Single-Molecule SERS Hotspot Dynamics in Both Dry and Aqueous Environments
Single-Molecule SERS Hotspot Dynamics in Both Dry and Aqueous Environments
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DOI：
10.1021/acs.jpcc.2c00319
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发表时间：
2022-04
期刊：
影响因子：
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通讯作者：
N. Lindquist;A. Bido;A. Brolo
中科院分区：
文献类型：
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作者：
N. Lindquist;A. Bido;A. Brolo
表面增强拉曼光谱(SERS)信号的波动是少数到单一分子事件的标志。最近的实验表明，这些SERS强度波动(SIF)发生在从几秒到微秒的极宽的时间范围内。虽然已经提出了许多机制，如分子扩散或瞬时等离子体热点产生，但这些波动的潜在来源可能是不同效应的复杂相互作用。例如，用完全包覆但干燥的纳米颗粒进行的SERS实验中，探针分子的移动较少，但由于金属原子的流动性，可能仍然会产生瞬时热点。或者，用液体中低浓度的分子探测器进行的实验可能倾向于看到由自由扩散的分子访问并被困在静态热点中而引起的波动。在这篇文章中，我们比较了干燥和潮湿纳米颗粒环境中的高速SIF活性。通过仔细分析SERS信号的整体波动，例如时间统计，我们提出了一个简单的模型，该模型解释了上述各种机制的贡献。这些结果加深了对SERS效应的物理理解，并可能促进单分子SERS的进一步研究、实验优化和潜在的应用。
Fluctuations in Surface Enhanced Raman Spectroscopy (SERS) signals are a hallmark of few-to-single molecule events. Recent experiments have shown these SERS intensity fluctuations (SIFs) to occur over an extremely wide range of time scales, from seconds to microseconds. While many mechanisms have been proposed, such as molecular diffusion or transient plasmonic hotspot generation, the underlying source of these fluctuations is likely to be a complex interplay of different effects. For example, SERS experiments done with fully coated, but dry, nanoparticles would have less movement of the probe molecule but may still have transient hotspot generation due to the mobility of metallic atoms. Alternatively, experiments done with low concentrations of a molecular probe in liquid might tend to see fluctuations caused by freely diffusing molecules that visit and become trapped within a static hotspot. In this paper we compare high-speed SIF activity in both dry and wet nanoparticle environments. By carefully analyzing the overall SERS signal fluctuations, such as the timing statistics, we propose a simple model that accounts for the contributions from the various mechanisms discussed above. These results provide a deeper physical understanding of the SERS effect and may promote further research into single-molecule SERS, its experimental optimization, and potential applications.