A facile hydrothermal approach to the synthesis of nanoscale rare earth hydroxides

Nanoscale Research Letters, Mar 2015

Nanosized rare earth (RE) hydroxides including La(OH)3, Nd(OH)3, Pr(OH)3, Sm(OH)3, Gd(OH)3, and Er(OH)3 with rod-like morphology are fabricated via a convenient hydrothermal approach. This strategy calls for the first preparation of metal complexes between RE precursors and dodecylamine (DDA) in water/ethanol mixture at room temperature and subsequent thermal decomposition at elevated temperature. The influence of reaction time and water/ethanol volume ratios on the morphology and size of as-prepared RE hydroxides are investigated. CeO2 nanoparticles with spherical shape could be directly obtained by hydrothermal treatment of complexes formed between Ce precursors and DDA. In addition, by further calcinating the RE hydroxides at high temperature in air, RE oxide nanorods could be readily produced.

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A facile hydrothermal approach to the synthesis of nanoscale rare earth hydroxides

Li et al. Nanoscale Research Letters A facile hydrothermal approach to the synthesis of nanoscale rare earth hydroxides Chengyin Li 0 1 Hui Liu 0 Jun Yang 0 0 State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences , Beijing 100190 , China 1 University of Chinese Academy of Sciences , No. 19A Yuquan Road, Beijing 100049 , China 2015 Li et al. ; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. Rare earth; Hydrothermal; Hydroxide; Nanorod; Oxide - Background Recent years have witnessed considerable interest in the design and preparation of rare earth (RE) nanomaterials due to their great potential applications as phosphors, magnets, catalysts, superconductors, and electrolytes [1-8]. In general, the physical and chemical properties of nanomaterials are closely related to their size, chemical composition, and morphology, which render the synthesis of nanosized RE materials an important prerequisite for further scientific or industrial investigations [9]. Among a large number of nanosized RE candidates, the RE hydroxides, which can be easily modified into corresponding oxides, oxysulfides, oxyfluorides, and fluorides, have attracted much attention in recent years [10-14]. So far, the preparation of the nanosized RE hydroxides is mainly based on a hydrothermal/solvothermal treatment in the presence of an inorganic base/organic base at a designed temperature. Typically, a hydrothermal system for preparing RE hydroxides consists of precursor, solvent, and organic additive. The RE precursors are usually simple nitrates or chlorides. The solvent mainly includes water, ethanol, and ethylene glycol. As the physicochemical properties of the solvent can influence reactivity, solubility, and diffusion behavior of the reagents, different solvents benefit morphology and size control. For instance, ethanol, with low RE3+ solubility, and ethylene glycol, with high viscosity and tunable diffusion rate of ions, both have been proved to be effective solvents to slow down the nucleation and growth rate of nanoparticles [15]. Besides, a great number of reports have demonstrated that, in the hydrothermal method, the most efficient and straightforward strategy for fine-tuning the shape and size of a targeted material is to select addition of organic additives, including hydrophilic and hydrophobic ones. On the one hand, the coordination effect between the hydrophilic ligands and RE ions will affect the actual concentration of free ions, thereby influencing the concentration of monomer and growth kinetics. On the other hand, the selective adsorption of ligands on different facets of crystallites favors morphology control. In this work, we demonstrate a hydrothermal approach to the fabrication of RE hydroxide nanorods, labeled as RE (OH)3 (RE = La, Nd, Pr, Sm, Gd, and Er). This strategy is based on the thermal decomposition of metal complexes formed by RE precusors and dodecylamine at room temperature. As we will demonstrate, the RE hydroxide nanorods could be further manipulated into corresponding nanosized RE oxides via a simple calcination procedure. Considering the remarkable simplicity of the synthetic approaches, the studies in this work might be promising for creating nanosized RE hydroxides and RE oxides on a large scale for a given technological application (e.g., as phosphors, magnets, and catalysts) copper grid. Excessive solution was removed by an absorbent paper, and the sample was dried at room temperature in air. Methods General materials The RE precursors, including lanthanum(III) nitrate (La (NO3)36H2O, 99%), praseodymium(III) nitrate (Pr(NO3) 36H2O, 99%), neodymium(III) nitrate (Nd(NO3)36H2O, 99%), samarium(III) nitrate (Sm(NO3)36H2O, 99%), gadolinium(III) nitrate (Gd(NO3)36H2O, 99%), and erbium(III) nitrate (Er(NO3)35H2O, 99.9%), were from Aladdin Reagents, Shanghai, China; cerium(III) nitrate (Ce(NO3)36H2O, 99%) was from Sinopharm Chemical Reagent Co., Ltd., Beijing, China; ethanol (99.5%) was from Beijing Chemical Works, Beijing, China; and dodecylamine (DDA, 98%) was from J&K Scientific Ltd., Beijing, China. All glassware and autoclave Teflon liner were cleaned with aqua regia, followed by copious rinsing with deionized water before drying in an oven. Synthesis of lanthanide hydroxide nanoparticles In a typical synthesis of RE hydroxide nanorods, 0.2 mmol of RE precursors (La(NO3)3, Pr(NO3)3, Nd(NO3)3, Sm (NO3)3, Gd(NO3)3, Er(NO3)3, or Ce(NO3)3) was dissolved in 10 mL of deionized water, and then 10 mL of ethanol containing 5 mL of DDA was added. After sufficient mixing, the mixture was transferred into an autoclave with a volume of 50 mL, which was kept at 180C for 18 h. After the hydrothermal process, (...truncated)


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Chengyin Li, Hui Liu, Jun Yang. A facile hydrothermal approach to the synthesis of nanoscale rare earth hydroxides, Nanoscale Research Letters, 2015, pp. 144, Volume 10, Issue 1, DOI: 10.1186/s11671-015-0850-2