Semiconductor metal oxide (SMO) as a sensing layer for gas detection has been widely used. Many researches have been performed to enhance the sensing performance including its sensitivity, reliability and selectivity. Electrical sensors that use resistivity as an indicator of its sensing are popular and well established. However, the optical based sensor is still much to explore in detecting gas. By integrating it with SMO, the sensor offers good alternative to overcome some drawbacks from electrical sensors.
Room temperature carbon nanotubes (CNT)-based gas sensor was utilised in detection of methane, CH4 gas. The CNT was functionalized with amide group via Fischer esterification process and labelled as CNT-Amide. Silicon dioxide, SiO2 substrate with interdigitated prepatterned gold electrodes were employed as transducers and drop casting technique was used to deposit the multi walled-CNT samples. The electrical properties of the functionalized CNT samples in the exposure of CH4 gas are studied by recorded the changes of resistance using digital multimeter. Concentration of CH4 gas was varied from 1250 ppm to 10 000 ppm. The changes of electrical resistance of CNT-Amide increases with the concentration of tested gas. Sensor response of functionalized CNT are improved more than 10% as compared to pristine CNT. The sensitivity of CNT-Amide also better than CNT-Carboxyl due to the presence of nitrogen element in amide functional group which chemically active to react with CH4 gas. Additionally, fast response of CNT-Amide towards CH4 gas suggested that the functional group enhanced the rate of gas adsorption on sensing layer.
Multi walled-carbon nanotubes (CNT) functionalized with ester was used for detecting methane, CH4 gas at room temperature. Quartz substrate with interdigitated prepatterned gold electrodes was employed as transducers and drop casting method was used to deposit the CNT samples. The electrical properties of the functionalized CNT samples in the presence of CH4 gas were studied and the changes of resistance were recorded using digital multimeter. Concentration of CH4 gas was varied from 0.125 % to 1.0 %. The resistance variation of functionalized CNT increased with the concentration of tested gas. Sensor response of functionalized CNT was improved more than 10 % as compared to pristine CNT. CNT-Ester gives the higher sensitivity due to the presence of ester functional group which act as active site to react with CH4 gas. The fast response of functionalized CNT towards CH4 gas suggested that the functional group enhanced the rate of gas adsorption on sensing layer