Study of microwave non-thermal effects on hydrogen bonding in water by Raman spectroscopy
Study of microwave non-thermal effects on hydrogen bonding in water by Raman spectroscopy
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拉曼光谱研究微波非热效应对水中氢键的影响
DOI：
10.1016/j.saa.2022.121877
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发表时间：
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通讯作者：
Shunli Ouyang
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作者：
Gang Han;Fang Liu;Tiezhu Zhang;Wence Xu;Yuxuan Zhang;Nannan Wu;Shunli Ouyang
微波化学在有机合成中发挥着重要作用。微波非热效应是否存在一直存在争议。通过分析纯水在两种不同加热方式（油浴和微波）下的拉曼光谱，验证了微波非热效应的存在。研究结果表明，温度对 OH 伸缩带的拉曼位移有显着影响，随着温度升高，该伸缩带会向高波数移动，并使氢键 (HB) 网络结构变形。由于微波电场选择性地加热水分子（极性分子）并破坏水中的氢键结构，导致微波加热对完全氢键结构的破坏比油浴更严重，并更快地将其转变为部分氢键和游离的H2O结构。在微波的非热效应下，最初以稳定四面体结构存在的氢键更快地转变为链状结构。通过比较拉曼位移可以发现，微波非热效应可以长时间（>1h）影响水中的氢键。该研究为丰富微波非热效应对氢键作用的机理提供了实验基础。
Microwave chemistry plays an important role in organic synthesis. It has been debatable whether or not there are microwave non-thermal effects. Through analyzing the Raman spectra of pure water under two different heating methods (oil bath and microwave), the existence of microwave non-thermal effect is verified in this paper. The findings demonstrate that temperature has a significant impact on the Raman shift of the OH stretching band, which shifts to a high wave number as temperature rises and deforms the hydrogen bond (HB) network structure. Because microwave electric fields selectively heat water molecules (polar molecules) and destroy hydrogen bond structures in water, results in microwave heating more severe destruction of fully hydrogen-bonded structure than oil bath and transforms it more quickly into the partially hydrogen-bonded and free H2O structure. Under the non-thermal effects of microwaves, hydrogen bonds that initially existed as stable tetrahedral structures are transformed into chain-like structures more rapidly. By comparing the Raman shift, it can be found that the microwave non-thermal effect can affect the hydrogen bonding in water for a long time (>1h). This study provides an experimental basis for enriching the mechanism of microwave non-thermal effects on hydrogen bonding.