Facile synthesis of upconversion nanoparticles with high purity using lanthanide oleate compounds.

A novel strategy for preparing highly pure NaYF4-based upconversion nanoparticles (UCNPs) was developed using lanthanide oleate compounds [Ln(OA)3] as the precursor, denoted as the Ln-OA preparation method. Compared to the conventional solvothermal method for synthesizing UCNPs using lanthanide chloride compounds (LnCl3) as the precursor (denoted as the Ln-Cl method), the Ln-OA strategy exhibited the merits of high purity, reduced purification process and a uniform size in preparing core and core-shell UCNPs excited by a 980 or 808 nm near infrared (NIR) laser. This work sheds new insight on the preparation of UCNPs and promotes their application in biomedical fields.