Tunable Gold‐on‐SiO₂ Nanopillar Arrays with Functionalized Nanoporous Layer for Enhanced Fluorescence Immunoassays

Porous metal plasmonic resonators demonstrate large on‐chip resonance areas and expanded light‐absorption bandwidth, which are favorable in sensitive plasmonic‐based biosensors. However, the conventional fabrication methods can only provide porous metal resonators less degree‐of‐freedom in morphology, significantly limiting their optical properties. This work proposes a porous bimetallic nanopillar array biosensing platform, the nanoporous gold pillar (NPGP), enabled by a hybrid porosity‐on‐nanoarray nanofabrication method. NPGP achieves spectral tunability by setting the main resonance through the morphology of nanopillar‐supported transition gold inner core while expanding the resonance spectra through the nanoporous gold outer crust. The capability of NPGP as an on‐chip fluorescence sensing platform is demonstrated in the detection of soybean stay‐green associated geminivirus (SoSGV). With trace amounts of virus in ground leaf buffer solutions, the porous metal morphology captures the virus with high efficacy. Combined with the high field‐strength region of NPGP, a fluorescence enhancement two orders of magnitude higher than that of a gold plane is achieved. This work has provided a new hybrid nanofabrication method and nanoporous plasmonic architecture that can create highly tunable porous optical resonating devices for wide use in biological and chemical molecule detections.