Analysis of sensing properties of thermoelectric vapor sensor made of carbon nanotubes/ethylene-octene copolymer composites
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We designed a novel self-powered thermoelectric vapor sensor, whose thermogenerated voltage was modulated by chemical vapors. The sensor was made of composites of oxidized multi-walled carbon nanotubes within ethylene-octene copolymer. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy of the multi-walled carbon nanotubes within ethylene-octene copolymer showed that the oxidation with HNO3 or KMnO4 enhanced its p-type electrical conductivity and that the thermoelectric power increase was proportional to the formation of new oxygen-containing functional groups on the surface of carbon nanotubes. When this composite was subjected to a saturated vapor of either heptane (aliphatic hydrocarbon), toluene (aromatic hydrocarbon) or ethanol (alcohol), its respective relative resistance increased in average by 3.6, 1.1 and 0.05. Consequently, the magnitude of voltage generated by the thermoelectric device containing the oxidized multi-walled carbon nanotubes within ethylene-octene copolymer determined the absence or presence of the aforementioned chemical vapors.