Kompetenzzentrum für Mikro- und Nanotechnologien

Surface enhanced Raman spectroscopy (SERS) is an established technique for specific detection of fingerprint spectra of molecules at lowest concentrations. In particular, the application of silver-based SERS substrates is promising due to their favorable physical properties for enhancing Raman signals. However, the silver substrates are prone to deterioration over time. In this study, the prevention of such degradation is explored by passivating the silver SERS substrates with aromatic self-assembled monolayers (SAMs). The SAMs of biphenyl-4-thiol and 4′-nitro-4-biphenylthiol molecules are prepared by vapor deposition in vacuum and characterized in situ by X-ray photoelectron spectroscopy (XPS) and ex situ with SERS. After exposing these samples for up to ten months to ambient conditions, a comparative analysis is conducted using both techniques. Furthermore, the substrates are characterized by scanning electron microscopy (SEM). The results demonstrate an enhanced stability of the passivated substrate compared to the bare substrates. In addition, the presence of amine groups in the SAMs paves the way toward specific chemical and biochemical functionalization of the SERS substrates for analytic purposes.