Advances in Nanoparticles, 2013, 2, 32-38
http://dx.doi.org/10.4236/anp.2013.21007 Published Online February 2013 (http://www.scirp.org/journal/anp)
Deposition of Monodisperse Platinum Nanoparticles of
Controlled Size on Different Supports
Zinaida Kaidanovych, Yevhen Kalishyn, Peter Strizhak
L.V. Pisarzhevsky Institute of Physical Chemistry, The National Academy of Sciences of Ukraine, Kyiv, Ukraine
Email : z.kaida n ovych@gmail.c om, kali s hyn.yevhen@gma il.com
Received December 18, 2012; revised January 20, 2013; accepted January 30, 2013
ABSTRACT
Monodisperse platinum nanoparticles with controlled size were synthesized by polyol synthesis and supported on
γ-Al2O3, SiO2 and carbon nanotubes (CNT) by the colloid deposition method. The average size of Pt nanoparticles in
colloidal solutions and on supports was determined by TEM images and from XRD patterns. The size of Pt nanoparti-
cles supported on SiO2 and CNT determined from XRD patterns is in a good agreement with size obtained from the
TEM analyses. There were shown that no agglomeration and size changing of Pt nanoparticles on these supports were
observed. All these findings illustrate that the method of colloid deposition allows one to obtain catalyst with monodis-
perse platinum nanoparticles of controlled size deposited on different supports without changing the nanoparticle’s size
and morphology.
Keywords: Platinum Nanoparticles; Pt/γ-Al2O3; Pt/SiO2; Pt/CNT
1. Introduction
The pure suppo rted Pt nanopar ticles catalysts are of great
interest owing to their specific features resulting from
their size and morphology that are exploited as efficient
catalysts in both homogeneous and heterogeneous cata-
lytic technologies [1,2]. In addition, these have led to
investigate the dependence of catalytic activity on the
size and shape of Pt nanoparticles as well as the sur-
face-to-volume ratio and quantum size effect because of
their potential applications in electronics, catalysis, and
biology [1-5]. Performance of Pt nanosized catalysts is
affected by numerous factors, one of which is the nature
and structure of the support materials. Mostly studies of
platinum catalysts have been performed with the metal
supported on SiO2, Al2O3, MgO, zeolites, and carbon
[1-6]. Materials with supported Pt nanoparticles are
known to have good catalytic characteristics. For exam-
ple, carbon nanotubes (CNT) supported platinum catalyst
shows superior activity in catalytic oxidation of various
organic compounds [7,8]. Also, the electrocatalytic ac-
tivity of Pt/CNT towards methanol oxidations was dis-
covered [9].
Silica supported nanoparticles have been used to cata-
lyze a wide variety of reactions such as hydrogenations,
oxidations, and other organic synthetic reactions. A wide
variety of transition metal nanoparticles have also been
adsorbed onto Pt/SiO2 shows selective hydrogenation of
acetophenone [10] and high catalytic activity in ethanol
electrooxidation [11].
Platinum supported on alumina catalyzes a variety of
chemical reactions, particularly, processes used in oil
refinery [12]. Cubic platinum nanoparticles supported on
alumina have been used to catalyze the NO reduction
reaction [13]. It was observed a conversion of the low
index facets of the cubic nanoparticles to higher index
planes that occurs during the reaction conditions, which
is attributed to substantial changes in the catalytic activ-
ity and selectivity to reaction products [13]. A large
morphological evolution of large platinum nanoparticles
is also observed during the NO reduction reaction [14].
Moreover, Pt/γ-Al2O3 shows catalytic activity in ethylene
glycol reforming [15].
Discovery of carbon nanotubes (CNTs), followed by
extensive studies of their properties, has also resulted in
highlighting their catalytic properties [16-20]. Particu-
larly, comparison of the catalytic activity of metal cata-
lysts supported on various oxides, amorphous carbon,
and CNTs showed that catalytic performance is generally
better for CNTs. For example, a CNT-supported plati-
num catalyst shows superior activity in catalytic oxida-
tion of vario us organic compo un ds [ 19] .
Many studies show that size- and shape-controlled
metallic nanoparticles supported onto mesoporous mate-
rials are responsible in changing catalytic activity and
selectivity [21-24]. The metal-support interaction, which
refers to support-induced changes in reaction selectivity
of metal nanoparticles, has been shown mostly on 2-di-
mensional nanoparticle arrays on oxide substrates, be-
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opyright © 2013 SciRes. ANP

