Ultrasensitive formaldehyde gas sensors based on a hollow assembly and its 3-dimensional network formation of single-crystalline Co3O4 nanoparticles

The detection of formaldehyde at a very low concentration is a significant research topic, because of its harmful impact on human health. In this current study, we have fabricated a hierarchical structure by the reasonable assembly of single-crystalline Co₃O₄ nanoparticles. A hollow morphology using sacrificial ZnO spheres could make a three-dimensional conducting network in a solid state. The resulting structure was quite active for formaldehyde sensing, and the detection limit was 50 ppb, which was nearly close to the record-high value among the other semiconducting materials. Such superior properties were attributed to the regular, hierarchically assembled structures with a small crystalline domain size, a thin hollow morphology with a large surface area, and a three-dimensional conductive network with a narrow diameter. We think that this hierarchical assembly can show great potential as a platform for improving human health through the monitoring of indoor environments.