基于微流控芯片的电解质溶液太赫兹吸收特性研究

由于许多生物分子的振动和转动能级均在太赫兹波段，且太赫兹波具有电子能量低（约4 meV），不会破坏待测样品的特性，因此可以采用太赫兹光谱技术检测生物样品。然而许多生物分子在液体环境中才能保持其生物活性，需要在盐溶液中来探究酸碱环境对其的影响，以及在盐类缓冲液中研究其生物特性。但水作为极性液体对太赫兹波有强烈的吸收，因此，探究如何减少水对太赫兹吸收的方法非常必要。水对太赫兹的吸收主要因水分子间氢键造成，现阶段最常见的方法是减少水与太赫兹波的作用距离以及破坏水分子间的氢键。利用夹心式微流控芯片在太赫兹时域光谱系统下通过观察光谱强度变化来探究电解质对水分子间氢键的影响，既减少了水和太赫兹波的作用距离，又探究了电解质对水分子间氢键的作用。在微流控芯片中分别加入不同种类以及不同浓度的电解质，通过观察其在0.1～1.0 THz范围内的光谱强度变化来分析不同电解质对水分子间氢键的影响。部分电解质促进氢键的缔合，而另一部分则破坏氢键的形成，在太赫兹光谱范围内表现为光谱强度的变化。若促进氢键的缔合则对太赫兹吸收变大，光谱强度减弱；若破坏氢键的缔合则对太赫兹吸收减弱，光谱强度增加。研究结果发现：在水中加入KCl和KBr时，太赫兹光谱强度增加，表明二者对氢键有破坏作用，使得光谱强度变大；然而当加入MgCl₂和CaCl₂时，太赫兹光谱强度减弱，表明二者对氢键有缔合作用，从而使光谱强度变小。利用太赫兹技术在0.1～1.0 THz范围内研究KCl，KBr，MgCl₂和CaCl₂这四种不同浓度的电解质溶液特性，发现它们只会对光谱强度造成一定影响，不会引入新的特征吸收峰以及对待测样品造成干扰。这对于研究诸如大肠杆菌、枯草芽孢杆菌等在0.1～1.0 THz范围内有特征吸收谱的生物分子具有一定的实用价值。在溶液中加入所需的电解质并借助微流控芯片不仅可以识别待测样品、研究待测样品的光谱信息、探究其生物特性，而且为进一步推动太赫兹技术在生化方面的应用研究提供了先决条件。

Terahertz Absorption Properties of Electrolyte Solutions Based on Microfluidic Chip

As the vibration and rotational energy levels of many biological molecules fall in the terahertz band, which has the characteristics of low electron energy (about 4meV) and not destroying the samples, terahertz wave can be used to detect biological samples. Many biological molecules need to keep their bioactivity in the liquid environment, to explore the influences of acid and alkali environment in the salt solution, and to study their biological characteristics in the salt buffer solution. However, water as a polar liquid has strong absorption of terahertz wave, so it is necessary to explore how to reduce the absorption of terahertz wave by water, which is mainly caused by hydrogen bonds between water molecules. At present, the most common method is to reduce the distance between water and the terahertz wave and to destroy the hydrogen bonds between the water molecules. In this paper, by the aid of the terahertz time-domain spectroscopy system, the influences of different kinds and different concentrations of electrolyte on the hydrogen bond between water molecules are investigated by observing the change of spectral intensity in the range of 0.1～10 THz by using a sandwich microfluidic chip, which can not only reduce the distance between water and the terahertz wave, but also explore the influences of electrolyte on hydrogen bonds between water molecules. The specific performances are that some electrolytes can promote the association of hydrogen bonds, while the other destroy the formation of hydrogen bonds between water molecules, and this can be shown by the intensity of the spectra. If the association of hydrogen bonds between water molecules is promoted, terahertz absorption will increase and spectral intensity will decrease, and if the association is destroyed, terahertz absorption will decrease and spectral intensity will increase. The research results show that the strength of the terahertz spectrum increases when potassium chloride and potassium bromide are injected into the water, which indicates that they can destroy the hydrogen bonds and make the spectral intensity become larger. However, when magnesium chloride and calcium chloride are injected, the intensity of the terahertz spectrum is weakened. This indicates that they have an associative effect on hydrogen bonds, which makes the spectral intensity smaller. By using terahertz technology in the range of 0.1 to 1.0 THz to study the characteristics of potassium chloride, potassium bromide, magnesium chloride and calcium chlorideelectrolyte solutions with different concentration, it is found that these electrolytes can only affect the spectral intensity, and do not introduce new characteristic absorption peaks and cause interference to the sample. This has some practical value for the study of biological molecules such as Escherichia coli, Bacillus subtilis etc., which have characteristic absorption spectra in the range of 0.1～1.0 THz. With the help of microfluidic chip, injecting the required electrolyte in the solution can not only identify the samples to be measured, study the spectral information of the samples, and explore its biological characteristics, but also provide a prerequisite for further promoting the application of the terahertz technology in biochemistry.