Synthesis and gas sensing performance of NiO decorated SnO2 vertical-standing nanotubes composite thin films.

Highlights • A new type NiO decorated SnO 2 vertical-standing nanotubes composite thin film was synthesized via a facile hydrothermal method. • Numerous SnO 2 vertical-standing nanotubes with the size of 200–300 nm in diameter and 1.5 μm in length formed a porous microstructure. • NiO nanoplates with the size of 20 nm in diameter decorated on the inside or outside surface of SnO 2 nanotubes formed a heterojunction structure. • The NiO/SnO 2 thin film gas sensor with an Ni2+/Sn4+ molar ratio of 5% exhibited excellent response characteristics to ethanol at 250 ℃. Abstract In this work, a new type NiO decorated SnO 2 vertical-standing nanotubes composite thin film was synthesized successfully via a facile hydrothermal method. The microstructure, physico-chemical surface state and morphology of the composite thin film were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The results showed that the NiO decorated SnO 2 vertical-standing nanotubes composite thin film with a coral-like microstructure was built of numerous 1D SnO 2 nanotubes with the size of 200–300 nm in diameter and 1.5 μm in length; while NiO nanoplates with the size of 20 nm in diameter decorated on the surface of SnO 2 nanotubes. Due to the enhanced adsorption of oxygen molecules, formation of p -NiO/ n -SnO 2 heterojunction and porous structure, the NiO/SnO 2 thin film gas sensor with an Ni2+/Sn4+ molar ratio of 5% exhibited high response value, good selectivity and quick response characteristics to ethanol at the optimum working temperature of 250 ℃. [ABSTRACT FROM AUTHOR]