MWCNTs-OH was used to prepare a flexible gas sensor by deposition as a network on a filter cake using the method of filtration from suspension (FFS). The morphological and structural properties of the MWCNTs network were characterized before and after exposure to Freon gas using FTIR spectra and X-ray diffractometer, which confirmed that the characteristics of the sensor did not change after exposure to the gas. The sensor was exposed to a pure Freon134a gas as well as to a mixture of Freon gas and air with different ratios at room temperature. The experiments showed that the sensor works at room temperature and the sensitivity values increased with increasing operating temperature, to be 58% until 150 ºC. The fabricated flexible sensor has good response and recovery times at low gas concentrations of 1.3, 2, and 2.7 ppm.

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This study is about gas sensor preparation of hydroxyl functionalized multiwall carbon nanotubes (MWCNTs-OH) network use filtration from suspension (FFS) method. Improve the properties of the sensor use embedded nanoparticles (PANI, Pt-CNT active, Ni). the gas sensor good responce toward Exposure (NH3, NO2) gases at room temperature and at low concentration (1ppm). The sensor was more responsive when exposure to NO2 gas because it is an oxidizing gas(corroded), When exposure NH3 gas for concentration (1ppm ) and embedded Ni NP the sensitivity value (3.41, 3.49, 9.7 and 5.4) % at the temperatures (RT, 50, 100 and 150 ) C˚. The recovery time was decreases at (150)C˚ as it was (5.4)sec , the factors to improve the properties of the sensor was increase temperature and embedded NPs.