Photoswitchable Fluorescent Liquid Crystal Nanoparticles and Their Inkjet‐Printed Patterns for Information Encrypting and Anti‐Counterfeiting

Abstract

AbstractLiquid crystal nanoparticles (LCNPs) with desirable multifunctionality are catching increasing attention due to their promising applications in various fields. However, reversible photoswitchable fluorescent LCNPs are not reported until now. Here, the first example of water‐dispersible, reversibly phototunable fluorescent LCNPs prepared through a miniemulsion polymerization technique is presented. The LCNPs mainly consist of an aggregation‐induced emission enhancement (AIEE)‐active dicyanodistyrylbenzene‐based monomer, a LC cross‐linking monomer, and a dithienylethene (DAE) derivative as a photochromic molecular switch. The fluorescence of the resultant LCNPs can be switched reversibly between bright (ON) and dark (OFF) states with a high contrast and excellent repeatability upon alternating irradiation of 365 nm UV light and visible light (λ > 450 nm). This observation could be attributed to ring‐opening/ring‐closing photoisomerization of the DAE structure on the basis of an intraparticle fluorescence resonance energy transfer process between the AIEE‐active monomer and DAE derivative. More importantly, the potential for aqueous dispersion of the photoswitchable fluorescent LCNPs as a security ink for information encryption and anti‐counterfeiting is further demonstrated. The results demonstrate that the reversible photoswitchable fluorescent LCNPs as multifunctional nanomaterials exhibit promising applications in photonic fields.