Humidity sensors have attracted considerable attention for their capability for real-time, continuous monitoring of critical physiological information, thus offering valuable insights into human health. Two-dimensional hexagonal boron nitride (h-BN) has emerged as an attractive material for humidity sensing due to its high specific surface area and excellent chemical stability. However, the low hydrophilicity of h-BN limits its ability to adsorb water molecules, resulting in reduced sensitivity and slow response times. Herein, capacitive humidity sensors consisted of amine-functionalized h-BN nanosheets have been developed. The introduction of amine groups modulates the hydrophilicity of pristine h-BN by forming hydrogen bonds, promoting interactions with water molecules. The h-BN-based sensor shows significantly improved performance, including high sensitivity (124,136 pF/%RH), large response (5,268,192%), and rapid response and recovery time (2.39 s/1.77 s). These findings demonstrate that amine functionalization can effectively enhance both water adsorption capacity and sensor performance, providing a promising approach for highly sensitive and responsive humidity sensors.

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.

Piezochromic luminescent materials have shown great potential in advanced optoelectronic applications. However, most of luminescent materials usually undergo emission quenching under external stimuli. Herein, we demonstrate for the first time that the photoluminescence of carbon dots (CDs) confined within sodium hydroxide can be enhanced when high pressure is applied. They exhibit a 1.6-fold fluorescence enhancement compared with pristine CDs. Importantly, the enhanced fluorescence intensity can be retained after the release of pressure to ambient conditions. A combination of experimental analysis and theoretical simulations indicates that such an enhanced emission is mainly attributed to the strong confinement resulting from the sodium hydroxide matrix, which can separate the CDs spatially and restrict the nonradiative pathway. These results provide a rational strategy for manipulating the optical properties of CDs with enhanced and retainable photoluminescence (PL) performance, thus opening up a venue for designing luminescent CDs-based materials.