Novel Dialdehyde Cellulose Nanocrystals‐Based Silver Nanoclusters for Anti‐Counterfeiting Fluorescent Multifunctional Ink

Silver nanoclusters (AgNCs) have attracted considerable interest due to their optical properties and diverse applications. However, their synthesis remains challenging, primarily owing to issues of instability and the reliance on strong reducing agents. Cellulose nanocrystals (CNC) are regarded as desired candidates for encryption and anti‐counterfeiting applications owing to their modifiability, renewability, and favorable rheological properties. In this study, glutathione (GSH)‐capped AgNCs (DCNC/AgNCs@GSH) with an average size of 1.94 nm are synthesized using dialdehyde cellulose nanocrystals (DCNC) as green templates and stabilizers in an aqueous phase system. The results indicate that the obtained DCNC/AgNCs@GSH possess excellent photoluminescence properties, including a tunable Stokes shift (171–243 nm) and high fluorescence intensity (8.54 × 10 5 a.u.), along with notable antibacterial performance. Expectedly, the as‐prepared DCNC/AgNCs@GSH‐based fluorescent ink exhibits multifunctional anti‐counterfeiting properties, enabling low‐cost dynamic optical encryption while performing effectively in screen printing and fingerprint recognition. Furthermore, DCNC enhances the rheological properties of the DCNC/AgNCs@GSH fluorescent ink and contributes to exceptional photostability, with only an 18.66% decrease in fluorescence intensity over 6 months. This work thus presents a DCNC‐based strategy for synthesizing structurally stable and high‐performance AgNCs, offering a novel approach for the development of AgNCs‐based optical functional materials.