Si/TiO₂/Ag Multistorey Structures with Interfacial Charge Transfer for a Recyclable Surface-Enhanced Raman Scattering...

In this work, highly ordered TiO₂/Ag bilayer structures on p-type silicon (Si) wafers are prepared by photolithography and electrochemical self-assembly methods. The interfacial charge transfer (CT) of this Si/TiO₂/Ag multistorey structure with a specially aligned work function is studied. This is important to deduce the interfacial electron migration behavior of SERS. The three-dimensional finite-difference time-domain (3D FDTD) simulation is used to explore the combined CT-EM enhancement mechanism. The result shows that the electron movement under the CT mechanism can induce the resonance effect of free electrons to further improve EM performance. In addition, the effect of agglomerated Ag nanoparticle size distribution on the SERS property and the self-cleaning property of Si/TiO₂/Ag multistorey structures is investigated. Finally, this unique structure of highly ordered Si/TiO₂/Ag SERS substrate shows superior sensitivity, reproducibility, and stability. Rhodamine 6G (R6G) with trace concentrations as low as 10^-15 M can be detected, and the EF is estimated to be about 8.9 × 10¹³. The relative standard deviation (RSD) at 1511 cm^-1 is about 4.7%. These results are very promising for the practical application of the SERS technique in the rapid trace determination in many fields.