Design Synthesis of ZnO Tube Bundles Rich in Oxygen Vacancies Assembled by Nanorods/Quasi-Nanospheres for Enhanced Sensing to NO/NO2

How to in situ construct homo-nanostructures assembled from diverse nanobuilding blocks and achieve high sensing of NO/NO2 gases is still challenging. To this end, two biomorphic ZnO materials cross-linked by nanorods and quasi-nanospheres were obtained through facile zinc nitrate solution infiltration and calcination using kitchen garbage of a discarded loofah sponge as the biotemplate. Among the tube bundles obtained by calcination at 600 °C, ZnO-6 possesses good crystallinity, small-sized mesopore distribution, and large specific surface area, as well as abundant oxygen vacancies. The synergy of the aforementioned microstructural features can improve electron transport efficiency, promote fast gas diffusion, increase the content of adsorbed oxygen species, and expose more surface active sites, thereby efficiently improving its sensing properties toward nitrogen oxides. At 92 °C, the ZnO-6 sensor simultaneously achieves large response values from 100 to 10 ppm of NO and 342 to 10 ppm of NO2, and their recovery times are reduced to 12 and 15 s, respectively. These indicators have apparent superiority over most reported corresponding metal oxide-based sensors. In addition, the sensor can apply the detection of trace NOx in real environments.