Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK.
Nano Lett. 2012 Aug 8;12(8):4242-6. doi: 10.1021/nl302029p. Epub 2012 Jul 17.
Metal oxide nanoparticles (MONPs) have widespread usage across many disciplines, but monitoring molecular processes at their surfaces in situ has not been possible. Here we demonstrate that MONPs give highly enhanced (×10(4)) Raman scattering signals from molecules at the interface permitting direct monitoring of their reactions, when placed on top of flat metallic surfaces. Experiments with different metal oxide materials and molecules indicate that the enhancement is generic and operates at the single nanoparticle level. Simulations confirm that the amplification is principally electromagnetic and is a result of optical modulation of the underlying plasmonic metallic surface by MONPs, which act as scattering antennae and couple light into the confined region sandwiched by the underlying surface. Because of additional functionalities of metal oxides as magnetic, photoelectrochemical and catalytic materials, enhanced Raman scattering mediated by MONPs opens up significant opportunities in fundamental science, allowing direct tracking and understanding of application-specific transformations at such interfaces. We show a first example by monitoring the MONP-assisted photocatalytic decomposition reaction of an organic dye by individual nanoparticles.
金属氧化物纳米粒子（MONPs）在许多学科中都有广泛的应用，但在其表面原位监测分子过程一直难以实现。在这里，我们证明了当 MONPs 置于平整金属表面上时，它们会从界面处的分子产生高度增强（×10(4)）的拉曼散射信号，从而可以直接监测它们的反应。用不同的金属氧化物材料和分子进行的实验表明，这种增强是普遍存在的，并且在单个纳米粒子水平上起作用。模拟结果证实，这种放大主要是电磁的，是由 MONPs 对底层等离子体金属表面的光学调制引起的，MONPs 作为散射天线，将光耦合到由底层表面夹在中间的受限区域中。由于金属氧化物具有磁性、光电化学和催化材料等额外功能，通过 MONPs 介导的增强拉曼散射为基础科学开辟了重大机遇，允许直接跟踪和理解此类界面处特定于应用的转化。我们通过监测单个纳米颗粒对有机染料的 MONP 辅助光催化分解反应，展示了第一个示例。
