Humidity Sensing by Graphitic Carbon Nitride Nanosheet/TiO₂ Nanoparticle/Ti₃C₂T_x Nanosheet Composites for Monitoring Respiration and Evaluating the Waxing of Fruits

Relative humidity (RH) is an important physical quantity in industry, agriculture, and medical treatment. However, it is still challenging to exploit high-performance humidity sensors that can meet the detection requirement for responding to both high humidity variation and low humidity variation. In this work, ternary graphitic carbon nitride (g-C3N4) nanosheet/TiO2 nanoparticle/Ti3C2Tx nanosheet composites were synthesized by in situ oxidation and thermal polymerization. The response of the g-C3N4/TiO2/Ti3C2Tx sensor reaches 531 from 11–95% RH, which enhances 4, 11, and 450 times compared with that of TiO2, g-C3N4, and TiO2/Ti3C2Tx sensors. Moreover, the ternary g-C3N4/TiO2/Ti3C2Tx sensor demonstrates excellent reproducibility, fast response speed, low hysteresis loop, and good anti-interference ability. The as-fabricated g-C3N4/TiO2/Ti3C2Tx sensor is further utilized in practical applications for human respiration detection and evaluation of waxing of fruits. The test results show that our fabricated sensor is capable of precisely sensing breathing status and distinguishing the waxing of fruits. In addition, our sensor can be used in most application scenarios and accelerate the integration of the Internet of Things (IoT).