Negatively­Doped Single­Walled Carbon Nanotubes Decorated with Carbon Dots for Highly Selective NO2 Detection

Abstract

In this study, we demonstrated a highly selective chemiresistive­type NO2 gas sensorusing facilely prepared carbon dot (CD)­decorated single­walled carbon nanotubes (SWCNTs). TheCD­decorated SWCNT suspension was characterized using transmission electron microscopy(TEM), X­ray diffraction (XRD), and UV­visible spectroscopy, and then spread onto an SiO2/Sisubstrate by a simple and cost­effective spray­printing method. Interestingly, the resistance of oursensor increased upon exposure to NO2 gas, which was contrary to findings previously reported forSWCNT­based NO2 gas sensors. This is because SWCNTs are strongly doped by the electron­richCDs to change the polarity from p­type to n­type. In addition, the CDs to SWCNTs ratio in the activesuspension was critical in determining the response values of gas sensors

here, the 2:1 deviceshowed the highest value of 42.0% in a sensing test using 4.5 ppm NO2 gas. Furthermore, the sensorselectively responded to NO2 gas (response ~15%), and to other gases very faintly (NO, response~1%) or not at all (CO, C6H6, and C7H8). We propose a reasonable mechanism of the CD­decoratedSWCNT­based sensor for NO2 sensing, and expect that our results can be combined with those ofother researches to improve various device performances, as well as for NO2 sensor applications.