Morphology control and upconversion luminescence enhancement of Na1-xLixY.78-yLuyF4:Er.02Yb.2 microcrystals by doping ions with different valences

Trivalent lanthanide ion (Ln3+) doped UC materials can emit visible light under near-infrared (NIR) excitation due to anti-stokes shift and have received wide attention. In this paper, we presented a new strategy to synthesize the uniform and smooth microstructures (rodlike and tubular) based on hexagonal phase NaYF4 microcrystals. Moreover, we systematically discussed the method of enhancing the upconversion (UC) luminescence intensity via co-doping the ions with different valences (Li+ and Lu3+) in order to tailor the environment around lanthanide ions. The UC intensities in the two microstructures were significantly improved. The results suggested the great application potential of tubes and rods of β-NaYF4 microcrystals in anti-counterfeiting, laser media, photonic crystals, and waveguides.