A novel Fe2O3@CeO2 heterojunction substrate with high surface‐enhanced Raman scattering performance

Abstract

Abstract Surface‐enhanced Raman scattering (SERS) has been applied in many fields due to its advantages of fast and nondestructive detection. For semiconductors, the large‐scale electron‐hole pair separation of heterojunction is conducive to efficient charge transfer, which is a promising SERS substrate. Here, we designed a Fe2O3@CeO2 heterojunction substrate by hydrothermal method and explored its enhancement mechanism in detail. α‐Fe2O3 is a promising semiconductor with a narrow bandgap, and CeO2 has adequate oxygen vacancies on the surface. Combing α‐Fe2O3 and CeO2 into a shell‐core structure, Fe2O3@CeO2 heterojunction presents higher SERS performance than pure Fe2O3 and CeO2 for methyl orange (MO) molecule with a limit of detection (LOD) of 5 × 10−8 mol/L. Under the excitation of 514 nm, Fe2O3 can produce an effective exciton resonance due to its narrow bandgap (2.01 eV). The oxygen vacancy in CeO2 acts as the active site to promote the adsorption of molecules and facilitate the photo‐induced charge transfer (PICT) between the substrate and MO molecules. Therefore, the high SERS performance of Fe2O3@CeO2 heterojunction is achieved due to the coupling effect of excitons resonance, molecular resonance, and PICT resonance. It is found that Fe2O3@CeO2 has good SERS performance and stability to organic pesticides, especially metamitron (LOD = 5 × 10−9 mol/L). This work combines the advantages of Fe2O3 being prone to producing photoelectrons and abundant oxygen vacancies of CeO2, providing a reference for designing semiconductor SERS.

Keywords

• Fe2O3@CeO2 heterojunction
• oxygen vacancy
• photo‐induced charge transfer
• SERS