Huang Yi-Fan, Wang Wei, Guo Hong-Yu, Zhan Chao, Duan Sai, Zhan Dongping, Wu De-Yin, Ren Bin, Tian Zhong-Qun
The State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, Department of Chemistry, College of Chemistry & Chemical Engineering, Xiamen University, Xiamen 361005, China.
School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
J Am Chem Soc. 2020 May 6;142(18):8483-8489. doi: 10.1021/jacs.0c02523. Epub 2020 Apr 27.
The rational design and applications of plasmon-mediated chemical reactions (PMCRs) are fundamentally determined by an understanding of photon-electron-molecule interactions. However, the current understanding of the PMCR of plasmon-decayed hot electron-mediated reactions remains implicit, since there has not been a single measurement of both hot-electron transfer and molecular transformation following photon excitation. Therefore, we invented a method called microphotoelectrochemical surface-enhanced Raman spectroscopy (μPEC-SERS) that uses an ultramicroelectrode (UME) whose dimensions match those of the focused laser spot. This system can simultaneously record the photocurrent (∼picoamps) of hot-electron transfer with a high signal-to-noise ratio and the SERS spectra of a molecular reaction in the same electrode area. The responses of the photocurrent and SERS spectra to laser illumination can correlate the surface reaction activated by hot electrons with the SERS spectral changes. A typical PMCR of -aminothiophenol (PATP) on a Ag UME was used to illustrate that the correlation of the photocurrent with the spectral changes is capable of revealing the reaction mechanism in terms of the formation of activated oxygenated species. The laser power-, laser wavelength-, and surface roughness-dependent photocurrents link the formation of activated oxygenated species to the hot-electron transfer. Further comparisons of the photocurrent with the conventional electrochemical current of the oxygen reduction reaction indicate that the activated oxygenated species are oxidative in transforming PATP to ,'-dimercaptoazobenzene, which is supported by a density functional theory (DFT) calculation. Therefore, μPEC-SERS could be a powerful tool for investigating PMCRs and other systems involving photon-electron-molecule interactions.
等离子体介导的化学反应（PMCRs）的合理设计与应用，从根本上取决于对光子 - 电子 - 分子相互作用的理解。然而，目前对于等离子体衰变热电子介导反应的PMCR的理解仍不明确，因为在光子激发后，尚未有对热电子转移和分子转化进行同时测量的情况。因此，我们发明了一种名为微光电化学表面增强拉曼光谱（μPEC - SERS）的方法，该方法使用尺寸与聚焦激光光斑相匹配的超微电极（UME）。这个系统能够在同一电极区域，以高信噪比同时记录热电子转移的光电流（约皮安）和分子反应的SERS光谱。光电流和SERS光谱对激光照射的响应，可以将热电子激活的表面反应与SERS光谱变化关联起来。以Ag UME上的对氨基苯硫酚（PATP）的典型PMCR为例，说明光电流与光谱变化的相关性能够揭示活性氧化物种形成方面的反应机理。激光功率、激光波长和表面粗糙度相关的光电流，将活性氧化物种的形成与热电子转移联系起来。将光电流与氧还原反应的传统电化学电流进一步比较表明，活性氧化物种在将PATP转化为4,4'-二巯基偶氮苯的过程中具有氧化性，这得到了密度泛函理论（DFT）计算的支持。因此，μPEC - SERS可能是研究PMCRs以及其他涉及光子 - 电子 - 分子相互作用系统的有力工具。
