Na_yWO_3–x Nanosheet Array via In Situ Na Intercalation for Surface-Enhanced Raman Scattering Detection of Methylene Blue

Nonmetal plasmonic semiconductors have shown promising surface plasmon properties with advantages including abundance, low cost, and flexibility in synthesis and tuning. However, it is urgently desired to explore semiconductor materials for improving the plasmonic effect. Herein, a plasmonic oxygen-deficient sodium tungsten bronze Na_yWO_3–x nanosheet array has been facilely achieved on the glass substrate by in situ Na intercalation, followed by hydrogen reduction. The Na_yWO_3–x nanosheet array manifested a visible localized surface plasmon resonance band centered at 558 nm, which, to the best of our knowledge, was the bluest absorption peak for sodium tungsten bronze. Based on this unique surface plasmon property, the Na_yWO_3–x nanosheet array exhibited a good surface-enhanced Raman scattering (SERS) effect, and a detection limit of 10^–7 M for methylene blue was achieved. In addition, as a SERS substrate, the Na_yWO_3–x nanosheet arrays not only guaranteed high SERS signal stability but also had a much easier and facile operation. Therefore, the plasmonic oxygen-deficient Na_yWO_3–x nanosheet array with low cost and easy availability shows great potential for applications in light harvesting and optoelectronic devices in addition to sensing devices.