Sensing mechanism of carbon nanotube-metal oxide gas sensors

6 Sensing mechanism of carbon nanotube-metal oxide gas sensors 

It is widely known that many MOXs (such as WO3, Sn02, and T1O2) are n-type senuconductors, while CNT is a p-type semiconductor. CNT/MOX 

From many studies, it was found that CNTs are embedded in the MOX layer leading to the formation of p-n heterojunctions. Therefore, there are 

10 Model of a potential barrier to electronic conduction at grain boundary for hybrid SWNT/SnOj sensors. The dashed and continuous lines show the potential barriers of hybrid SWNT/SnOj in environment of air and environment of oxidizing gas (i.e. NOj), respectively. 

The unique structure and electronic properties of CNTs provide a tremendous potential for construction of CNTs and MOX hybrid materials in the field of gas-sensing applications. Advantages for mixing CNTs in metal oxides for gas sensors are the reduction of operating temperature and enhancement of sensitivity and selectivity due to the amplification effects of p-n heterojunctions with the gas reaction, formation of nanochannels for gas diffusion, high specific surface area, and increase of charge carrier on the surface. As a result of these advantages, the hybrid CNT/metal oxide gas sensor may be used instead of the popular commercial metal oxide gas sensors (such as TGS gas sensors) in the near future. 

---