Department of Biomedical Engineering, Washington University, St Louis, MO 63130, USA.
Nanotechnology. 2009 Oct 28;20(43):434020. doi: 10.1088/0957-4484/20/43/434020. Epub 2009 Oct 2.
This paper describes a systematic study of the surface-enhanced Raman scattering (SERS) activity of hot spots formed between a Ag nanowire and a Ag nanocube with sharp corners. We investigated two distinct dimer structures: (i) a nanocube having one side face nearly touching the side face of a nanowire, and (ii) a nanocube having one edge nearly touching the side face of a nanowire. The field enhancements for the dimers displayed a strong dependence on laser polarization, and the strongest SERS intensities were observed for polarization along the hot-spot axis. Moreover, the detected SERS intensities were dependent on the hot-spot structure, i.e., the relative orientation of the Ag nanocube with respect to the nanowire's side face. When the dimer had a face-to-face configuration, the enhancement factor EF(dimer) was 1.4 x 10(7). This corresponds to 22-fold and 24-fold increases compared to those for individual Ag nanowires and nanocubes, respectively. Conversely, when the dimer had an edge-to-face configuration, EF(dimer) was 4.3 x 10(6). These results demonstrated that the number of probe molecules adsorbed at the hot spot played an important role in determining the detected SERS intensities. EF(dimer) was maximized when the dimer configuration allowed for a larger number of probe molecules to be trapped within the hot-spot region.
本文系统研究了银纳米线和具有锐利角的银纳米立方体之间形成的热点的表面增强拉曼散射（SERS）活性。我们研究了两种不同的二聚体结构：（i）一个纳米立方体的一个侧面几乎与纳米线的侧面接触，和（ii）一个纳米立方体的一个边缘几乎与纳米线的侧面接触。二聚体的场增强强烈依赖于激光偏振，在沿着热点轴的偏振方向上观察到最强的 SERS 强度。此外，检测到的 SERS 强度取决于热点结构，即银纳米立方体相对于纳米线侧面的相对取向。当二聚体具有面对面配置时，增强因子 EF(dimer)为 1.4 x 10(7)。这分别比单个银纳米线和纳米立方体的增强因子分别增加了 22 倍和 24 倍。相反，当二聚体具有边缘到面配置时，EF(dimer)为 4.3 x 10(6)。这些结果表明，吸附在热点处的探针分子数量在确定检测到的 SERS 强度方面起着重要作用。当二聚体配置允许更多的探针分子被困在热点区域时，EF(dimer)最大化。
