Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712, USA.
Nano Lett. 2010 Sep 8;10(9):3777-84. doi: 10.1021/nl102559d.
We present the first super-resolution optical images of single-molecule surface-enhanced Raman scattering (SM-SERS) hot spots, using super-resolution imaging as a powerful new tool for understanding the interaction between single molecules and nanoparticle hot spots. Using point spread function fitting, we map the centroid position of SM-SERS with +/-10 nm resolution, revealing a spatial relationship between the SM-SERS centroid position and the highest SERS intensity. We are also able to measure the unique position of the SM-SERS centroid relative to the centroid associated with nanoparticle photoluminescence, which allows us to speculate on the presence of multiple hot spots within a single diffraction-limited spot. These measurements allow us to follow dynamic movement of the SM-SERS centroid position over time as it samples different locations in space and explores regions larger than the expected size of a SM-SERS hot spot. We have proposed that the movement of the SERS centroid is due to diffusion of a single molecule on the surface of the nanoparticle, which leads to changes in coupling between the scattering dipole and the optical near field of the nanoparticle.
我们展示了单分子表面增强拉曼散射（SM-SERS）热点的首个超分辨率光学图像，将超分辨率成像作为理解单分子与纳米粒子热点相互作用的强大新工具。通过点扩散函数拟合，我们以 +/-10nm 的分辨率绘制了 SM-SERS 的质心位置，揭示了 SM-SERS 质心位置与最高 SERS 强度之间的空间关系。我们还能够测量 SM-SERS 质心相对于与纳米粒子光致发光相关的质心的独特位置，这使我们能够推测在单个衍射受限点内存在多个热点。这些测量允许我们随着质心位置在空间中采样不同位置并探索大于 SM-SERS 热点预期尺寸的区域，来跟踪 SM-SERS 质心位置随时间的动态运动。我们提出 SERS 质心的运动是由于单个分子在纳米粒子表面上的扩散，这导致散射偶极子与纳米粒子的光学近场之间的耦合发生变化。
