Recent studies have revealed that metal–insulator–metal-based plasmonic antennas can couple with higher-order gap-plasmon modes in sub-10-nm gaps to overcome quenching. However, these tiny gaps are often physically inaccessible for functionalization and challenging to manufacture at scale. To address this, researchers have developed a biomimetic batch-fabrication method to create a plasmonic metasurface made of closely-coupled nanodisks and nanoholes in a metal–insulator–metal configuration. This system’s quadrupolar mode shows strong broadband resonance in the visible-near-infrared range with minimal losses, effectively suppressing quenching and enhancing broadband plasmon-enhanced fluorescence. Functionalizing the insulator nanogap allows for the selective immobilization of analytes onto the plasmonic hotspot, enabling highly localized detection. In experiments, sensing the streptavidin–biotin complex resulted in significant fluorescence enhancement for various Alexa Fluor dyes. Additionally, the detection of single-stranded DNA relevant to HIV-1 pathogenesis and CD4 mRNA in cell lysate showed promising results, demonstrating the potential of biomimetic Au metasurfaces as platforms for detecting low-abundance nucleic acids.-Journal cover picture by scapiens

https://pubs.rsc.org/en/content/articlelanding/2019/nr/c9nr03178b#!divAbstract