Molecular Spectroscopy Laboratory, RIKEN, Wako, Saitama, Japan.
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, Ibaraki, Japan.
Nat Chem. 2021 Apr;13(4):306-311. doi: 10.1038/s41557-020-00619-5. Epub 2021 Feb 8.
Reactions at the interface between water and other phases play important roles in nature and in various chemical systems. Although some experimental and theoretical studies suggest that chemical reactions at water interfaces can be different from those in bulk water-for example, 'on-water catalysis' and the activation of photochemically inert fatty acids at the air-water interface upon photoexcitation-directly investigating these differences and generating molecular-level understanding has proved difficult. Here, we report on the direct probing of a photochemical reaction occurring at the air-water interface, using ultrafast phase-sensitive interface-selective nonlinear vibrational spectroscopy. The femtosecond time-resolved data obtained clearly show that the photoionization reaction of phenol proceeds 10 times faster at the water surface than in the bulk aqueous phase (upon irradiation with photons with the same energy). This finding demonstrates that photochemical reactions at water interfaces are very different from those in bulk water, reflecting distinct reaction environments at the interface.
水相与其他相之间的界面反应在自然界和各种化学体系中都起着重要的作用。虽然一些实验和理论研究表明，水界面上的化学反应可能与体相中的化学反应不同，例如“水相催化”以及在光激发下空气-水界面上的光化学惰性脂肪酸的激活，但直接研究这些差异并产生分子水平的理解一直很困难。在这里，我们使用超快相敏界面选择性非线性振动光谱报告了在空气-水界面上发生的光化学反应的直接探测。获得的飞秒时间分辨数据清楚地表明，在水表面上苯酚的光离子化反应比在体相水溶液中快 10 倍（在相同能量的光子照射下）。这一发现表明，水界面上的光化学反应与体相中的光化学反应非常不同，反映了界面处截然不同的反应环境。
