Sonochemistry theory reactions and syntheses and applications chemistry engineering methods and technology

CHEMICAL ENGINEERING METHODS AND TECHNOLOGY

SONOCHEMISTRY: THEORY,
REACTIONS, SYNTHESES,
AND APPLICATIONS

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CHEMICAL ENGINEERING METHODS AND TECHNOLOGY

SONOCHEMISTRY: THEORY,
REACTIONS, SYNTHESES,
AND APPLICATIONS

FILIP M. NOWAK

EDITOR

Nova Science Publishers, Inc.
New York


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LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA
Sonochemistry : theory, reactions, syntheses, and applications / [edited by]
Filip M. Nowak.
p. cm.
Includes index.
ISBN 978-1-62100-147-8 (eBook)
1. Sonochemistry. I. Nowak, Filip M.
QD801.S665 2009
660'.2842--dc22
2010025362

Published by Nova Science Publishers, Inc.  New York


CONTENTS
Preface
Chapter 1

Chapter 2

Chapter 3

vii
Sonochemistry: A Suitable Method for Synthesis of NanoStructured Materials
M. F. Mousavi and S. Ghasemi
Industrial-Scale Processing of Liquids by High-Intensity Acoustic
Cavitation: The Underlying Theory and Ultrasonic Equipment
Design Principles
Alexey S. Peshkovsky and Sergei L. Peshkovsky

Some Applications of Ultrasound Irradiation in Pinacol Coupling of
Carbonyl Compounds
Zhi-Ping Lin and Ji-Tai Li

1

63

105

Chapter 4

Ultrasound and Hydrophobic Interactions in Solutions
Ants Tuulmets, Siim Salmar and Jaak Järv

129

Chapter 5

Synthetic Methodologies Using Sonincation Techniques
Ziyauddin S. Qureshi, Krishna M. Deshmukh
and Bhalchandra M. Bhanage

157

Chapter 6

Sonochemotherapy Against Cancers
Tinghe Yu and Yi Zhang

189

Chapter 7

Application of Ultrasound for Water Disinfection Processes
Vincenzo Naddeo, Milena Landi and Vincenzo Belgiorno

201

Chapter 8

Use Of Ultrasonication in the Production and Reaction of C60 and
C70 Fullerenes
Anne C. Gaquere-Parker and Cass D. Parker

Chapter 9
Index

Application of Ultrasounds to Carbon Nanotubes
Anne C. Gaquere-Parker and Cass D. Parker

213
231
265



PREFACE
The study of sonochemistry is concerned with understanding the effect of sonic waves
and wave properties on chemical systems. This book reviews research data in the study of

sonochemistry including the application of sonochemistry for the synthesis of various nanostructured materials, ultrasound irradiation in pinacol coupling of carbonyl compounds,
ultrasound and hydrophobic interactions in solutions, as well as the use of ultrasound to
enhance anticancer agents in sonochemotherapy and the ultrasound-enhanced synthesis and
chemical modification of fullerenes.
Chapter 1 - Recently, sonochemistry has been employed extensively in the synthesis
of nano-structured materials. Rapid reaction rate, controllable reaction conditions, simplicity
and safety of the technique as well as the uniform shape, narrow size distribution, and high
purity of prepared nano-sized materials are some of the main advantage of sonochemistry.
Sonochemistry uses the ultrasonic irradiation to induce the formation of particles with smaller
size and high surface area.
Because of its importance, sonochemistry has experienced a large promotion in various fields
concerned with production of new nano-structured materials and improvement of their
properties during the recent years. However, it has encountered limitations in the case of
production of some nano-materials with specific morphology, size and properties, but the
growth of the number of researches and published articles in the field of sonochemistry
during the recent years shows a large interest and attempt to apply sonochemistry in
nanotechnology. The improvement of shape, size, purity and some other chemical and
physical properties of such produced materials has been the scope of the researchers recently.
Sonochemistry uses the powerful ultrasound irradiation (20 kHz to 10 MHz) to induce
chemical reaction of molecules. During the ultrasonic irradiation, the acoustic cavitations will
occur which consist of the formation, growth and implosive collapse of bubbles in a liquid.
The implosive collapse of the bubbles generates a localized hotspot or shock wave formation
within the gas phase of the collapsing bubbles (The hot-spot theory).
This chapter is planned to deal with the application of sonochemistry for the synthesis of
various nano-structured materials such as metals, metal carbides, metal oxides, chalcogenides
and nanocomposites with unique properties. The effect of different ultrasonic parameters on
the prepared structures including their size, morphology and properties are investigated. Also,
some applications of prepared nano-materials are introduced, e.g. electrochemical energy
storage, catalysis, biosensor and electrooxidation.
Chapter 2 - A multitude of useful physical and chemical processes promoted by

ultrasonic cavitation have been described in laboratory studies. Industrial-scale


viii

Filip M. Nowak

implementation of high-intensity ultrasound has, however, been hindered by several
technological limitations, making it difficult to directly scale up ultrasonic systems in order to
transfer the results of the laboratory studies to the plant floor. High-capacity flow-through
ultrasonic reactor systems required for commercial-scale processing of liquids can only be
properly designed if all energy parameters of the cavitation region are correctly evaluated.
Conditions which must be fulfilled to ensure effective and continuous operation of an
ultrasonic reactor system are provided in this chapter, followed by a detailed description of
"shockwave model of acoustic cavitation", which shows how ultrasonic energy is absorbed in
the cavitation region, owing to the formation of a spherical micro-shock wave inside each
vapor-gas bubble, and makes it possible to explain some newly discovered properties of
acoustic cavitation that occur at extremely high intensities of ultrasound. After the theoretical
background is laid out, fundamental practical aspects of industrial-scale ultrasonic equipment
design are provided, specifically focusing on:
 electromechanical transducer selection principles;
 operation principles and calculation methodology of high-amplitude acoustic horns used
for the generation of high-intensity acoustic cavitation in liquids;
 detailed theory of matching acoustic impedances of transducers and cavitating liquids in
order to maximize the ultrasonic power transfer efficiency;
 calculation methodology of ―barbell horns‖, which provide the impedance matching and
can help achieving the transference of all available acoustic energy from transducers into the
liquids. These horns are key to industrial implementation of high-power ultrasound because
they permit producing extremely high ultrasonic amplitudes, while the output horn diameters
and the resulting liquid processing capacity remain very large;

