Zhao Wenqi, Tian Xiaochaoran, Fang Zhening, Xiao Shiyi, Qiu Meng, He Qiong, Feng Wei, Li Fuyou, Zhang Yuanbo, Zhou Lei, Tan Yan-Wen
State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, 200433, China.
Shanghai Institute for Advanced Communication and Data Science, Shanghai University, Shanghai, 200444, China.
Light Sci Appl. 2021 Apr 14;10(1):79. doi: 10.1038/s41377-021-00522-9.
As a powerful tool for studying molecular dynamics in bioscience, single-molecule fluorescence detection provides dynamical information buried in ensemble experiments. Fluorescence in the near-infrared (NIR) is particularly useful because it offers higher signal-to-noise ratio and increased penetration depth in tissue compared with visible fluorescence. The low quantum yield of most NIR fluorophores, however, makes the detection of single-molecule fluorescence difficult. Here, we use asymmetric plasmonic nano-antenna to enhance the fluorescence intensity of AIEE1000, a typical NIR dye, by a factor up to 405. The asymmetric nano-antenna achieve such an enhancement mainly by increasing the quantum yield (to ~80%) rather than the local field, which degrades the molecules' photostability. Our coupled-mode-theory analysis reveals that the enhancements stem from resonance-matching between antenna and molecule and, more importantly, from optimizing the coupling between the near- and far-field modes with designer asymmetric structures. Our work provides a universal scheme for engineering single-molecule fluorescence in the near-infrared regime.
作为生物科学中研究分子动力学的有力工具，单分子荧光检测提供了隐藏在整体实验中的动力学信息。近红外（NIR）荧光特别有用，因为与可见荧光相比，它具有更高的信噪比和在组织中更大的穿透深度。然而，大多数近红外荧光团的低量子产率使得单分子荧光检测变得困难。在这里，我们使用不对称等离子体纳米天线将典型的近红外染料AIEE1000的荧光强度提高了高达405倍。这种不对称纳米天线实现如此增强主要是通过提高量子产率（至约80%）而非局部场，局部场会降低分子的光稳定性。我们的耦合模式理论分析表明，增强源于天线与分子之间的共振匹配，更重要的是，源于用设计的不对称结构优化近场和远场模式之间的耦合。我们的工作为在近红外区域设计单分子荧光提供了一个通用方案。
