金属-电介质复合结构实现荧光远场增强

本文提出一种大尺度的金属-电介质复合微纳结构(银-硅结构),用于提高荧光生物检测的灵敏度及解决荧光物质距离结构远场范围时荧光增强的近场局限。这种大尺度的金属-电介质复合微纳结构与之前的金属-电介质复合微纳结构不同,其通过光的散射和干涉实现了荧光物质距离结构远场范围时的荧光增强。在本文中,通过采用时域有限差分法,主要从荧光激发和荧光发射两个过程研究银-硅结构。结果表明,在激发过程中,银-硅结构的荧光强度高于玻璃结构且位于银-硅结构两柱之间的狭缝中的电场分布比金属结构(银结构)更均匀,因此在银-硅结构中可以实现荧光增强,而且分子运动行为的检测更准确。在发射过程中,当荧光纳米粒子距离结构远场范围内时,与玻璃相比,银-硅结构可以实现更好的荧光增强效果。利用银-硅结构实现荧光增强的机理是光的散射和干涉,荧光被银膜向上散射,同时,结构两侧的银/硅柱也散射一部分荧光,荧光相互干涉传播至远场实现荧光增强。此外,银-硅结构易于制备和集成。因此,其可以很好地应用于生物传感领域。

Far-field range fluorescence enhancement by a hybrid metal-dielectric structure

In order to improve the sensitivity of fluorescence biosensing and solve the near-field limitations to enhancement when the fluorescent nanoparticle is in the structure's far-field range,a large-scale hybrid metal-dielectric structure(Ag-Si structure)is proposed to enhance fluorescence in the far-field range.This hybrid metal-dielectric structure is different from previous metal-dielectric structures because it achieves fluorescence enhancement when the fluorescent nanoparticle is in the structure's far-field range due to scattering and interference.In this paper,the Ag-Si structure is investigated with respect to its excitation process and the emission process using the Finite-Difference Time-Domain(FDTD)method.In the excitation process,the intensity of the Ag-Si structure's fluorescence is higher than that of the bare glass structure and the electric field distribution of the Ag-Si structure is more uniform in the slit between the two pillars than it is in the metal structure(Ag structure).With this structure,fluorescence enhancement can be achieved and its detection of molecular motion behavior is more accurate.In the emission process,fluorescence enhancement in the Ag-Si structure is higher than that of the bare glass structure when the fluorescent nanoparticle is in the structure's far-field range.The mechanisms that achieve fluorescence enhancement in the Ag-Si structure are scattering and interference.Fluorescence is scattered upward by the silver film while the silver and silicon pillars on both sides of the structure simultaneously scatter the partial fluorescence,then the fluorescence interferes and propagates to the far-field to achieve fluorescence enhancement.Further advocating its use,an Ag-Si structure is simple to fabricate and integrate,allowing seamless application in biosensing.