Investigating the effect of synthesis parameters on the structure and upconversion luminescent properties of NaYF4:Tm,Yb for anticounterfeiting printing ink

Abstract

Introduction: In this study, NaYF4:Tm,Yb upconversion microparticles were prepared by a hydrothermal method. Methods: The effects of fabrication parameters such as rare earth concentration, reaction temperature and reaction time on the structure and luminescence properties of the materials were studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). Depending on the reaction temperature and time, the morphology of NaYF4:Tm,Yb is either a nanoparticle or a branched structure. Results: The crystallite size is approximately 70 nm and remains almost unchanged with increasing reaction temperature and time. These NaYF4:Tm,Yb powders strongly emit at 450 nm and 798 nm. In addition, the surface of the UCMPs was also modified with maleic anhydride to improve their dispersibility in solvents and binding to biological molecules. Conclusion: Printing ink based on UCMPs modified with maleic anhydride and polyamide for screen printing was prepared. The printed patterns on paper and polymer substrates glow blue light under LED excitation at 980 nm, and they are completely transparent in daylight.