 optimization of the reactor chamber geometry.
Chapter 3 - Carbon-carbon bond formation is one of the most important topics in
organic synthesis. One of the most powerful methods for constructing a carbon-carbon bond
is the reductive coupling of carbonyl compounds giving 1,2-diols. Of these methods, the
pinacol coupling, which was described in 1859, is still a useful tool for the synthesis of
vicinal diols. 1, 2-Diols obtained in the reaction were very useful synthons for a variety of
organic synthesis, and were also used as intermediates for the construction of biologically
important natural product skeletons and asymmetric ligands for catalytic asymmetric reaction.
In particular, pinacol coupling has been employed as a key step in the construction of HIVprotease inhibitors.
Generally, the reaction is effected by treatment of carbonyl compounds with an appropriate
metal reagent and/or metal complex to give rise to the corresponding alcohols and coupled
products, The coupling products can have two newly chiral centers formed. Threo, erythro
mixtures of diols are usually obtained from reactions. As a consequence, efficient reaction
conditions have been required to control the stereochemistry of the 1,2-diols. Recent efforts
have focused on the development of new reagents and reaction systems to improve the
reactivity of the reagents and diastereoselectivity of the products.
In some of the described methods, anhydrous conditions and long reaction time are required
to get satisfactory yields of the reaction products, some of the used reductants are expensive
or toxic; excess amounts of metal are needed. Sonication can cause metal in the form of a
powder particle rupture, with a consequent decrease in particle size, expose new surface and
increase the effective area available for reaction. It was effective in enhancing the reactivity


Preface

ix

of metal and favorable for single electron transfer reaction of the aldehydes or ketones with
metal to form diols. Some recent applications of ultrasound in pinacol coupling reactions are
reviewed. The results are mostly from the author research group.

Chapter 4 - Sonochemistry and solution chemistry have been explicitly brought
together by analyzing the effect of ultrasound on kinetics of ester hydrolysis and benzoin
condensation, measured by the authors, and similar kinetic data for the solvolysis of tert-butyl
chloride, compiled from literature. For the first time the power ultrasound, reaction kinetics
and linear free-energy relationships were simultaneously exploited to study ionic reactions in
water and aqueous-organic binary solvents and the importance of hydrophobic ground-state
stabilization of reagents in aqueous solutions was discussed. This approach has opened novel
perspectives for wider understanding of the effect of sonication on chemical reactions in
solution, as well as on solvation phenomena in general.
Chapter 5 - Ultrasound generates cavitation, which is "the formation, growth, and
implosive collapse of bubbles in a liquid. Cavitation collapse produces intense local heating
(~5000 K), high pressures (~1000 atm), and enormous heating and cooling rates (>109
K/sec)" and liquid jet streams (~400 km/h), which can be used as a source of energy for a
wide range of chemical processes. This review will concentrate on theory, reactions and
synthetic applications of ultrasound in both homogeneous liquids and in liquid-solid systems.
Some recent applications of ultrasound in organic synthesis, such as, Suzuki reaction,
Sonogashira reaction, Biginelli reaction, Ullmann coupling reaction, Knoevenagel
condensation, Claisen-Schmidt condensation, Reformatsky reaction, Bouveault reaction,
Baylis-Hillman reaction, Michael addition, Curtius rearrangement, Diels-Alder reaction,
Friedal-Craft acylation, Heck reaction, Mannich type reaction, Pechmann condensation and
effect of ultrasound on phase transfer catalysis, oxidation-reduction reactions, ionic liquids
and photochemistry are reviewed. Ultrasound found to provide an alternative to traditional
techniques by means of enhancing the rate, yield and selectivity to the reactions.
Chapter 6 - Sonochemotherpy is the use of ultrasound to enhance anticancer agents.
Preclinical trials have manifested this modality is effective against cancers including
chemoresistant lesions. Sonochemotherapy is a target therapy, in which cavitation plays the
leading role. Making the occurrence and level of cavitation under control improves the safety
and therapeutic efficacy. Sonosensitizers and microbubbles enhance cavitation, being a
measure to adjust the level of cavitation. Free radicals due to cavitation have the potentials of
restructuring a molecule and changing the conformation; thus the molecular structure and

anticancer potency of a cytotoxic agent must be investigated, especially when sonosensitizer
and microbubble are employed. A potential clinical model for investigating
sonochemotherapy is the residual cancer tissues when performing palliative high intensity
focused ultrasound treatment.
Chapter 7 - Ultrasound (US) is a sound wave of a frequency greater than the superior
audibility threshold of the human hearing. Sonochemistry is the application of ultrasound in
chemistry. It became an exciting new field of research over the past decade. Some
applications date back to the 1920s. The 1950s and 1960s subsequently represented the first
extensive sonochemical research years and significant progresses were made throughout
them. Then it was realized that ultrasound power has a great potential for uses in a wide
variety of processes in the chemical and allied industries. In these early years, experiments
were often performed without any real knowledge of the fundamental physical background
about the US action. The situation changed in the 1980s when a new surge of activity started


