Electrospun ZnO Nanotubes\nDecorated with Zinc Ferrite\nNanoparticles as Sensing Material for Hydrogen Sulfide Detection

Coaxial electrospinning is first employed for loading\nzinc ferrite\n(ZnFe<sub>2</sub>O<sub>4</sub>) nanoparticles onto zinc oxide (ZnO)\nnanotubes for sensing hydroxide sulfite (H<sub>2</sub>S) in the gaseous\nphase. The obtained ZnFe<sub>2</sub>O<sub>4</sub>/ZnO composite consists\nof protruding ZnFe<sub>2</sub>O<sub>4</sub> nanoparticle-decorated\ninner ZnO nanotubes, forming a unique double-layer core–shell\nstructure with a large amount of p–n heterojunction interfaces\nand oxygen vacancy defects. The nanotubes have a diameter range from\n47 to 88 nm and a wall thickness range from 17 to 46 nm. The ZnFe<sub>2</sub>O<sub>4</sub>/ZnO sensors demonstrate enhanced sensitivity,\nselectivity, and fast response to H<sub>2</sub>S gas compared to the\nZnO nanowire sensor, particularly at lower operating temperatures\n(50–240 °C). With the molar ratio of zinc nitrate to iron\nnitrate at 7:3, the derived ZnFe<sub>2</sub>O<sub>4</sub>/ZnO sensor\nhad maximal responses of 3.3–98.5 to H<sub>2</sub>S at 0.1–10\nppm under the optimal temperature of 130 °C, significantly higher\nthan that of the ZnO nanowire sensor. The significant enhancement\nin H<sub>2</sub>S-sensing is attributed to the synergistic effect\nbetween the ZnFe<sub>2</sub>O<sub>4</sub> and ZnO species and the\npresence of abundant oxygen vacancies. This research suggests exploiting\nhigh-performance H<sub>2</sub>S-sensing materials based on coaxial\nelectrospinning.