Zuo Tiancheng, Goldwyn Harrison J, Isaacoff Benjamin P, Masiello David J, Biteen Julie S
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
Department of Chemistry, University of Washington, Seattle, Washington 98195, United States.
J Phys Chem Lett. 2019 Sep 5;10(17):5047-5054. doi: 10.1021/acs.jpclett.9b02270. Epub 2019 Aug 19.
The strong light-matter interactions between dyes and plasmonic nanoantennas enable the study of fundamental molecular-optical processes. Here, we overcome conventional limitations with high-throughput single-molecule polarization-resolved microscopy to measure dye emission polarization modifications upon near-field coupling to a gold nanorod. We determine that the emission polarization distribution is not only rotated toward the nanorod's dominant localized surface plasmon mode as expected, but it is also unintuitively broadened. With a reduced-order analytical model, we elucidate how this distribution broadening depends upon both far-field interference and off-resonant coupling between the molecular dipole and the nanorod transverse plasmon mode. Experiments and modeling reveal that a nearby plasmonic nanoantenna affects dye emission polarization through a multicolor process, even when the orthogonal plasmon modes are separated by approximately 3 times the dye emission line width. Beyond advancing our understanding of plasmon-coupled emission modifications, this work promises to improve high-sensitivity single-molecule fluorescence imaging, biosensing, and spectral engineering.
染料与等离子体纳米天线之间强烈的光与物质相互作用，使得对基本分子光学过程的研究成为可能。在此，我们利用高通量单分子偏振分辨显微镜克服了传统限制，以测量染料在与金纳米棒近场耦合时发射偏振的变化。我们确定，发射偏振分布不仅如预期那样朝着纳米棒的主导局域表面等离子体模式旋转，而且还出人意料地变宽了。通过一个降阶分析模型，我们阐明了这种分布变宽如何取决于远场干涉以及分子偶极子与纳米棒横向等离子体模式之间的非共振耦合。实验和模型表明，即使正交等离子体模式之间的间隔约为染料发射线宽的3倍，附近的等离子体纳米天线仍会通过多色过程影响染料发射偏振。这项工作不仅增进了我们对等离子体耦合发射变化的理解，还有望改善高灵敏度单分子荧光成像、生物传感和光谱工程。
