Solvothermal synthesis, cubic structure and multicolor upconversion emission of ultrasmall monodisperse lanthanide-doped BaYF5 nanocrystals

► Monodisperse ultrasmall BaYF5 nanocrystals of mean 10 nm were synthesized. ► BaYF5 nanocrystals are cubic structures, not the reported tetragonal structures. ► Upconversion from NIR to UV was obtained in BaY0.664Yb0.33Tm0.006F5 nanocrystals. ► Blue, yellow and white-color upconversion emission can be tuned by elaborate doping.