双金属核壳纳米结构中荧光单分子的表面能量转移及金属操控自发辐射效应

贵金属表面附近的荧光分子因其表面等离子体共振的影响，荧光发射特性发生显著变化，被广泛应用在荧光探针等纳米器件的设计、开发中。荧光分子与金属之间的能量转移机制是设计此类荧光探针的基础。使用时域有限差分(FDTD)方法，对Au/SiO₂/Ag核壳纳米复合结构的等离子体杂化场中荧光单分子的表面能量转移（SET）效应和金属操控自发辐射效应进行了理论仿真研究。研究了金核和银壳共同作用时，荧光分子的SET和金属调控自发辐射过程随荧光分子位置及分子偶极矩取向的变化规律。计算结果表明，由于金核和银壳之间的局域表面等离子体共振杂化耦合，荧光分子与金属间的能量转移效率与距离d呈现出10次方的关系，这一结果明显区别于常规的荧光共振能量转移（FRET）效应，较之单金属结构的SET效应更加剧烈。这一结果有希望在生物光子学领域的纳米级局域光源的创建和生物分子的检测中得到应用。

Surface energy transfer and metal regulated spontaneous emission of single fluorescent molecules in bimetallic core-shell nanostructures

The emission characteristics of fluorescent molecules near the surface of noble metals have changed significantly due to the influence of surface plasmon resonance (SPR). They are widely used in the design of nano-devices such as fluorescent probes. The energy transfer mechanism between fluorescent molecules and metals is the basis for the design of such fluorescent probes. Therefore, in this paper, surface energy transfer (SET) and metal regulated spontaneous emission effect of single fluorescent molecules in the Au/SiO₂/Ag core-shell nanostructure were theoretically simulated by using finite difference time domain (FDTD) method. The SET between fluorescent molecules and the hybrid plasmonic mode was studied. The results showed that due to the local surface plasmon resonance coupling between gold core and silver shell, the energy transfer efficiency between fluorescent molecules and metals shows a d¹⁰ relationship, which d is the distance from the fluorescent molecules to gold surface. That result is obviously different from the conventional FRET effect and the SET effect of single metal structure. It is expected to be applied in the development of nano light sources and biosensors.