Unidirectionally aligned copper hydroxide crystalline nanorods from two-dimensional copper hydroxy nitrate

Article abstract of DOI:10.1021/ja047425w

We were able to synthesize unidirectionally aligned copper hydroxide nanorods from two-dimensional copper hydroxide nitrate by anion exchange reaction using NaOH without any membrane or template. The structural conversion from Cu₂(OH)₃NO₃ to Cu(OH)₂ was confirmed by XRD and FT-IR data. The synthesized copper hydroxide nanorods showed unidirectionally aligned and tightly bound arrays on a hexagonal plate, leading to giant nanorod bundles. Copyright

Full text of DOI:10.1021/ja047425w

Published on Web 10/14/2004
Unidirectionally Aligned Copper Hydroxide Crystalline Nanorods from
Two-Dimensional Copper Hydroxy Nitrate
Seong-Hun Park and Hae Jin Kim*
Nano Material Team, Korea Basic Science Institute, Daejeon 305-806, Korea
Received May 3, 2004; E-mail: hansol@kbsi.re.kr
Developing a method for the controlled synthesis of nanostruc-
tures at mesoscopic levels is one of the most challenging issues
presently faced by materials scientists.1 The requirement for
dimensional control is especially true of one-dimensional (1D)
structures (e.g., nanotube, nanorod, and nanowire), for which the
control of nucleation and growth seems to be particularly difficult.
Many methods have been used to control the size and morphology
2
of the nanomaterials, such as vapor-liquid-solid (VLS) growth,
3
4
laser-assisted catalytic growth, and templating method. The most
important problem in these fields is the development of a method
that can synthesize reasonable quantities of product while maintain-
ing dimensional monodispersion. Further to these aims, it would
be advantageous to prepare these nanorods in crystal form and with
preferred crystallographic orientations.
Figure 1. XRD patterns of (a) Cu2(OH)3NO3 (starting material) and (b)
as-prepared Cu(OH)2 (direct reaction).
Over the past few years, numerous works have investigated the
morphology of basic copper(II) salts and Cu(OH) . These materials
2
possess a well-known layered structure and have proven to be
promising candidates for the fabrication of 1D nanostructures.5
Figure 1 compares X-ray diffraction patterns of the as-prepared
product and parent material. The starting Cu (OH) NO possesses
2 3 3
a lamellar structure as is evident from XRD patterns shown in
Figure 1a. They can be indexed on the monoclinic structure with
lattice constants a ) 5.5983, b ) 6.0848, and c ) 6.9303 Å, â )
-11
In detail, Cu(OH)
synthesized in copper(II) solutions, and the relationship between
the morphologies of homogeneously precipitated Cu(OH) and the
2
colloid particles have been conventionally
2
solution compositions was systematically investigated by Matijevic´
9
4.747°. The copper hydroxide nanorods were prepared starting
from bulk Cu (OH) NO by direct reaction with aqueous NaOH
solution. An XRD pattern of the obtained Cu(OH) product is shown
in Figure 1b. All of the reflections of Figure 1b could be indexed
to the Cu(OH) phase with the orthorhombic structure with
8
and co-workers. Polycrystalline Cu(OH)
2
nanowires and nanor-
2
3
3
ibbons were synthesized by exploiting a two-step wet chemical
2
9
process and by coordination self-assembly in solution using Cu
2
S
nanowires as precursors,10 respectively. Finally, other Cu(OH)
and
2
2
CuO nanoribbons were also successfully synthesized on a copper
surface in a controlled fashion.11 However, despite their excellent
approaches on the synthesizing route, no monodispersive nano-
structures could be obtained in a controlled fashion. To accomplish
this purpose, we pay attention to layered materials, which are
necessary for the formation of 1D structure. Accordingly, as starting
calculated lattice constants a ) 2.9817, b ) 10.622, and c ) 5.3224
15
Å (JCPDS 13-420). No impurity could be detected in the XRD
