Ultrafast Ion Sputtering Modulation of Two-Dimensional Substrate for Highly Sensitive Raman Detection

Two-dimensional (2D) materials are typical plasmon-free substrates for surface-enhanced Raman scattering with atomic uniformity and moderate spectral background. The low intrinsic enhancement limits the application in trace detection, remaining a challenging issue to regulate both dipole–dipole interaction and charge transfer resonance. Herein, we developed an ultrafast low-energy ion sputtering method to controllably modify 2D substrate which pronouncedly enhances the charge transfer. The enhancement factor of Ti-modified monolayer MoS2 reaches 2.67 × 108 and detection limit is 10–10 M. We further demonstrated the universality by modifying other plasmon-free metals and using MoSe2 as a substrate. The enhancement mechanism was investigated by the density functional theory calculation, indicating a charge transfer between dye molecules and substrate enhanced by new states in the bandgap from Ti clusters. It is believed that this new strategy gives rise to the remarkable feasibility for fabricating metal clusters and improves the chemical mechanism enhancement.