Z. KAIDANOVYCH ET AL. 33
cause the oxide thin films and corresponding catalysts
are easily prepared and characterized providing kinetic
differences which invokes different mechanisms [25,26].
However, there are some studies abou t deposition of col-
loidal Pt nanoparticles on different supports [27]. There is
no information about size changing of nanoparticles after
their deposition. A choice of support is vitally important
to improve catalytic characteristics, because a nanoparti-
cle-based catalyst can induce reciprocal electronic or
chemical interactions.
The goal of this study is to show that the method of
deposition from colloid solution gives a reliable root to
prepare catalyst with monodisperse Pt nanoparticles with
controlled size.
2. Experimental
All chemicals and solvent were of the highest purity
available and were used as purchased without further
purification or distillation.
A solution o f 3 g of Poly(N-vin yl-2-pyrrolido ne) (PVP,
Mw = 40,000) and 0.06 g of sodium hydroxide in 300 ml
ethylene glycol were heated to 120˚C under stirring.
Varying amounts (40, 60, 160, 240 and 360 ml) of 1%
hexachloroplatinic acid in water solution were dosed
slowly to the hot ethylene glycol. Next, the solutions
were stirred for an additional 30 min and cooled to room
temperature. PVP-protected Pt nanoparticles were pre-
cipitated by adding acetone and then redispersed in
ethanol.
CNTs were synthesized by the catalytic decomposition
of ethylene according to procedure described elsewhere
[28]. γ-Al2O3 and SiO2 was grinded and the fraction of
0.25 - 0.5 mm was heat-treated at 300˚C in air. Deposi-
tion of Pt nanoparticles on supports was performed by
mixing appropriate amounts of SiO2, γ-Al2O3 or CNTs
and colloidal solution of nanoparticles in ethanol under
stirring. The obtained samples were dried in air. The ob-
tained samples contained 1.0% of platinum.
The average particle size was determined from trans-
mission electron spectroscopy (TEM) images. TEM stud-
ies were carried out using PEM-125K (Selmi, Ukraine).
The samples of colloidal solution of nanoparticles for
TEM analysis were dropped onto carbon-coated copper
grid. The samples of Pt/support previously were grinded
into powder and mixed with drop of water. At least 600
nanoparticles per sample were analyzed to determine
their size and distribution.
The samples of γ-Al2O3, SiO2, CNTs, and Pt/support
were grinded into powder and analyzed using the X-ray
diffractometer Bruker D8 Advance. The mean particle
size also was determinate using the Scherrer equation:

0.9 cosD

 , (1)
where λ is the wavelength used (1.54184 Å), β is the line
broadening at half the maximum intensity in radians and
θ is the angle of diffraction.
3. Results and Discussion
Figures 1(a), (c), (e), (g) show a typical TEM images of
Pt nanoparticles in colloidal solutions prepared using
different amount of hexachloroplatinic acid. Figures 1(b),
(d), (f), (h) give corresponding size distributions of Pt
nanoparticles. The presented data indicate that the
nanoparticles are almost spherical. It was shown that the
average size of Pt nanoparticles depends on concentra-
tion of hexachloroplatinic acid. If the concentration of
hexachloroplatinic acid is 3.3 mmol/L than the average
size of Pt nanoparticles is 1.3 nm as it is shown in Figure
1(a). The 29.3 mmol/L of concentration of hexachloro-
platinic acid gives 3.1 nm of Pt nanoparticles. The av-
erage size of Pt nanoparticles in colloidal solution in-
creases from 1.3 to 3.1 nm with increasing of precursor
concentration. Corresponding size distribution of Pt nano-
particles is presented in Figures 1(b), (d), (f), (h) show-
ing that size distribution is almost Gaussian. All samples
are characterized by narrow width of particle size distri-
bution with typical standard deviations (SD) less than
15%. Therefore, the synthesized Pt nanoparticles are al-
most monodispersed.
Pt nanoparticles with average size in colloidal solutio n
2.8 nm (Figure 1(e)) were supported on γ-Al2O3, SiO2
and CNTs in order to determine their size changing after
deposition on different supports. Figures 2(a), (c), (e)
show typical TEM images of Pt nanoparticles supported
on γ-Al2O3, SiO2 and CNTs. The presented data indicate
that supported nanoparticles ar e not aggregating and stay
almost spherical. Figures 2(b)-(f) give corresponding
size distributions of supported Pt nanoparticles. The av-
erage size of supported Pt nanoparticles is nearly the
same as average size of those particles in solution –2.9
nm for Pt/γ-Al2O3 and 2.8 nm for Pt/SiO2 and Pt/CNTs.
Size distribution of supported Pt nanoparticles is almost
gaussian with nearly the same SD as for Pt nanoparticles
in solution 0.3 - 0.4 nm, what is amount less than 15% of
particles size. Therefore, the Pt nanoparticles on these
supports stay almost monodispersed as in solution. Com-
parison of data presented in Figures 1 and 2 allows one
to conclude that deposition of platinum nanoparticles on
γ-Al2O3, SiO2 and CNTs does not prod uce changing par-
ticles size and morphology.
In order to synthesis Pt/γ-Al2O3 with different size of
supported nanoparticles the concentration of hexachloro-
platinic acid in reaction solution was varying. The ob-
tained colloidal solutions of Pt nanoparticles with differ-
ent nanoparticles sizes were deposited on γ-Al2O3. The
mean sizes and standard deviations of supported nano-
particles were measured using their TEM images.

