Few-layered vdW MoO3 for sensitive, uniform and stable SERS applications

[Display omitted] •Rapid growth of uniform large size FL-vdW MoO3 nanosheets.•FL (13 L) MoO3 nanosheet shows LOD of 2 × 10−8 M and EF of 2.28 × 104.•Uniformity as small as 2.95%, and high stability for 160 days was demonstrated.•Intercalation improves the SERS signal without sacrifice of stability.•The charge transfer mechanism at the interface for SERS was illustrated. Metal oxides have been considered as active substrates for surface-enhanced Raman scattering (SERS) through morphology-engineering and defect-introduction with the sacrifice of the uniformity and stability of the materials. In this work, large-size, few-layered (FL) wide band gap van der Waals (vdW) MoO3 nanosheets were prepared as SERS substrates. It’s shown that the decrease of layer number converted the intrinsic MoO3 from non-SERS active to sensitive SERS substrate, with limit of detection (LOD) of 2 × 10−8 M for R6G. The SERS of MoO3 showed high homogeneity with RSD as small as 2.95%, The Raman intensity of R6G on the SERS substrate remained higher than 90% after exposing in atmosphere for 160 days, demonstrating excellent air-stability. Experimental results demonstrated that the SERS effect of the plasmon-free MoO3 substrate comes from chemical enhancement mechanism (CM) when reducing its thickness. Furthermore, the CM effect can be further improved through non-destructive atomic intercalation into the vdW gap, resulting in more charges separation between the adsorbed molecules and substrates. Our result showed that non-destructive modulation strategy is effective for preparation of sensitive, uniform and stable SERS substrate.