Room temperature ammonia vapour detection on hBN flakes

Abstract

The chemical vapour sensing behaviour of pristine and variously modified hexagonal boron nitride (hBN) nanostructures was investigated towards the polar protic analyte in the form of ammonia. Morphological characterization with TEM revealed formation of well-define shaped and crystal sized hBN flakes (2.9 ± 0. 7 µm to 3.3 ± 0.3 µm) by using a low temperature and atmospheric pressure modified polymer derived ceramics (PDCs) route. Room temperature chemical sensing studies showed that the hBN-based devices were sensitive to ammonia, at sensitivity values of 2.8 × 10−2 ppm−1 for the pristine hBN flakes, and 2.0 × 10−2 ppm−1, 2.4 × 10−2 ppm−1, 2.1 × 10−2 ppm−1 for the 2.5, 5 and 10 wt.% BaF2 modified hBN flakes, respectively. On the contrary, improvement in structure for the 5 wt.% BaF2 modified hBN flakes had detrimental influence on the detection performance of ammonia, as evidenced by the poor LoD value of 49.7 ppm, in comparison to 1.1, 2.4 and 1.7 ppm for the pristine, 2.5, and 10 wt.% BaF2 modified hBN flakes, respectively. The improved sensing performance was attributed to the presence of nitrogen vacancies generated during the modification process, as well as the presence of impurities. Indeed, the values measured were higher than those reported for other 2D nanomaterial based sensors. This study demonstrates the critical role played by structural properties on the surface chemistry in the ammonia sensing properties of hBN flakes. Generally, the study highlighted the potential application of hBN nanostructured materials for detection of ammonia vapours at room temperature.