Surface-enhanced Raman spectroscopy (SERS) is a powerful tool to monitor various interfacial behaviors providing molecular level information with high spatial and temporal resolutions. However, it is a challenge to obtain SERS spectra with high quality for analytes having a weak binding affinity with plasmonic nanostructures due to the short dwell time of the analyte on the surface. Here, we employed dynamic SERS, an acquisition method consisting of the rapid acquisition of a series of consecutive SERS spectra, to study the adsorption/desorption behavior of R6G on Ag surfaces. We demonstrated that the signal-noise ratio of SERS spectra of mobile molecules can be improved by dynamic SERS even when the acquisition time cannot catch up with the diffusion time of the molecule. More interestingly, we captured the neutral R6G⁰ state (spectroscopically different from the dominated positive R6G⁺ state) of R6G at the single-molecule level, which is a rare molecule event hardly detectable by traditional SERS. Dynamic SERS provides near real-time molecular vibrational information with an improved signal-noise ratio, which opens a new avenue to capture metastable or rare molecule events for the comprehensive understanding of interfacial processes related to catalysis and life science.

中文翻译：

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动态表面增强拉曼光谱揭示了单分子水平的稀有事件

表面增强拉曼光谱（SERS）是监视各种界面行为的强大工具，可提供具有高时空分辨率的分子水平信息。然而，由于分析物在表面上的短停留时间，对于与等离激元纳米结构具有弱结合亲和力的分析物，要获得高质量的SERS光谱是一个挑战。在这里，我们采用动态SERS（一种由一系列连续SERS光谱的快速采集组成的采集方法）来研究R6G在Ag表面上的吸附/解吸行为。我们证明，即使采集时间不能赶上分子的扩散时间，通过动态SERS可以提高移动分子SERS光谱的信噪比。更有趣的是，我们捕获了中立R6G ⁰单分子水平的R6G状态（光谱上不同于支配的正R6G ⁺状态），这是传统SERS几乎无法检测到的罕见分子事件。动态SERS提供具有改善的信噪比的近实时分子振动信息，这为捕获亚稳态或稀有分子事件开辟了一条新途径，以全面了解与催化和生命科学有关的界面过程。