Plasma-Engineered Anisotropic Nanostructures with Multipolar Plasmon Coupling for Label-Free Biosensing

High Resolution Image Download MS PowerPoint Slide The development of anisotropic plasmonic nanostructures with controllable morphology and exceptional surface-enhanced Raman scattering (SERS) activity remains a major challenge, particularly for scalable, green, and reproducible synthesis. Here, we report a plasma-engineering strategy for synthesizing anisotropic silver nanooctapods (AgNOs) under ambient conditions without the use of toxic reducing agents or high-temperature processing. The shape evolution is directed by plasma-induced reduction and selective facet stabilization, yielding nanostructures that exhibit extreme plasmonic coupling at interarm junctions. This unique geometry supports hybridized multipolar plasmon resonances, enabling dense electromagnetic hotspots and dramatically enhanced Raman cross sections. The resulting SERS substrates achieve an outstanding enhancement factor (EF) of 5.9 × 10 9 and a sensitive detection limit (LoD) down to 1 × 10 –14 M for Rhodamine 6G (R6G). More importantly, they demonstrated label-free, serotype-specific detection of dengue virus NS1 proteins, clearly distinguishing DENV1 and DENV4 through unique spectral Raman fingerprints. This study establishes a direct structure–plasmon–function correlation and introduces a sustainable, rapid fabrication platform for high-performance SERS sensors. Beyond biosensing, plasma-programmed nanostructures and their tunable plasmonic properties offer broad potential in nanooptoelectronics, photocatalysis, and surface-mediated energy conversion, paving the way for real-world deployment in diagnostics and multifunctional sensing technologies.