A novel route for the preparation of monodisperse silver nanoparticles via a pulsed sonoelectrochemical technique

Article abstract of DOI:10.1016/j.inoche.2004.02.003

Monodisperse silver nanoparticles stabilized with PVP have been prepared in a saturated solution of silver citrate (Ag₃C₆H ₅O₇) in the presence of poly(vinyl pyrrolidone) (PVP) by a pulsed sonoelectrochemical technique.

Full text of DOI:10.1016/j.inoche.2004.02.003

Inorganic Chemistry Communications 7 (2004) 506–509
www.elsevier.com/locate/inoche
A novel route for the preparation of monodisperse silver
nanoparticles via a pulsed sonoelectrochemical technique
*
Li-Ping Jiang, An-Ning Wang, Yu Zhao, Jian-Rong Zhang, Jun-Jie Zhu
Department of Chemistry, State Key Laboratory of Coordination Chemistry, Institute of Analytical Science, Nanjing University, Nanjing 210093, China
Received 15 January 2004; accepted 6 February 2004
Published online: 4 March 2004
Abstract
Monodisperse silver nanoparticles stabilized with PVP have been prepared in a saturated solution of silver citrate (Ag3C6H5O7)
in the presence of poly(vinyl pyrrolidone) (PVP) by a pulsed sonoelectrochemical technique.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Sonoelectrochemistry; Silver; Nanoparticles; PVP
Noble metal nanoparticles have been extensively
studied in recent years because of their unique catalytic,
electric, magnetic, optical and mechanical properties that
are different from bulk materials [1–4]. Therefore, vari-
ous approaches have been employed for the preparation
of nanosized metal particles. These approaches include
the following: solution phase method [5–8], laser abla-
tion [3], sonochemical method [9,10], electrochemical
synthesis [11–14] and so on. Among the noble metal
nanoparticles, silver nanoparticles have been widely
studied. Silver nanoparticles have various important
applications in many aspects such as photographic pro-
cess [15], surface-enhanced Raman spectroscopy [2] and
catalysis process[10]. It is well known that the catalytic
reactivity of metal nanoparticles depends on their size
and shape greatly. Therefore, it is very essential to de-
velop a simple and effective preparation method of metal
nanoparticles for well-controlled size and shape.
which enable many chemical reactions to occur. In re-
cent years, sonochemistry combined with electrochem-
istry have attracted great interest. Reisse et al. [18] and
Mason [19] have described a novel method for the
production of particulate metals, alloys and semicon-
ductors using a pulsed sonoelectrochemical reduction.
With this method, several kinds of metal and semicon-
ductors nanoparticles have been prepared [13,14,18–21].
In the present paper, a novel route was used to pre-
pare monodisperse silver nanoparticles in a saturated
solution of silver citrate in the presence of poly(vinyl
pyrrolidone) (PVP) by a pulsed sonoelectrochemical
technique. The products were characterized by powder
X-ray diffraction (XRD), transmission electron micro-
scope (TEM) and UV–Vis spectroscopy. The influence
of current density and the concentration of PVP were
also discussed in the present paper.
In the experiments, all chemicals were of analytical
grade and were used without further purification. The
experimental setup employed in this study was similar to
those of Reisse et al. and Gedanken et al. [13,20,21].
Ultrasound irradiation was accomplished with a high-
intensity ultrasonic probe (Xinzhi Co., China, JY92-2D,
0.6 cm diameter; Ti-horn, 20 kHz). A titanium horn acts
both as the cathode and the ultrasound emitter. The
electroactive part of the sonoelectrode is the planar
circular surface, of area 0.28 cm2, at the bottom of the
Sonochemical method has been used extensively to
generate novel materials with unusual properties since
1934. The chemical effects of ultrasonic irradiation are
due to the very high temperature and pressure that are
transiently formed (sub-ls) in collapsing bubbles [16,17],
* Correspondence author. Tel.: +86-25-3594976; fax: +86-25-
3317761.
E-mail address: jjzhu@netra.nju.edu.cn (J.-J. Zhu).
1387-7003/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2004.02.003

