Clusterization-triggered emission of polysaccharide-based microclusters induced by the co-assembly of chitosan nanofibers and dialdehyde carboxymethyl cellulose

Abstract The emerging nonaromatic and nonconjugated clusteroluminogens possess the potential to overcome the common drawbacks of aromatic π-conjugated luminophores such as aggregation-caused quenching, synthetic complexity, bio-toxicity, and environmental pollution. Because of the presence of heteroatoms and carbonyl functional groups, some natural polymers show potential as clusteroluminogens. In this study, co-assembled microclusters were fabricated using chitosan nanofibers cross-linked with dialdehyde carboxymethyl cellulose. Microclusters form stable structures under aqueous conditions owing to the formation of cross-links via imine bonds, ionic interactions, and hydrogen bonds between the polysaccharides. These multiple interactions and the heteroatomic nature of both chitosan nanofibers and dialdehyde carboxymethyl cellulose enable the realization of clusterization-triggered emission by through-space conjugation. Microclusters exhibit stable fluorescence behavior under aqueous conditions. A composite gel of microclusters and poly(vinyl alcohol) (PVA-MCs) was synthesized using the freeze–thaw method to develop clusterization-triggered emission hydrogel. The microclusters and PVA-MCs gels demonstrated the detection ability toward specific metal ions such as Cu2+ and Fe3+, by the quenching of the emission. This strategy for the creation of clusterization-triggered emission microclusters based on cross-linked polysaccharides widens the scope of the practical and sustainable application of water-containing fluorescent materials in the fields of sensing and biomedicines.