天然纤维素太赫兹和红外光谱分析研究

为研究太赫兹波技术在植物中纤维素检测的应用前景。选取玉米、麦壳、芦苇进行太赫兹时域光谱检测，并与纤维素粉作为参考样品进行比较，分析结果表明上述三种植物样品和参考样品在1.75，1.62，1.1和0.7 THz等频率处均有明显特征吸收峰。比较几种样品的吸收强度情况，纤维素粉在1.62 THz处吸收最强，采用化学分析方法检测玉米、麦壳以及芦苇中纤维素含量，并与太赫兹波检测比较，发现在该频率处植物中纤维素含量越高，则其在太赫兹波中的吸收峰也越高，说明植物纤维素能在该频率段内发生晶格振动，使其官能团出现变形、弯曲或伸缩等变化。利用密度泛函理论对纤维素进行量子化学计算，也获得纤维素在0.7，1.1和1.75 THz处特征吸收峰，表明了太赫兹时域光谱能用于植物纤维素检测。最后，用红外光谱技术对玉米和纤维素粉进行检测，探讨纤维素分子微结构的扭转及振动模式，并把它们的特征吸收谱与量子化学计算进行比较，实验结果和理论计算基本一致。这为植物纤维素的检测判断提供了一种新方法。

Terahertz and Infrared Spectroscopic Investigation of Cellulose

To investigate the Terahertz’s application prospect, corn, wheat husk and reed were used to detect their Terahertz Time Domain Spectroscopy, and be compared with that of cellulose powder. The experimental results show that all of their absorption peaks exist at 1.75, 1.62, 1.1, and 0.7 THz. Absorption intensity of cellulose powder, corn, wheat husk and reed were compared in some frequencies points. It finds that corn, wheat husk and reed have higher absorption intensity than cellulose powder in early frequency domain. However, absorption intensity of cellulose powder is the strongest at 1.62 THz. Cellulose content in corn, wheat husk and reed were detected by using the method of chemical analysis. The peaks of absorption coefficient are related to their cellulose content at this frequency. It shows that plant cellulose occur lattice vibration in the frequency. Deformation, bending, flexing, and other changes appear to their functional keys. Quantum chemical calculation was carried out by using density functional theory to cellulose and the structure diagram of cellulose molecular formula was obtained. It also finds some absorption peaks exist at 0.7, 1.1, and 1.75 THz. Characterization of cellulose clusters mainly includes CH₂, OH, CH, and so on. Glucose hydroxyl radical on the ring is active in the cellulose chain. Where hydroxyl related chemical reaction can occur, Hydroxyl can also be integrated into the intermolecular and intramolecular hydrogen bond. Terahertz wave can promote hydrogen bond vibration. This kind of vibration is weak in the intermolecular interaction. The vibration and rotating happen in dipole transition. The crystal lattice rotates and is absorptive in low frequency, and large molecular skeleton vibrates. All of them can show different intensity and position of the absorption peak in the terahertz band. Corn and cellulose were analyzed by infrared spectrum. The reverse and vibration mode of cellulose was discussed. The absorption peak is basically in line with its theoretical calculating result. It is feasible that Terahertz Time Domain Spectroscopy can detect cellulose, and it provides a new method for the detection and judgement of cellulose in plants.