Design and Construction\nof Highly Luminescent Transparent\nWoody Materials Exhibiting Unique Fluorescence-Enhanced Staining Effects\nfor Visualization of Intrinsic Microporous Networks

Luminescent wood materials are an emerging class of biomass\nhybrid\nhost materials owing to the hierarchical porous structure and functionalization\nversatility. The fluorescence properties are largely dependent on\nexogenous fluorophores, which are, however, often plagued by notorious\naggregation effects. In this work, an efficient strategy for the preparation\nof luminescent transparent wood materials is developed by incorporating\ntetraphenylethylene-derived aggregation-induced emission (AIE)-active\nfluorophores during a delignification-backfill transparency process.\nThese wood hybrids showed unexpected luminescence enhancement that\nsignificantly increased the fluorescence quantum yield of the fluorophores\nup to 99%, much higher than that of the fluorophores in other states\nsuch as crystalline solids or doped in a polymer substrate. Mechanistic\ninvestigations reveal that <i>in situ</i> polymerization\nof prepolymerized methyl methacrylate in delignified microporous wood\nframes produces high molecular weight ordered PMMA polymers, resulting\nin a rigid molecular environment that improves the luminescence efficiency\nof TPE-based fluorophores at the interfaces of PMMA polymer and cell\nwalls. By confocal laser scanning microscopy (CLSM), this excellent\nfluorescence staining capability was furthermore utilized to visualize\nthe intrinsic porous network of wood in three dimensions over a large\nvolume with submicrometer resolution, thus providing an alternative\napproach to the study of structure–function relationships in\nsuch wood hybrids.