analysis; therefore, pure Cu(OH)
XRD analysis obviously indicates that the starting bulk Cu
NO was transferred into Cu(OH) by direct reaction. This
2
must have been obtained. The
2
(OH)
3
-
3
2
transformation is also confirmed by FTIR spectra (Figure S-1,
Supporting Information). In addition, the intensities of (111), (130),
and (020) of Figure 1b are significantly enhanced compared to the
material we adopt copper hydroxide nitrate (Cu
2
(OH)
3
NO
3
), the
crystal structure12 of which is similar to that of Mg(OH)
(brucite),
2
-
where one-fourth of the OH groups are substituted by nitrate
ligands in an ordered way. In this communication, we report a novel
powder XRD pattern, indicating that the crystalline Cu(OH)
2
is
oriented in a particular crystallographic direction.
The morphology of the as-prepared Cu(OH) products was
2
obtained by field-emission scanning electron microscopy (FE-SEM).
It is evident that starting material possesses hexagonal plate
morphology, as shown in Figure 2a. However, FE-SEM images,
and facile method for providing unidirectionally aligned Cu(OH)
nanorods from 2D Cu (OH) NO by anion exchange reaction using
2
2
3
3
NaOH solution without any membrane or template. Similar
approaches to fabricate 1D structure using NaOH can be found in
the literature.13
2
Figure 2b-d, reveal that the Cu(OH) products consist of nanorod
The Cu(OH)
Cu (OH) NO with aqueous NaOH solution at room temperature.
The starting material was synthesized according to standard
2
nanorods are prepared from direct reaction of
arrays with diameters of 10-20 nm and lengths up to several µm.
It is an important feature of the present system that most of Cu-
(OH)2 nanorods are uniformly aligned in a particular crystal-
lographic direction within hexagonal plates.
The nanorodlike structure of the products was further examined
by high-resolution TEM (HRTEM) (Figure 3). Bulk quantities of
nanorods were formed with relatively uniform diameters of about
10 nm. The nanorods are relatively straight and long and tightly
packed, leading to giant bundle arrays of few µm (Figure 3a). Figure
2
3
3
14
literature procedures. In a typical synthesis, 2.5 g of starting
material was dispersed in distilled water and added to aqueous
NaOH solution (2 M). The mixture was stirred in an air-free round
flask for 48 h at room temperature. The faint-blue powder was then
filtered, washed with distilled water and ethanol, and dried in a
vacuum at 35 °C.
14368
9
J. AM. CHEM. SOC. 2004, 126, 14368-14369
10.1021/ja047425w CCC: $27.50 © 2004 American Chemical Society

C O M M U N I C A T I O N S
place in a plane almost parallel to (001).16 In the present system,
-
replacement of the nitrate group position with a OH ion allows
strong deformations of the octahedral cationic coordination, in
17
special “antiferrodistortive” ordering, which might be realized in
18
2
Cu(OH) . It is worth noting that our strategy for the fabrication
of 1D nanostructure is based on the modification of interlayer
interactions (van der Waals or hydrogen bonding) in layered
materials by exchange or substitution, leading to instability of
intralayer interactions.
Acknowledgment. This work was performed for the Hydrogen
Energy R&D Center, a 21st Century Frontier R&D Program, funded
by the Ministry of Science and Technology of Korea.
Supporting Information Available: FTIR spectra of Cu(OH)
nanorods and starting material, Cu (OH) NO (PDF). This material is
2
2
3
3
available free of charge via the Internet at http://pubs.acs.org.
Figure 2. FESEM images of (a) Cu2(OH)3NO3, exhibiting hexagonal thin
plates, (b) as-prepared Cu(OH)2, displaying unidirectionally aligned textures
on a hexagonal thin plate, and (c and d) end-sides of a hexagonal plate in
Cu(OH)2 arrays, exhibiting uniform rods in size of diameters (see
magnification)
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