Center for Nanophotonics, AMOLF, Science Park 102, Amsterdam, NL-1098XG, The Netherlands.
Biological Soft Matter Group, AMOLF, Science Park 102, Amsterdam, NL-1098XG, The Netherlands.
Sci Rep. 2017 Jul 20;7(1):5985. doi: 10.1038/s41598-017-06325-6.
We propose two-focus fluorescence correlation spectroscopy (2fFCS) on basis of plasmonic nanoantennas that provide distinct hot spots that are individually addressable through polarization, yet lie within a single diffraction limited microscope focus. The importance of two-focus FCS is that a calibrated distance between foci provides an intrinsic calibration to derive diffusion constants from measured correlation times. Through electromagnetic modelling we analyze a geometry of perpendicular nanorods, and their inverse, i.e., nanoslits. While we find that nanorods are not suited for nano-antenna enhanced 2fFCS due to substantial background signal, a nanoslit geometry is expected to provide a di tinct cross-correlation between orthogonally polarized detection channels. Furthermore, by utilizing a periodic array of nanoslits instead of a single pair, the amplitude of the cross-correlation can be enhanced. To demonstrate this technique, we present a proof of principle experiment on the basis of a periodic array of nanoslits, applied to lipid diffusion in a supported lipid bilayer.
我们提出了基于等离子体纳米天线的双焦荧光相关光谱（2fFCS），该方法提供了独特的热点，可通过偏振单独寻址，且位于单个衍射受限显微镜焦点内。双焦 FCS 的重要性在于，焦点之间经过校准的距离可以为从测量相关时间推导出扩散常数提供内在校准。通过电磁建模，我们分析了垂直纳米棒及其逆结构（纳米狭缝）的几何形状。虽然我们发现由于背景信号过大，纳米棒不适合用于纳米天线增强的 2fFCS，但纳米狭缝几何形状预计会在正交偏振检测通道之间提供明显的互相关。此外，通过利用纳米狭缝的周期性阵列而不是单个对，互相关的幅度可以增强。为了证明这种技术，我们在纳米狭缝的周期性阵列的基础上提出了一个原理验证实验，该实验应用于支撑脂质双层中的脂质扩散。
