Biomass-derived hierarchical porous ZnO microtubules for highly selective detection of ppb-level nitric oxide at low temperature

Highly sensitive and selective detection of nitric oxide (NO) has recently attracted much attention due to its environmental pollution and biological role. Herein, hierarchical porous ZnO microtubules were simply and massively prepared through zinc salt immersion and air calcination using hemp fiber as biotemplate. The effect of different calcination temperature on the microstructure and gas-sensing performance was investigated. The ZnO-600 microtubules calcined at 600 °C are assembled from the cross-linking nanoparticles with good crystallinity. Especially, the multi-pores and diverse nano-channels are in favor of the quick diffusion and adsorption of target gas, enabling ZnO-600 material to present excellent gas-sensing performance towards trace NO. At low working temperature of 92 °C, the sensor fabricated by ZnO-600 microtubules to NO exhibits high response (10 ppm, S = 78.54), fast response-recovery, good selectivity as well as satisfactory stability and anti-humidity. Meanwhile, this sensor represents the lowest detection limit of 5 ppb (S = 1.22) among all reported ZnO-based sensors. Moreover, the gas-sensing mechanism for ZnO-600 material is demonstrated to be surface adsorption control model.