Europium(III)-Doped ZnO Obtained by a Hierarchically Nanostructured Multilayer Growth Strategy

Abstract

A layer-by-layer growth method, named herein as impregnation–decomposition cycles (IDCs), was used to build hierarchically nanostructured multilayered nanoparticles, alternating undoped ZnO and Eu­(III)-doped ZnO layers in order to thermally induce Eu­(III) migration into the ZnO structure. Porous Vycor glass (PVG) was used as a mesoporous silica host, where the pores were used as a confined environment for preparation of ZnO nanoparticles. The proposed method allowed the control over the growth and size of the nanoparticles and prevented their coalescence. HRTEM images and XRD data revealed that ZnO nanoparticles are spheroidal with a wurtzite crystal structure and an average diameter of 4.8 nm for 10 IDCs. UV–vis DRS data indicated that the formation of ZnO nanoparticles is favored by europium­(III) doping, indicated by the band-gap absorption detection that also undergoes a red-shift by increasing the IDC number. Photoluminescence emission spectra have shown Eu­(III) intraconfigurational 4f–4f and ZnO excitonic emissions. Excitation spectra have shown energy transfers from ZnO to the silica as well as an energy transfer from ZnO to Eu­(III) ions, indicating the migration of these ions into the ZnO structure.

Importance of the Hierarchical Core@Multishell Nanostructure in Obtaining White Light Emission in Ln(III)-Doped ZrO2 Nanoparticles

“…The downside to the use of a silica host for such application, however, is the radiative energy loss through nonradiative decay by the surface hydroxyl oscillations (∼3600 cm –1 ). In the previous work by Oliveira et al, using the same method to grow pure ZnO on porous silica Vycor glass (PVG) resulted in a majority of Si–O–Zn species at the surface instead of ZnO nanoparticles, meaning ZnO could be used as a coating layer to suppress the hydroxyl groups and thus improve the luminescence of the nanoparticles.…”