Constructing chinky zinc oxide hierarchical hexahedrons for highly sensitive formaldehyde gas detection

The gas sensing performances of chemical sensors can be optimized not only by functionalization of sensing materials, but also via artful structural design. Herein, we develop a highly sensitive formaldehyde (HCHO) gas sensor by exploiting chinky zinc oxide (ZnO) hexahedrons, which are successfully synthesized by a facile room-temperature solution strategy combined with a subsequent calcination process. Microstructural characterizations by means of scanning electron microscopy and X-ray diffraction indicate that as-prepared ZnO hexahedrons are assembled by numerous nanoparticles and present porous chinky hexahedron architectures. When applied as a gas sensing material, the resulting ZnO hexahedrons show enhanced response towards formaldehyde gas compared with ZnO nanoparticles. Moreover, rapid response (1 s) and recovery speed (12 s), superior selectivity, and well stability and reproducibility are also observed in ZnO hexahedrons based sensors. Benefiting from synergistic sensitization effect of more surface defects, larger surface area and three dimensional hierarchical assembly pattern, ZnO hierarchical hexahedrons facilitate full exposure of active sites and easy adsorption of oxygen and target gases, producing enhanced formaldehyde gas sensing performances. This work not only highlights the advantage of simultaneous sensitization of different strategies, but also further demonstrates the contribution of the assembly pattern of building blocks in improving gas sensing performances of oxide semiconductor based gas sensors.