Tip‐enhanced Raman spectroscopy (TERS) is a promising technique for structural studies of biological systems and biomolecules, owing to its ability to provide a chemical fingerprint with sub‐diffraction‐limit spatial resolution. This application of TERS has thus far been limited, due to difficulties in generating high field enhancements while maintaining biocompatibility. The high sensitivity achievable through TERS arises from the excitation of a localized surface plasmon resonance in a noble metal atomic force microscope (AFM) tip, which in combination with a metallic surface can produce huge enhancements in the local optical field. However, metals have poor biocompatibility, potentially introducing difficulties in characterizing native structure and conformation in biomolecules, whereas biocompatible surfaces have weak optical field enhancements. Herein, a novel, biocompatible, highly enhancing surface is designed and fabricated based on few‐monolayer mica flakes, mechanically exfoliated on a metal surface. These surfaces allow the formation of coupled plasmon enhancements for TERS imaging, while maintaining the biocompatibility and atomic flatness of the mica surface for high resolution AFM. The capability of these substrates for TERS is confirmed numerically and experimentally. We demonstrate up to five orders of magnitude improvement in TERS signals over conventional mica surfaces, expanding the sensitivity of TERS to a wide range of non‐resonant biomolecules with weak Raman cross‐sections. The increase in sensitivity obtained through this approach also enables the collection of nanoscale spectra with short integration times, improving hyperspectral mapping for these applications. These mica/metal surfaces therefore have the potential to revolutionize spectromicroscopy of complex, heterogeneous biological systems such as DNA and protein complexes.

中文翻译：

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制备用于尖端增强拉曼光谱的生物相容性云母/金表面。

尖端增强拉曼光谱 (TERS) 是一种很有前景的生物系统和生物分子结构研究技术，因为它能够提供具有亚衍射极限空间分辨率的化学指纹。迄今为止，由于难以在保持生物相容性的同时产生高场增强，因此 TERS 的这种应用受到限制。通过 TERS 可实现的高灵敏度源于贵金属原子力显微镜 (AFM) 尖端中局部表面等离子体共振的激发，其与金属表面相结合可以在局部光场中产生巨大的增强。然而，金属的生物相容性很差，可能会给表征生物分子的天然结构和构象带来困难，而生物相容性表面的光场增强较弱。在此，基于少量单层云母薄片，在金属表面上机械剥离，设计和制造了一种新颖的、生物相容的、高度增强的表面。这些表面允许形成用于 TERS 成像的耦合等离子体增强，同时保持云母表面的生物相容性和原子平坦度以用于高分辨率 AFM。这些底物对 TERS 的能力已通过数值和实验得到证实。我们证明了与传统云母表面相比，TERS 信号最多可提高五个数量级，从而将 TERS 的灵敏度扩展到具有弱拉曼截面的各种非共振生物分子。通过这种方法获得的灵敏度提高还能够以较短的积分时间收集纳米级光谱，从而改善这些应用的高光谱映射。因此，这些云母/金属表面有可能彻底改变复杂、异质生物系统（如 DNA 和蛋白质复合物）的光谱显微镜。