Copper‐Based Multiwavelength UV Surface Enhanced Raman Spectroscopy

Abstract Herein, it is demonstrated that copper (Cu) nanoparticle‐based surfaces prepared via a wet‐chemical method exhibit considerable enhancement of the Raman signal for a monolayer of adenine, guanine, riboflavin, 4‐mercaptobenzoic acid, and potassium thiocyanate analytes upon excitation with a laser in the wavelength range of 229–325 nm. The results reveal a notable enhancement of the Raman signal in the surface‐enhanced Raman scattering (SERS) spectra of the analytes in the deep UV(ultraviolet) spectral ranges, a phenomenon previously unreported for Cu‐based surfaces, which, according to current knowledge, typically exhibit enhancement only in the red and near‐infrared spectral regions. Several analytes of different chemical natures are tested, which allow to test the hypothesis that π‐conjugated molecules localized on the copper surface are more likely to contribute to the chemical enhancement of Raman signal. This enhancement arises from their capacity for charge delocalization, effective orbital alignment with the metal and resonance with electronic transitions in the UV spectral region. Based on these findings, the chemical enhancement mechanism related to charge transfer is the most plausible explanation for the observed enhancement in the UV‐SERS signals of the investigated molecules on Cu surfaces.