Highly sensitive humidity sensors based on hexagonal boron nitride nanosheets for contactless sensing

Humidity sensors with high sensitivity, rapid response, and facile fabrication process for contactless sensing applications have received considerable attention in recent years. Herein, humidity sensors based on hexagonal boron nitride (h-BN) nanosheets that are synthesized by a facile ultrasonic process have been fabricated, which display an ultrahigh sensitivity of 28,384% at 85% relative humidity (RH), rapid response/recovery time (3.0/5.5 s), and long-term stability in a wide humidity detection range (11%-85% RH), superior to most of the reported humidity sensors. The high sensitivity can be ascribed to the massive hydrophilic functional groups absorbed on the h-BN nanosheet surface. Benefiting from the high humidity sensing performances, contactless Morse code messaging and human writing and speech recognition have been demonstrated. This work demonstrates the great potential of the high-performance h-BN nanosheet-based humidity sensors for future contactless sensing devices.