of the coated quartz crystal and thereby caused an increase of the frequency difference between the two crystals. The frequency difference change response towards trimethylamine was evident and could be recovered by N2 purgation easily. The calibration curve towards trimethylamine, its long-term stability and selectivity were investigated. The thermal behavior of the sensing characteristics was compared with that of a polyaniline QCM sensor. Fourier transform infrared (FTIR) spectra of polyaniline and polyaniline–TiO2 nano-composite and QCM data under various conditions were used to study the effect of thermal treatment.