The effect of sonication power on the sonochemical synthesis of ...

<strong>effect</strong> <strong>of</strong> <strong>sonication</strong> <strong>power</strong> on the sonochemical synthesis <strong>of</strong> titania nanoparticles 

<strong>The</strong> 

Department, Islamic Azad University, Karaj Branch, Tehran, Iran 

Engineering 

Advanced Materials and Nanotechnology Research Center, Faculty <strong>of</strong> Mechanical Engineering, K.N. Toosi University <strong>of</strong> 

c 

dioxide (TiO 2 ) nanoparticles were synthesized by a sonochemical method. C 12 H 28 O 4 Ti (Tetraisopropyl titanate), 

Titanium 

(C 2 H 5 OH), sodium hydroxide (NaOH) and deionized water were used as the initial materials. <strong>The</strong> output <strong>power</strong> <strong>of</strong> the 

ethanol 

device plays the most important role in the size and morphology <strong>of</strong> the final products. Sonochemical processes at 

ultrasonic 

<strong>sonication</strong> <strong>power</strong> were carried out at synthesis temperature (50 o C) for 1.5 h and then the materials were washed and 

different 

at room temperature for 48 h. To determine the particle size and also evaluate the morphological properties, X-ray 

dried 

(XRD) and transmission electron microscopy (TEM) were used. TG/DTA analysis was used to for determine the 

diffraction 

and time <strong>of</strong> crystallization. From TEM observations the size <strong>of</strong> titanium dioxide nanoparticles is estimated to be 

temperature 

smaller than ~12 to ~30 nm. 

significantly 

nano-semiconductors have become one <strong>of</strong> 

Nowadays 

most attractive aspects <strong>of</strong> materials research. Among 

the 

nano materials, titanium dioxide has become the most 

these 

material due to its physical and chemical 

interesting 

properties. 

control <strong>of</strong> morphology, particle size, particle size 


phase composition and porosity <strong>of</strong> TiO 2 

nanoparticles 

distribution, 

are vital factors in determining the properties <strong>of</strong> 

final material. TiO 2 

has three polymorphic phases 


anatase, rutile and brookite. Among these three 

namely 

phases, the anatase phase exhibits the highest 

crystalline 

activity.Rutile- TiO 2 

is known as a white 

photocatalytic 

because <strong>of</strong> its high scattering <strong>effect</strong> which leads 

pigment 

protection from the ultraviolet light [1, 2]. 

to 

2 

is one <strong>of</strong> the most extensively studied oxides because 

TiO 

its remarkable optical and electrical properties [3]. TiO 2 

<strong>of</strong> 

extensive applications in photocatalysts [4], gas sensors 

has 

self cleaning surfaces [6], water and air purification 

[5], 

[7] and pigments [8]. Moreover, the rutile 

components 

a has high dielectric constant, electrical resistivity 

structure 

and refractive index which makes it a relevant choice 

[9] 

dye-sensitized solar cells(DSCs) [10] and capacitors 

for 

as well. 

[11] 

recent years, nano TiO 2 

has been synthesized via 

In 

author: 

*Corresponding 

: +98-21-33362478 

Tel 

+98-261-6201888 

Fax: 

amir_hassanjani@yahoo.com 

E-mail: 

methods such as thermal hydrolysis [12], chemical 

different 

deposition (CBD) [13], sol-gel [14-17], hydrothermal 

bath 

[18-20], microemulsion processes [21-24] and 

processes 

laser evaporation [25] etc. Among the different 

pulsed 

<strong>of</strong> synthesis which have been used by several 

methods 

the direct chemical method has some advantages 

researchers, 

easy operation, being fast, low cost and high 

including 

In addition to TiO 2 

, this method has been also 

efficient. 

applied for the synthesis <strong>of</strong> several other 

successfully 

<strong>of</strong> nanostructured materials such as ZnO [26]. 

