Ultra-thin Au tip structure: a novel SERS substrate for in situ observation of a p-aminothiophenol surface-catalytic reaction

A novel surface-enhanced Raman scattering (SERS) substrate based on an ultra-thin Au nano-tip structure was prepared using a simple and quick electrochemical etching method in this study. After decorating Au nanoparticles on the surface of the fabricated nanotip using an electrostatic absorption method, SERS measurement was performed on the substrate by using 4-mercaptobenzoic acid (4-MBA) as a Raman probing molecule, showing a good enhancement effect for the sample molecules adsorbed on the nanotip region. Furthermore, the Au tip structure Raman substrate was applied in monitoring and assessing the plasmon-driven surface-catalytic reaction of para-aminothiophenol (PATP) transforming to 4,4-dimercaptoazobenzene (DMAB), and the laser power-dependent and tip size dependent experiments were performed and discussed in this work. The results show high catalytic efficiency on the nanotip with about 40 nm apex diameter under definite laser power, providing a new application in pinpoint monitoring on surface-catalytic reaction within the nanotip region.