Preparation of NaYF4:Yb3+,Tm3+@NaGdF4:Ce3+,Eu3+ double-jacket microtubes for dual-mode fluorescent anti-counterfeiting
(1. Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Sciences and Chemistry, Hunan University of Technology, Zhuzhou 412007, China;
2. Key Laboratory of Electrochemical Green Metallurgy Technology of Hunan Higher Education Institutions, College of Metallurgy and Materials Engineering, Hunan University of Technology, Zhuzhou 412007, China)
2. Key Laboratory of Electrochemical Green Metallurgy Technology of Hunan Higher Education Institutions, College of Metallurgy and Materials Engineering, Hunan University of Technology, Zhuzhou 412007, China)
Abstract: Novel hydrophilic NaYF4:Yb3+,Tm3+@NaGdF4:Ce3+,Eu3+ double-jacket microtubes (DJMTs) with upconversion/ downconversion dual-mode luminescence were designed and prepared through epitaxial growth of NaGdF4:Ce3+, Eu3+ shell onto the NaYF4:Yb3+,Tm3+ microtube via poly(acrylic acid) (PAA) mediated hydrothermal method. It is demonstrated that PAA ligand played an important role in guiding the direct growth of NaGdF4:Ce3+,Eu3+ shell onto the surface of NaYF4:Yb3+,Tm3+ parent microtubes. The growth of NaGdF4:Ce3+,Eu3+ shell experienced a crystal phase transition from β-NaGdF4 and β-NaYF4 mixture to β-NaYF4@NaGdF4 composite crystal, and morphology evolution from mixture of β-NaGdF4:Ce3+,Eu3+ nanorods and β-NaYF4:Yb3+,Tm3+ microtubes to NaYF4:Yb3+,Tm3+@NaGdF4: Ce3+,Eu3+ DJMTs. The formation mechanism of DJMTs was the dissolution-renucleation of β-NaGdF4:Ce3+,Eu3+ nanorods and the growth of β-NaGdF4:Ce3+,Eu3+ shell via the classical Ostwald ripening mechanism. The as-prepared DJMTs could exhibit blue upconversion and red downconversion luminescence, which was further made into environmentally benign luminescent inks for creating highly secured and fluorescent-based anti-counterfeiting patterns via inkjet printing.
Key words: lanthanide-doped fluoride; core-shell structure; dual-mode luminescence; inkjet printing; anti- counterfeiting