Enhancement in NO 2 sensing properties of SWNTs: A detailed analysis on functionalization of SWNTs with Z-Gly-OH

Present work deals with the development of high-speed NO 2 sensor based on functionalized Single Walled Carbon Nanotubes (SWNTs). To improve the sensing properties of SWNTs, SWNTs is functionalized with the enzyme N -benzyloxycarbonylglycine (Z-Gly-OH). Various parameters of the functionalization process such as time and temperature are also optimized and analysed in detail. Z-Gly-OH has created a functionalization of the 1,3-dipolar cycloaddition type, which is capable of doing modification in the properties of CNTs while maintaining the electronic properties of CNTs. The functionalization with Z-Gly-OH makes it possible to obtain amino groups on the surface of nanotubes in the absence of a solvent, while during this reaction it is possible to obtain intermediate functionalization in the form of benzyl carbamate, which can affect the sensitivity of sensors. In order to develop solid state device, Ti(8 nm)/Au(100 nm) interdigitated electrodes (IDEs) are fabricated on thermally oxidized Si substrate by using standard photolithography process. Dielectrophoresis is employed for deposition of as-functionalized SWNTs (f-SWNTs) between the IDEs. The gas sensing performance of as-developed is tested for NO 2 gas as function of NO 2 concentration (70 ppm to 20 ppm). As-developed gas sensor shows fast response/recovery (~ 88 s/95 s) as well as high sensitivity 27%. In order to analysed selectivity of as-developed gas sensor, the cross sensitivity has been observed for carbon monoxide (CO) and Methane (CH 4 ). Before development of sensor, as-prepared f-SWNTs is analysed by SEM, Raman and FT-IR for its morphological and structural characteristics.