UV surface-enhanced Raman scattering properties of SnSe₂ nanoflakes

Two-dimensional (2D)-layered semiconductor materials have attracted considerable attention in surface-enhanced Raman scattering spectroscopy (SERS) technology owing to their high uniformity, excellent reproducibility, and ultra-flat surfaces without dangling bonds. However, they are rarely used in the UV laser-excited surface-enhanced Raman scattering spectroscopy (UV–SERS) field. In this article, 2D-layered tin diselenide (SnSe₂) nanoflakes were investigated as a UV–SERS substrate for the first time. The strong absorption in the UV region of SnSe₂ induces a pre-resonance Raman (pre-RR) effect and charge transfer (CT) between the substrate and the probe molecules. The UV–SERS signal of crystal violet (CV) molecules adsorbed on SnSe₂ nanoflakes was obtained even though the concentration was low at 10⁻⁷ mol/L. The indirect band gap structure of the SnSe₂ nanoflake plays a significant role in promoting the electrons excited by incident photons and the CT process. This is a new phenomenon for 2D semiconductor materials in the UV–SERS field. The results will be helpful to develop UV–SERS technology based on 2D-layered materials and to provide a promising method to understand the chemical enhancement mechanism of UV–SERS.