Multicolor Lu2O3:Ln (Ln = Eu3+, Tb3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanocrystals (NCs) with uniform spherical morphology were prepared through a facile urea-assisted homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and photoluminescence (PL) spectra as well as kinetic decays were employed to characterize these samples. The XRD results reveal that the as-prepared nanospheres can be well indexed to cubic Lu2O3 phase with high purity. The SEM images show the obtained Lu2O3:Ln samples consist of regular nanospheres with the mean diameter of 95 nm. And the possible formation mechanism is also proposed. Upon ultraviolet (UV) excitation, Lu2O3:Ln (Ln = Eu3+ and Tb3+) NCs exhibit bright red (Eu3+, D-5(0) --> F-7(2)), and green (Tb3+, D-5(4) --> F-7(5)) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu2O3:Ln (Ln = Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) NCs display the typical up-conversion (UC) emissions of green (Er3+, S-4(3/2),H-2(11/2) --> I-4(15/2)), blue (Tm3+, (1)G(4) --> H-3(6)) and yellow-green (Ho3+, F-5(4), S-5(2) --> I-5(8)), respectively. (C) 2011 Elsevier Inc. All rights reserved.