UV Photoelectron Spectroscopy of Aqueous Solutions.
UV Photoelectron Spectroscopy of Aqueous Solutions.
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DOI：
10.1021/acs.accounts.2c00523
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发表时间：
2022-12-20
影响因子：
18.3
通讯作者：
Fielding, Helen H.
中科院分区：
文献类型：
--
作者：
Fortune, William G.;Scholz, Michael S.;Fielding, Helen H.
了解水溶液的电子结构是了解其化学和生物活性以及对光的反应的先决条件。确定电子结构的最直接方法之一是使用光电子能谱来测量电子结合能。最初，光电子能谱仅限于气相或固相，因为需要高真空来最小化发射电子的非弹性散射。20世纪90年代末，同步加速器引进了液体喷注及其与强X射线源的结合，将光电子能谱的范围扩大到包括液体。液体喷射光电子能谱现在是一个活跃的研究领域，涉及的研究小组越来越多。水溶液的X射线光电子能谱的一个局限性是需要使用浓度相当高的溶质，以便在减去水的光谱后获得具有足够信噪比的光电子光谱。这排除了对有机分子的大多数研究，因为有机分子往往只是弱溶解的。解决这一问题的一种方法是使用带有紫外光脉冲(hν≲6 eV)的共振增强光电子能谱。然而，由于对低动能电子(≲5 eV)的非弹性散射及其对谱线形状和位置的影响缺乏定量的了解，UV液体喷射光电子能谱的发展一直受到阻碍。在本文中，我们描述了测量水溶液紫外光电子能谱所涉及的关键步骤：光电离/脱离，低动能电子通过导带的电子传输，水-真空界面的传输，以及通过光谱仪的传输。我们还解释了我们采取的步骤，以良好的信噪比准确地记录液体的紫外光电子光谱。然后，我们描述了如何将电子散射和光谱反转的蒙特卡罗模拟与有机溶质在水溶液中的深度分布的分子动力学模拟相结合，开发出一种有效且广泛适用的方法来反演水溶液的真实紫外光电子光谱。我们的实验和光谱反演方法的巨大潜力被用三个例子来说明。首先是测量绿色荧光蛋白发色团的垂直分离能，绿色荧光蛋白发色团是一种难溶的有机阴离子，其电子结构支持其荧光和光氧化特性。第二个是测量液态水的垂直电离能，自1997年第一次X射线光电子能谱测量以来，这一直是讨论的主题。第三个是苯酚水溶液垂直电离能的紫外光电子能谱研究，它证明了从不同浓度分布的组分的贡献测量中恢复真实光电子光谱的可能性。
Knowledge of the electronic structure of an aqueous solution is a prerequisite to understanding its chemical and biological reactivity and its response to light. One of the most direct ways of determining electronic structure is to use photoelectron spectroscopy to measure electron binding energies. Initially, photoelectron spectroscopy was restricted to the gas or solid phases due to the requirement for high vacuum to minimize inelastic scattering of the emitted electrons. The introduction of liquid-jets and their combination with intense X-ray sources at synchrotrons in the late 1990s expanded the scope of photoelectron spectroscopy to include liquids. Liquid-jet photoelectron spectroscopy is now an active research field involving a growing number of research groups. A limitation of X-ray photoelectron spectroscopy of aqueous solutions is the requirement to use solutes with reasonably high concentrations in order to obtain photoelectron spectra with adequate signal-to-noise after subtracting the spectrum of water. This has excluded most studies of organic molecules, which tend to be only weakly soluble. A solution to this problem is to use resonance-enhanced photoelectron spectroscopy with ultraviolet (UV) light pulses (hν ≲ 6 eV). However, the development of UV liquid-jet photoelectron spectroscopy has been hampered by a lack of quantitative understanding of inelastic scattering of low kinetic energy electrons (≲5 eV) and the impact on spectral lineshapes and positions. In this Account, we describe the key steps involved in the measurement of UV photoelectron spectra of aqueous solutions: photoionization/detachment, electron transport of low kinetic energy electrons through the conduction band, transmission through the water-vacuum interface, and transport through the spectrometer. We also explain the steps we take to record accurate UV photoelectron spectra of liquids with excellent signal-to-noise. We then describe how we have combined Monte Carlo simulations of electron scattering and spectral inversion with molecular dynamics simulations of depth profiles of organic solutes in aqueous solution to develop an efficient and widely applicable method for retrieving true UV photoelectron spectra of aqueous solutions. The huge potential of our experimental and spectral retrieval methods is illustrated using three examples. The first is a measurement of the vertical detachment energy of the green fluorescent protein chromophore, a sparingly soluble organic anion whose electronic structure underpins its fluorescence and photooxidation properties. The second is a measurement of the vertical ionization energy of liquid water, which has been the subject of discussion since the first X-ray photoelectron spectroscopy measurement in 1997. The third is a UV photoelectron spectroscopy study of the vertical ionization energy of aqueous phenol which demonstrates the possibility of retrieving true photoelectron spectra from measurements with contributions from components with different concentration profiles.
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影响因子：
8.4
作者：
Bochenkova AV;Mooney CRS;Parkes MA;Woodhouse JL;Zhang L;Lewin R;Ward JM;Hailes HC;Andersen LH;Fielding HH
通讯作者：
Fielding HH
影响因子：
5.7
作者：
Hummert, Johan;Reitsma, Geert;Kornilov, Oleg
通讯作者：
Kornilov, Oleg
影响因子：
3.3
作者：
Mandal, D;Tahara, T;Meech, SR
通讯作者：
Meech, SR
影响因子：
3.3
作者：
Buchner, Franziska;Schultz, Thomas;Luebcke, Andrea
通讯作者：
Luebcke, Andrea
影响因子：
4.4
作者：
Elles, Christopher G.;Rivera, Christopher A.;Bradforth, Stephen E.
通讯作者：
Bradforth, Stephen E.