Ammonia and nitrogen dioxide detection using ZnO/CNT nanocomposite synthesized by sol–gel technique

Through the use of sol–gel method, a composite material was created based on zinc oxide (ZnO) and multi-walled carbon nanotubes (CNT). As evidenced by the color of the solution and SEM images, colloidal nanoparticles were produced. For the construction of the devices, thin layers were deposited utilizing the spray pyrolysis on glass substrates and interdigitated electrodes. Samples were heated at different annealing temperatures ranging from 200 to 400 °C. The samples heated at 400 °C, have shown better interaction between zinc oxide and carbon nanotubes and achieved the sensitivity goal. Utilizing Tauc calculations and UV–visible absorption spectroscopy in the range of 300–1000 nm wavelength, the optical energy gap has been studied to address the effect of the existence of carbon nanotubes in the prepared samples. Using a homemade sensor system, the interaction of gases, including ammonia, nitrogen dioxide, and other organic odorants with the samples was investigated. Samples containing carbon nanotubes have exhibited better sensitivity and reversibility toward vapors, while zinc oxide only does not show reasonable performance at room temperature. The sensitivity toward nitrogen dioxide was found to be 96.6% for samples containing carbon nanotubes, while the sensitivity was 10.09% for samples of zinc oxide only.