L.-P. Jiang et al. / Inorganic Chemistry Communications 7 (2004) 506–509
507
3000
2500
2000
1500
1000
500
horn. The immersed cylindrical part is covered by an
isolating plastic jacket. The sonoelectrode produces a
sonic pulse that is triggered immediately following a
current pulse [14]. The home-made potentiostat is op-
erated in the constant current regime (without using a
reference electrode). The basis of the sonoelectrochem-
ical technique to form nanoparticles is massive nucle-
ation by using a current pulse, followed by a burst of
ultrasonic pulse that removes the deposit from the
electrode before the next current pulse. The typical
current pulses were 70 mA/cm2. The duration of the
current pulse was 3 s and the duration of ultrasonic
pulse was also 3 s. A platinum sheet (5 ꢀ 5 mm2) was
used as the counter electrode in our electrochemical cell.
The volume of electrolysis cell was 50 ml.
(111)
(200)
(220)
(311)
0
40
60
2θ/degree
80
Fig. 1. The XRD patterns of the prepared silver nanoparticles.
The XRD pattern was recorded using a Philp XÕpert
X-ray diffractometer. The TEM images were recorded
on a JEOL JEM-200CX transmission electron micro-
scope, using an accelerating voltage of 200 kV. The
UV–Vis absorption spectrum was obtained using a
SHIMADZU UV–3100 spectrophotometer, the pre-
pared silver nanoparticles were dispersed in distilled water
under ultrasound, and the concentration of silver nano-
particles was 1.2 ꢀ 10ꢁ2 mol/l.
Silver citrate was prepared as follows: 0.05 mol so-
dium citrate (Na3C6H5O7 ꢂ 2H2O) and 0.15 mol silver
nitrate (AgNO3) were dissolved in water, respectively,
then Na3C6H5O7 solution was added dropwise into the
AgNO3 solution, and white silver citrate (Ag3C6H5O7)
began to precipitate. The prepared Ag3C6H5O7 was
centrifuged, washed by distilled water, absolute alcohol
in sequence and dried in air. A pH ¼ 4.6 NaAc–HAc
buffer solution was prepared according to the literature
[22]. In a typical synthesis, 0.15 g Ag3C6H5O7 was dis-
solved in a pH ¼ 4.6 NaAc–HAc buffer solution, and the
concentration of poly(vinyl pyrrolidone) (PVP-K30,
Mw 40,000) is 0.2 g/l. The electrolyte volume was 40 ml.
The pulsed sonication was continued for an hour. After
that, aqua ammonia was added into the solution in or-
der to remove remnant reaction materials. Then the
precipitate was centrifuged, washed repeatedly with
water, alcohol and dried in air. The products were
characterized by XRD, TEM and UV–Vis spectroscopy.
Fig. 1 is the typical powder XRD pattern of the
prepared silver nanoparticles. The diffraction peaks
correspond to the (1 1 1), (2 0 0), (2 2 0) and (3 1 1)
planes, which can be indexed to a face-centered cubic
structure (JCPDS no. 4-0787).
Fig. 2. TEM image of the prepared silver nanoparticles.
0.5
0.4
0.3
0.2
0.1
0.0
5
10
15
20
25
30
35
As is shown in Fig. 2, the prepared silver nanoparticles
were spherical and monodisperse and the prepared silver
nanoparticles have an average size of 20–25 nm. Fig. 3
indicates that the particle size distribution is very narrow
and is in accord with Gaussian distribution. Fig. 4 is the
UV–Vis absorption spectrum of the prepared silver
nanoparticles. The absorption peak centered at 410 nm is
the characteristic peak for silver nanoparticles [11,13,23].
diameter (nm)
Fig. 3. The particle size distribution of the prepared silver nanoparti-
cles.
Current density affects the size and shape of the
prepared silver nanoparticles. According to [24], current
density can affect crystal size in at least two opposing

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L.-P. Jiang et al. / Inorganic Chemistry Communications 7 (2004) 506–509
1.0
0.5
0.0
tained (Fig. 5(a)). When the current was set as 140 mA/
cm2, the products had a larger size and some of them
even agglomerated (Fig. 5(b)). This indicates that the
former effect is dominant in this case, that is, small
amount of material deposited at a lower current.
The presence of PVP is a key factor for the formation
of monodisperse silver nanoparticles. When PVP was
not used, silver dendrites became the main products
(Fig. 6(a)); when the concentration of PVP was used as
0.1 g/l, agglomerated silver nanoparticles were the main
products (Fig. 6(b)); when the concentration of PVP
increased to 0.2 g/l, spherical monodisperse silver
nanoparticles formed. It can be interpreted as follows:
the electrodeposition is carried out in a saturated solu-
tion of Ag3C6H5O7, in which there is dissociation
equilibrium as follows:
300
400
500
600
700
800
900
Wavelength (nm)
Fig. 4. UV–Vis absorption spectrum of the prepared silver nanopar-
ticles the as-prepared silver nanoparticles.
Ag3C6H5O7 ꢀ3Agþ þ C6H5O3ꢁ
7
Therefore, the concentration of Agþ could be controlled
through this equilibrium in a certain buffer solution of a
certain pH value. PVP could serve as one kind of stabi-
lizer which prevents the prepared silver nanoparticles from
being agglomerated [5,9,11]. PVP molecules have a
structure of a polyvinyl skeleton with polar groups and
they strongly adsorb on the surface of silver particles
through the coordination bond between the silver atom and
oxygen atom of the carbonyl group. When PVP was not
directions. A smaller size would be expected, on the
basis of the small amount of material deposited at a
lower current. On the other hand, lower current density
allow more time for atomic diffusion processes to occur
which can lead to larger crystal size. Fig. 5 shows the
TEM images of silver nanoparticles under different
current density. When current density was set as 70 mA/
cm2, monodisperse silver nanoparticles could be ob-
Fig. 5. Silver nanoparticles prepared under different current density: (a) 70 mA/cm2; (b) 140 mA/cm2.
Fig. 6. Silver nanoparticles prepared under different concentration of PVP (a) without PVP (b) 0.1 g/l PVP.

