Facile Synthesis of Highly Water-Soluble Lanthanide-Doped t-LaVO 4 NPs for Antifake Ink and Latent Fingermark Detection.

In the information age, it is important to protect the security and integrity of the information. As a result, the fluorescent ink as an antifake technology and the fingermark as an information carrier have aroused great interest. In this work, highly water-soluble lanthanide (Ln ³⁺ )-doped tetragonal phase (t-) LaVO ₄ nanoparticles (NPs) are successfully obtained via a simple, fast, and green microwave-assisted hydrothermal method. The average size of t-LaVO ₄ NPs is about 43 nm. The aqueous solutions of Ln ³⁺ -doped t-LaVO ₄ exhibit excellent fluorescence properties under ultraviolet light (UV) excitation (t-LaVO ₄ :10%Eu is bright red and t-LaVO ₄ :0.5%Dy is close to white). Some superb antifake fluorescent patterns are printed using Ln ³⁺ -doped t-LaVO ₄ aqueous solution as ink, which indicates the as-prepared Ln ³⁺ -doped t-LaVO ₄ NPs as fluorescent ink can meet the various antifake requirements. Notably, the designed convenient antifake fluorescent codes with improved security could be directly scanned and decoded by a smart phone. What's more, the as-prepared NPs can be used for the development of latent fingermark on various substrates and the second-level detail information can be clearly obtained from the magnification of a fingermark. These results indicate that the as-prepared Ln ³⁺ -doped t-LaVO ₄ fluorescent NPs have great potential in security application.
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