Rare earth doped spherical mesoporous metal oxide nanospheres with upconversion emission ability and large surface area were successfully synthesized by a rapid one-pot single-step method. The reaction medium comprised supercritical methanol with carboxylic acid as an organic additive. Mesoporous Er doped CeO2 and Er and Yb co-doped CeO2 nanospheres emit green light under even low-power IR laser irradiation (980 nm, 10 mW) without calcination. Stronger intensity was achieved by high-temperature calcination. Spherical mesoporous nanoparticles were successfully doped with other metals and nitrogen to form TiO2:Eu, TiO2:Ce, TiO2:Yb, Ti-2:Fe, and TiO2:N according to the similar procedure combining supercritical methanol. (C) 2013 Elsevier B.V. All rights reserved.