x

Filip M. Nowak

and the use of US as a real tool in chemistry began. It was in 1986 that the first ever
international symposium on Sonochemistry was held at Warwick University U.K.
Chapter 8 - In this chapter, the use of ultrasounds on fullerenes (C60 and C70) and
fullerene derivatives is described. The focus is on the articles reporting the ultrasoundpromoted treatment of these nanoparticles written in English. The ultrasound-enhanced
synthesis and chemical modification of fullerenes are detailed. The improvement obtained by
sonicating the reaction mixtures while carrying out traditional organic reactions is discussed.
This includes many types of reactions, such as oxidation, cycloaddition, reduction and
amination. Also the ultrasound-enhanced crystallization of fullerenes, producing fullerites,
and the formation of colloids when the fullerenes are sonicated in various solvent mixtures
are detailed, providing the role of ultrasound in these processes.
Chapter 9 - In this chapter, the use of ultrasounds on carbon based nanotubes is

reviewed with a focus on the English written articles. The synthesis of carbon nanotubes and
their surface modification such as oxidation and covalent functionalization under ultrasounds
are reported. The synthesis of hybrid nanocomposite materials where carbon nanotubes are
added as a reinforcement agent via ultrasound-induced assembly is not described in this
chapter. A detailed survey of the literature concerning the purification and separation of
carbon nanotubes under ultrasounds is provided. The effect of sonication on carbon nanotubes
suspensions which covers aqueous and organic solutions in the presence of surfactants is
discussed with an emphasis being placed on the effect that ultrasounds have on non-covalent
interactions between the carbon nanotubes and the components of the suspensions. The effect
of ultrasounds on the physical properties of the carbon nanotubes, especially the introduction
of wall defects is analyzed. Finally the advantages and shortcomings of sonochemistry
described in this chapter are summarized, showing a possible trend in the direction of future
research in this field.


In: Sonochemistry: Theory, Reactions, Syntheses …
ISBN: 978-1-61728-652-0
Editor: Filip M. Nowak
© 2010 Nova Science Publishers, Inc.

Chapter 1

SONOCHEMISTRY: A SUITABLE METHOD FOR
SYNTHESIS OF NANO-STRUCTURED MATERIALS
M. F. Mousavi1 and S. Ghasemi
1

Department of Chemistry, Tarbiat Modares
University, Tehran, Iran
2

Department of Chemistry, The University of Qom,
Qom, Iran

ABSTRACT
Recently, sonochemistry has been employed extensively in the synthesis of nanostructured materials. Rapid reaction rate, controllable reaction conditions, simplicity and
safety of the technique as well as the uniform shape, narrow size distribution, and high
purity of prepared nano-sized materials are some of the main advantage of
sonochemistry. Sonochemistry uses the ultrasonic irradiation to induce the formation of
particles with smaller size and high surface area [1].
Because of its importance, sonochemistry has experienced a large promotion in
various fields concerned with production of new nano-structured materials and
improvement of their properties during the recent years. However, it has encountered
limitations in the case of production of some nano-materials with specific morphology,
size and properties, but the growth of the number of researches and published articles in
the field of sonochemistry during the recent years shows a large interest and attempt to
apply sonochemistry in nanotechnology. The improvement of shape, size, purity and
some other chemical and physical properties of such produced materials has been the
scope of the researchers recently [2].
Sonochemistry uses the powerful ultrasound irradiation (20 kHz to 10 MHz) to
induce chemical reaction of molecules. During the ultrasonic irradiation, the acoustic
cavitations will occur which consist of the formation, growth and implosive collapse of
bubbles in a liquid. The implosive collapse of the bubbles generates a localized hotspot or

1

Corresponding author. M.F. Mousavi, Department of Chemistry, Tarbiat Modares University, P.O. Box 14115175, Tehran, Iran Tel.: +98 21 82883474/9; fax: +98 21 82883455. E-mail addresses:
, (M.F. Mousavi).


2

M. F. Mousavi and S. Ghasemi
shock wave formation within the gas phase of the collapsing bubbles (The hot-spot
theory) [3].
This chapter is planned to deal with the application of sonochemistry for the
synthesis of various nano-structured materials such as metals, metal carbides, metal
oxides, chalcogenides and nanocomposites with unique properties. The effect of different
ultrasonic parameters on the prepared structures including their size, morphology and
properties are investigated. Also, some applications of prepared nano-materials are
introduced, e.g. electrochemical energy storage, catalysis, biosensor and electrooxidation.

1. INTRODUCTION
When ultrasound radiations interact with molecules, chemical reactions can be initiated.
Sonochemistry is an interesting research area deal with the processes occurs during the
application of powerful ultrasound (20 KHz–10 MHz). Sonochemistry arises from acoustic
cavitations. Bubbles undergo the formation, growth, and implosive collapse in a liquid under
ultrasonic irradiation. Bubble growth occurs through the diffusion of solute vapor into the
bubble. A bubble can be included evaporated water molecules and dissolved gas molecules.
When the bubble size reaches to a radius down to several µm, the bubbles collapse provides
extreme conditions of transient high temperature(as high as 5000K) and high pressure (up to
~1800 atm) within the collapsing bubbles, shock wave generation, and radical formation. The
collapsing bubbles provide reaction sites, named hot spots. At this sites, sonolysis of water
molecules to hydrogen radicals (H•) and hydroxyl radicals (OH•) is occurred which is
responsible to sonochemical reaction. Also, organic molecules in solution can form organic
radicals with a reducing ability. The size of a bubble depends on ultrasonic frequency and
intensity. Bubbles collapse occurs in very short time (nanosecond) and cooling rate of 1011
K/s is obtained. The fast kinetics of such process can hinders the growth of nuclei produced
during the collapse of bubbles. This may be the reason of formation of nanostructured
materials.
Sonochemical synthesis of different types of nanostructured materials consisted of metals

