Microwave hydrothermal synthesis and upconversion properties of NaYF4:Yb3+, Tm3+ with microtube morphology

Efficient upconversion Yb3+ and Tm3+ codoped β-NaYF4 is firstly synthesized via a novel and rapid microwave hydrothermal process. The as-prepared sample is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The sample shows a microtube morphology, which may be formed by the curliness of flakes. It is found that NaYF4:Yb3+, Tm3+ microtubes can be synthesized using microwave hydrothermal method in a much shorter reaction time compared with conventional hydrothermal method, and the upconversion fluorescent intensity is also greatly enhanced under 976 nm laser excitation. The energy transfer upconversion mechanisms and the possible reason for the enhancement of the fluorescent intensity are also proposed.