Two-dimensional ultra-thin MoOx / in-situ perovskite nanoparticles generated the increase of Raman scattering performance

Abstract

Recent advancements in metal oxide Surface-Enhanced Raman Spectroscopy (SERS)substrates, particularly using semiconductor materials like perovskites, present a promising avenue. This study addresses the challenge of enhancing Raman performance by optimizing a series of the deposition of ultrathin molybdenum oxide (MoOx) films on perovskite substrates and employing an optical fiber probe tip. The MoOx layer's thickness modulates residual stress, resulting in a rough, block-like wrinkled morphology that increases “hot spots” and significantly boosts Raman signals. XPS analysis confirmed the composite's stability, indicating that mixed valence states of molybdenum and oxygen-related defects aid in stress release. The release of residual stress yielded a uniformly rough surface, enhancing Raman scattering through increased roughness and inducing notable spectral shifts, particularly at ∼912 cm⁻¹ (CH₃NH₃ rocking mode) and ∼ 968 cm⁻¹ (CN symmetric stretching mode). The CH₃NH₃PbBr₃@MoOx (MAPbBr₃@MoOₓ) substrate achieved a SERS analytical enhancement factor of 1.12 × 10⁴ and a detection limit of 10⁻⁸ mol/L for methylene blue. Significant agreement was found between the experimental and finite difference in time domain (FDTD) simulation results.