Vibrational spectroscopy techniques have evolved to measure gases, liquids, and solids at surfaces and interfaces. In the field of surface-sensitive vibrational spectroscopy, infrared spectroscopy measures the adsorption on surfaces and changes from reactions. Previous polarized modulated-infrared reflection–absorption spectroscopy (PM-IRRAS) measurements at the gas/solid interface were developed to observe catalytic reactions near reaction conditions. Other PM-IRRAS measurements use liquid cells where the sample is submerged and compressed against a prism that has traditionally been used for electrochemical reactions. This article presents a new method that is used to observe in situ adsorption of molecules using PM-IRRAS at the gas/liquid/solid interface. We demonstrate the meniscus method by measuring the adsorption of octadecanethiol on gold surfaces. Characterization of self-assembled monolayers (SAMs), the “gold standard” for PM-IRRAS calibration measurements, was measured in ethanol solutions. The condensed-phase (air/liquid) interface in addition to the liquid/solid interface was measured simultaneously in solution. These are compared with liquid attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy measurements to confirm the presence of the SAM and liquid ethanol. A model of the three-phase system is used to approximate the thickness of the liquid ethanol layer and correlate these values to signal attenuation using PM-IRRAS. This proof-of-concept study enables the measurement of reactions at the gas/liquid/solid interface that could be adapted for other reactions at the electrode and electrolyte interfaces with applications in environmental science and heterogeneous catalysis.

中文翻译：

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新方法的同时原位气/液/固界面的测量使用PM-IRRAS

振动光谱技术已经发展为可以测量表面和界面处的气体，液体和固体。在表面敏感振动光谱学领域中，红外光谱测量表面上的吸附和反应引起的变化。以前在气/固界面上的偏振调制红外反射吸收光谱（PM-IRRAS）测量方法已经开发出来，用于观察反应条件附近的催化反应。其他PM-IRRAS测量使用液池，其中样品被浸没并压在传统上用于电化学反应的棱镜上。本文介绍了一种用于现场观察的新方法使用PM-IRRAS在气/液/固界面吸附分子。我们通过测量十八烷硫醇在金表面的吸附来证明弯月面方法。在乙醇溶液中测量了自组装单分子膜（SAMs）的表征，这是PM-IRRAS校准测量的“金标准”。除了液/固界面外，还同时在溶液中测量了冷凝相（空气/液体）界面。将这些与液体衰减全反射率（ATR）-傅立叶变换红外（FTIR）光谱测量结果进行比较，以确认SAM和液体乙醇的存在。三相系统的模型用于近似液体乙醇层的厚度，并将这些值与使用PM-IRRAS的信号衰减相关。