Controllable synthesis, upconversion luminescence, and paramagnetic properties of NaGdF ₄:Yb ³⁺,Er ³⁺ microrods

Hexagonal phase NaGdF ₄ microrods have been successfully synthesized via a facile hydrothermal method with ethylene diamine tetraacetic acid (EDTA) as the structure-directing agent. The additive amounts of NaF and NaNO ₃ as well as the reaction time have great effect on the morphology evolution of the products. A possible growth mechanism was proposed for the formation of β-NaGdF ₄ microrods. Under the excitation of 980 nm near-infrared laser, bright green upconversion (UC) emissions can be readily achieved from NaGdF ₄:10%Yb ³⁺,1%Er ³⁺ microrods. In addition, the NaGdF ₄ microrods exhibit excellent paramagnetic features with the magnetization value of 5.02 emu/g (18 kOe) at room temperature. Both the UC luminescent and magnetic properties are closely related to the size of as-prepared products. These multifunctional β-NaGdF ₄ microrods would have potential applications in the fields such as solid-state lasers, lighting, displays, and magnetic resonance imaging (MRI), and so on.