Monodisperse bifunctional Fe3O4@NaGdF4:Yb/Er@NaGdF4:Yb/Er core–shell nanoparticles

We report for the first time the synthesis of monodisperse, magnetic and up-conversion luminescent Fe3O4@NaGdF4:Yb/Er@NaGdF4:Yb/Er core–shell structured nanoparticles (NPs) by a seed-growth process. The growth of a NaGdF4:Yb/Er shell on Fe3O4@NaGdF4:Yb/Er NPs can significantly enhance the up-conversion emission intensity.