Xing Dong, Meng Yifan, Yuan Xu, Jin Shuihui, Song Xiaowei, Zare Richard N, Zhang Xinxing
College of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center (RECAST), Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, China.
Haihe Laboratory of Sustainable Chemical Transformations, Tianjin, 300192, China.
Angew Chem Int Ed Engl. 2022 Aug 15;61(33):e202207587. doi: 10.1002/anie.202207587. Epub 2022 Jul 8.
Despite the high stability of bulk water, water microdroplets possess strikingly different properties, such as the presence of hydroxyl radicals (OH⋅) at the air-water interface. Previous studies exhibited the recombination of OH⋅ into H O molecules and the capture of OH⋅ by oxidizing other molecules. By spraying pure water microdroplets into a mass spectrometer, we detected OH⋅ in the form of (H O ) that is essentially OH⋅-H O , a hydroxyl radical combined with a hydronium cation through hydrogen bonding. We also successfully captured it with two OH⋅ scavengers, caffeine and melatonin, and key oxidation radical intermediates that bear important mechanistic information were seen. It is suggested that some previous reactions involving (H O ) should be attributed to reactions with OH⋅-H O rather than with the water dimer cation (H O-OH ) .
尽管 bulk water 具有高度稳定性，但水微滴具有截然不同的性质，例如在气-水界面存在羟基自由基（OH⋅）。先前的研究表明 OH⋅ 会重新组合成 H₂O 分子，并且 OH⋅ 会通过氧化其他分子而被捕获。通过将纯水微滴喷入质谱仪，我们检测到了以（H₃O₂）形式存在的 OH⋅，其本质上是 OH⋅-H₂O，即一个羟基自由基通过氢键与一个水合氢离子结合。我们还成功地用两种 OH⋅ 清除剂咖啡因和褪黑素捕获了它，并且观察到了带有重要机理信息的关键氧化自由基中间体。有人认为，一些先前涉及（H₃O₂）的反应应归因于与 OH⋅-H₂O 的反应，而不是与水二聚体阳离子（H₂O-OH₂⁺）的反应。
