Palladium nanoparticle arrays using template-assisted electrodeposition

Article abstract of DOI:10.1063/1.1572465

Palladium nanoparticle arrays were investigated using template-assisted electrodeposition. Scanning electron microscopy and energy dispersive spectroscopy were used to characterize Al film on a polymeric substrate. High-resolution transmission electron microscopy results showed that Pd nanoparticles consisted of a large number of nanocrystallites in the size range of 5-10 nm.

Full text of DOI:10.1063/1.1572465

Palladium nanoparticle arrays using template-assisted electrodeposition
D. Bera, S. C. Kuiry, S. Patil, and S. Seal
Citation: Applied Physics Letters 82, 3089 (2003); doi: 10.1063/1.1572465
View online: http://dx.doi.org/10.1063/1.1572465
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APPLIED PHYSICS LETTERS
VOLUME 82, NUMBER 18
5 MAY 2003
Palladium nanoparticle arrays using template-assisted electrodeposition
D. Bera, S. C. Kuiry, S. Patil, and S. Seala)
Advanced Materials Processing Center (AMPAC), and Mechanical, Materials and Aerospace Engineering
(MMAE), Surface Engineering and Nanotechnology Facility, Eng. 1, No. 381, University of Central
Florida, 4000 Central Florida Boulevard, Orlando, Florida 32816
͑Received 14 November 2002; accepted 12 March 2003͒
Palladium nanoparticles are being increasingly considered as room-temperature hydrogen sensors
and storage materials. Pd nanoparticle arrays have been synthesized using template-assisted
electrodeposition. The template based on Al film on a polymeric substrate was characterized by
scanning electron microscopy and energy dispersive spectroscopy. X-ray photoelectron
spectroscopy study confirmed that the deposited nanoparticles were of metallic Pd. High-resolution
transmission electron microscopy investigation revealed that Pd nanoparticles consisted of a large
number of nanocrystallites in the size range of 5–10 nm. © 2003 American Institute of Physics.
͓DOI: 10.1063/1.1572465͔
Metal nanomaterials in various forms such as wire, rod,
tube, and spherical shapes are of great interest1–3 as compo-
nents of technologically important microsystems for gas
sensing and other systems pertaining to hydrogen storage,
with the cross section of the Pt layer which was deposited on
the template-surface prior to FIB milling to protect it from
the ion beam. Energy dispersive spectroscopy ͑EDS͒ spec-
trum of the top surface of template prior to Pd deposition, as
shown in Fig. 1͑b͒, confirms the presence of aluminum, car-
bon, and oxygen. Carbon and oxygen peaks in the EDS spec-
magnetic
storage
media,
electrical
and
optical
applications.4–7 Template and step-edge methods8 are used
for the preparation of metallic nanowires and nanorods of Pt,
Au, and Mo. Synthesis of mesoscopic wires of palladium
through the step-edge method has also been reported4 using a
graphite surface as an electrode. Pd nanoparticles and nano-
rods in the form of periodic arrays are of great importance
because of their potential applications for sensing4 and stor-
age of hydrogen at room temperature. However, an easy and
versatile method for the synthesis of uniformly spaced arrays
of Pd nanoparticles and nanorods with a narrow size distri-
bution is yet to be reported for aforesaid applications. The
present study is an attempt to develop a method to synthesize
arrays of Pd nanoparticles combining template and elec-
trodeposition processes.
Palladium nanoparticles were deposited on the surface of
a template through potentiostatic electrodeposition at 0.3 V
for 400 s from a 2mM palladium nitrate solution using
EG&G Potentiostatic Instruments ͑Model 263A͒. The cur-
rent density was optimized in the range of 8–20 ␮A cmϪ2
under such electrochemical conditions. The template used in
the present investigation was an aluminum thin film on top
of a polycarbonate substrate derived from a compact disk.
Regular arrays of circular- and oblong-shaped holes were
formed on the top surface of the aluminum thin film with the
help of a compact disk drive with data recording capability
using a laser. The surface morphology and the cross section
of the blank template have been characterized using scanning
electron microscopy ͑SEM͒ ͑Model: JEOL T-300͒ and fo-
cussed ion beam ͑FIB͒ equipment ͓Model: FEI FIB 200
transmission electron microscope ͑TEM͔͒, respectively. Fig-
ure 1͑a͒ presents SEM micrograph of such periodic holes or
pits on the aluminum substrate. An FIB image of the cross
sections of two pits are shown in the inset of Fig. 1͑a͒ along
FIG. 1. ͑a͒ SEM micrograph of the top surface and FIB cross section show-
ing the depth of the holes ͑inset͒ of template prior to Pd deposition, and ͑b͒
corresponding EDS spectrum.
a͒
Electronic mail: sseal@pegasus.cc.ucf.edu
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0003-6951/2003/82(18)/3089/3/$20.00 3089 © 2003 American Institute of Physics
128.235.8.170 On: Thu, 11 Dec 2014 19:45:30