and their oxides, alloy, semiconductors, carbon carbonic and polymeric materials and their
nanocomposite have received much attention in recent years.
A number of factors can influence on cavitation efficiency and the properties of the
products. The dissolved gas, ultrasonic power and frequency, temperature of the bulk
solution, and type of solvent are all important factors that control the yield and properties of
the synthesized materials.
In the field of sonochemistry, a number of book chapter and reviews have been published
4. Y. Mastai and A. Gedanken reviewed articles in the field of sonochemistry published
before 2004 in a chapter of book entitled ―Sonochemistry and Other Novel Methods
Developed for the Synthesis of Nanoparticles‖ [2]. Also a review articles was published by
Gedanken in 2004 entitled ―Using sonochemistry for the fabrication of nanomaterials‖
focused on the typical shape of products obtained in sonochemistry [1]. Another review
articles also published dealt with insertion of nanoparticles into mesoporous materials [5] and
the sonochemical doping of various nanoparticles into ceramics and polymers [6].
In this chapter, we will present a literature survey on the various inorganic,
organic/inorganic and inorganic/inorganic systems more recently have been synthesized by
using ultrasonic method from January 2004 to January 2010s.


Sonochemistry: A Suitable Method for Synthesis of Nano-Structured Materials

3

2. SYNTHESIS OF NANOMETALS
Intensive works on metal nanostructures such as noble metals (Au, Pt, Pd) with various
size and morphology have been achieved due to their potential applications in the fabrication
of electronic, optical, optoelectronic, and magnetic devices. They can be obtained form
sonication of solution containing related metal ion in the absence and presence of capping
agents. With controlling size, shape, and crystallinity of nanometals, it can be possible to tune
the intrinsic properties of a metal nanostructure.

2.1. Gold
Gold and other noble metal nanoparticles have been extensively considered in recent
years because of their potential applications in optics, electronics, and catalysis, etc. Okitsu et
al reported the synthesis of Au nanoparticles and investigate the dependence of sonochemical
reduction rate of Au(III) to Au nanoparticles in aqueous solutions containing 1-propanol as
accelerator and their particle size to the ultrasound frequency so that the highest reduction rate
was at 213 kHz in the range of 20 to 1062 kHz [7]. The average size of Au particles was 15.5
nm in 20 mM 1-propanol.
This group also synthesized Gold nanorods by using sonochemical reduction (frequency,
200 kHz; power, 200 W) of gold ions in aqueous solution (60 mL) containing of HAuCl4 and
CTAB including 1.2 mL of AgNO3 (4.0 mM) and 240 μL of ascorbic acid (0.050 M) with pH
3.5 [8]. During the reaction, Au (III) is immediately reduced to Au (I) by reaction with the
ascorbic acid. CTAB and AgNO3 act as effective capping agents for the shape controlled
growth of gold seeds. The solution was purged with argon for 15 min and then sonicated in a
water bath (at 27 ºC) by a water circulation system. In the presence of ultrasonic, the
following reactions are proposed:
)))
H 2O 
H   OH 

(1)

CTAB  OH  ( H  )  H 2 O( H 2 ) + reducing species

(2)

CTAB  H 2 O  pyrolysis radicals and unstable products

(3)

Au   M  Au 0  H   M 

(4)

nAu 0  ( Au 0 ) n

(5)

Au 0  ( Au 0 ) n  ( Au 0 ) n1

(6)

Where M corresponds to various reducing species, pyrolysis radicals and unstable
products. In reaction 3, pyrolysis radicals and unstable products are formed via pyrolysis of


4

M. F. Mousavi and S. Ghasemi

CTAB and water. The size of the sonochemically formed gold nanorods was less than 50 nm,
and their average aspect ratio decreased with increasing pH of the solution.
At pH 7.7, irregular shaped gold nanoparticles were formed. At pH 9.8, most of the
particles formed had a spherical shape with a smaller particle size than those formed in the
lower pH solutions. Based on the obtained results, it was clear that the size and shape of the
sonochemically formed gold nanoparticles are dramatically dependent on the pH value of the
solution (Figure 1).
From the obtained results, it was demonstrated that longer gold nanorods would be
obtained if the synthesis was performed in solution with acidic pH.

Li et al. reported the synthesis of single-crystal Au nanoprisms with triangular or
hexagonal shape, 30-40 nm planar dimensions, and 6-10 nm thickness from solution of
HAuCl4 and PVP in ethylene glycol solution [9]. Ethylene glycol, the surfactant
poly(vinylpyrrolidone), and ultrasonic irradiation play important roles in the formation of Au
nanoprisms.
Single-crystalline gold nanobelts have been prepared sonochemically from aqueous
solution of HAuCl4 in the presence of α-D-glucose, a biological directing agent, under
ambient conditions (Figure 2).

Figure 1. TEM images of gold nanorods and nanoparticles formed in different pH solutions of (a) pH
3.5, (b) pH 5.0, (c) pH 6.5, (d) pH 7.7, and (e) pH 9.8 after 180 min irradiation under argon. (f) TEM
image of gold nanoparticles formed in pH 9.8 without ultrasonic irradiation.


