Investigation of Microstructure Effect on NO2 Sensors Based on SnO2 Nanoparticles/Reduced Graphene Oxide Hybrids

The microstructures of metal oxide-modified reduced graphene oxide (RGO) are expected to significantly affect room-temperature (RT) gas sensing properties, where the microstructures are dependent on the synthesis methods. Herein, we demonstrate the effect of microstructures on RT NO 2 sensing properties by taking typical SnO 2 nanoparticles (NPs) embellished RGO (SnO 2 NPs-RGO) hybrids as examples. The samples were synthesized by growing SnO 2 NPs on RGO through hydrothermal reduction (SnO 2 NPs-RGO-PR), which display the advantages such as high reactivity of the SnO 2 surface with NO 2, more oxygen vacancies (O V ) and chemisorbed oxygen (O C ), close contact between SnO 2 NPs and RGO, and large surface area, compared to the samples prepared by one-pot hydrothermal synthesis from Sn 4+ and GO (SnO 2 NPs-RGO-IS), and the assembly of SnO 2 NPs on RGO (SnO 2 NPs-RGO-SA). As expected, the SnO 2 NPs-RGO-PR-based sensor presents high sensitivity towards 5 ppm NO 2 (65.5%), but 35.0% for the SnO 2 NPs-RGO-IS-based sensor and 32.8% for the SnO 2 NPs-RGO-SA-based sensor at RT. Meanwhile, the corresponding response time and recovery time calculated by achieving 90% of the current change of the SnO 2 NPs-RGO-PR-based sensor for exposure to NO 2 is 12 s and to air is 17 s, respectively, whereas 74/42 s for the SnO 2 NPs-RGO-IS-based sensor and 77/90 s for the SnO 2 NPs-RGO-SA-based sensor. The results can prove the tailoring sensing behavior of the gas sensor according to different structures of materials.