Borophene and BC2N quantum dot heterostructures: ultrasensitive humidity sensing and multifunctional applications

Abstract

Precise and real-time monitoring of the humidity value is of great significance to the living comfort and also to many applications in the field of agriculture, food and medicine. Although humidity sensors have become one of the most widely used chemical sensors, the low sensitivity and long response or recovery time have been hindering the development of this field. Due to the synergistic effect, the selection of heterostructures as sensing layers has been proven to be a simple and effective method for the next generation of high-performance humidity sensors among the proposed solutions to improve sensing performances. Here, we have successfully prepared borophene-BC₂N heterostructures by in situ self-assembly under ultrasonic irradiation and fabricated the corresponding high-performance humidity sensor via a facile method. The sensor exhibits a wide detection range (11–97%), ultra-high sensitivity (up to 22 001% at 97% RH), low hysteresis, good repeatability and fast response (11.82 s)/recovery (1.41 s). Compared to pristine borophene or BC₂N QDs, borophene-BC₂N heterostructures show a 100 or 20 times higher sensitivity at 97% RH at room temperature, which is the highest sensitivity among all the typical humidity sensors in previous studies. In addition, the sensor also exhibits long-term stability, excellent flexibility and high selectivity. Because of the excellent sensing performances, the heterostructured sensor can be successfully used in diaper monitoring of infants and critically ill patients, wireless monitoring of respiratory behavior and speech recognition by detecting humidity in exhalation, and non-contact switch by detecting the humidity value of the fingertip surface. This work can provide effective strategies for developing smart diapers, auxiliary voice systems, human health monitoring and prevention, and promote the development of non-contact man–machine interface systems without risks of infection.