State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, Jilin University, Changchun 130012, PR China.
Department of Chemistry, and Institute for Molecular Science and Fusion Technology, Kangwon National University, Chunchon 24341, South Korea.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Nov 5;204:532-536. doi: 10.1016/j.saa.2018.06.063. Epub 2018 Jun 23.
p-Aminothiophenol (PATP) is a preferred molecule in research on surface-enhanced Raman scattering (SERS) because of its unique characteristics of high spectral activity, easily induced charge-transfer (CT), and sensitivity to molecular structural changes. However, some aspects are still unclear, such as the initial steady state of PATP on noble metallic substrates without strong additional excitation with incident and/or induced electromagnetic radiation. Information about the initial steady state, especially the intrinsic CT state, is of great importance to elucidate the dynamic processes of CT and/or molecular structural changes under additional excitation. To investigate the native state of an adsorbed molecule, a suitable probe method that does not disrupt the native state of the whole system, including both molecules and substrates, is required. SERS is not applied in this context because of its use of high-energy visible and near-infrared light. Herein, a low-energy probe method, surface-enhanced infrared-absorption (SEIRA) spectroscopy, is employed as a suitable method for studying the native adsorption state of PATP on silver nanoisland films. The molecular structure and adsorption state were investigated. The intrinsic CT state received particular attention by analyzing the CT-related vibration of B modes. Using Fourier transform infrared (FTIR), transmission SEIRA and reflection SEIRA spectroscopy, we explained why the relative intensities of some bands were different under different conditions. A quasi-standing orientation of PATP adsorbed on the substrates was also confirmed. More importantly, we demonstrated that there is no perceptible CT between PATP and silver nanoisland films; in contrast, CT generally occurs in a disruptive manner in SERS. Density functional theory (DFT) calculations and the selection rules for infrared (IR) transmission and reflection-absorption spectroscopy were used to analyze the spectra throughout the paper. SEIRA proved to be an effective technique to explore the native adsorption state of molecules without the excessive external disturbance induced by excitation. The results are very important in providing insight into molecules in surface-interface chemistry, enhanced spectroscopy and photoelectronics.
对氨基苯硫酚（PATP）因其光谱活性高、易诱导电荷转移（CT）以及对分子结构变化敏感等独特特性，成为表面增强拉曼散射（SERS）研究中的首选分子。然而，仍有一些方面尚不清楚，例如在没有外加电磁场激发的情况下，PATP 在贵金属基底上的初始稳态。关于初始稳态的信息，特别是本征 CT 态，对于阐明外加激发下的 CT 动力学过程和/或分子结构变化具有重要意义。为了研究吸附分子的本征态，需要一种合适的探针方法，该方法不会破坏整个系统（包括分子和基底）的本征态。由于其使用高能可见和近红外光，SERS 在此背景下不适用。在此，采用低能探针方法，即表面增强红外吸收（SEIRA）光谱法，作为研究 PATP 在银纳米岛薄膜上本征吸附态的合适方法。研究了分子结构和吸附态。通过分析 B 模的 CT 相关振动，特别关注本征 CT 态。利用傅里叶变换红外（FTIR）、透射 SEIRA 和反射 SEIRA 光谱，我们解释了为什么在不同条件下某些谱带的相对强度不同。还证实了 PATP 在基底上的准静止取向。更重要的是，我们证明了 PATP 与银纳米岛薄膜之间没有明显的 CT；相比之下，CT 通常在 SERS 中以破坏性方式发生。密度泛函理论（DFT）计算和红外（IR）透射和反射吸收光谱的选择定则用于分析整篇论文中的光谱。SEIRA 被证明是一种有效的技术，可以在没有激发引起的过度外部干扰的情况下探索分子的本征吸附态。这些结果对于深入了解表面界面化学、增强光谱学和光电子学中的分子非常重要。
