The Effect of Hydrothermal Treatment on the Morphologies and Optical Properties of Upconversion NaYF ₄:Ln ³⁺ Crystals

Abstract

This work deals with the synthesis and characterization of upconversion NaYF₄:Ln³⁺ crystals. Co-precipitation and hydrothermal methods were used to synthesize NaYF₄:Ln³⁺ crystals. The experimental procedures were modified to obtain crystals in the cubic (α) phase, hexagonal (β) phase or a mixture between cubic and hexagonal (α/β) phases. Reaction temperature was maintained at 200 °C and the time of hydrothermal treatments were maintained at 24 and 48 h. The average diameter of the crystals ranged from 25 nm to 6.4 µm, depending on the chosen synthetic route. These materials can be applied in areas such as photodynamic therapy and bioimaging.

Keywords:
upconversion; lanthanides; luminescence; NaYF₄ crystals