摘要/Abstract
表面等离激元共振(SPR)驱动的催化反应近年来广受关注, 研究集中在SPR等外场作用下发生单一的界面催化反应生成新的物质, 这对于表面反应设计和实现多步骤界面有机合成反应仍存在一定困难. 本工作以对氯苯硫酚(4-CBT)为探针, 利用表面增强拉曼光谱(SERS)的极高表面灵敏度并结合金粒子单层膜(Au MLF)的玻碳电极(Au MLF@GC电极)作为基底在均匀性方面的优势, 实现了电化学和SPR协同作用下界面催化反应及其过程的精准监测. 结果表明, 较负电位区间内, 在光电协同催化作用下, 4-CBT先发生脱氯反应生成苯硫酚(TP), 然后4-CBT脱氯与偶联同时发生生成联苯-4,4'-二硫醇(4,4'-BPDT). 提高激光功率可显著加快反应速率, 且在中性溶液中反应速率最快. 溴代苯硫酚以及邻位或间位二氯取代苯硫酚均可发生类似的脱卤素取代基和偶联反应, 但邻位二氯取代物因空间位阻而导致偶联效率降低.
关键词: 表面等离激元共振, 表面增强拉曼光谱, 电化学, 对氯苯硫酚, 偶联反应
Surface-enhanced Raman spectroscopy (SERS) has become a promising technique widely utilized in the field of interface science due to its extremely high sensitivity and selectivity. Among this, surface plasmon resonance (SPR)-driven interfacial reactions have been attracted considerable attention because of their potential practical applications in the field of photocatalysis and photoelectrocatalysis. However, the relevant investigation was mainly focused on the single interfacial reaction for producing new compounds catalyzed by SPR or other external fields and it still remains significant challenge in designing of surface reaction and achieving the interfacial organic reaction with multi-steps. In this paper, 4-chlorothiophenol (4-CBT) was served as the probe molecule and glassy carbon electrode attached with gold nanoparticle monolayer film (Au MLF@GC electrode) was used as substrate due to its excellent uniformity. The extremely high surface sensitivity of SERS was utilized to realize the precise in situ monitoring of the interface catalytic reaction and its process with the synergistic effect of electrochemistry and SPR. In addition, several effects, involving potential, laser power, the pH value of solution and substituents, were systematically investigated. The results reveal that the surface catalysis reaction was absent by the control of single external field, such as potential or laser irradiation. In the relatively negative potential region, 4-CBT underwent a dechlorination reaction to produce thiophenol (TP) under the photoelectric synergistic catalysis, then dechlorination of 4-CBT was followed with a coupling reaction to generate biphenyl-4,4'-dithiol (4,4'-BPDT) as the potential further negatively shifts. The increase of laser power allows to significantly accelerate the reaction rate. The reaction rate is fastest in the neutral solution. Both 4-bromothiophenol (4-BTP) and ortho- or meta-dichloro-substituted thiophenol undergo similar dehalogenation substituents and surface coupling reactions. For ortho-dichloro-substituted thiophenol, the coupling efficiency is reduced due to steric hindrance. It provides a novel approach for surface multi-step organic synthesis reactions.
Key words: surface plasmon resonance, surface enhanced Raman spectroscopy, electrochemistry, 4-chlorothiophenol, coupling reaction
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