Significantly increased Raman enhancement on defect-rich O-incorporated 1T-MoS2 nanosheets

Improving charge transfer is the key to the performance of non-noble metal semiconductor-based surface enhanced Raman scattering (SERS) substrates. In this work, the O-incorporated 1T-MoS2 nanosheets with rich sulfur defects (ID-MoS2) are obtained by simple calcination of 1T-MoS2 nanosheets in air atmosphere. Using rhodamine 6G (R6G) as typical probe molecules, ID-MoS2 nanosheets show ultrahigh Raman enhancement effects with an enhancement factor of 1.24 × 107 due to sulfur defects and O incorporation in the 1T-MoS2 lattice. First-principle density functional theory calculations suggest that the existence of sulfur defects and O incorporation significantly increase the Fermi energy level (Ef) and electronic density of states of ID-MoS2. Moreover, O incorporation can enhance the interactions between the substrate and the adsorbed molecules through electrostatic and hydrogen bonding. All these improve the charge transfer resonance and result in the remarkable SERS activity of ID-MoS2 nanosheets. This is the first study on the increasing SERS performance of semiconductor substrates by simultaneously employing defect and dopant incorporation. This study provides an approach to optimize the performance of semiconductor-based SERS substrates.