A novel Fe 2 O 3 @CeO 2 heterojunction substrate with high surface‐enhanced Raman scattering performance

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 Fe 2 O 3 @CeO 2 heterojunction substrate by hydrothermal method and explored its enhancement mechanism in detail. α‐Fe 2 O 3 is a promising semiconductor with a narrow bandgap, and CeO 2 has adequate oxygen vacancies on the surface. Combing α‐Fe 2 O 3 and CeO 2 into a shell‐core structure, Fe 2 O 3 @CeO 2 heterojunction presents higher SERS performance than pure Fe 2 O 3 and CeO 2 for methyl orange (MO) molecule with a limit of detection (LOD) of 5 × 10 −8 mol/L. Under the excitation of 514 nm, Fe 2 O 3 can produce an effective exciton resonance due to its narrow bandgap (2.01 eV). The oxygen vacancy in CeO 2 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 Fe 2 O 3 @CeO 2 heterojunction is achieved due to the coupling effect of excitons resonance, molecular resonance, and PICT resonance. It is found that Fe 2 O 3 @CeO 2 has good SERS performance and stability to organic pesticides, especially metamitron (LOD = 5 × 10 −9 mol/L). This work combines the advantages of Fe 2 O 3 being prone to producing photoelectrons and abundant oxygen vacancies of CeO 2 , providing a reference for designing semiconductor SERS.