三八面体金纳米晶局域表面等离子体激元的表面增强拉曼散射研究
Probing Localized Surface Plasmons of Trisoctahedral Gold Nanocrystals for Surface Enhanced Raman Scattering
摘要：
三八面体（TOH）形状的金纳米晶体（NCs）由于其高折射率面上存在高密度的原子台阶和悬挂键而具有优异的催化和表面增强拉曼光谱（SERS）活性，成为一类新型的金属纳米颗粒（MNP）。我们研究了辐射局部表面等离子体共振（LSPR）模式的一个孤立的单一的TOH金NC使用阴极发光（CL），与高分辨率的空间信息的局部光学态密度（LDOS）在整个可见光谱范围。此外，我们通过对Si衬底上的罗丹明6G（R6G）覆盖的TOH Au NPs聚集体进行拉曼光谱测量，显示出明显的拉曼散射增强因子。我们认为，两个相邻的MNP表面（纳米间隙）之间的热点可以比单个颗粒LSPR明显更强。这种纳米间隙热点可能对本报告中观察到的实质性SERS增强起着至关重要的作用。因此，本研究表明，MNP聚集体比单个等离子体纳米颗粒更适合于基于SERS的生物传感中的可能应用。
英文摘要：
Trisoctahedral (TOH) shaped Au nanocrystals (NCs) have emerged as a new class of metal nanoparticles (MNP) due to its superior catalystic and SERS activities caused by the presence of high density atomic steps and dangling bonds on their high index facets. We examine the radiative localized surface plasmon resonance (LSPR) modes of an isolated single TOH Au NC using cathodoluminescence (CL), with high resolution spatial information of the local density of optical states (LDOS) across the visible spectral range. Further we show pronounced enhancement factor in the Raman scattering by performing Raman spectroscopic measurements on Rhodamine 6G (R6G) covered TOH Au NPs aggregates on a Si substrate. We believe that the hot spots between two adjacent MNP surfaces (nanogaps) can be significantly stronger than single particle LSPRs. Such nanogaps hotspots may have crucial role on the substantial SERS enhancement observed in this report. Consequently, the present study indicates that MNPs aggregates are highly desirable than individual plasmonic nanoparticles for possible applications in SERS based biosensing.
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