Chemically functionalized 3D graphene hydrogel for high performance gas sensing

The performance of chemical sensors can be optimized not only by material structural design, but also via functionalization of sensing materials. For the first time, we develop a high performance, cost-effective NO2 and CO2 sensor by exploiting a 3D chemically functionalized reduced graphene oxide hydrogel (FRGOH). The self-assembly and chemical modification of the 3D FRGOH are realized using hydroquinone molecules in a simple, one-step hydrothermal synthesis process. Compared with an unmodified RGOH counterpart, the chemically derived FRGOH sensor not only displays twofold higher sensitivity in both NO2 and CO2 sensing, but also exhibits significantly faster recovery and a lower limit of detection (LOD). Thus, a theoretical LOD of 57 ppb NO2 is obtained and a low concentration of 200 ppb NO2 is detected experimentally by the FRGOH sensor. Importantly, an integrated microheater is employed not only to significantly improve the selectivity of NO2 sensing, but also to accelerate the response and recovery. This work sheds light on improving the performance of a graphene-based gas sensor by simultaneous chemical functionalization, 3D structural design and temperature modulation.