Highly repeatable and sensitive three-dimensional γ-Fe2O3@reduced graphene oxide gas sensors by magnetic-field assisted assembly process

[Display omitted] •3D γ-Fe2O3@RGO core-shell hybrids have been prepared via an electrostatic self-assembly and in-situ thermal reduction method.•The gas sensors with repeatable uniform sensing film are fabricated using magnetic-field assisted assembly method.•The 3D γ-Fe2O3@RGO gas sensor exhibits a high sensitivity of 1.23 toward 100 ppb NO2 at room temperature. Reduced graphene oxide (RGO)/metal oxide hybrids are considered as an ideal candidate for high-performance gas sensors due to their large specific surface areas and heterostructures. However, they usually suffer from the poor and unrepeatable sensing performance due to the sheet stacking of RGO nanosheets and the uncontrollable drop-coating process. In this work, three-dimensional (3D) γ-Fe2O3@GO core-shell hybrids have been synthesized by an electrostatic self-assembly method. The sensing device based on uniform 3D γ-Fe2O3@RGO film can be fabricated using the magnetic-field assisted drop-coating and in-situ thermal reduction. Experimental results show that the as-fabricated 3D γ-Fe2O3@RGO sensor exhibits a good selectivity and high sensitivity of 3.43 toward 50 ppm NO2, which is about 2.5 times higher than that of the pure plane-stacked RGO sensor. The response value is still 1.23 when the NO2 concentration drops down to 100 ppb. The high performance can be attributed to the larger surface area, less agglomeration and the formed heterostructures which significantly promotes charge transfer. Importantly, the magnetic-field assisted drop-coating method results in a good stable and repeatable sensing performance due to the magnetic properties of γ-Fe2O3. The architecture strategy opens a new general route to large-scale practical fabrications of high-performance gas sensors based on RGO/magnetic oxide hybrids.