Gas Sensors- A Review

Chemical sensors for specific species with varying sensitivity levels are commercially available. Common chemical sensors defer in terms of the sensing material and the nature of property change such as electrical conductivity, optical characteristics and temperature. Some of the current sensor technologies include high temperature oxide thin- film sensors, polymer based sensors, catalytic based sensors and surface acoustic wave sensors are described. In this, the sensor array consists of Carbon Nano Tube(CNT) as sensing material and an interdigitated electrode as a transducer is described. The gas sensors fabricated by using conducting polymers such as polyaniline, polypyrrole as the active layers have been reviewed. The macroscopic coaxial carbon cylinders consisting of aligned CNT stacks have been used in CNT- polymer composite. The advantages and disadvantages of each sensor technology are also highlighted. All these technologies have been used for the development of highly sensitive and responsive gas sensors for the detection of flammable and hazardous gases. However, for improved sensitivity and selectivity for these sensors, future trends and outlook for researchers are suggested in this review.