关键词: 原位电化学扫描隧道显微镜(In-situ EC-STM), 对巯基苯胺(PATP), 4′-巯基-N-苯醌二亚胺(NPQD), 电化学表面增强拉曼光谱(EC-SERS)

Abstract: Para-aminothiophenol (PATP) is not only a widely-used probe molecule in the field of surface-enhanced Raman spectroscopy (SERS), but also an important model molecule for interfacial reactions, exhibiting distinct photo- and electro-oxidation pathways, so that PATP is selectively activated under different external fields. The evolution of products and intermediates during electrochemical oxidative coupling remains unknown. In this study, we have investigated the dynamic electrochemical oxidation process of PATP on the Au(111) surface using cyclic voltammetry, EC-SERS, and in situ electrochemical scanning tunneling microscopy (EC-STM). The results show that PATP forms unsaturated adsorption coverage on Au(111) in acidic solution. When the potential is positively shifted to the oxidation potential range, the cation radical generated by PATP oxidation alternate with PATP molecules in arrangement. Once the coupling reaction occurs, the adsorption structure of alternating arrangement is transformed into stripe structure in STM images. Finally, the coverage on Au(111) decreases and a √¯3 × 4√¯6. structure is formed. The oxidation reaction product 4′-mercapto-N-phenylquinone diimine (NPQD) adopts the arrangement of mixed adsorption sites of bridge and hollow sites on Au(111). By determining the adsorption structure evolution of PATP during the electrooxidation process on the gold surface, the mechanism of interfacial electrochemical oxidation coupling reaction is revealed from a spatial perspective. This lays the foundation for further modulation and design of the interfacial reaction of aromatic amine molecules.

Key words: In-situ electrochemical scanning tunneling microscopy (In-situ EC-STM), Para-aminothiophenol (PATP), 4'-mereapto-N-phenylquinone diimine (NPQD), Electrochemical surface-enhanced Raman spectroscopy (EC-SERS)