Highly Sensitive Room-Temperature NO2 Gas Sensors Based on Three-Dimensional Multiwalled Carbon Nanotube Networks on SiO2 Nanospheres

The electrical conductivity of carbon nanotubes (CNTs) has been demonstrated to be highly sensitive to the change of vapor/gas molecules in the local environment owing to the large specific surface area and quantum size effect, which enable CNTs to be an ideal sensing material for next-generation room-temperature gas sensors. However, the sensing properties of CNT films or networks cannot be maximized because of the inevitable agglomeration during the fabrication process. Herein, three-dimensional (3D) SiO2@multiwalled CNTs (MWCNTs) core-shell nanospheres have been first used to fabricate room-temperature gas sensors, which were prepared using an electrostatic self-assembly method. The as-fabricated 3D SiO2@MWCNTs sensor exhibits a recorded sensitivity of 82.61% toward 1 ppm nitrogen dioxide (NO2) at room temperature, which is 1.97 times higher than that of devices based on random two-dimensional (2D) MWCNTs. Meanwhile, the recovery time of similar to 44 s is smaller than that of a 2D MWCNT gas sensor. Such an ultrahigh sensing performance is attributed to an effective utilization of the large specific surface area of MWCNT networks with 3D structures. We believe that our findings will contribute to the further development of high-performance CNT-based sensing devices and also provide a new approach to fabricate the sensing devices using one-dimensional nanomaterials.