基于单个金属纳米棒和金属薄膜间纳米间隙模近场增强的发光、局域热效应及SERS机理研究

The propagating surface plasmon polariton (SPP) on metal film and the local surface plasmon (LSP) resonance mode of metal nano-rod can couple each other and form the 'hot spot'based on the nano gap mode which has the localized electric field enhancement. Based on this nano gap mode, not only the photoluminescence of metal nano-rod can be enhanced, but also the surface enhanced Raman scattering (SERS) can be realized.These two enhanced effects are very useful and promising in the fields of biological sensing and imaging.In this proposal,the coupling process between the SPP on metal film and the LSP of metal nano-rod and the corresponding physical model will be studied. And the physical mechanisms of the dark-field scattering, photoluminescence and SERS of the single metal nano-rod on metal film will be demonstrated. By analyzing the effects of the characteristics of the incident light (such as wavelength, incident angle, polarization) and the nano structure (such as metal film thickness, metal nano-rod size, aspect ratio, gap size between metal nano-rod and metal film), the tuning mechanisms of the photoluminescence and SERS on single metal nano-rod will be investigaged. Also the shape changing of the metal nano-rod and the Raman molecule degradation effects induced by the localized heat effect which caused by the incident laser will be analyzed. And the effects of the photoluminescence and the localized heating on the SERS spectra will be revealed. We expect this research will provide both theoretical foundation and experimental proof for the application of the SERS substrate based on this nano gap mode.

金属薄膜上的传输表面等离子激元波与金属纳米棒上的局域表面等离子共振模的耦合能够产生具有局域电场增强的纳米间隙模，形成"热点"。基于此纳米间隙模可以实现金属纳米棒自身的发光增强及其表面增强拉曼散射，在生物传感和成像领域有广泛的应用。本项目研究金属薄膜上传输表面等离子激元波与单个金属纳米棒上局域表面等离子共振模的耦合过程及相关物理模型，阐明金属薄膜上单个金属纳米棒的暗场散射、光致发光和表面增强拉曼散射的物理机制；研究入射光特性（如波长、角度、偏振）和结构参数（如金属薄膜厚度、金属纳米棒的尺寸、长径比、金属薄膜与金属纳米棒间间距）对单个金属纳米棒光致发光和表面增强拉曼散射的调控机理；并分析入射激光引入的局域热效应导致的金属纳米棒形变及其表面附着拉曼分子热降解现象；揭示光致发光和局域热效应对金属纳米棒表面增强拉曼散射光谱的影响，为基于此纳米间隙模的表面增强拉曼散射基底应用提供理论基础和实验验证。

金属薄膜上的传输表面等离子激元波与金属纳米棒上的局域表面等离子共振模的耦合能够产生具有局域电场增强的纳米间隙模，形成“热点”。基于此纳米间隙模可以实现金属纳米棒自身的发光增强及其表面增强拉曼散射，在生物传感和成像领域有广泛的应用，因此研究基于金属薄膜上单个金纳米棒间的纳米间隙模的近场增强的发光、局域热效应及SERS特性十分有必要。通过本项目的执行，我们建立了金属薄膜的传输表面等离子激元波与金属纳米棒的局域表面等离子共振模的耦合模型和仿真方法，并通过理论和实验掌握了通过金薄膜和单个金纳米棒间的介质隔离层厚度来调控其间隙模式的方法；发现了金薄膜表面粗糙度、金纳米棒的尺寸分散性、以及金纳米棒排列方向与入射激光偏振方向的不确定性对金薄膜上单个金纳米棒散射光谱的影响；并通过实验分析阐明了金薄膜上单个金纳米棒的光致发光、局域热效应及表面增强拉曼散射的调控机理，发现了纳米间隙模场增强导致的局域热效能够导致金纳米棒的形变，从而影响其散射光谱、光致发光谱和SERS光谱；并揭示了金属薄膜上单个金属纳米棒的光致发光是其表面增强拉曼散射谱中背景噪声的主要来源，为基于纳米间隙模的高灵敏度SERS基底提供基础支撑。