Enhancing the NO2 gas sensing properties of rGO/SnO2 nanocomposite films by using microporous substrates

Sensitive detection for low-concentration NO2 gas is imperative in the fields of environmental monitoring and human healthcare. In this work, reduced graphene oxide (rGO)/tin oxide (SnO2) nanocomposites were prepared by a simple blending and deposited onto different microporous substrates to explore their sensing performance to NO2 gas, combining with multiple characterization techniques such as SEM, TEM, XRD and XPS. The experimental results revealed an increased sensing response with rising SnO2 concentration ranging from 0 to 10 mg/ml. Especially, the sensing response at 10 mg/ml attained nearly three times larger than that of pure rGO. Investigation on long-term stability manifested a smaller response attenuation of rGO/SnO2 sensors toward NO2 gas of high concentration regime than that of low one. Besides, the largest sensing response of rGO film to 1 ppm NO2 was achieved under 200-μm microporous substrate, which was 350% enhancement of that under flat one. To analyze the dynamic equilibrium of adsorption/desorption process, two kinds of measurement methods were contrastively studied. Additionally, interfering factors including operation temperature and relative humidity were probed as well. The prepared rGO/SnO2 sensors exhibited an excellent selectivity toward NO2 gas as well as a nice detection limit as low as 15.7 ppb.