Sonochemistry: A Suitable Method for Synthesis of Nano-Structured Materials

5

Figure 2. a,b) SEM images and c,d) high-magnification SEM images of as-synthesized gold nanobelts;
[HAuCl4]=50 mgmL-1, [α-D-glucose]= 0.2 m, ultrasound time=1 h.

The formation of gold nanobelts depends on the concentration of α-D-glucose. When its
concentration was as low as 0.05 M, only gold particles with a size of approximately 40 nm
were obtained [10]. In the dilute solution, the glucose can not provide effective coverage or
passivation of gold facets. The gold nanobelts have a width of 30–50 nm and a length of
several micrometers with highly flexibility. Nanobelts have thickness of approximately 10
nm. Authors also showed that only spherical particles with a diameter of approximately 30
nm were obtained in the presence of β-cyclodextrin. It was mentioned that ultrasound
irradiation can enhance the entanglement and rearrangement of the α-D-glucose molecules on
gold crystals.

Park et al. showed the effects of concentration of stabilizer (sodium dodecylsulfate: SDS)
and ultrasonic irradiation power on the formation of gold nanoparticles (Au-NPs) [11]. The
multiple shapes and size distribution of Au-NPs are observed by different ratio of Au (III)
ion/SDS and ultrasonic irradiation power.
A sonochemical method in preparation of gold nanoparticles capped by thiolfunctionalized ionic liquid (TFIL) in the presence of hydrogen peroxide as a reducing agent
reported by Jin et al. [12]. It was demonstrated that the molar ratio of gold atom in
chloroauric acid to thiol group in TFIL (Au/S) has great effects on the particles size and
distribution of gold nanoparticles. Small gold nanoparticles size of 2.7±0.3 nm can be
synthesized when ultrasound irradiation applied to a solution with the molar ratio of Au/S =
1:2 for 12 h.


6

M. F. Mousavi and S. Ghasemi

2.2. Palladium
Nemamcha et al reported the sonochemical synthesis of stable palladium nanoparticles by
ultrasonic irradiation of palladium (II) nitrate solution in ethylene glycol and in the presence
of poly(vinylpyrrolidone) (PVP) for 180 min [13]. During the ultrasonic irradiation of the
palladium (II) nitrate mixture, the color of the solutions turned from the initial pale yellow to
a dark brown. The following mechanism was proposed:
))))
H 2 O 
OH   H 

(7)

HOCH2 CH 2 OH  OH  (OH  )  HOCH2 C  HOH  H 2 O( H 2 )

(8)

nPd ( II )  2nHOCH2 C  HOH  nPd (0)  2nHOCH2 CHO  nH 

(9)

The coordination of the PVP carbonyl group to the palladium atoms causes to the
stabilization of the Pd nanoparticles in ethylene glycol. It has been shown by TEM that the
increase of the Pd (II)/PVP molar ratio from 0.13 ×10-3 to 0.53 ×10-3 decreases the number
of palladium nanoparticles with a slight increase in particle size. For the highest Pd (II)/PVP
value, 0.53 × 10-3, the reduction reaction leads to the unexpected smallest aggregated
nanoparticles.

2. 3. Tellurium
Crystalline tellurium nanorods and nanorod branched structures are successfully prepared
at room temperature via an ultrasonic-induced process in alkaline aqueous solution containing
tellurium nitrate, D-glucose and polyethylene glycol (PEG-400,CP) for 2 h treatment in an
ultrasonic bath [14]. A yellow sol was produced and was kept in darkness for 24 h to allow
the growth of Te nanocrystals. The as-obtained nanorods are single crystalline with [0 0 1]
growth orientation, and have 30–60 nm in diameter with 200–300 nm in length. Some
branched architectures, consisting of several nanorods, are also found in the products. The
formation of the branched structures is suggested to be the result of multi-nuclei growth in
monomer colloid.

2.4. Tin
Metallic tin nanorods were synthesized by a sonochemical method employing the polyol
process [15]. In the reaction a solution of SnCl2 in ethylene glycol was exposed to highintense ultrasound irradiation. The crystallized metallic tin nanorods have diameters of 50–
100 nm and lengths of up to 3 µm were synthesized. In the absence of the high-intensity
ultrasonic irradiation, no reduction of tin ions occurs even at temperatures as high as 500 ºC
in a closed cell.

Sonochemistry: A Suitable Method for Synthesis of Nano-Structured Materials

7

2.5. Ruthenium
Ruthenium nanoparticles have been prepared by sonochemical reduction of a ruthenium
chloride solution in 0.1 M perchloric acid containing propanol and SDS for almost 13 h [16].
The effects of different ultrasound frequencies in the range 20–1056 kHz were investigated.
The Ru particles have diameters between 10 and 20 nm. The rate of Ru (III) reduction by the
sonochemical method is very slow. The sonochemical reduction rate has been found to
influence by ultrasound frequency. An optimum reduction rate was determined in the
frequency range 213–355 kHz.

2.6. Germanium

Wu et al. reported a method based on ultrasonic solution reduction of GeCl4 by metal
hydride (LiAlH4 and NaBH4) or alkaline (N2H4·H2O) in tetrahydrofuran (THF) and in
ambient condition [17]. The germanium nanocrystals have narrow size distribution with
average grain sizes ranging from 3 to 10 nm. Octanol was used as capping agent. To prevent
the formation of GeO2 formed in the presence of water, the anhydrous salt is added to form a
transparent ionic solution in THF.
2.7. Selenium
Single crystalline trigonal selenium (t-Se) nanotubes with diameters of less than 200 nm
and nanowires with diameters of 20-50 nm have been synthesized by the reduction of
H2SeO3 in different solvents with a sonochemical method [18]. The morphology of the
products depends on the reaction conditions including ultrasonic parameters (e.g., frequency,
power, and time), aging time, and solvent. Hydrazine hydrate was dissolved in ethylene
glycol, water, etc. to form solutions. The solution was added dropwise to the corresponding

selenious acid solution. At the same time, ultrasound was preceded to the solution, and the
ultrasonic time is 30-60 min. Selenium nanotube and nanowire formation involved several
stage:
)))
)))
H 2 SeO3  N 2 H 4 
Spherical (  Se) 
Spherical  like(t  Se)
)))

Nanowires (t  Se)

(10)

2.8. Silver
Dendritic silver nanostructures were formed by means of ultrasonic irradiation[19] of an
aqueous solution of silver nitrate with isopropanol as reducing agent and PEG400 as disperser
for 2 h.


