Ultimately simple one-pot single-step synthesis of rare earth doped spherical mesoporous metal oxide nanospheres with upconversion emission ability in supercritical methanol

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, TiO2:Fe, and TiO2:N according to the similar procedure combining supercritical methanol.