The effect of the size of raw Gd(OH)3 precipitation on the crystal structure and PL properties of Gd2O3:Eu

Our experiments show that cetyltrimethylammonium bromide (CTAB) has an obvious effect on the particle size of the precipitation of Gd(OH)3. Without CTAB, the particle size of the Gd(OH)3 precipitation is about 50 nm, whereas with CTAB, the particle size is less than 5 nm. We propose a mechanism where CTAB micelles work as a catalyst for the nucleation process and result in the precipitation of 5 nm particles. These small particles, after heat treatment at 1073 K, did not result in small Gd2O3 nanoparticles of the same size, but instead, forming crystals of 30–80 nm size in both cubic and monoclinic phases. When monitoring the photoluminescence (PL) peak at 610 nm, we found that the charge transfer state (CTS) absorption amplitude of Eu–O is reduced in the mixed structures. We speculate that the mixed structures modify the surface properties of the Gd2O3:Eu nanoparticles, leading to the reduction of Eu–O CTS absorption.

When CTAB were added in the solution, the size of the Gd(OH)3 deposition decreased from 50 nm to less than 5 nm. After they were heated at 1073 K, Gd2O3 nanoparticles of roughly 40 nm formed. The Gd2O3:Eu sample from Gd(OH)3 deposition with size of about 50 nm shows the characteristic emission of Eu3+ in a pure cubic structure (curve a). However, the sample from Gd(OH)3 of less than 5 nm presents the characteristic emissions of Eu3+ in both cubic and monoclinic structures (curve b).Figure optionsDownload as PowerPoint slide