Surface acoustic wave sensors with carbon nanotubes and SiO2/Si nanoparticles based nanocomposites for VOC detection

Surface acoustic wave sensors with nanocomposite sensitive films for detecting volatile organic compounds (VOCs) were fabricated and experimentally studied. The nanocomposite material consisted of SiO2/Si nanoparticles and multi-wall carbon nanotubes (MWCNTs) embedded in polyethylenimine (PEI). The sensor was “delay line” type (quartz substrate, 69.4 MHz central frequency). The study compared film morphology, sensitivity, response time, reversibility, and limit of detection for both plain polymeric (PEI) and nanocomposite films to the detection of VOCs. The nanocomposite-based sensors had improved sensitivities compared to the polymer devices (1.19, 0.79, 0.51 Hz/ppm, for MWCNTs-PEI, SiO2/Si-PEI and PEI, respectively), and better response times (six times faster). The SiO2/Si-PEI-based device showed the best limit of detection (15.2 ppm), having a reduced noise level due to improved surface morphology.