Badugu Ramachandram, Blair Steve, Descrovi Emiliano, Lakowicz Joseph R
Center for Fluorescence Spectroscopy, Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
Department of Electrical and Computer Engineering, University of Utah, 50 South Central Campus Drive, Room 2110, Salt Lake City, UT 84112, United States.
Opt Mater (Amst). 2024 Jan;147. doi: 10.1016/j.optmat.2023.114718. Epub 2023 Dec 15.
The metal-ligand complex tris(2,2'-bipyridine)ruthenium(II) chloride (Ru probe) displays a broad emission spectrum ranging from 540 to 730 nm. The emission spectra of Ru probe were measured when placed on top of a one-dimensional photonic crystal (1DPC), which supports both Bloch surface wave (BSW) and internal modes for wavelengths below 640 nm and only internal modes above 640 nm. The S-polarized emission spectra, with the electric vector parallel to the 1DPC surface, were found to be strongly dependent on the observation angle through the coupling prism. Also, the usual single broad-emission spectrum of Ru probe on glass was converted into two or more narrow-band-spectrum on the 1DPC, with emission band maxima dependent on the observation angle. The two S-polarized emission band peaks for Ru probe were found to be consistent with coupling to the BSW and first internal mode (IM1) of the 1DPC. The same spectral shifts and changes in emission maxima were observed by using Kretschmann and reverse Kretschmann illuminations. As the coupling requires the emitter to be in proximity with the photonic structure, we calculated near- and far-field distributions of a dipole directly located on the 1DPC surface. Finite-Difference Time-Domain (FDTD) simulations were performed to confirm fluorophore coupling to the BSW and internal modes (IMs). Both the measured and simulated results showed that IM coupled emission is significant. Coupling to the IM mode occurred at longer wavelengths where the 1DPC did not support a BSW. These results demonstrate that a simple Bragg grating, without a BSW mode, can be used for detection of surface-bound fluorophores.
金属-配体配合物二氯三（2,2'-联吡啶）钌（II）（Ru探针）呈现出范围从540至730nm的宽发射光谱。当将Ru探针置于一维光子晶体（1DPC）顶部时测量其发射光谱，该一维光子晶体对于波长低于640nm既支持布洛赫表面波（BSW）又支持内部模式，而对于波长高于640nm仅支持内部模式。发现电矢量平行于1DPC表面的S偏振发射光谱通过耦合棱镜强烈依赖于观测角度。此外，Ru探针在玻璃上通常的单一宽发射光谱在1DPC上转变为两个或更多个窄带光谱，发射带最大值取决于观测角度。发现Ru探针的两个S偏振发射带峰与耦合到1DPC的BSW和第一内部模式（IM1）一致。通过使用Kretschmann和反向Kretschmann照明观察到相同的光谱位移和发射最大值变化。由于耦合要求发射体靠近光子结构，我们计算了直接位于1DPC表面的偶极子的近场和远场分布。进行了时域有限差分（FDTD）模拟以确认荧光团与BSW和内部模式（IMs）的耦合。测量结果和模拟结果均表明IM耦合发射是显著的。在1DPC不支持BSW的较长波长处发生与IM模式的耦合。这些结果表明，没有BSW模式的简单布拉格光栅可用于检测表面结合的荧光团。
