Two-dimensional Bi2O2S based high-sensitivity and rapid-response humidity sensor for respiratory monitoring and Human-Machine Interaction

As a crucial component of the Internet of Things, humidity sensors exhibit tremendous potential in a variety of fields including industrial and agricultural monitoring, public safety, human health, and biomedicine. Chemically and electrically responsive two-dimensional (2D) materials have attracted considerable interest as viable candidates for humidity sensors. Bismuth oxysulfide (Bi2O2S) emerges as promising building blocks for the construction of humidity sensors due to its good electrical properties and stability. In this study, we successfully used one-step hydrothermal method to prepare Bi2O2S nanosheets with stacked lamellae. Its electrical humidity sensitive properties were demonstrated through contact angle tests and Fourier transform infrared spectroscopy characterization. The results indicated that Bi2O2S-based humidity sensor exhibited excellent electrical humidity sensing performance with high-sensitivity of 2582 and a rapid response/recovery time of 0.4/2.4 s (under 84% relative humidity, RH). The sensing mechanism was further explained through complex impedance measurement. As a proof of concept, we constructed humidity sensors for respiration monitoring and non-contact humanmachine interaction.