Facile synthesis of multifunctional β-NaGdF₄:Yb ³⁺/Er³⁺ nanoparticles in oleylamine

Multifunctional β-NaGdF₄:Yb³⁺/Er³⁺ nanoparticles (NPs) were successfully synthesized using oleylamine as both solvent and stabilizer via the thermolysis method. They have uniform morphology with a mean size of 12.7 nm and show efficient up-conversion emission when excited by a 980 nm laser. The up-conversion NPs demonstrated a nearly quadratic dependence of the photoluminescence intensity on the excitation power, which indicated a two-photon induced process. In addition, these NPs exhibit paramagnetic characteristics at both 300 and 77 K. The magnetic properties of β-NaGdF₄:Yb³⁺/Er³⁺ NPs are intrinsic to the Gd³⁺ ions. The measured mass magnetic susceptibility value of 0.79×10^-4 emμ/g ·Oe at room temperature is close to reported values of other NPs for bioseparation and optical-magnetic dual modal nanoprobes in biomedical imaging.