3090
Appl. Phys. Lett., Vol. 82, No. 18, 5 May 2003
Bera et al.
FIG. 2. ͑a͒ SEM micrograph of the array of Pd-nanoparticles clusters after
electrodeposition on the templates, and ͑b͒ Pd(3d) XPS envelope.
trum have come from the polycarbonate film which was
present underneath the aluminum thin film. Figure 2͑a͒
shows the SEM micrograph of the template after the elec-
trodeposition of Pd nanoparticles. Figure 2͑b͒ shows the
x-ray photoelectron spectroscopy ͑XPS͒ spectrum of Pd(3d)
envelope confirming the metallic Pd particles. XPS spectrum
was collected using PHI 5400 ESCA system. XPS Pd(3d5/2
)
and Pd(3d3/2) peaks were observed at binding energy values
of 335.9 and 341.2 eV, respectively. Such binding energy
values are similar to that reported for Pd metals in literature.9
Figure 2͑a͒ suggests that the stable Pd nuclei were pref-
erably nucleated at the holes of the templates. Subsequent to
exposure to the electrochemical system, the growth of such
nuclei took place eventually filling the pits. Further passage
of electrical current resulted in an overgrowth of particles.
Hence, the present study indicates that the size of these
template-assisted electrodeposited Pd particles can be con-
trolled by controlling the time and electrical current density
in the electrodeposition process. Pd arrays have been pre-
pared using the aforementioned template for their preferen-
tial growth at the holes. Although the exact reason of such
preferential nucleation is not clear at this time, however, the
influence of topography may not be ruled out. The effect of
curvature on altering the electrical charge density at the pits
may have possibly created a situation for easy nucleation at
these locations. The SEM micrograph in Fig. 2͑a͒ revealed
that the Pd particles were oriented as per the orientation of
the holes in the template. Such preferentially deposited Pd
FIG. 3. ͑a͒ FIB lift-out on a Cu grid showing cross section of agglomerated
Pd particles, ͑b͒ HRTEM image showing Pd nanocrystallites, and ͑c͒ SAED
pattern.
form nanowires under controlled conditions, which can be
used for hydrogen sensing applications.
Further examination reveals that these nanoparticles as
shown in Fig. 2͑a͒ consisted of a number of smaller nano-
particles. High-resolution TEM ͑HRTEM͒ study was carried
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nanoparticles could eventually be grown longitudinally to
out to investigate the size and structure of the individual
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Appl. Phys. Lett., Vol. 82, No. 18, 5 May 2003
Bera et al.
3091
nanocrystallite. A protective platinum coating was given on
Pd particles grown on the templates using the FIB and milled
to have a 200 nm thick Pd agglomerates lift-out specimen as
shown in Fig. 3͑a͒. The lift-out specimen was subsequently
used for HRTEM ͑Model: Philips 300 TECNAI͒ study at 300
kV. The HRTEM image of one such agglomerated particle is
shown in Fig. 3͑b͒, which reveals the presence of a number
of nanocrystallites of Pd in the size range of 5–10 nm. The
selected area electron diffraction ͑SAED͒ pattern of the Pd
crystallites is presented in Fig. 3͑c͒, which confirms the face-
centered-cubic lattice structure of these nanocrystallites.
The array of Pd nanoparticles with controlled size and
shape was synthesized using an easy procedure that com-
bines the template and the electrodeposition methods. Such
nanoparticles consist of a number of nanocrystallite Pd,
which are ideal starting materials for hydrogen sensing and
storage devices. These nanoparticle arrays can be grown in
the templates under a controlled manner leaving a nanospac-
ing between two adjacent particulates for the sensing of hy-
drogen gas at room temperature with high sensitivity.
The authors would like to thank the NSF for Grant Nos.
EEC 0136710 and 0085639, FSEC-NASA Glenn, Florida
Space Grant Consortium, and MCF facilities at AMPAC,
UCF, Orlando for financial and equipment supports.
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