Hotspot-Induced Transformation of Surface-Enhanced Raman Scattering Fingerprints
Hotspot-Induced Transformation of Surface-Enhanced Raman Scattering Fingerprints
复制标题
DOI：
10.1021/nn100269v
复制
发表时间：
2010-06-01
期刊：
影响因子：
17.1
通讯作者：
Chen, Hongyu
中科院分区：
文献类型：
--
作者：
Chen, Tao;Wang, Hong;Chen, Hongyu
表面增强拉曼散射 (SERS) 热点的研究最多的效应是其中分析物的巨大拉曼增强。然而，一个鲜为人知的影响是，热点的形成可能会导致捕获的分析物改变分子方向，从而导致 SERS 指纹的显着变化。在这里，我们通过在胶体溶液中创建和表征热点来证明这种效应。合成了各向异性功能化的金纳米棒，其侧面被聚苯乙烯-嵌段-聚(丙烯酸酯)专门封装，而末端未被封装并被SERS分析物4-巯基苯甲酸功能化。经过盐处理后，这些纳米棒组装成线性链，形成包含 SERS 分析物的热点。观察到巨大的 SERS 增强，特别是对于热点形成之前原始光谱中不存在的一些弱/非活动 SIRS 模式。详细的光谱分析表明，SIRS 指纹图谱的变化与分析物分子在 Au 表面上从几乎直立构象到平行/倾斜构象的重新取向一致。我们提出金纳米棒的聚集对热点中的分析物施加物理应力，导致分子重新取向。在使用不同分析物的其他几个系统中也观察到了这种由热点引起的 SIRS 指纹变化。
The most studied effect of surface-enhanced Raman scattering (SERS) hotspots is the enormous Raman enhancement of the analytes therein. A less known effect, though, is that the formation of hotspots may cause the trapped analytes to change molecular orientation, which in turn leads to pronounced changes in SERS fingerprints. Here, we demonstrate this effect by creating and characterizing hotspots in colloidal solutions. Anisotropically functionalized Au nanorods were synthesized, whereby the sides were specifically encapsulated by polystyrene-block-poly(acrylic add), leaving the ends unencapsulated and functionalized by a SERS analyte, 4-mercaptobenzoic acid. Upon salt treatment, these nanorods assemble into linear chains, forming hotspots that incorporate the SERS analyte. Enormous SERS enhancement was observed, particularly for some weak/inactive SIRS modes that were not present in the original spectrum before the hotspots formation. Detailed spectral analysis showed that the variations of the SIRS fingerprint were consistent with the reorientation of analyte molecules from nearly upright to parallel/tilted conformation on the Au surface. We propose that the aggregation of Au nanorods exerts physical stress on the analytes in the hotspots, causing the molecular reorientation. Such a hotspot-induced variation of SIRS fingerprints was also observed in several other systems using different analytes.