Surface-selective vibrational spectroscopy is a powerful tool to study various interfacial phenomena such as electrochemical reactions at electrode-electrolyte interfaces. Among various spectroscopic methods, surface enhanced Raman scattering (SERS) is a promising method for in-situ observation of electrode-electrolyte interfaces because both of the incident and scattered photons utilized in this method has much higher energy than the molecular vibration energy. According to recent technological advancements in fabrication of optical filters, elimination of Rayleigh scattering has become highly efficient. Thus, it is now expected that very low-frequency vibrations such as THz vibrations can be observed even in aqueous solutions. In this talk, we demonstrate in-situ observation of THz vibrations in electrochemical conditions using SERS spectroscopy.

Figure. THz-SERS spectra of 4-methylbenzenthiol monolayers on Au(111), Au(100), and roughened Au substrates