Z. KAIDANOVYCH ET AL.
34
(a) (b)
(c) (d)
(e) (f)
(g) (h)
Figure 1. TEM image of Pt nanoparticles prepared from colloidal solution (a, c, e, g); their distribution by size (b, d, f, h).

Z. KAIDANOVYCH ET AL. 35
(a) (b)
(c) (d)
(e) (f)
Figure 2. TEM image of Pt nanoparticles supported on γ-Al2O3 (a), SiO2 (c), CNT (e); their distribution by size (b), (d), (f)
respectively.
The obtained dependence presented in Figure 3. The
size of supported Pt nanoparticles increases non linear
with increasing the H2PtCl6 concentration, abruptly at
low amount of hexacloroplatinic acid and slightly at
higher precursor concentration. It is noticeable that for
larger particles the value of standard deviation is bigger,
but it is always less than 15% of mean size of the parti-
cles. Varying concentration of hexachloroplatinic acid in
reaction solution from 3.3 to 29.3 mmol/l allows one to
obtain Pt/γ-Al2O3 with average size of nanoparticles in
the range of 1. 3 - 3.3 nm.
The XRD patterns were obtained for all solids. Figure
4(a) gives the XRD pattern for γ-Al2O3 and Pt/γ-Al2O3.
The major features of Pt pattern overlaps with that for

Z. KAIDANOVYCH ET AL.
36
Figure 3. Dependence of average size of Pt nanoparticles
supported on γ-Al2O3 on concentration of hexachloroplatini c
acid in reaction solution.
γ-Al2O3, that is in agreement with data published in lit-
erature [29]. Figure 4(b) shows the XRD patterns for
SiO2 and Pt/SiO2. The XRD pattern for Pt/SiO2 shows a
presence of the crystalline Pt face centered cubic (fcc)
phase. The peaks belong to (111), (200), (220) faces cor-
responding to 2θ values of about 39.72˚, 46.08˚, 67.65˚.
The XRD peaks of Pt nanoparticles are broad and com-
parable comparing to those of the bulk Pt material. The
most intensive reflection (111) from the Pt nanoparticles
were used to calculate the average size of Pt nanocrystal-
lites on the basic of the width of the reflection according
to the Debye-Scherrer Equation (1). The crystallite size
of Pt particle was estimated about 4 nm, which is in a
good agreement with results of TEM analyses.
Figure 4(c) gives the results of XRD analysis of CNT
and Pt/CNT. The results represent the property of the
crystalline Pt face centered cubic (fcc) phase. Because of
the low concentration of Pt nanoparticles an d high inten-
sivity of CNTs reflections it is p ossible to determine on ly
the most intensive peak (111) of Pt, respective to 2θ
value of about 39.55˚. The estimated size of platinum
nanoparticles based on the Debye-Scherrer equation was
found about 4 nm, that is, again, in a good agreement
with results of TEM analyses.
4. Conclusions
In this study, nanoparticles with controlled size were
synthesized by reducing of hexachloroplatinic acid by
ethylene glycol, using PVP as protected agent. These
nanoparticles were deposited on γ-Al2O3, SiO2 and car-
bon nanotubes by the colloid deposition method. No ag-
glomeration of platinum nanoparticles on all of these
supports was observed. The average size determined by
TEM images of nanoparticles deposited on different
supports corresponds to their size in colloid solution be-
fore deposition. Deposition of platinum nanoparticles on
(a)
(b)
(c)
Figure 4. The XRD patterns of (a) γ-Al2O3 and Pt/γ-Al2O3;
(b) SiO2 and Pt/SiO2; (c) CNT and Pt/CNT.
γ-Al2O3, SiO2 and CNTs does not lead to changing of
particles size and morphology. The var ying of concentra-
tion of hexachloroplatinic acid in reaction solution allows
to obtain Pt/γ-Al2O3 with controlled size of monodisperse
Pt nanoparticles.
According to XRD analysis, supported platinum nano-
particles have the face centered cubic phase. The size of
Pt nanoparticles supported on SiO2 and CNT determined
from XRD patterns is in a good agreement with size ob-
tained from the TEM analyses.

Z. KAIDANOVYCH ET AL. 37
Therefore we show that the method of colloid deposi-
tion allows one to obtain catalyst with monodisperse
platinum nanoparticles of controlled size deposited on
different supports without changing the nanoparticle’s
size and morphology.
5. Acknowledgements
The work is supported by the grants of the National
Academy of Sciences of Ukraine and the Ministry of
Education and Science of Ukraine.
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