Interface-engineered plasmonic covalent organic framework nanofilms on TiO ₂ nanotubes for universal mass spectrometry imaging

Covalent organic frameworks (COFs) hold promise for surface-assisted laser desorption/ionization mass spectrometry imaging (MSI), yet their integration with plasmonic nanostructured platforms remains unexplored. Here, we report a liquid-liquid interfacial self-assembly strategy to construct plasmonic gold nanoparticle–decorated COF nanofilms on titanium dioxide nanotubes. This hierarchical design synergizes plasmonic enhancement, efficient charge transfer, and enhanced ionization efficiency, achieving sensitivity improvement over conventional matrices. The plasmonic platform affords universal compatibility with currently available biosample preparation protocols including imprinting, stamping, and cryo-sectioning for multitissue MSI. The first whole-plant imprinting MSI of Vigna unguiculata reveals tissue-specific distributions of three pollutants with distinct translocation rate and endogenous metabolites. In addition, 10-micrometer resolution lipid mapping was achieved in stamped fingerprints and cryo-sectioned murine brains. Moreover, we successfully visualized ischemic stroke biomarkers in rat brains for interrogating the pathogenesis of focal ischemia. Our findings highlight the advantages of plasmonic COF nanofilms on titanium dioxide nanoarrays for universal matrix-free MSI in complex biological systems, bridging advanced materials and life science applications.