GdF3:Eu(3+) nanocrystals (NCs) and nanorods were synthesized by a microemulsion-mediated hydrothermal process. The structure, shape and particle size were characterized by means of x-ray diffraction (XRD) and transmission electron microscopy (TEM). The vacuum ultraviolet (VUV) spectrum of GdF3:Eu(3+) NCs shows that the Gd(3+) ion can absorb one VUV photon excited in the (6)GJ levels and relaxes through two-step energy transfer to Eu(3+), yielding two visible photons at room temperature. The visible quantum efficiency of GdF3:Eu(3+) NCs was calculated to be close to 170% by the peak intensity ratio of correlative transition emission under VUV excitation at 160 nm.