Solution chemical analysis is a scientific means for people to obtain information about the composition and structure of substances. It has an important position in the disciplines of chemistry, biology, environment and geology.
At the same time, it is also the foundation of experimental disciplines, and has always been a hot topic in experimental and theoretical research, such as chemical composition analysis, food testing, and environmental trace analysis.
At present, the main instrumental analysis methods are optical analysis, electrochemical analysis and chromatography. However, they are all limited by the following three aspects:
First, the detection of samples is still based on offline analysis and testing, and the results obtained are static rather than intuitive field data.
Traditional optical, electrochemical, and chromatographic methods typically require samples to be brought back to the lab for analysis after collection.
Since the analysis results are not obtained in real time, they cannot meet the diverse needs of the real-time measurement environment. In addition, the more complex sample preparation process greatly reduces the detection rate.
Second, there are certain requirements for the chemical composition information of the sample. For example, traditional optical analysis requires the sample to have some transparency, absorption or fluorescence properties so that light can interact with the sample.
The electrochemical analysis method requires the sample to have good conductivity, and the chromatographic analysis method has certain requirements for the solubility and concentration of the sample.
Third, the sample preparation process is complex, and the instrument is expensive and cumbersome, which greatly reduces the portability and detection speed.
Therefore, it is very necessary to establish effective and practical in-situ, real-time and inexpensive new dynamic analytical detection methods through the development of new analytical principles.
Based on the above difficulties and challenges, Zhang Jinyang, an assistant researcher and his team from the Beijing Institute of Nanoenergy and Systems, Chinese Academy of Sciences, combined the triboelectric and interfacial transfer charge distribution at the liquid-solid interface for the first time.
图 | 张金洋（来源：张金洋）
They used the functional relationship between the triboelectric initiation and the trajectory position of the droplet as the triboelectric spectroscopy (TES) of the droplet, and developed the charge transfer map of the liquid-solid interface, and realized the rapid detection of the ion type and content in the solution by analyzing the peak position and peak charge in the map.
With this method, they measured more than 30 common acids, bases, salts, and organic solvents and built a spectral database with 93% qualitative and quantitative accuracy.
The experimental results show that different ions have a unique transfer charge distribution that can be distinguished in the droplet sliding direction, which lays a foundation and platform for the development of new portable chemical in-situ analysis instruments.
(Source: JACS)
TES is expected to have broad application prospects in the fields of environmental monitoring, catalytic mechanism research, biomedicine, and planetary science.
For example, TES can be used to monitor dissolved oxygen in water bodies, hazardous substances in wastewater, etc. Combined with advanced wireless transmission technology, environmental parameters can be monitored in real time, thus helping people better understand environmental changes and pollution sources.
(Source: JACS)
In fact, as early as 2021, Zhang Jinyang and his team used the principle of triboelectric initiation and charge transfer at the liquid-solid interface to measure the triboelectric charge generated by the droplets sliding across the solid surface by arranging two electrodes with a certain spacing under the solid film, which preliminarily proved the uneven distribution of the triboelectric transfer charge at the liquid-solid interface.
In their experiments, they found that although the dimensions of the two electrode probes were identical, there was a significant difference in the amount of charge transfer between the two points. At the same time, the amount of charge transfer between droplets containing different chemical compositions and ion concentrations can also be distinguished [1].
Based on the above findings, in 2023, the research group expanded the electrode density to 432 independent electrode probes (electrode probe size 0.12mm²), thereby developing a new method for detecting the high-resolution distribution of charge transfer at the liquid-solid interface in real time [2].
At that time, they found that the interfacial charge transfer did not increase gradually with the continuous movement of droplets on the surface of the plastic film. In order to verify the accuracy of the experiment, they performed a large number of repeated experiments and calculations.
Finally, the research group proved that the uneven distribution of charge transfer at the liquid-solid interface is affected by the type of ions in the droplet.
Based on this, the team developed a triboelectric map of the liquid-solid interface by taking advantage of the difference in the distribution of the transfer charge at the liquid-solid interface in the sliding direction of the droplet, and realized the rapid detection of the type and content of ions in the solution by analyzing the movement of the peak position and the peak charge amount in the map.
日前，相关论文以《用于液体原位化学分析的摩擦电谱》（Triboelectric Spectroscopy for In Situ Chemical Analysis of Liquids）为题发在 JACS 上 [3]。
Zhang Jinyang and Wang Xuejiao, a master's student at the Beijing Institute of Nanoenergy and Systems of the Chinese Academy of Sciences, co-authored the book, with Lin Shiquan and Academician Wang Zhonglin of the Beijing Institute of Nanoenergy and Systems of the Chinese Academy of Sciences, and Professor Simone Ciampi of Curtin University in Australia as co-corresponding authors.
Figure | Related papers (Source: JACS)
In the next step, they hope to realize the remote in-situ real-time monitoring of triboelectric spectrum through circuit integration and microcomputer control, so as to be used for real-time monitoring of environmental pollutants in real scenarios.
Resources:
1.ACS Nano, 2021, 15, 14830
2.ACS Nano, 2023, 17, 1646-1652
3.Zhang, J., Wang, X., Zhang, L., Lin, S., Ciampi, S., & Wang, Z. L. Triboelectric Spectroscopy for In Situ Chemical Analysis of Liquids. Journal of the American Chemical Society.2024, 146, 6125–6133
Typesetting: Mantle