Preparation of Upconversion Nanocrystals NaYF4:Yb/Tm with Hydro(solvo)thermal Methods

A upconversion nanocrystal of NaYF₄:Yb/Tm was synthesized successfully by two different methods of solvothermal and hydrothermal, respectively. The properties of the products were characterized and compared. The results showed that the nanocrystal prepared by hydrothermal method exhibited uniform hexagonal phase and large size, while the nanocrystal prepared by solvothermal method displayed high upconversion luminescence (UCL) and small size. The UCL intensity of the nanocrystal from solvothermal method was higher than that of hydrothermal method. This is the first time to systematically compare the performances of the upconversion nanocrystal prepared by solvothermal and hydrothermal methods, which provides some new insight into the preparation of upconversion nanomaterials with intense UCL and controllable morphology.