Atomic structure-dominated enhancement of acetone sensing for a ZnO nanoplate with highly exposed (0001) facet

Multilayer-assembled ZnO nanoplates (NP-ZnO) were synthesized, and the relationship between the exposed facets and the sensing performance was investigated. The XRD results showed that NP-ZnO predominantly exposed polar (0001) facets (I-0002/I-1010 = 2.9), while the PL and XPS spectra indicated that it contained very few oxygen vacancies. For comparison, ZnO nanosheet assemblies and ZnO commercial powder, both with less exposed (0001) facets but much more oxygen vacancies, were also studied. In the gas sensing test, the NP-ZnO sensor displayed the best sensing performance among the three ZnO microstructures sensor. The XPS analysis further confirmed that NP-ZnO was able to adsorb more oxygen species, despite having very few oxygen vacancies. These results revealed that: i) although more oxygen vacancies are generally considered the main reason for the high sensing activity of the (0001) polar facets, this might not be the dominant factor in NP-ZnO; ii) in NP-ZnO, the (0001) facets with few oxygen vacancies displayed an excellent sensing performance mainly due to its special atomic structure.