8

M. F. Mousavi and S. Ghasemi

Figure3. TEM image of a silver dendritic nanostructures obtained with ultrasonic irradiation of the
aqueous solutions of 0.04 M AgNO3, 4.0 M isopropanol and 0.01 M PEG400 for 2 h .

The side branches of the dendritic silver are constructed of well crystallized small
nanorods (Figure 3). The selected area electron diffraction (SAED) image of dendritic silver
nanostructures has single crystal nature with cubic phase and the side branch direction

assembles along <011> direction.
The irradiation time, the concentration of Ag+ and the molar ratio of PEG to AgNO3 are
parameters can influence the morphology of silver nanostructured. The low molar ratio of
PEG400 to AgNO3 (1:4 ~ 1:1) result in the formation of silver dendritic nanostructures but
the molar ratio of 10:1 will cause to formation of silver nanoparticles (in the range of 40–100
nm ) instead of dendritic nanostructures. Only silver spheroidal nanoparticles were obtained at
the beginning of the reaction but silver dendrites were observed with 1 h sonication. These
dendritic nanostructures transform to hexagonal compact crystals after 6 h later.
In another work, highly monodispersed Ag nanoparticles (NPs) were prepared by a
sonochemical reduction in which Ag+ in an ethanol solution of AgNO3 was reduced by
ultrasound irradiation in the presence of benzyl mercaptan without the additional step of
introducing other reducing reagents or protective reagents [20].

3. SYNTHESIS OF METALLIC NANOALLOYS
The nanoalloys are formed when two or more kinds of metals are melted together.
Nanoalloy materials can exhibit many novel properties, including electronic, catalytic,
magnetic and corrosion-resistant properties. The sonochemical method has been used as a
new technique for preparing alloy nanoparticles. Bimetallic nanoalloys show different


Sonochemistry: A Suitable Method for Synthesis of Nano-Structured Materials

9

properties such as high catalytic activity and catalytic selectivity in comparison with the
corresponding monometallic counterparts so that they can be used as catalysts and gas
sensors.

3.1. Sn–Bi
Sn–Bi alloy nanoparticles were prepared by sonicating bulk Sn–Bi alloy directly in

paraffin oil under ambient pressure and room temperature [21]. Twenty grams Sn and 30 g Bi
were melted together in a vessel to obtain the bulk Sn–Bi alloy. Then 0.5 g bulk Sn–Bi alloy
was added to 30 ml paraffin oil in a horniness test tube and the system was irradiated for two
hours at 1000Wcm−2 with a high intensity ultrasonic probe. The product was centrifuged
after cooled to room temperature and washed with chloroform and dried to get some grayblack powder. They show that when the ultrasonic power was increased from 700 to 1000
Wcm-2, the size distribution reduced from 60-80 nm to 10-25 nm. They also show that the
sonication time had little impact on the size of the nanoparticles.

3.2. Pd–Sn
Kim et al. prepared Pd–Sn nanoparticles from aqueous ethanol solution of Pd(NH4)2Cl4
and SnCl2 in the presence of citric acid by applying ultrasonic irradiation and investigate the
Pd–Sn nanoparticles for the oxygen reduction reaction (ORR) in alkaline media [22]. The
average size of Pd–Sn nanoparticles thus prepared was about 3–5 nm. The initial
concentrations of Pd and Sn and their molar ratio, the concentration of ethanol and the
concentration of citric acid affect the size distribution of the Pd–Sn nanoparticles. The Pd in
Pd–Sn nanoparticles is mostly in the metallic form.

3.3. Pt-Ru
Bimetallic catalysts comprised of Pt and Ru (Pt-Ru) are important in the development of
low temperature (<~120 ºC) H2-air and direct methanol fuel cells. Korzeniewski et al.
prepared Pt-Ru nanoparticles with diameters in the range of 2–6 nm as catalyst materials to
investigate the electrochemical oxidation of CH3OH and CO [23]. In Pt-Ru catalyst, Pt
provides sites for C-H bond cleavage and CO adsorption, and Ru activates water to produce
reactive oxides that enable conversion of carbon containing fragments to CO2.
Pt-Ru Nanoparticle bimetallic electrocatalysts with XRu ≈0.1 and XRu ≈ 0.5 were
synthesized and its response toward the electrochemical oxidation of CO and CH3OH in 0.1
M H2SO4 was investigate [24]. Syntheses were carried out in tetrahydrofuran (THF)
containing Ru3+ and Pt4+ in a fixed mole ratio of either 1:10 or 1:1 using high-intensity
sonochemistry.

10

M. F. Mousavi and S. Ghasemi

3.4. Co-B
Uniform spherical Co-B amorphous alloy nanoparticles were prepared by ultrasoundassisted reduction of Co(NH3)2+6 with BH−4 in aqueous solution which the particle size
distribution was controlled by changing the ultrasound power and the ultrasonication time
[25]. During liquid-phase cinnamaldehyde (CMA) hydrogenation, the as-prepared Co-B
catalyst exhibited much higher activity and better selectivity to cinnamyl alcohol (CMO) than
the regularCo-B in the absence of ultrasonic waves.

