Synthesis of Eu3+-doped Gd2O3 in hollow nanoparticle structures by controlled chemical etching with poly(acrylic acid)

Abstract

Hollow Eu3+:Gd2O3 nanoparticles were easily prepared, without employing templates, from spherical crystalline Eu3+:Gd2O3 nanoparticles (NPs) via the simple etching process induced by the acidic moieties in the sodium salt solution of poly(acrylic acid), PAA-Na. Some portion of carboxylate units in PAA-Na could bind to the surface of Eu3+:Gd2O3 NPs and control the etching rate of Eu3+:Gd2O3 in acidic conditions such that the rate becomes comparable to the cation migration rate within the crystalline NPs, generating hollow Eu3+:Gd2O3 NPs. This controlled etching process in the presence of additional acid after surface treatment of Eu3+:Gd2O3 NPs with PAA-Na, varied the resulting structures from solid NPs to core-shell, core-void-shell, yolk-shell, and finally, hollow NPs. Based on the low r2/r1 value obtained from the relaxation times measured by time-domain nuclear magnetic resonance (TD-NMR) spectrometry and the good photoluminescent properties of hollow Eu3+:Gd2O3 NPs, accelerated development of multimodal nanoprobes and drug delivery vessels is expected, using the various morphological novelties of synthesized Eu-doped Gd2O3 nanoparticles.