Reactive template method for synthesis of water-soluble fluorescent silver nanoclusters supported on the surface of cellulose nanofibers

Abstract

There is an emerging quest for fabrication of water-soluble fluorescent silver nanoclusters (AgNCs) with long-lasting fluorescent properties and dimensional stability while being sustainable and functional. Thus, a well-known seed-mediated growth strategy has been developed to manufacture AgNCs supported onto carboxyl and aldehyde modified cellulose nanofiber (DATCNF) with ultra-small and intense fluorescence. The DATCNF acts as a reductant, template, and stabilizer while the protective ligand, 2-Mercaptonicotinic Acid (2-H₂MA), provides AgNCs with luminous characteristic and constrained size of 4.47 nm. The structural feature of 2-H₂MA also governs the formation and stability of AgNCs, imparting them with hydrophobic nature and steady fluorescence emission in water. This aqueous colloidal suspension (DATCNF-AgNCs) is highly dispersed, photobleaching resistant, and hardly agglomerates. Even after two months of exposure to the sun, the fluorescence intensity had only fallen by 20 %. Furthermore, the aqueous colloidal suspension exhibits outstanding antibacterial property and UV shielding capability, making it suitable as an additive for the production of TCNF films with high UV blocking capacity and high tensile strength. This strategy opens the door to design and fabricate mechanically robust DATCNF-AgNCs composites for luminescent, antimicrobial, and UV protection applications.