Reducing the distance between the fluorescence molecules and noble metal (resonant) nanostructures is known to advance the process of electromagnetic coupling and energy transfer, which in return yields fluorescence enhancement particularly exploited for improved biomedical applications. In this study, Au-capped Si nanowhiskers (NWs) at various sizes were fabricated using a vapor–liquid–solid (VLS) mechanism for systematically investigating the dependence of the size of the Au-capped Si NWs on the fluorescence enhancement factor with respect to the fluorescence emission from Rhodamine 6G (Rh-6G) fluorophore. Opposite to what is anticipated from the literature, the maximum enhancement was obtained for the sample for which the Au-nanoparticle (NP) capping is well isolated from the fluorophore and the vertical distance between the fluorophore and the plasmonic metal nanoparticle is largest. Numerical simulations using the finite element method (FEM) were shown to support the experimental optical response results. Four-point probe I-V measurements also show that the Schottky ideality factor of Au-capped Si NWs decays exponentially upon the rise in the fluorescence enhancement factor.

Graphical abstract

已知减小荧光分子与贵金属（共振）纳米结构之间的距离可以促进电磁耦合和能量转移的过程，这反过来会产生荧光增强作用，特别是用于改进的生物医学应用。在这项研究中，使用汽-液-固（VLS）机制制造了各种尺寸的金包埋的硅纳米晶须（NWs），以系统地研究金包埋的硅纳米晶对荧光增强因子的依赖性。罗丹明6G（Rh-6G）荧光团发出的荧光。与文献预期相反，对于从荧光团中很好地分离了金纳米颗粒（NP）封端的样品，荧光团与等离子体金属纳米颗粒之间的垂直距离最大，获得了最大增强。显示了使用有限元方法（FEM）进行的数值模拟，以支持实验的光学响应结果。四点探针IV测量还显示，随着荧光增强因子的增加，Au覆盖的Si NWs的肖特基理想因子呈指数衰减。

图形概要