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
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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)