Sandwich-Structured In<sub>2</sub>S<sub>3</sub>/In<sub>2</sub>O<sub>3</sub>/In<sub>2</sub>S<sub>3</sub> Hollow Nanofibers as Sensing Materials for Ethanol Detection
Shi Kun Wang, Ao Chen Wang, Chaoyue Zhang, Qian Yu Liu, Jun Cheng, Yan Chun Wang, Xiu Ping Gao, Qing Feng Xie, Zhenxing Zhang, Gengzhi Sun, Xiao Jun Pan, Jinyuan Zhou
Abstract
Core–shell heterojunction nanostructure-based sensors often suffer from the blocking effect from the shell layer. Here, a type of sandwich-structured hollow nanofiber of In 2 S 3 /In 2 O 3 /In 2 S 3 (ISOS HNF) was designed via an electrospinning technique combining with postvulcanization treatments. The resultant ISOS HNF possesses double In 2 S 3 /In 2 O 3 heterointerfaces at both sides of In 2 O 3 tube walls, which highly enhance the junction effect on the electron transport during the gas-sensing processes. Also, the two In 2 S 3 coatings are particle-filled and porous, which often allows the target gas to easily diffuse through them to the In 2 O 3 core. As a result, toward 100 ppm ethanol at a work temperature of 200 °C, the ISOS HNF sensors show a high response improved by 23% and 76% compared to those of the In 2 S 3 /In 2 O 3 core–shell NF and In 2 O 3 HNF ones, respectively. Moreover, the ISOS HNF sensors also exhibit a fast response/recovery rate (<1 s/25 s) and a good gas selectivity property. Series analysis indicates that this highly improved response is mainly due to the double In 2 S 3 /In 2 O 3 heterointerfaces and increased O vacancies, the accelerated response/recovery rate is due to the double-constructed heterojunction and the suitable mesopores in the coatings, and the improved gas selectivity is due to the In 2 S 3 shell.