The sensing properties of carbon nanotube filled copolymers for VOC vapors detection

Abstract

Nowadays, carbon nanotubes are a widely available material, especially multiwall carbon nanotubes. In addition to many other applications, they find use in all kinds of sensors, like deformation, motion, tensile and pressure responsive elements. Numerous applications in sensors for volatile organic compounds (VOCs) are reported as well, nevertheless, they mainly suffer from low selectivity. Therefore, in this research, a sensor containing MWCNTs dispersed in a functional polymer matrix was prepared. As a polymer matrix, styreneisoprene-styrene elastomer was chosen. The standard sensing mechanism of entangled MWCNTs is based on the quality of the contacts (charge transfer) between the individual nanotubes. In the prepared nanocomposite, the mechanism is modified due to the presence of the otherwise non-conductive matrix. The changes of conductivity depend on the response of the percolating nanotube filler network to the swelling of the polymer matrix due to adsorption of VOCs. The tested gas substances have high values of diffusion coefficient for the polymer, so they have a quick response. Then, the selectivity is ensured by differences in solubility of the tested VOCs in the polymer. The effect was demonstrated for four VOCs differing by their affinity to the polymer matrix, namely, heptane, toluene, acetone, and ethanol.

Giant Response and Selectivity of Hansen Solubility Parameters-Based Graphene-SBS Co-Polymer Matrix Composite Room Temperature Sensor to Organic Vapours

“…Specimens for determining the percolation threshold and interdigitated electrode (IDE) sensors were made similarly to our previous works with carbon nanotubes [17,18]. Rectangular substrates (sized 50 mm × 20 mm) with two side electrodes were prepared for percolation curve measurements, whereas IDE patterned substrates (sized 20 mm × 13 mm, gap width 0.5 mm) were prepared for the fabrication of sensors as depicted in Figure 1.…”

“…Polymer swelling was also noticed as the sensing mechanism for polymer-coated carbon nanotubes. Our pioneering work demonstrated the ability of various polymer matrices to induce reasonable selectivity in carbon nanotube-filled nanocomposite layers in VOC sensors [17]. Furthermore, the sensitivity of the graphene-filled composite should be enhanced (2) by choosing its composition close to the percolation threshold.…”