Effects of graphene on the microstructures of SnO2@rGO nanocomposites and their formaldehyde-sensing performance

Performance modulation of formaldehyde (HCHO) sensing active nanomaterials is of great significance in environmental monitoring and disease diagnosis. This paper reports a simple but robust solvothermal process to synthesize SnO2@rGO nanocomposites for HCHO sensors with rGO mass fractions of 0-2%. The phases, chemical compositions, microstructures and surface states of the as-obtained SnO2@rGO nanocomposites are well characterized. The results indicate that the addition of GO overcomes the agglomeration of SnO2 nanocrystals (3-5 nm) and highly enhances the specific surface area (SSA) of the SnO2@rGO nanocomposites, leading to higher response and lower operating temperature in the HCHO-sensing application. The SSA of SnO2@rGO is 133.1 m2/g, much larger than that (58.3 m2/g) of pure SnO2 nanocrystals. The SnO2@rGO nanocomposites exhibit highly selective and sensitive to HCHO vapors at a relatively low operating temperature range of 100-200 °C. The amount of GO added has a key effect on the HCHO-sensing performance, and the sample of SnO2@rGO-0.5% exhibits the highest response at 100 160 °C. Their recovery/response times are shorter than 20 s to HCHO vapors (less than 25 ppm). The enhanced HCHO-sensing performance is attributed to the formation of porous SnO2@rGO nanostructures with high SSAs and suitable electron transfer channels.