Acid based synthesis of monodisperse rare earth doped colloidal SiO2 spheres

Rare-earth-doped SiO₂ colloids can be grown in a wet chemical procedure by adding the appropriate rare earth chloride to a solution of tetraethoxysilane, glacial acetic acid, and water. The size polydispersity of the particles can be controlled in a seeded growth process, and monodisperse Er³⁺-doped particles were grown by covering 183-nm-diameter seed particles with a 5-6-nm-thick (Er-doped) shell. After annealing, typical Er luminescence is observed with long luminescence lifetimes.