High-speed imaging of surface-enhanced Raman scattering fluctuations from individual nanoparticles
High-speed imaging of surface-enhanced Raman scattering fluctuations from individual nanoparticles
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DOI：
10.1038/s41565-019-0535-6
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发表时间：
2019-10-01
影响因子：
38.3
通讯作者：
Brolo, Alexandre G.
中科院分区：
文献类型：
--
作者：
Lindquist, Nathan C.;de Albuquerque, Carlos Diego L.;Brolo, Alexandre G.
等离子体热点是解释表面增强拉曼散射(SERS)效应的核心概念。尽管等离子体热点通常被描述为静态特征，但单分子表面增强拉曼散射(SM-SERS)具有信号强度随时间变化的特征。这些波动的起因可以归结为各种动态和复杂的过程，包括分子吸附或解吸、表面扩散、分子重定向和金属表面重构。由于这些机制中的每一种都同时导致了SERS信号的波动，因此探索它们在SM-SERS中的相对影响仍然是一个实验挑战。在这里，我们介绍了一种采集速率为80万帧/秒的超分辨率成像技术，以探测单个银纳米壳层SM-SERS涨落的空间和时间特征。该技术的空间分辨率接近7 nm。这些图像显示出类似于10亩S散射事件的短片，分布在单个纳米粒子的不同区域。值得注意的是，即使是一个功能齐全的纳米颗粒，也有98%以上的时间是暗的。零星的SERS发射表明了一种由金属表面的随机重构驱动的瞬时热点形成机制，这种效应主导着粒子本身的任何等离子体共振。我们的结果为SERS领域提供了一种高速的实验方法来研究SM-SERS热点在典型的室温实验条件下的快速动态特性，这可能对催化和传感具有潜在的意义。
The concept of plasmonic hotspots is central to the interpretation of the surface-enhanced Raman scattering (SERS) effect. Although plasmonic hotspots are generally portrayed as static features, single-molecule SERS (SM-SERS) is marked by characteristic time-dependent fluctuations in signal intensity. The origin of those fluctuations can be assigned to a variety of dynamic and complex processes, including molecular adsorption or desorption, surface diffusion, molecular reorientation and metal surface reconstruction. Since each of these mechanisms simultaneously contributes to a fluctuating SERS signal, probing their relative impact in SM-SERS remains an experimental challenge. Here, we introduce a super-resolution imaging technique with an acquisition rate of 800,000 frames per second to probe the spatial and temporal features of the SM-SERS fluctuations from single silver nanoshells. The technique has a spatial resolution of similar to 7 nm. The images reveal short similar to 10 mu s scattering events localized in various regions on a single nanoparticle. Remarkably, even a fully functionalized nanoparticle was 'dark' more than 98% of the time. The sporadic SERS emission suggests a transient hotspot formation mechanism driven by a random reconstruction of the metallic surface, an effect that dominates over any plasmonic resonance of the particle itself. Our results provide the SERS community with a high-speed experimental approach to study the fast dynamic properties of SM-SERS hotspots in typical room-temperature experimental conditions, with possible implications in catalysis and sensing.