Kraack Jan Philip, Lotti Davide, Hamm Peter
Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
J Chem Phys. 2015 Jun 7;142(21):212413. doi: 10.1063/1.4916915.
We present two-dimensional infrared (2D IR) spectra of organic monolayers immobilized on thin metallic films at the solid liquid interface. The experiments are acquired under Attenuated Total Reflectance (ATR) conditions which allow a surface-sensitive measurement of spectral diffusion, sample inhomogeneity, and vibrational relaxation of the monolayers. Terminal azide functional groups are used as local probes of the environment and structural dynamics of the samples. Specifically, we investigate the influence of different alkyl chain-lengths on the ultrafast dynamics of the monolayer, revealing a smaller initial inhomogeneity and faster spectral diffusion with increasing chain-length. Furthermore, by varying the environment (i.e., in different solvents or as bare sample), we conclude that the most significant contribution to spectral diffusion stems from intra- and intermolecular dynamics within the monolayer. The obtained results demonstrate that 2D ATR IR spectroscopy is a versatile tool for measuring interfacial dynamics of adsorbed molecules.
我们展示了在固液界面固定于薄金属膜上的有机单层的二维红外（2D IR）光谱。实验是在衰减全反射（ATR）条件下进行的，该条件允许对单层的光谱扩散、样品不均匀性和振动弛豫进行表面敏感测量。末端叠氮官能团用作样品环境和结构动力学的局部探针。具体而言，我们研究了不同烷基链长度对单层超快动力学的影响，结果表明随着链长度增加，初始不均匀性减小，光谱扩散加快。此外，通过改变环境（即在不同溶剂中或作为裸样品），我们得出结论，对光谱扩散贡献最大的是单层内的分子内和分子间动力学。所得结果表明，二维ATR红外光谱是测量吸附分子界面动力学的通用工具。
