Fabrication of High-Stability and -Sensitivity Perovskite Nanoparticles with a Core–Shell Structure for Surface-Enhanced Raman Scattering

High-stability and -sensitivity perovskite nanoparticles with a core–shell structure were fabricated by an in situ one-step growth annealing technique, followed by the deposition of an ultrathin alumina film on its surface using the magnetron sputtering method. X-ray diffraction, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy were used to characterize the structures and the morphologies of the samples. The as-modified CH3NH3PbBr3@Al2O3 core–shell nanoparticles demonstrated excellent uniformity and reproducibility in surface-enhanced Raman scattering (SERS) measurements, achieving a detection limit for methylene blue down to 10–9 mol/L with an enhancement factor of up to 4.09 × 105. The diffraction peaks of the (100) and (300) crystal planes were enhanced, while the intensities of the (210) and (220) planes were suppressed. The CH3NH3PbBr3@Al2O3 core–shell substrate maintains its Raman detection stability over 30 days, broadening the application of SERS technology for high-sensitivity molecular detection on various substrate surfaces. Furthermore, finite-difference time-domain simulations showed high consistency with the experimental results. Our study provides a solid foundation for the practical application of perovskite-based SERS probes, especially in the fields of chemical, biological, material, and surface sciences. The applications span environmental monitoring, medical diagnostics, food safety, and forensic science.