3.5. Au-Ag
Au-Ag nanoalloys were prepared sonochemically form solution containing gold
nanoparticles and silver nitrate in the presence of different surfactant (sodium borohydride in
water; poly(vinyl pyrrolidone) in ethylene glycol; poly(ethylene glycol); sodium dodecyl
sulfate in water or propanol) [26]. It was suggested that the degradation of the surfactants
occurred during the ultrasonic treatment and allowed modification of the shape of gold
nanoparticles in their interaction with silver ions. Monodisperse gold-silver nanocomposite of
triangular or polygonal structure was obtained with reduction of the silver by NaBH4 on the
gold surface in the presence of ultrasonic irridation. Uniformly distributed gold-silver with
round shapes was resulted after sonication in poly (ethylene glycol). Multiangular Au-Ag
nanocomposites of larger size appeared after ultrasonic irradiation of the gold-silver mixture
in the presence of poly (vinyl pyrrolidone) in ethylene glycol due to the capping effect and the
relatively low rate of degradation of PVP. With SDS, worms or netlike gold-silver
nanostructures obtained after 1 h of ultrasonic irradiation of AgNO3 in propanol and water,
respectively.

3.6. Bimetallic Nanoparticles with Core-Shell Morphology
Sonochemically assisted synthesis of bimetallic nanoparticles with core-shell morphology

have been reported for materials such as Co/Cu [27], Au/Pd 28 and Pt-Ru [29].
A sequential sonolysis method was used to synthesis of Pt-Ru core shell (Pt@Ru)
structure [29]. Pt-Ru has been used as a methanol oxidation catalyst in direct methanol fuel
cells (DMFC). A potassium tetrachloroplatinate (K2PtCl4) solution containing 8 mM SDS,
200 mM propanol, and 0.1 M HClO4 were sonicated to reduce the Pt (II) to colloidal Pt (0)
during 3h at 20 °C. When all of the Pt (II) has been reduced, the RuCl3 solution was added to
the Pt colloidal solution and sonication continued. TEM image of the nanoparticles showed
that the ruthenium formed a layer around the platinum particles and Pt-Ru core-shell particles
in the range of 5-10 nm were formed (Figure 4). The platinum particle sizes are ~7 nm, while
the thickness of the ruthenium shell was estimated to be between 2 and 3 nm.
When 1mg/mL of polyvinyl-2-pyrrolidone, PVP (MW =55000) is used as the stabilizer,
the formation of colloidal platinum is very rapid and become complete within 1 h of
sonication. At the end of 1 h, when all of the Pt (II) was reduced, the RuCl3 solution was
added to the Pt colloidal solution and sonication continued.


Sonochemistry: A Suitable Method for Synthesis of Nano-Structured Materials

11

Figure 4: (a) TEM of Pt-Ru nanoparticles synthesized by sonocation of a solution containing 1 mM
PtCl4 2- in 200 mM propanol, 0.1 M HClO4, and 8 mM SDS followed by the reduction of 1 mM RuCl3
under argon atmosphere. The RuCl3 solution was added after the PtCl4 2- solution was sonicated for 4 h.
The total time of sonication was 7h at 213 kHz. (b) Absorption spectra Pt-Ru nanoparticles.

The TEM images showed ultrasmall 2 nm sized particles without core-shell morphology and
only the presence of bimetallic ruthenium and platinum was confirmed by energy-dispersive
X-ray analysis of the TEM.
Figure 4b shows the change in absorption spectra of the colloidal solutions with time.
Curve a shows the absorption spectrum of PtCl4 2- solution at time t = 0 and continuing

through the addition of the RuCl3 and its reduction. Curve e shows the absorption spectrum
immediately upon addition of the ruthenium chloride. Only one prominent peak at 400 nm
appears in the curve indicating an instantaneous partial reduction of Ru (III) upon addition to
the solution.
As mentioned above, Vinodgopal et al used a sequential reduction method to prepare PtRu core-shell nanoparticles but Anandan and his coworker prepared Au-Ag bimetallic
nanoparticles by the sonochemical co-reduction of Au(III) and Ag(I) ions in aqueous
solutions containing polyethylene glycol (0.1 wt %) and ethylene glycol (0.1 M) [30]. The
average diameter of the bimetallic clusters prepared by the simultaneous reduction is about 20
nm. The stabilizing polymers can coordinate to metal ions before the reduction. This
interaction between the polymer and the metal ions lead to the formation of smaller size core-


12

M. F. Mousavi and S. Ghasemi

shell nanoparticles with a narrow size distribution. They also suggested that the formation of
core-shell morphology is most likely due to the difference in the reduction rates of the
individual metal ions and the involvement of a polymer-Ag ion complex. Gold ions are firstly
reduced under the sonochemical conditions followed by the reduction of Ag+ ions on the
surface of the gold particles.

4. METAL OXIDE
During the last years, the ultrasonically assisted synthesis of metallic oxides and
hydroxides has been considered by some of researchers. Due to their importance in various
area of science, some of them are investigated in the following paragraph.

