Molecular enrichment strategy enhanced SERS performance of bacterial Nanocellulose V₂O₅ composite substrate

Semiconductor-based Surface-enhanced Raman Scattering (SERS) substrates generally suffer from critical drawbacks, including insufficient surface adsorption sites and weak enrichment capability toward target probe molecules. To address the bottleneck of limited adsorption and enrichment performance of semiconductor SERS materials, this study proposes a molecular enrichment strategy. V₂O₅ nanorods rich in oxygen vacancies and with V⁵⁺/V⁴⁺ mixed valence states are used as the SERS-active component. Benefiting from the three-dimensional porous network, high specific surface area and abundant surface functional groups of bacterial nanocellulose (BNC), efficient adsorption and enrichment of probe molecules are realized, thereby achieving synergistic enhancement. The V₂O₅/BNC composite SERS substrate is fabricated via a facile vacuum filtration method. The results demonstrate that the composite substrate exhibits a 237.39% higher SERS signal intensity toward methylene blue (MB) than the pure V₂O₅ substrate, achieving a low limit of detection of 1 × 10^-6 mol/L, along with excellent signal reproducibility and long-term stability. Adsorption and surface analyses suggest that electrostatic interactions and hydrogen bonding facilitate MB enrichment within the composite membrane. The enhanced Raman response is attributed to the combined effects of BNC-mediated molecular enrichment, possible V₂O₅-MB interfacial charge transfer, and morphology-dependent optical contributions. This work presents a facile strategy for constructing flexible, noble-metal-free semiconductor composite SERS substrates with good reproducibility and storage stability.