Triboelectric Spectroscopy for In Situ Detection of Gas Molecules in Liquid

The rapid and accurate identification of gas molecules in liquids is of critical importance for environmental science, biomedical research, and industrial process control. However, traditional techniques, such as gas chromatography-mass spectrometry, electrochemical sensors, and optical methods, often require complex sample pretreatment, can detect only a single gas, and frequently depend on specific indicators, limiting their real-time monitoring capability and the general applicability in gas detection. Here, we extend the concept of triboelectric spectroscopy (TES) to the in situ chemical analysis of gas molecules in liquids. This approach relies on the unique charge transfer patterns generated when a liquid droplet containing a specific dissolved gas molecules slides across an insulating surface. Based on TES, we have successfully identified six types of common gas molecules, including CO₂, NH₃, CH₄, Ar, N₂, and O₂, with an identification accuracy of 96% and a detection limit of 0.02 mmol L^-1. Furthermore, we demonstrate the practical utility of TES in complex biological matrices by efficiently detecting CO₂ in plasma with a detection limit in the millimolar range. The measured TES peak charge transfer and total charge transfer exhibited strong linear correlations with CO₂ concentration, with R² values of 0.923 and 0.996, respectively, confirming a strong linear dependence and reliable predictability.