Printable Monodisperse All-Inorganic Perovskite Quantum Dots: Synthesis and Banknotes Protection Applications

All-inorganic perovskite quantum dots (PQDs) have drawn great attention recently, which are newcomer materials for banknotes protection. Herein, CsPbX3 (X = Cl, Br, I) PQDs are synthesized via one-step hot-injection method. It is interesting to find that the fluorescent colors can be tuned over wide visible spectra region of 506 and 636 nm by changing the ratio of halide ions. Then, the PQDs with strong fluorescence intensity, narrow full width at half maximum of 15-35 nm, and high quantum yields of 86.6% are formulated as fluorescent anticounterfeiting inks. Finally, the designable patterns are successfully printed on paper, polyethylene terephthalate, and banknotes by multiple printing techniques, including screen printing, inkjet printing, and roll-to-roll printing. The desired printed patterns are colorless under visible light but exhibit bright red, green, and cyan color outputs when exposed to 365 and 254 nm light. Moreover, the polydimethylsiloxane film of PQDs still emits bright color outputs even after 60 days. The excellent dual-modal fluorescent properties make PQDs potential candidates in the field of banknotes protection.