Discrimination between enantiomers is achieved by tip‐enhanced Raman scattering (TERS) using a silver tip that is chemically modified by an achiral para‐mercaptopyridine (p MPY) probe molecule. Differences in the relative intensities of the p MPY spectra were monitored for three pairs of enantiomers containing hydroxy (−OH) and/or amino (−NH₂) groups. The N: or N⁺−H functionality of the p MPY‐modified tip participates in hydrogen‐bond interactions with a particular molecular orientation of each chiral isomer. The asymmetric arrangement of silver atoms at the apex of the tip induces an asymmetric electric field, which causes the tip to become a chiral center. Differences in the charge‐transfer (CT) states of the metal‐achiral probe system in conjunction with the asymmetric electric field produce different enhancements in the Raman signals of the two enantiomers. The near‐field effect of the asymmetric electric field, which depends on the number of analyte functional groups capable of hydrogen‐bond formation, improves the degree of discrimination.

中文翻译：

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通过尖端增强的拉曼散射区分对映体：具有不对称原子排列的化学修饰的银尖端。

对映体之间的区别是通过使用由非手性对巯基吡啶（p MPY）探针分子进行化学修饰的银质尖端，通过尖端拉曼散射（TERS）来实现的。对于包含羟基（-OH）和/或氨基（-NH ₂）的三对对映异构体，监测了p MPY光谱相对强度的差异。p的N：或N ⁺ -H功能MPY修饰的末端以每个手性异构体的特定分子取向参与氢键相互作用。银原子在尖端的顶点处的不对称排列会引起不对称电场，这会导致尖端成为手性中心。金属-非手性探针系统的电荷转移（CT）状态与不对称电场的差异会导致两种对映体的拉曼信号产生不同的增强。不对称电场的近场效应取决于能够形成氢键的分析物官能团的数量，从而提高了区分度。