Ag-Modified 3D Reduced Graphene Oxide Aerogel-Based Sensor with an Embedded Microheater for a Fast Response and High-Sensitive Detection of NO2.

A chemiresistive gas sensor based on a three-dimensional Ag-modified reduced graphene oxide (3D Ag-rGO) aerogel is reported. We improve the graphene-based sensor performance by optimization of operating temperature, chemical modification, and new design of the material geometrical structure. The self-assembly and Ag nanoparticle (NP) decoration of the Ag-rGO aerogel are realized by a facile, one-step hydrothermal method. An integrated low-power microheater fabricated on a micromachined SiO2 membrane is employed to enhance the performance of the sensor with a fast response to NO2 and a shortened recovery time. The 3D Ag-rGO-based sensor at a temperature of 133 °C exhibits the highest response. At the same time, the response to other gases is suppressed while the response of the Ag-rGO sensor toward ammonia at 133 °C is reduced to half of the value at room temperature, demonstrating a greatly improved selectivity toward NO2. Additionally, the sensor exhibits a remarkably fast response to 50 ppb NO2 and a low limit of detection of 6.9 ppb.