A novel approach of combining conventional infrared spectroscopy (IR) and atomic force microscopy (AFM) is presented to better understand the behavior of a drug adsorbed on a metal substrate at the nanoscale level. Tip-enhanced infrared nanospectroscopy (TEIRA) was used for the first time to investigate Lu AA33810, a selective brain-penetrating Y5 receptor antagonist, after immobilization on gold nanoparticles (GNPs). Here, a gold coated AFM tip and gold substrate were used to obtain the near-field electromagnetic field trapping effect. Because of the huge signal enhancement, it was possible to obtain the spectral information regarding the self-assembled monolayer of the investigated molecule. The effect of two orthogonal polarizations (p- and s-polarization modulations) of the excitation laser beam on the spectral patterns is also discussed. The results show that there is a strong relationship between the state of polarization of the incident radiation and the relative infrared band intensities. Another factor affecting the observed spectral differences is the topology of the metal substrate, which may result in the induction of a cross-polarization effect. The performed analysis indicates that the C–C bond from the cyclohexyl group is oriented almost parallel to the metal surface. Conversely, the p- and s-polarized spectral variations suggest that the O=S=O angle is high enough to enable the simultaneous interaction of both oxygen atoms with the GNPs.

中文翻译：

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选择性Y5受体拮抗剂Lu AA33810的尖端增强红外纳米光谱研究中的偏振效应

提出了一种结合常规红外光谱（IR）和原子力显微镜（AFM）的新颖方法，以更好地了解纳米级水平吸附在金属基质上的药物的行为。固定在金纳米颗粒（GNP）上后，首次使用尖端增强型红外纳米光谱（TEIRA）来研究Lu AA33810，一种可选择性渗透脑的Y5受体拮抗剂。在这里，使用镀金的AFM尖端和金基底来获得近场电磁场捕获效果。由于巨大的信号增强，有可能获得有关所研究分子自组装单分子层的光谱信息。两个正交极化（p-和s还讨论了在光谱图案上激发激光束的偏振调制）。结果表明，入射辐射的偏振态与相对红外波段强度之间存在很强的关系。影响观察到的光谱差异的另一个因素是金属基板的拓扑结构，这可能会导致产生交叉极化效应。进行的分析表明，来自环己基的C–C键几乎与金属表面平行。相反，p极化和s极化的光谱变化表明O = S = O角足够高，可以使两个氧原子与GNP同时相互作用。