拉曼光谱技术在液体检测方面具有诸多优点, 如多组分同时探测、 非接触、 检测周期短、 分子指纹特性等, 已成功用于多个领域的样品分析, 但是较低的探测灵敏度制约了该技术的进一步发展。 为了提高液体样品拉曼光谱探测灵敏度, 文章报道了一种基于新型液体样品池的拉曼光谱增强方法。 该方法在传统比色皿底端加入一个凹面反射镜, 一方面可以使作用于样品后的激光再次反射聚焦重新作用于样品, 另一方面凹面反射镜可以使拉曼光谱探测装置同时收集前向与后向拉曼散射信号, 相较于传统拉曼光谱技术该方法可提高液体拉曼探测灵敏度。 首先理论分析了影响拉曼散射强度的因素以及在非偏振光激发下拉曼散射信号强度与收集角度之间的关系, 得出结论: 当收集角度相较于光源传播方向为前向或后向时(即0°或180°)拉曼散射强度最大, 为样品池的设计提供理论基础。 进一步设计并制作了一种新型样品池, 采用UV胶将镀银凹面反射镜(直径12.5 mm, 焦距10 mm)与石英管(外径12 mm, 壁厚1 mm, 长度30 mm)粘合形成新型液体样品池。 为了验证新型样品池的效果, 搭建了785 nm拉曼探头装置并开展了相关实验研究, 对三种典型的液体样品(75%乙醇、 异丙醇、 甲醇)进行探测并与传统比色皿的探测效果进行对比, 结果表明: 新型样品池对不同液体样品探测灵敏度均有明显的增强, 增强因子近4倍。 为了分析新型样品池制作方法的重复性, 制作了3个样品池, 实验对比了三个样品池的探测效果, 并对其结果进行分析。 为了验证该方法对低浓度样品的探测能力, 对稀释20倍的75%乙醇溶液进行探测, 利用新型样品池可获得样品的拉曼光谱信息, 而传统拉曼光谱技术无法获得有效的拉曼信号。 上述结果表明报道的新型样品池具有结构简单、 适用范围广的优点, 且可有效提高液体拉曼光谱探测灵敏度。

The most significant advantages include multi-component, noncontact detection, short testing period and molecular fingerprint characteristics. Raman spectroscopy has been successfully used in many fields. However, the low Raman-scattering signal limits its further development. In order to improve the sensitivity of Raman liquid detection, a method for enhancing the liquid Raman signal based on a new sample cell is reported in this paper. A concave mirror is added to the bottom of the traditional cuvette. On the one hand, the laser can be reflected and focused again after acting on the sample. On the other hand, the Raman scattering signals of forward and backward are collected by the setup at the same time. Thereby the Raman signal can be improved. Firstly, the influencing factors of Raman scattering intensity and the relationship between the Raman scattering signal intensity and the collection angle excited by unpolarized light are analyzed theoretically. It is concluded that the scattering intensity is the largest when the collection angle is forward and backward (0° or 180°). A new sample cell was designed, and the silver-plated concave mirror (diameter 12.5 mm, focal length 10 mm) and quartz tube (outer diameter 12 mm, wall thickness 1 mm, length 30 mm) was bonded with UV glue to form a liquid sample cell. A 785 nm Raman probe setup was used to conduct relevant experimental research, and different samples (75% ethanol, isopropanol, methanol) were detected and compared with traditional cuvettes. The results showed that the new sample cell is effective for different liquid samples, and the detection sensitivity can be improved, the enhancement factor is nearly 4 times. In order to analyze the repeatability of the new sample cell manufacturing method, the detection effects of the three sample cells were compared in the experiment. Lastly, to verify the detection ability of low-concentration samples, the 75% ethanol solution diluted 20 times was detected using the new sample cell. The result shows that the new sample can obtain effective Raman spectroscopy information. The experimental results prove that the new sample cell can improve the detection sensitivity of liquid Raman spectroscopy. It has a simple structure and a wide range of applications.