Surmounting the issues of high-sensitivity and room-temperature detection toward trace NO 2 gas is of paramount importance in the fields of human health and ultralow emission. Recently, black phosphorus (BP), a novel two-dimensional material, has gained considerable interest to achieve this goal. However, related work is far from satisfactory due to sluggish response, insufficient recovery, and fragile stability. In this scenario, we report on an inspiring NO 2 sensor featuring composite film of few-layer BP nanosheets and zinc oxide (ZnO) nanowires serving as the sensing layer. Compared with BP-only counterpart, BP-ZnO sensor exhibited enhanced performance including boosted response (74% vs. 37.7% toward 50 ppb, which was among the best performances of BP involved NO 2 sensors), accelerated response speed, better long-term stability, and strengthened humidity-repelling properties. In addition, excellent selectivity toward trace NO 2 gas was revealed. These improvements could be ascribed into porous film, abundant sorption sites, numerous p-n heterojunctions, and passivation effect of ZnO nanowires on BP nanosheets. Furthermore, the proposed basic-solution assisted BP exfoliation favored film deposition, and enabled versatile composition design involving BP nanosheets in the future. In brief, the as-prepared BP-ZnO NO 2 sensors paved the avenue for further BP applications and enriched its underlying transduction mechanism in gas sensing.
Industrial production, environmental monitoring, and clinical medicine put forward urgent demands for high-performance gas sensors. Twodimensional (2D) materials are regarded as promising gas-sensing materials owing to their large surface-to-volume ratio, high surface activity, and abundant surfaceactive sites. However, it is still challenging to achieve facilely prepared materials with high sensitivity, fast response, full recovery, and robustness in harsh environments for gas sensing. Here, a combination of experiments and density functional theory (DFT) calculations is performed to explore the application of tellurene in gas sensors. The prepared tellurene nanoflakes via facile liquid-phase exfoliation show an excellent response to NO 2 (25 ppb, 201.8% and 150 ppb, 264.3%) and an ultralow theory detection limit (DL) of 0.214 ppb at room temperature, which is excellent compared to that of most reported 2D materials. Furthermore, tellurene sensors present a fast response (25 ppb, 83 s and 100 ppb, 26 s) and recovery (25 ppb, 458 s and 100 ppb, 290 s). The DFT calculations further clarify the reasons for enhanced electrical conductivity after NO 2 adsorption because of the interfacial electron transfer from tellurene to NO 2 , revealing an underlying explanation for tellurene-based gas sensors. These results indicate that tellurene is eminently promising for detecting NO 2 with superior sensitivity, favorable selectivity, an ultralow DL, fast response-recovery, and high stability.
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