Graphene Oxide@3D Hierarchical SnO₂ Nanofiber/Nanosheets Nanocomposites for Highly Sensitive and Low-Temperature Formaldehyde Detection

In this work, we reported a formaldehyde (HCHO) gas sensor with highly sensitive and selective gas-sensing performance at low operating temperature based on graphene oxide (GO)@SnO₂ nanofiber/nanosheets (NF/NSs) nanocomposites. Hierarchical SnO₂ NF/NSs coated with GO nanosheets showed enhanced sensing performance for HCHO gas, especially at low operating temperature. A series of characterization methods, including X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) were used to characterize their microstructures, morphologies, compositions, surface areas and so on. The sensing performance of GO@SnO₂ NF/NSs nanocomposites was optimized by adjusting the loading amount of GO ranging from 0.25% to 1.25%. The results showed the optimum loading amount of 1% GO in GO@SnO₂ NF/NSs nanocomposites not only exhibited the highest sensitivity value (R_a/R_g = 280 to 100 ppm HCHO gas) but also lowered the optimum operation temperature from 120 °C to 60 °C. The response value was about 4.5 times higher than that of pure hierarchical SnO₂ NF/NSs (R_a/R_g = 64 to 100 ppm). GO@SnO₂ NF/NSs nanocomposites showed lower detection limit down to 0.25 ppm HCHO and excellent selectivity against interfering gases (ethanol (C₂H₅OH), acetone (CH₃COCH₃), methanol (CH₃OH), ammonia (NH₃), methylbenzene (C₇H₈), benzene (C₆H₆) and water (H₂O)). The enhanced sensing performance for HCHO was mainly ascribed to the high specific surface area, suitable electron transfer channels and the synergistic effect of the SnO₂ NF/NSs and GO nanosheets network.