Zinc oxide–black phosphorus composites for ultrasensitive nitrogen dioxide sensing

Multi-layer black phosphorus (m-BP) has been successfully incorporated in zinc oxide (ZnO) hollow spheres, thus forming hetero-structured ZnO-BP composites; a study performed on their properties reveals that the BP environmental stability can be significantly enhanced by the introduction of ZnO, and the sensors based on ZnO-BP composites exhibit high response, fast response behavior, outstanding selectivity, and ultralow detection limit of 1 ppb towards NO₂ gas molecules. The ultrasensitive sensing performance is suggested to be due to the large surface area, excellent carrier mobility, and enhanced charge transfer of ZnO-BP in the presence of BP. Moreover, the mechanism of NO₂ sensing with ZnO-BP is confirmed by the calculations obtained from the first-principle studies.