Fabrication of a sensitive gas sensor based on PPy/TiO₂ nanocomposites films by layer-by-layer self-assembly and its application in food storage

An extra sensitive quartz crystal microbalance (QCM) gas sensor coated with thin PPy/TiO₂ nanocomposite film was fabricated by using layer by layer self-assembly (SA) technology. The synthetic procedure and the resultant nanocomposites were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FE-SEM). It was found that an ultra-sensitive PPy/TiO₂ nanocomposite film with very thin layer can be successfully obtained by. It was also found that the number of deposited layers strongly impacted on sensor response with ten bilayers showing best sensor performance. The obtained gas sensor coating with PPy/TiO₂ sensitive film was found to exhibit a better performance with respect to sensor responses, which is based on frequency data. The resultant sensor represented high sensitivity toward 10 ppm of different targeted gases with evident frequency shift, fast response and recovery time. Long-term stability and excellent reversibility were also observed. In real-time application, a designed measurement set-up based on PPy/TiO₂ based sensor showed a good ability on shelf-life evaluation of foodstuffs (mango, egg and fish). The resulting QCM based gas sensor coated with PPy/TiO₂ nanocomposite via Layer by Layer self-assembly presented a promising capability to detect trace irritant gases and food quality evaluation.