Enhanced Gas Sensitivity Based on CNTs@SnO2@ZIF-67 Composite Materials for an NO2 Gas Sensor at Room Temperature

In this paper, we investigated the CNTs (single-walled carbon nanotubes)@SnO2@ZIF-67 material combined with a silicon micropillar structure, aiming to improve gas sensitivity for the NO2 sensor at room temperature and 46% relative humidity (RH). First, the gas composite materials of CNTs@SnO2 has been obtained by a hydrothermal process, then a gas sensor on a silicon planar substrate with good gas sensitive performance was fabricated by varying the doping ratio of the two materials. Second, ZIF-67 nanoparticle materials were doped in CNTs@SnO2 gas sensor to enhance the sensitivity of the sensor. Third, the good doping ratio of the CNTs@SnO2@ZIF-67 composite gas-sensitive material was then placed onto the silicon micropillar substrate, where the tiny structure increased the surface area and improved gas flow. It was found that the best results occurred when the micropillar’s diameter-to-depth ratio was 1:2, giving a 77 s response to 50 ppm NO2, a detection limit of 1.13 ppm, good selectivity, long-term steadiness, and dependable work at 46% RH. The results suggest a combined method that links material mixing with structural improvement, providing a new direction for making high-performance room-temperature NO2 sensors. Finally, the gas mechanism by the silicon micropillar sensor with CNTs@SnO2@ZIF-67 has been explored.