Clusterization-Triggered Emission of Polysaccharide-based Microclusters induced by the Co-assembly of Chitosan nanofibers and Dialdehyde carboxymethyl cellulose

The emerging non-aromatic and non-conjugated 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 micro-clusters (MCs) were fabricated using chitosan nanofibers (CSNFs) cross-linked with dialdehyde carboxymethyl cellulose (DACMC). MCs 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 CSNFs and DACMC enable the realization of clusterization-triggered emission (CTE) by through-space conjugation. MCs exhibit stable fluorescence behavior under aqueous conditions. A composite gel of MCs and poly(vinyl alcohol) (PVA) (PVA-MCs) was synthesized using the freeze-thaw method to develop CTE hydrogel. The MCs 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 CTE MCs 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.