Near-infrared PS-SiNCs/PDMS nanocomposite inks and their anti-counterfeiting applications

Silicon nanocrystals (SiNCs) have triggered tremendous attention both in academia and industry due to their size-tunable optical properties, exceptional biocompatibility and environmental benignity. However, their less than 10 % synthetic yield and high reactive surface severely impede practical applications. Herein, we propose a strategy for gram-scalable preparation of polystyrene-capped SiNCs (PS-SiNCs) by an AIBN-initiated thermal hydrosilylation. The resulting PS-SiNCs exhibit a near-infrared emission centered at 838 nm with an absolute quantum yield of 13.28 %, and exceptional environmental stability even after storage for 180 days under ambient conditions. Subsequently, a novel nanocomposite ink is developed by incorporating the PS-SiNCs into a polydimethylsiloxane (PDMS) matrix reinforced with vinyl-terminated MQ silicone resin. Both printability and practicability of the PS-SiNCs/PDMS nanocomposite ink are examined on flexible substrates including cotton fabric and cellulose paper through screen-printed technique. Interestingly, the customized labels exhibit distinguishable and full patterns with NIR-I fluorescence under 365 nm UV lamp, demonstrating a promising anti-counterfeiting application. Notably, these screen-printed patterns show unprecedented PL stability even after immersed in various aqueous solutions and organic solvents. This work not only presents an innovative strategy for scalable preparation of stable and eco-friendly NIR-I luminescent materials, but also pave a new way to advanced anti-counterfeiting applications.