Cs4PbX6-UCLNPs/PS film for multimodal anti-counterfeiting and information encryption storage upon triple strategies of water treatment, light excitation and heating/cooling†

Development of advanced materials and techniques for anti-counterfeiting and information encryption storage still faces tremendous challenges of complex preparation, few anti-counterfeiting strategies and low anti-counterfeiting levels. To address these challenges, based on phase transition from non-luminescent Cs₄PbX₆ (X = Cl, Br and I) quantum dots (QDs) to down-conversion luminescent (DCL) CsPbX₃ QDs after water treatment and NaYF₄:Yb³⁺,Er³⁺ up-conversion luminescent nanoparticles (UCLNPs), a brand-new Cs₄PbX₆-UCLNPs/polystyrene (PS) film with multimodal anti-counterfeiting and information encryption storage is devised and constructed through favorable electrospinning. Three different strategies are developed to achieve multimode anti-counterfeiting by leveraging UCL and DCL: 980-nm laser acts as the excitation source for Cs₄PbX₆-UCLNPs/PS films to produce green UCL to realize UCL static and dynamic anti-counterfeiting; multicolor DCL static and dynamic anti-counterfeiting are, respectively, achieved in Cs₄PbX₆-UCLNPs/PS films with different halogen ion compositions via water-based ink silk-screen printing and wet brush writing under 365-nm ultraviolet (UV) light irradiation; DCL patterns on CsPbX₃-UCLNPs/PS films can be eliminated or restored by heating/cooling cycles to achieve thermal static anti-counterfeiting. Furthermore, multicolor DCL of CsPbX₃-UCLNPs/PS films is encoded as ASCII binary code to store information. Meanwhile, water treatment, UV light and heating/cooling process are employed for information encryption and decryption. This research contributes to the advancement of sophisticated anti-counterfeiting and information encryption storage technologies.