Increasing Response to NO<sub>2</sub> Gas of Carbon Nanotube-based NO<sub>2</sub> Gas Sensor by Decorating TiO<sub>2</sub> Nano Particles

There has been increasing attention on carbon nanotubes (CNTs) as a material with suitable characteristics for gas sensors, such as a large specific surface area and the advantage that all constituent elements are located on the surface. CNTs come in various forms, and among them, the (9,4) chirality CNT is reported to demonstrate high performance. However, synthesizing (9,4) CNTs in isolation presents a challenge. Therefore, in this study, we aim to enhance the performance of CNT-based gas sensors by utilizing the (6,5) chirality CNT, which is readily available and commercially sold, and decorating TiO2 to form a p-n junction. This approach seeks to create a high-performance, easily obtainable CNT-based gas sensor. Experimental results show that the sensor response is maximized when the weight ratio of carbon atoms in the CNT to TiO2 is 1:100. Additionally, sensors with smaller particle sizes exhibited higher performance. These findings highlight the importance of controlling the particle size and amount of TiO2 to improve the performance of CNT/TiO2-based p-n heterojunction gas sensors.