Surface Engineering Enabled Capacitive Gas-Phase Water Molecule Sensors in Carbon Nanodots

Gas-phase water molecule sensors are essential in scientific, industrial, and environmental applications, playing a crucial role in ensuring human safety, monitoring pollution, and optimizing processes. However, developing gas-phase water sensors with high sensitivity remains a significant challenge. Herein, the effect of molecular adsorption on capacitive response is explored, and a facile surface engineering strategy to achieve sensitive carbon nanodots (CDs)-based sensors for H₂O is demonstrated.hydrophilic raw precursor is utilized to prepare the hydrophilic CDs and further employ these CDs as active media in the capacitive sensors, demonstrating how surface adsorption influences the capacitive response to H₂O molecules. By applying surface engineering, the molecular affinity potential of CDs is regulated, resulting in sensors that exhibit a broad detection range from 11% to 98% relative humidity (RH), with a remarkable sensitivity of 3.3 × 10⁵ pF/RH and an impressive response of 1.8 × 10⁸% at 98% RH. These CDs-based sensors present great potential for applications in respiratory monitoring, information exchange, contactless recognition of finger trajectories, etc. The findings unveil the unique influence of molecular affinity on capacitive response, opening new avenues for the design and applications of highly sensitive molecular sensors.