Fabrication of iron-doped titanium dioxide quantum dots/molybdenum disulfide nanoflower for ethanol gas sensing.

In this paper, a high-performance ethanol sensor based on iron (Fe)-doped titanium dioxide (TiO2)/molybdenum disulfide (MoS2) nanocomposite was demonstrated. Flower-like MoS2 and Fe-TiO2 quantum dots (QDs) were synthesized by a facile hydrothermal route, and the Fe-TiO2/MoS2 composite was prepared via layer-by-layer (LbL) self-assembly technique. The Fe-TiO2/MoS2 film sensor was fabricated on a flame resistant (FR-4) epoxy substrate with interdigital electrodes. The microstructure, elementary composition, and morphology of the as-prepared samples were fully characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). The gas sensing properties of the Fe-TiO2/MoS2 film sensor were determined at room temperature upon exposure to different concentration of ethanol gas. The experimental results illustrated that high response, short response/recovery time, stable repeatability, excellent selectivity long-term stability, and a detection limit of low ppb level was achieved by the Fe-TiO2/MoS2 sensor. The underlying sensing mechanism of the Fe-TiO2/MoS2 sensor toward ethanol is explored through systematically experimental investigation combining with first-principle density-functional theory (DFT) simulations. The enhanced ethanol sensing properties were ascribed to the Fe3+ ion doping, and p-n heterojunctions created at interfaces of n-type Fe-TiO2 and p-type MoS2.