Hydrothermal synthesis of β-NaYF4 nanotubes by in situ ion exchange reaction using Y(OH)3 nanotubes as templates

In this article, we reported the synthesis of uniform hexagonal NaYF4 (β-NaYF4) nanotubes through in situ ion exchange reaction using Y(OH)3 nanotubes as templates via a facile hydrothermal route. The structure and morphology of the products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the as-prepared β-NaYF4 with a length of about 4 μm, an external diameter of about 160 nm, and a thickness of about 50 nm preserved the basic morphology of the initial Y(OH)3 nanotubes. The influence of pH value of the precursor on the morphology and structure of the products was also studied, and the results indicated that β-NaYF4 nanotubes could only be obtained at proper pH value. The strength of acids adjusting the pH value of the precursor had no influence on the morphology and structure of the products. Additionally, the upconversion luminescence properties of Yb3+/Er3+ codoped β-NaYF4 were investigated. Yb3+/Er3+ codoped NaYF4 emitted bright green and red light, both of which were two-photon processes.