2D/2D DyO Nanosheet/MoO Nanoflake Heterostructures for Humidity-Independent and Sensitive Ammonia Detection.

Chemiresistive ammonia gas (NH) sensors have been playing a significant role in the fields of environmental protection, food safety monitoring, and air quality evaluation. Nevertheless, balancing the high sensitivity and humidity tolerance remains challenging. Herein, the two-dimensional (2D) heterostructures of molybdenum trioxide (MoO) nanoflakes decorated with dysprosium oxide (DyO) nanosheets (termed DyO/MoO) were synthesized via a facile probe-sonication method. With respect to pristine MoO counterparts, the optimal DyO/MoO sensors possessed a 4.49-fold larger response at a lower temperature (30.52@328.2 °C vs 6.8@369.7 °C toward 10 ppm of NH), shorter response/recovery times (11.6/2.9 s vs 26.9/43.4 s), 52.6-fold higher sensitivity (17.35/ppm vs 0.33/ppm), and a lower theoretical detection limit (1.02 vs 32.82 ppb). Besides the nice reversibility, wide detection range (0.45-100 ppm) and robust long-term stability, inspiringly, the DyO/MoO sensors showed a nearly humidity-independent response. These impressive improvements in the NH-sensing performance were attributed to numerous heterojunctions to strengthen the carrier concentration modulation and the compensation/protection effect of DyO to mitigate the humidity effect. Moreover, the DyO/MoO sensors showed preliminary application potential in monitoring pork freshness. This work provides a universal methodology for constructing NH gas sensors with high sensitivity and good humidity resistance and probably extends the application scenarios of MoO-based sensors in the Internet of Things in the future.