Carbon nanotubes and graphene oxide networks for gas sensing

• Main Author: Ramli, Muhammad M.
• Other Authors: Silva, S. R. P.
• Published: University of Surrey 2015
• Subjects: 621.3815
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.655528

Nowadays, Carbon Nanotubes (CNTs) and Graphene Oxide (GO) have attracted enormous interest in various applications such as thin film transistors, chemical sensors, field emission devices and transparent conductive coatings. In this report, thin films of CNT and GO networks were fabricated as a two-terminal device for gas sensing applications. These devices were fabricated using vacuum filtration and drop casting methods at room temperature in order to get a thin and uniform film. The electrical measurement was conducted in order to investigate the film resistance as the solution concentration increased. The multi – walled carbon nanotubes (MWCNTs) solutions were acid treated by attaching carboxylic acid (-COOH) groups, in order to form a stable aqueous suspension with a neutral pH. The conductivity of the networks film was increased as the solution concentration increased where the sheet resistance at the highest concentration (0.125 mg/ml) was around 7.09 kΩ/sq. The single – walled carbon nanotubes (SWCNTs) suspension was produced using an organic dye in order to improve its solubility in water. Raman spectroscopy showed that no damage to the structure of SWCNTs was occurred. The GO suspension was produced by the chemical exfoliation of graphite through oxidation. The basal plane and edges of GO were decorated by oxygen functional groups, hence improving its solubility in water. To decrease the concentration of solutions, the solutions were diluted with methanol or water and various concentrations were achieved. The extreme sensitivity to changes in CNTs and GO local chemical environment makes them an ideal candidate for gas sensing application. The devices were tested by exposure to gasses such as NO2 and NH3. Results show a tremendous sensitivity towards NO2 and NH3 gasses. The sensitivities of the MWCNTs sensor device were ranging from 2 to 20 %. Whereas for the SWCNTs sensor device, the sensitivities were ranging from 20 to 50 %. For the GO sensor devices, the optimum sensitivity was achieved when the device was exposed at room temperature. The changes in resistance of the devices reflected the interaction mechanism that happened between exposure gasses (NO2 and NH3) and the materials.