Ultrathin Graphene Oxide Sheets Wrapped MoO2 Nanoparticles with Molecule Enrichment Function for Sensitive SERS Detection.

Benefiting from their low price, high performance stability, and moderate-to-high detection sensitivity, surface-enhanced Raman scattering (SERS) substrates made of noble metal-free materials have received much attention in the past few years. Improving the SERS sensitivity of non-noble metal materials is of great significance. Here, we propose a strategy of combining ultrathin graphene oxide (GO) sheets with plasmonic non-noble metal materials to enhance SERS sensitivity. By leveraging the adsorption property of GO and plasmonic hotspots of MoO₂ nanoparticles (MoO₂-NPs), the enrichment of target molecules around hotspots can be realized, thereby achieving high detection sensitivity. Highly surface-roughened plasmonic MoO₂ nanospheres are wrapped by ultrathin-GO sheets, forming an ultrathin-GO/MoO₂-NP hybrid. GO sheets with a huge specific surface area and high adsorption ability can trap analyte molecules in the locations near or in hotspots of MoO₂-NPs. A uniform film of ultrathin-GO-wrapped MoO₂-NPs shows a high enhancement factor of ∼1.12 × 10⁸ and good spectral homogeneity (relative standard deviation, RSD = 9.7%). The detectable concentration limit for rhodamine 6G molecules is ∼10 pM, demonstrating high SERS sensitivity. In addition, the ultrathin-GO/MoO₂-NP hybrid also exhibits excellent structural and chemical stabilities. The fabricated GO/MoO₂-NP hybrid has promising applications in the SERS-based detection of trace chemical molecules.