Effect of Grain-Boundaries in NiO Nanosheet Layers Room-Temperature Sensing Mechanism under NO₂

The discovery of gas sensing properties of single-crystalline nanostructures comparable or even better than their polycrystalline counterparts has triggered the attention of the gas sensor research community. To eleborate the sensing mechanisms of single-crystalline and polycrystalline nanostructures, the single-crystalline (SC) NiO hexagonal nanosheet and the nanoparticle self-assembled polycrystalline (PC) NiO nanosheet were prepared for room-temperature NO₂ sensing studies. The gas sensing studies revealed that the SC NiO exhibited a remarkably higher response to NO₂ at room temperaure than the PC NiO. The correlation between the structural features of NiO and the room temperature NO₂ sensing performances was discussed in detail via the grain boundary scattering theory. It was found that the scattering potential played a vital role in the sensing process. Because the absence of grain boundary in the SC NiO reduced the NO₂ chemisorption-induced carrier scattering at interfaces, the SC NiO performed the largely enhanced sensitivity. Here we hope that this work can help us to further understand the gas sensing mechanism and open up a new generation of gas sensors