Ultrathin Two-Dimensional Nanostructures: Surface Defects for Morphology-Driven Enhanced Semiconductor SERS.

Two-dimensional (2D) semiconductors have recently become attractive candidate substrates for surface-enhanced Raman spectroscopy, exhibiting good semiconductor-based SERS sensing for a wider variety of application scenarios. However, the underlying mechanism remains unclear. Here, we propose that surface defects play a vital role in the magnification of the SERS performances of 2D semiconductors. As a prototype material, ultrathin WO 3 nanosheets is used to demonstrate that surface defect sites and resulting increased charge-carrier density can induce strong charge-transfer interactions at the substrate-molecule interface, thereby improving the sensitivity of the SERS substrate by 100 times with high reproducibility. Further work with other metal oxides suggests the reduced dimension of 2D materials can be advantageous in promoting SERS sensing for multiple probe molecules.