Porous In2O3:RE (RE = Gd, Tb, Dy, Ho, Er, Tm, Yb) Nanotubes: Electrospinning Preparation and Room Gas-Sensing Properties

In2O3:RE (RE = Gd, Tb, Dy, Ho, Er, Tm, Yb) as well as In2O3 nanotubes (NTs) with a diameter of ∼85 nm and wall thickness of ∼15 nm were systematically fabricated by the electrospinning method for the first time and characterized by various techniques. The results demonstrate that, except for In2O3:Tb, which contained a mixed phase (cubic and rhombohedral), the lattice constants of cubic In2O3:RE gradually decreased and the band-gap energies and the resistances in air gradually increased with the increase of doped RE atom order. As a consequence, it is exciting to observe that the doping of RE gradually and significantly improved the gas-sensing properties of In2O3 NTs to H2S gas as the RE varied from Gd to Yb in order. In contrast to undoped In2O3 NTs, the room-temperature response sensitivity of the In2O3:Yb NT sensors to 20 ppm H2S increased about 7 times and reached as high as 1241, whereas the response time of the In2O3:Yb NT sensors was shortened 4 times and reached ∼49 s. The present electrospun In2O3:RE NTs are highly promising H2S gas sensors that can work under soft conditions.