Polarized Raman spectroscopy for determining the orientation of cellulose microfibrils in wood cell wall
Polarized Raman spectroscopy for determining the orientation of cellulose microfibrils in wood cell wall
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DOI：
10.1007/s10570-022-04915-w
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发表时间：
2022-10
期刊：
影响因子：
5.7
通讯作者：
Xun Zhang;Li Li-Li;Feng Xu
中科院分区：
文献类型：
--
作者：
Xun Zhang;Li Li-Li;Feng Xu
木材纤维素在细胞壁中具有高度有序的结构，其尺度从几纳米到几微米。通过偏振拉曼光谱可以原位研究其择优取向。然而，由于样品制备、仪器访问和预测模型可用性方面的挑战，该技术目前未得到充分利用。在这里，提出了一种新的策略来分析微纤维的取向，而不需要事先知道的纤维排列。推导了入射光偏振角与拉曼信号强度之间的数学关系。因此，一个更新的预测模型的微纤维取向，以取代以前的经验函数。通过调节激光功率和缩短采集时间，解决了降解和烧毁问题。纤维素微纤丝的取向方向可以在不旋转样品的情况下通过偏振相关的1096 cm-1强度来确定。该策略被成功地用于研究轻木细胞壁中分子取向的变化。结果表明，纤维素微纤丝呈平行排列形成细胞壁。
It is well established that wood cellulose has highly ordered architecture at scales from a few nanometres to several microns in wood cell wall. Its preferred orientation could be in-situ investigated by polarized Raman spectroscopy. However, the technique is currently underused due to the challenges in sample preparation, instrumentation access and availability of prediction models. Here, a novel strategy is proposed to analyse the microfibril orientation without requiring prior knowledge of the fiber alignment. We derive the mathematical dependence between the incident light polarization angle and the intensity of Raman signal. An updated prediction model of microfibril orientation was thus constructed to replace the previous empirical functions. The problems of degradation and burning were addressed by adjusting the laser power and shortening the acquisition time. The orientation direction of cellulose microfibrils can be determined by the polarization-dependent 1096 cm−1intensity without rotating sample. The strategy was successfully used to study the variations in molecular orientation throughout a cell wall of balsa wood. It was found that the cellulose microfibrils are arranged spirally to form the cell wall.