Tuning the Architecture of Mesostructures by Electrodeposition

Article abstract of DOI:10.1021/ja0315154

When the dimension of materials decreases to mesoscale, their properties can change dramatically, depending on the boundary conditions imposed by the sample architecture including geometry, morphology, and hierarchical structures. Here we show that electrodeposition, a method for reducing materials from a solution onto a substrate, can provide a versatile pathway to tailor the architecture of mesostructures. Novel lead (Pb) structures ranging from nanowires, mesoparticles with octahedral, decahedral, and icosahedral shapes to porous nanowires, multipods, nanobrushes, and even snowflake-shaped structures were synthesized through systematically exploring electrodeposition parameters including reduction potentials, solution concentration, starting materials, supporting electrolytes, and surfactants. Copyright

Full text of DOI:10.1021/ja0315154

Published on Web 02/10/2004
Tuning the Architecture of Mesostructures by Electrodeposition
Zhi-Li Xiao,* Catherine Y. Han, Wai-Kwong Kwok, Hsien-Hau Wang, Ulrich Welp, Jian Wang, and
George W. Crabtree
Materials Science DiVision, Argonne National Laboratory, Argonne, Illinois 60439
Received December 4, 2003; E-mail: xiao@anl.gov
The physical and chemical properties of mesostructures1 depend
on their architectures, including geometry, morphology and hier-
archical structures, and can be fine-tuned by controlling these
parameters.2,3 The synthesis of mesostructures with well-controlled
architectures opens new pathways for the development of future
nanodevices. Various methods including template synthesis,4,5 vapor
deposition,6 and colloidal synthesis7,8 have demonstrated success
in fabricating certain architectures, such as cylindrical cobalt
nanowires,5 triangular platinum2 and cubic silver8 nanoparticles,
zinc oxide in the forms of nanobelts, nanosprings, and other novel
hierarchical nanostructures.9,10 Here we show that electrodeposi-
tion1,11 can provide versatility in tailoring the architectures of
mesostructures. Novel lead (Pb) mesostructures ranging from
nanowires with cylindrical and square cross sections to mesopar-
ticles with triangular, hexagonal, octahedral, decahedral, and
icosahedral shapes and complicated structures such as multipods,
porous nanowires, nanobrushes, and snowflakes were synthesized
through systematically exploring electrodeposition parameters.
To obtain individual particles or clusters, the surface energy of
the substrate (working electrode) needs to be much smaller than
that of the deposits, leading to island formation through a Volmer-
Weber growth mode.1 All the results reported here were obtained
by using the basal planes of highly oriented pyrolytic graphite
(HOPG) as substrates. The architecture of the deposits is strongly
affected by the growth rate, controlled by the electrolyte concentra-
tion. The best concentration range for growing lead mesostructures
Figure 1. Architecture evolution with applied potential for solution
containing 5 mM lead nitrate and 0.1 M boric acid. The reduction potentials
with controlled architectures is from 1 to 10 mM (most experiments
were carried out with a concentration of 5 mM). Hydrogen evolution
resulting from the proton reduction is very sensitive to the pH value
of the solution, which can be adjusted by the supporting electrolyte.
Macroscopic hydrogen bubbles could be seen at reduction potential
below -1 V when the pH value was below 3. The supporting
electrolyte we used is boric acid with a pH value of 4.80 at a
concentration of 0.1 M.
Scanning electron microscopy images of mesostructures obtained
at various reduction potentials with starting materials of lead nitrate
and lead acetate are delineated in Figures 1 and 2, respectively. In
general, mesoparticles (icosahedron, decahedron, and octahedron
in Figure 1a-c; icosahedron, decahedron, hexagon, and triangle
in Figure 2a-d, respectively) form at applied voltages close to the
thermodynamic equilibrium potential, while nanowires (Figures 1d,e
and 2g), nanobrushes (Figures 1f and 2h), and monopods and
multipods (Figure 2e,f) are obtained at high reduction potentials.
