Blue-fluorescent cellulose nanofibers grafted with acridon-2-yl-alanine

Cellulose nanofibers (CNFs) are ecofriendly biopolymers with remarkable thixotropic properties and Pickering emulsification stability due to their native amphiphilicity. In this study, we successfully synthesized Acd-CNF by covalently binding acridon-2-yl-alanine (Acd) to TEMPO-oxidized CNF (TOCNF), imparting blue fluorescence while maintaining its aqueous properties. The modified Acd-CNF displayed blue fluorescence at 424–447 nm and exhibited rheological properties similar to TOCNF, with enhanced viscosity and gel-like behavior. Furthermore, Acd-CNF functioned as a fluorescent stabilizer in Pickering emulsions. Confocal laser scanning microscopy (CLSM) demonstrated its interfacial localization in oil-in-water Pickering emulsions, facilitating Förster resonance energy transfer (FRET) to Nile Red-stained oil. Unlike conventional dyes prone to nonspecific adsorption, Acd-CNF enables direct fluorescence observation of CNFs, offering a reliable approach for emulsion microimaging. The modification enhances emulsion visualization and water dispersion behavior, broadening CNFs’ applications in fluorescence-based micro imaging and traceability.