Phase Transition of Non-equilibrium Wurtzite CoO: Spontaneous Deposition of Sensing Material for Ultrasensitive Detection of Acetone

•Phase transition of wurtzite CoO to spinel Co3O4 was used to prepare novel gas sensor.•Preparation was facile and induced preferential (111) plane exposure.•Nanostructured Co3O4 shows improved sensing performance from phase transition.•Exposed (111) planes enhance acetone sensitivity.