However, there are differences in the morphology of the deposits,
depending on the starting material. For example, the surfaces of
the mesoparticles initiated with lead nitrate are considerably
smoother than those obtained with lead acetate. The cross sections
of the nanowires are square with lead acetate and cylindrical with
lead nitrate precursors. The symmetry of the nanobrushes changes
from random to four-fold when lead nitrate is replaced with lead
acetate or lead chloride (left panel in the graphic shown on the
for a-f are -0.8, -0.95, -1.1, -1.2, -1.7, and -2.0 V, respectively. The
scale bar length is 500 nm. The growth time is 60 s.
Table of Contents for this Communication). Furthermore, mesos-
tructures such as monopods and multipods appear only in solution
containing acetate or chloride.
The shape evolution from mesoparticles to nanowires and
multipods with increasing reduction potentials parallels the findings
in colloidal synthesis,7 where the formation of nanowires and other
elongated structures requires an environment with a high electro-
chemical potential achieved with high monomer concentrations. In
electrodeposition, the reduction potential equals the electrochemical
potential of the electrode and that of the deposited materials. With
increasing reduction potential, structures with higher chemical
potential and higher aspect ratio such as nanowires are expected to
form on the cathode. In fact, the appearance of mesoparticles
follows the sequence of their specific surface energies that determine
their chemical potentials. For example, icosahedra-shaped meso-
particles appear at the lowest reduction potential because an
icosahedron has the lowest specific surface energy, followed by a
decahedron.12 In colloidal synthesis, some capping molecules can
block certain faces and enhance growth of other facets, leading to
the formation of multipods at high monomer concentration. The
electrodeposited multipods shown in Figure 2 indicate that acetic
and chloric anions have similar preference for certain facets of the
lead structure and serve as effective capping agents.
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C O M M U N I C A T I O N S
affect the architecture of the mesostructures. For example, snowflake-
shaped mesostructures were observed in the presence of ethanol
(right panel of the graphic in Table of Contents for this Com-
munication). Truncated mesoparticles appeared when nitric anions
were partially replaced with acetic anions. As shown in the
Supporting Information, high yields of these mesostructures can
be produced, though more effort is needed to achieve monodis-
persive architectures. In summary, the abundance of controllable
parameters enables electrodeposition to be a versatile and facile
pathway to fabricate mesostructures with novel architectures. We
also show that electrodeposition provides a convenient way to
pursue the architecture-formation mechanisms of mesostructures
that will enable scientists to tailor mesostructures of other emerging
systems and to seek for novel fundamental phenomena and for new
applications.
Acknowledgment. This work was supported by the U.S.
Department of Energy, BES-Materials Science, Contract No. W-31-
109-ENG-38. Z.L.X. also acknowledges support from the Consor-
tium for Nanoscience Research at Argonne National Laboratory
and the University of Chicago. Electron microscopy was carried
out in the Electron Microscopy Center at Argonne. We are also
thankful for M. P. Zach’s comments.
Supporting Information Available: More experimental details and
some SEM images at low magnifications. This materials is available
free of charge via the Internet at http://pubs.acs.org.
References
(1) Mesoscopic structures are characterized by dimension scale ranging from
10 nm to micrometers. See: Penner, R. M. J. Phys. Chem. B 2002, 106,
3339-3353.
(2) Ahmadi, T. S.; Wang, Z. L.; Green, T. C.; Henglein, A.; El-Sayed, M. A.
Science 1996, 272, 1924-1926.
(3) (a) Xu, Z.; Xiao, F. S.; Purnell, S. K.; Alexeev, O.; Kawi, S.; Deutsch, S.
E.; Gates, B. C. Nature 1994, 372, 346-348. (b) Alivisatos, A. P. Science
1996, 271, 933-937. (c) Bruchez, M., Jr.; Moronne, M.; Gin, P.; Weiss,
S.; Alivisatos, A. P. Science 1998, 281, 2013-2016. (d) Bezryadin, A.;
Lau, C. N.; Tinkham, M. Nature 2000, 404, 971-974.
(4) Hulteen, J. C.; Martin, C. R. J. Mater. Chem. 1997, 7, 1075-1087.
(5) (a) Whitney, T. M.; Jiang, J. S.; Searson, P. C.; Chien, C. L. Science
1993, 261, 1316-1319. (b) Thurn-Albrecht, T.; Schotter, J.; Kastle, C.
