Complex bifunctional metal nanostructures for in situ monitoring of nanoparticle-catalyzed reactions by surface-enhanced Raman spectroscopy

多相催化反应的现场监测需要界面/表面选择技术。表面增强拉曼光谱(SERS)提供了吸附在等离子体纳米结构(如贵金属纳米颗粒)表面的化学物种的分子结构信息。SERS和催化在纳米颗粒功能方面没有直接的局部重叠，因为等离子体/SERS和催化性质通常是分离的。因此，尽管振动光谱可以获得丰富的化学信息，但胶体表面增强拉曼光谱在多相催化中的应用目前还很少见。为了克服SERS在多相催化中应用的局限性，需要在等离子体金属的局域表面等离子体共振场中引入催化剂的双功能金属纳米结构。这项建议的中心目标是设计和合成定制的具有等离子体/SERS和催化活性的双功能金属胶体，用于原位监测纳米粒子催化的反应。将合成复杂的金属超结构，包括硅壳隔离的SERS活性核心和组装在核心上的催化活性卫星颗粒，以及双功能杂化纳米颗粒，并分析其表面增强拉曼光谱和催化活性。为了理解和预测双功能纳米结构的等离子体性质，将进行计算模拟。模型反应的SERS监测将利用微流控装置来研究双功能纳米结构表面的多相催化动力学。实验SERS谱将用多元方法进行分析，以获得有关催化反应中所涉及的化学物种和分子变化的定量信息。为了将这种方法扩展到没有表面寻找基团的分子，将在双功能纳米结构上涂覆一层，以捕获或浓缩金属表面附近涉及的物种。最后，通过单粒子水平的研究，我们的目标是建立双功能纳米结构的形态与其催化和等离子体/SERS活性之间的基本关联。

In situ monitoring of heterogeneously catalyzed reactions requires interface/surface-selective techniques. Surface-enhanced Raman spectroscopy (SERS) provides molecular structural information on chemical species adsorbed onto the surface of plasmonic nanostructures such as noble metal nanoparticles. SERS and catalysis have no direct topical overlap in terms of nanoparticle functionalities since plasmonic/SERS and catalytic properties are usually disjunct. Therefore, applications of colloidal SERS in heterogeneous catalysis are currently rare, despite the wealth of chemical information accessible by vibrational spectroscopy. In order to overcome the limited use of SERS in heterogeneous catalysis, bifunctional metal nanostructures with catalysts inside the localized surface plasmon resonance field of the plasmonic metal are required. The central aim of this proposal is to design and synthesize tailor-made bifunctional metal colloids with both plasmonic/SERS and catalytic activities for in situ monitoring of nanoparticle-catalyzed reactions. Complex metal superstructures comprising a silica shell-isolated SERS-active core and catalytically active satellite particles assembled onto the core as well as bifunctional hybrid nanoparticles will be synthesized and analyzed with respect to their SERS and catalytic activities. Computational simulations will be performed in order to understand and predict the plasmonic properties of the bifunctional nanostructures. SERS monitoring of model reactions will be carried out by using microfluidic devices to study the kinetics of heterogeneous catalysis on the surface of the bifunctional nanostructures. Experimental SERS spectra will be analyzed with multivariate methods to obtain quantitative information on the involved chemical species and molecular changes during the catalytic reaction. For expanding this approach to molecules without surface-seeking groups, the bifunctional nanostructures will be coated for either capturing or enriching the involved species near the metal surface. Finally, via investigations at the single-particle level, we aim at establishing fundamental correlations between the morphology of a bifunctional nanostructure and both its catalytic and plasmonic/SERS activities.