Chen Yu-Ting, Liu Quan, Schneider Felix, Brecht Marc, Meixner Alfred J, Zhang Dai
Institute of Physical and Theoretical Chemistry, Eberhard Karls University of Tübingen, 72076 Tübingen, Germany.
Process Analysis and Technology (PA&T), Reutlingen University, 72762 Reutlingen, Germany.
Nanophotonics. 2024 Feb 2;13(7):1039-1047. doi: 10.1515/nanoph-2023-0882. eCollection 2024 Mar.
An analytic model is used to calculate the Raman and fluorescence enhancement of a molecule in between two closely spaced gold nanospheres. Instead of using the conventional approach that only the dipolar plasmonic mode is considered, we calculate the electric field enhancement in the nanometre sized gap, by taking account of the higher order modes in one gold sphere, which couples to the dipolar mode of the other sphere. The experimental confirmation is performed by gap-dependent tip-enhanced Raman spectroscopy (TERS) measurements. The photoluminescence and Raman enhancement are both observed with different growing trends as the gap width decreases. Red-shift of the background spectra is observed and implies the increasing coupling between the nanospheres. This analytic model is shown to be able to interpret the enhancement mechanisms underlying gap-dependent TERS experimental results.
一个分析模型用于计算处于两个紧密间隔的金纳米球之间的分子的拉曼和荧光增强。我们不是采用仅考虑偶极等离子体模式的传统方法，而是通过考虑一个金纳米球中的高阶模式（该高阶模式与另一个纳米球的偶极模式耦合）来计算纳米级间隙中的电场增强。通过依赖间隙的针尖增强拉曼光谱（TERS）测量进行实验验证。随着间隙宽度减小，观察到光致发光和拉曼增强都呈现出不同的增长趋势。观察到背景光谱的红移，这意味着纳米球之间的耦合增强。该分析模型能够解释依赖间隙的TERS实验结果背后的增强机制。
