Highly sensitive semiconductor gas sensors hold great potential for applications in trace gas detection. Reliable detection of ppb-level NO2 is crucial for environmental monitoring, which however still remains a challenge. In this work, we demonstrated ultrahigh NO2 sensitivity of indium-doped ZnO porous hollow cages. Doping of In into ZnO was accomplished via a facile one-pot MOF encapsulation-calcination route, which led to remarkably enhanced NO2 sensing performance. In-doped ZnO exhibited a large response of 3.7 to 10 ppb NO2, an ultrahigh sensitivity of 187.9 ppm-1, and a limit of detection of 0.2 ppb, outperforming state-of-the-art ZnO-based NO2 sensors. The superior NO2 sensing properties were attributed to a synergy of excellent gas accessibility of the porous hollow structure, abundant adsorption sites, and electronic sensitization by In doping. Our findings could be extended to design other porous doped ZnO oxides for high performance gas sensors and other applications.
Keywords: MOF; NO2 detection; ZnO; gas sensor; porous structure.