4.1. ZnO
ZnO is one of the most important multifunctional semiconductors with wide direct energy
band gap of 3.37 eV and large exciton binding energy (about 60 meV). Sonochemical

synthesis of ZnO nanostructures with different shapes such as nanowires, nanotubes,
nanoparticles have been considers by some of authors. The effects of various parameters on
the morphology of ZnO nanostructures were investigated. ZnO nanostructure with
morphologies such as flower-like clusters [31], cauliflower-like [32], nanorods [33], needleshape [34], trigonal-shaped [35], nanosheet [36] and Hollow ZnO microspheres [37].
Jung et al fabricated ZnO nanorods, nanocups, nanodisks, nanoflowers, and nanospheres
in a horn-type reaction vessel using an ultrasonic technique at a power of 50 W (intensity of
39.5 W/cm2) and frequency of 20 kHz (Figure 5) [38]. The kind of hydroxide aniongenerating agents, concentration of reactants, sonication time and additives are dominant
factor affect on preparation of different morphology of ZnO. For the production of ZnO
nanorods and ZnO nanocups, different concentration of Zn(NO3)2 and
hexamethylenetetramine (HMT, (CH2)6N4 as well as different sonication time (30 min for
nanorods in comparison with 2h for nanocups) were used. An increase in ultrasonication time
provides such energy indicates to the reaction System that hinders the ZnO nanorod growth.
Triethyl citrate was used as an additional chemical additive to synthesize ZnO nanodisks.
ZnO nanocrystals grow preferentially along the [0001] direction to form nanorods. The
growth rate of the ZnO crystal along the [0001] direction decreases dramatically due to the
addition of triethyl citrate.
For the synthesis of ZnO nanoflowers and nanospheres, ammonia–water (28–30 wt %)
solution were used as hydroxide anion precursors. In the case of ZnO nanospheres, triethyl
citrate was added to the mixture of zinc acetate dihydrate solution (90 mL) and ammonia–
water (10 mL). The sonochemical growth mechanism of ZnO nanostructures was suggested
by authors as follows:

(CH 2 ) 6 N 4  6H 2 O  4 NH 3  6HCHO

(11)

NH 3  H 2 O  NH 4  OH 

(12)

Sonochemistry: A Suitable Method for Synthesis of Nano-Structured Materials

13

Zn 2  4OH   Zn(OH ) 24

(13)

)))
Zn(OH ) 24 
ZnO  H 2 O  2OH 

(14)

3
)))
Zn 2  2  O2 
ZnO  O2
2

(15)





The sonolysis of water produces O2 radicals in solution.

Figure 5. SEM (left) and TEM (right) images of ZnO nanostructures. (a,b) Nanorods. (c,d) Nanocups.

(e,f) Nanodisks. (g, h) Nanoflowers. (i, j) Nanospheres. (Insets: HRTEM image) .

The same authors presented in another paper a sonochemical method for fabricating
vertically aligned ZnO nanorods arrays on various substrates such as a large-area Zn sheet, Si


14

M. F. Mousavi and S. Ghasemi

wafer, transparent glass, and flexible polymeric materials, in an aqueous solution under
ambient conditions [39].
A template-free, sonochemical route to prepare porous hexagonal ZnO nano-disks has
been developed by Bhattacharyya and Gedanken. The nano-disks are 260–400 nm across the
edges and 290–430 nm across the vertices[40]. Some of authors used ultrasonic irradiation to
fabricate well-defined dentritic ZnO nanostructures in a room-temperature ionic liquid [41].
The ZnO nanostructures have been used to sensing etanol [42], high performance NO2
gas sensor [43], gas sensitivity to NO [44].

4.2. CuO
The synthesis of one-dimensional (1D) Cu(OH)2 nanowires [45] in a aqueous solution of
CuCl2 and NaOH was done under ultrasound irradiation with 40 kHz ultrasonic waves at the
output power of 100% at 70 ºC for 5-60 min. The morphology of products is highly depends
on time of ultraonication. Under continuous ultrasonic irradiation, Cu(OH)2 nanowires
integrated into nanoribbons, then parts of nanoribbons crosswise grew to form 3D Cu(OH)2
nanostructures; finally, 3D nanostructures disrupted and transformed into 3D CuO
microstructures. The effect of ultrasonic irradiation time on conversion process of Cu(OH)2
to CuO was investigated. A color change of the product from the pale-blue to the black was
observed in the range of 15 to 45 min of irradiation implied the gradual conversion of
Cu(OH)2 to CuO. The XRD analyses of the products confirmed the conversion process. It

was demonstrated that the ultrasound plays two roles besides dispersion: shortening the
conversion time from Cu(OH)2 to CuO and inducing the formation of 3D CuO
microstructures. The CuO microstructures showed better electrochemical property than
Cu(OH)2.

4.3. V2O5
A sonochemical method has been developed to preparation self-assemble V2O5
nanowires with spindle-like morphology (Figure 6). Vanadium oxide (V2O5, 0.46 g, 2.5
mmol) and sodium fluoride (NaF, 0.21 g, 5 mmol) were dissolved in 50 mL of distilled water
in a 100-mL round-bottom flask and exposed to high-intensity ultrasound irradiation (20 kHz,
100 W/cm2) under ambient air for 2 h. The organization of 1D V2O5 nanostructured subunits
into spindle -like V2O5 bundles was occurred
Each bundles composed of several tens of homogeneous nanowires with diameters of 3050 nm and lengths of 3-7 µm. Also, a sensitive resonance light scattering (RLS) method was
developed to detect bovine serum albumin (BSA) based on the ultrasonically V2O5 bundles
[46]. An increase in the scattered light signals of V2O5 bundles were observed by the
addition of BSA. The enhanced RLS intensity at 468 nm of V2O5 bundles-BSA varies
linearly with the concentration of BSA in the range from 0.5 to 20 µg mL-1.
Synthesis of self-assembled nanorod vanadium oxide bundles by sonochemical technique
were reported by a Malaysian group [47].