Synthesis and Photoluminescent Properties of Rare Earth Doped ZnO Hierarchical Microspheres

Hierarchical ZnO microspheres constructed by mesoporous quasi-single-crystalline ZnO nanosheets were fabricated by pyrolysis of the microspheres of layered hydroxide zinc carbonate, Zn 5 (CO 3 ) 2 (OH) 6, which was the hydrothermal precipitate of zinc nitrate and urea. A growth mechanism of Zn 5 (CO 3 ) 2 (OH) 6 microspheres was proposed. During the pyrolysis process, single-crystalline Zn 5 (CO 3 ) 2 (OH) 6 nanosheets were transformed into mesoporous quasi-single-crystalline ZnO nanosheets. When the samples were doped with trivalent rare earth ion, RE 3+ (RE = Pr, Sm, Tb, Ho, Tm), no ZnO → RE 3+ energy transfer was observed. However, the ZnO:Eu 3+ sample showed efficient Eu 3+ emissions under UV photon excitation (λ < 365 nm), which is attributed to energy transfer from photon-generated electron−hole pairs to Eu 3+ ions in the surface layer of the ZnO nanosheet.