Review—The Development of Gas Sensor Based on Carbon Nanotubes

Carbon nanotubes (CNTs) are one of the carbon nanomaterial that is very popular in the field of gas sensors. It has unique properties, large surface area and hollow structure that makes its potentially applicability for using as a gas sensor. Several attempts have been made to improve the sensing performances of carbon nanotubes including the sensitivity and selectivity of CNTs by modifying CNTs with a noble metals, metal oxides and polymers. From these studies, there are evident that the modifications of CNTs with certain materials can improve the sensitivity and selectivity of CNTs for the sensor applications for several harmful gases. Decorating carbon nanotubes with metal oxides can improve the CNTs to reach the highest sensitivity. Moreover the increasing sensitivity of polymer/ CNTs is higher than the metal/CNTs. The modification of metal in CNTs aims to accelerate the reaction surface and as channel for electrons path from or to the CNTs. Therefore the used of metal oxides on CNTs built a p-n junction that can increase sensitivity. Subsequently the addition of polymer can increase the charge carrier density in CNTs.