表面增强拉曼光谱的增强机理及等离激元光电化学反应

Enhancement mechanism of surface-enhanced Raman spectroscopy and plasmon photoelectrochemical reactions

电化学界面是能量转换和物质转化的重要场所.光与电化学界面等离激元金属纳米结构的作用可以显著地改变表面光谱性质、以及界面化学反应的热力学和动力学.表面等离激元共振(SPR)效应在化学反应中以金属纳米结构作为介质,将光子能量重新分配和转换为局域光电场、热电子、热空穴和热能,其不仅产生表面增强光谱,特别是表面增强拉曼光谱(SERS),而且也诱导界面发生新的化学反应、引入新的能量转化机制,同时SERS也可以作为表征方法用于研究纳米结构表面物理化学过程.本文首先介绍了SERS的SPR增强机理和化学增强机理,阐述了SERS作为界面高灵敏度表征手段的基本原理.其次,在三个模型体系中具体讨论热载流子(热空穴和热电子)诱导化学反应的作用机制,并针对等离激元光电化学反应表现出与传统化学反应的区别和潜在优势,分析了等离激元光电化学实现调控化学反应过程的选择性和光量子效率.最后,针对等离激元光电化学反应仍存在选择性和光量子效率低等挑战问题,结合目前该研究方向在国内外的研究进展,依据等离激元共振效应及其结构特征提出了两点展望,为光能的转化和利用提供新思路.

Electrochemical interfaces are important places for energy conversion and chemical transformation.The interaction of light with metallic nanostructures at electrochemical interfaces can significantly change the surface spectroscopic properties,as well as the thermodynamics and kinetics of chemical reactions at the interfaces.Surface plasmon resonance(SPR)effect in chemical reactions with metal nanostructures as a medium redistribute and convert the photon energy into localized photoelectric field,hot electrons,hot holes and photothermal energy,which not only produces surface-enhanced spectroscopy,especially surface-enhanced Raman spectroscopy(SERS),but also induces the interface to occur in new mechanisms of chemical reactions and energy conversion.Meanwhile,SERS can be used as a characterization method to study the surface physical and chemical processes on nanostructures.In this review article,the electromagnetic enhancement mechanism and chemical enhancement mechanism of SERS are firstly introduced to reflect the basic principle of SERS as a means of high sensitivity characterization of interfaces.Secondly,the action mechanism of hot carriers(hot holes and hot electrons)-induced chemical reactions is specifically discussed in three model systems of para-thiophenol,adenine derivatives and 8-bromoadenine,and the selectivity and photon quantum efficiency of plasmon photoelectrochemical realizations to modulate the chemical reaction process are analyzed with respect to the fact that plasmon photoelectrochemical reactions exhibit distinctions and potential advantages over the conventional chemical reactions.Finally,in view of the challenges of selectivity and low photon quantum efficiency of the plasmon photoelectrochemical reaction,combined with the current research progress in this research direction at home and abroad,two outlooks are put forward based on the resonance effect of surface plasmons and their structural features,which will provide a new way of thinking for the conversion and utilization of light energy.