A.; Emley, N.; Shibauchi, T.; Krusin-Elbaum, L.; Guarini, K.; Black, C.
T.; Tuominen, M. T.; Russell, T. P. Science 2000, 290, 2126-2129.
(6) (a) Duan, X. F.; Huang, Y.; Cui, Y.; Wang, J. F.; Lieber, C. M. Nature
2001, 409, 66-69. (b) Gudiksen, M. S.; Lauhon, L. J.; Wang, J.; Smith,
D. C.; Lieber, C. M. Nature 2002, 415, 617-620.
Figure 2. Architecture evolution with reduction potential for solution
containing 5 mM lead acetate and 0.1 M boric acid. The reduction potentials
for a-h are -0.65, -0.8, -1.0, -1.1, -1.3, -1.4, -1.6, and -1.9 V,
respectively. The scale bar length is 500 nm. The growth time is 60 s.
The novel shapes of icosahedron, decahedron, and octahedron
lead mesostructures obtained at applied voltages close to the
equilibrium potential can be understood with a model based on a
modified Wulff construction for shape formation used to interpret
the organization of thermally annealed gold and silver particles and
clusters of inert gas atoms.12 According to this model, which
minimizes the total surface and twin-boundary energies of an
assembly of single-crystal units at constant volume, the polyhedra
can be described as a collection of single-crystal tetrahedra that
are twin-related at their adjoining faces. For examples, five
tetrahedra arranged symmetrically about an axis form a decahedron,
and 20 tetrahedra in a three-dimensional configuration assembled
about a common vertex produce an icosahedron. A strong evidence
for this interpretation is the observation of the theoretically predicted
notches12 at the twin boundaries of a decahedron, as shown in Figure
1b. The formation mechanisms for porous nanowires and nano-
brushes are still under investigation. Possible scenarios can be
hydrogen evolution, the capping effect at high growth rate, or an
oscillatory behavior in the nucleation kinetics that can result in
branched structures.13 Other electrodeposition parameters can also
(7) (a) Peng, X. G.; Manna, L.; Yang, W. D.; Wickham, J.; Scher, E.;
Kadavanich, A.; Alivisatos, A. P. Nature 2000, 404, 59-61. (b) Manna,
L.; Scher, E. C.; Alivisators, A. P. J. Am. Chem. Soc. 2000, 122, 12700-
12706. (c) Jun, Y. W.; Jung, Y. Y.; Cheon, J. J. Am. Chem. Soc. 2001,
123, 5150-5151. (d) Jana, N. R.; Gearheart, L.; Murphy, C. J. J. Phys.
Chem B 2001, 105, 4065-4067. (e) Puntes, V. F.; Krishnan, K. M.;
Alivisatos, A. P. Science 2001, 291, 2115-2117. (f) Lee, S. M.; Jun,
Y.-W.; Cho, S. N.; Cheon, J. J. Am. Chem. Soc. 2002, 124, 11244-11245.
(g) Peng, X. AdV. Mater. 2003, 15, 459-463.
(8) Sun, Y.; Xia, Y. Science 2002, 298, 2176-2179.
(9) (a) Pan, Z. W.; Dai, Z. R.; Wang, Z. L. Science 2001, 291, 1947-1949.
(b) Kong, X. Y.; Wang Z. L. Nano Lett. 2003, 3, 1625-1631.
(10) (a) Gao, P.; Wang, Z. L. J. Phys. Chem. B 2002, 106, 12653-12658. (b)
Lao, J. Y.; Wen, J. G.; Ren, Z. F. Nano Lett. 2002, 2, 1287-1292. (c)
Tian, Z. R.; Voigt, J. A.; Liu, J.; Mckenzie, B.; Mcdermott, M. J.;
Rodriguez, M. A.; Konishi, H.; Xu, H. Nature Mater. 2003, 2, 821-826.
(11) Zach, M. P.; Ng, K. H.; Penner, R. M. Science 2000, 290, 2120-2123.
(12) (a) Marks, L. D. Philos. Mag. A 1984, 49, 81-83. (b) Marks, L. D. Rep.
Prog. Phys. 1994, 57, 603-649.
(13) Fleury, V. Nature 1997, 390, 145-148.
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