L.-P. Jiang et al. / Inorganic Chemistry Communications 7 (2004) 506–509
[2] E.J. Bjerneld, F. Svedberg, M. Kall, NanoLett. 3 (2003) 593.
509
used, the prepared silver nanoparticles agglomerated
to be dendritic crystals through ‘‘diffusion-limited ag-
gregate’’ [13,25]; when 0.1 g/l PVP was used, silver
nanoparticles were less agglomerated; when the con-
centration of PVP became 0.2 g/l, monodisperse silver
nanoparticles stabilized with PVP were the main products.
In summary, the spherical monodisperse silver nano-
particles stabilized with PVP were prepared by a pulsed
sonoelectrochemical technique. Saturated solution of
Ag3C6H5O7 precipitate was used as the starting material
in our experiments. The residual Ag3C6H5O7 could be
removed through the addition of aqua ammonia so that
the products could be purified easily. The shape of pre-
pared silver nanoparticles could be controlled by varying
the current intensity of the electrodeposition and the
concentration of PVP. Thus, a novel method could be
applied to prepare monodisperse silver nanoparticles.
This convenient and simple method could be also applied
to other precipitate of metal ions with other organic acid.
[3] C.B. Hwang, Y.S. Fu, S.J. Yu, J. Catal. 195 (2000) 336.
[4] G. Schmid, Chem. Rev. 92 (1992) 1709.
[5] I. Pastoriza-Santos I, L.M. Liz-Marzan, Langmuir 18 (2002)
2888.
[6] Y.D. Yin, Z.Y. Li, Z.Y. Zhong, B. Gates, Y.N. Xia, S.
Venkateswaran, J. Mater. Chem. 12 (2002) 522.
[7] X.Z. Lin, X. Teng, H. Yang, Langmuir 19 (2003) 10081.
[8] P. Raveendran, J. Fu, S.L. Wallen, J. Am. Chem. Soc. 125 (2003)
13940.
[9] G. Carotenuto, Appl. Organometal. Chem. 15 (2001) 344.
[10] K. Okitsu, A. Yue, S. Tanabe, H. Matsumoto, Chem. Mater. 12
(2000) 3006.
[11] B.S. Yin, H.Y. Ma, S.Y. Wang, S.H. Chen, J. Phys. Chem. B 107
(2003) 8898.
[12] R.M. Penner, J. Phys. Chem. B 106 (2002) 3339.
[13] J.J. Zhu, S.W. Liu, O. Palchik, Y. Koltypin, A. Gedanken,
Langmuir 16 (2000) 6396.
[14] X.F. Qiu, J.Z. Xu, J.M. Zhu, J.J. Zhu, S. Xu, H.Y. Chen,
J. Mater. Res. 18 (2003) 1399.
[15] M. Mostafari, J.L. Marignier, J. Amblard, J. Belloni, Radiat.
Phys. Chem. 34 (1989) 605.
[16] K.S. Susilck, A.A. cichowlas, M.W. Grinstaff, Nature 353 (1991)
414.
[17] Y.T. Didenko, W.B. McNamara, K.S. Suslick, J. Am. Chem. Soc.
121 (1999) 5817.
Acknowledgements
[18] J. Reisse, H. Francois, J. Vandercammen, O. Fabre, K.D.
Mesmaeker, D. Maerschalk, J.L. Delphlancke, Electrochim. Acta
39 (1994) 37.
This work is supported by National Natural Science
Foundation of China (Grant No. 20325516, 90206037),
and the Research Foundation for the Doctoral Program
of the Ministry of Education of China (Grant No.
20020284022). The authors also thank Mr. Jian-Min
Hong, Modern Analytic Center of Nanjing University,
for extending research facilities to us.
[19] T.J. Mason, Sonochemistry: The Uses of Ultrasoud in Chemistry,
The Royal Society of Chemistry, 1990, p. 136.
[20] J.L. Deiplancke, J. Dille, J. Reisse, G.J. Long, A. Mohan, F.
Grandjean, Chem. Mater. 12 (2000) 946.
[21] Y. Mastai, R. Polsky, Y. Koltypin, A. Gedanken, G. Hodes,
J. Am. Chem. Soc. 121 (1999) 10047.
[22] J.A. Dean, LangeÕs Handbook of Chemistry, Science Press,
Beijing, 1991, Chapter 5, p. 102.
[23] A. Taleb, C. Petit, M.P. Pileni, J. Phys. Chem. B 102 (1998)
2214.
References
[24] J.J. Zhu, S.T. Aruna, Y. Koltypin, A. Gedanken, Chem. Mater.
12 (2000) 143.
[25] B. Jacob, P. Garik, Nature 343 (1999) 523.
[1] R. Narayanan, M.A. El-Sayed, J. Am. Chem. Soc. 125 (2003)
8340.