types 

sonochemical methods, a chemical reaction 

Recently, 

the starting materials in the presence <strong>of</strong> applied high 


ultrasonic waves, has been employed for several 

frequency 

and the <strong>effect</strong> <strong>of</strong> ultrasound on chemical reactions 

purposes 

not well understood, however it is mostly believed that 

is 

<strong>sonication</strong> acoustic cavitation phenomenon generates 

a 

in the liquid solution <strong>of</strong> the reactants. <strong>The</strong> cavitation 

cavities 

consist <strong>of</strong> the creation, growth and implosive 

processes 

<strong>of</strong> gas vacuoles in the solution. According to the 

collapse 

theory, extreme temperatures (> 5000 K) and 

‘‘hot-spot’’ 

pressures (> 1000 atm) occur within the bubbles during 

high 

collapse [27-30]. Under such extreme conditions 

cavitational 

solvent undergo hemolytic bond breakage 

the + 

molecules 

radicals, H and OH − when H 2 

O is sonicated 

generate to 

example. <strong>The</strong> liberated radicals therefore, may lead to 

for 

chemical and physical <strong>effect</strong>s in reaction pathways 

various 

mechanisms. Moreover, the other benefit in using 

and 

waves in reactions is believed to be providing 

ultrasonic 

mixing especially in viscous media. This 

highly-intensive 

lead to an acceleration <strong>effect</strong> in chemical dynamics 

would 

J O U R N A L O F 

Journal <strong>of</strong> Ceramic Processing Research. Vol. 12, No. 3, pp. 299~303 (2011) 

Ceramic 

Processing Research 

a,b, 

*, a c 

a,b Kazemzadeh , Mohammad Reza Vaezi and Ali Shokuhfar Amir Hassanjani-Roshan Seyed Mohammad 

Research Center, P.O. Box 14155-4777, Karaj, Iran 

Energy and Materials 

a 

b 

Technology, Tehran, Iran 

Key words: Sonochemical, Cavitation, Sonication <strong>power</strong>, Nanoparticles, Titanium dioxide. 

Introduction 

and rates <strong>of</strong> the reactions. <strong>The</strong>refore, by this circumstance, 

299

properties <strong>of</strong> the final products such as particle 

different 

shape and its purity would be controlled by as <strong>sonication</strong> 

size, 

<strong>power</strong>, temperature, the solvent, the chemical species 

output 

their concentrations in the reaction mixture. 

and 

ultrasonic wave to synthesis as an external source 

Using 

energy, affects the final properties <strong>of</strong> products. As 


before, this energy even can change the chemical 

mentioned 

<strong>of</strong> synthesized particles. Due to the mentioned 

route 

and by considering the reduction in size by 

phenomena 

<strong>sonication</strong> <strong>power</strong>, the whole optical properties 

increasing 

synthesized nano particles could change. This can cause 


differences in the nature <strong>of</strong> the materials obtained. 

severel 

semiconductors, the reduction in size can influence the 

In 

<strong>of</strong> optical absorption edge and consequently 

wavelength 

band gap energy [31]. Thus besides the differences in 


and particles size <strong>of</strong> synthesized particle, 

morphology 

band gap energy which acts as a main character <strong>of</strong> 


in all aspects, should be investigated 

semiconductors 

[32]. 

carefully 

the present paper, TiO 2 nanoparticles were synthesized 

In 

a sonochemical method. Temperature and <strong>sonication</strong> 

via 

were investigated in current issue as variables. TEM 

<strong>power</strong> 

XRD investigations were used to studying morphological 

and 

structural characteristics <strong>of</strong> nanomaterials. 

and 

and equipment 

Materials 

amount <strong>of</strong> tetraisopropyl titanate (C 12 H 28 O 4 Ti, Merck), 

An 

hydroxide (NaOH, Merck), ethanol (C 2 H 5 OH, 

sodium 

99.99%) and deionized water were used to synthesize 

Merck, 

pure nanosized TiO 2 particles. 


high-intensity ultrasonic probe (Misonix S3000, Ti horn, 

A 

kHz, 100 W/cm 2 , USA) and a flat-bottomed Pyrex 

20 

vessel (total volume <strong>of</strong> 150 ml) were used for the 

glass 

<strong>of</strong> nano TiO 2 via sonochemical method 

Synthesis 

was dissolved in deionized water and the solution 

NaOH 

M, 50 ml) was added drop-wise to an aqueous C 12 H 28 O 4 Ti 

(1 

that was dissolved in ethanol (0.25 M, 50 ml) 

solution 

about 30 minutes at a synthesis temperature <strong>of</strong> 

within o C. During this process, the solution was irradiated 

50 

an ultrasonic horn at different <strong>sonication</strong> <strong>power</strong>s. <strong>The</strong> 

with 

was irradiated with ultrasonic irradiation for the 

solution 

initial <strong>sonication</strong> <strong>power</strong>s listed in Table 1. <strong>The</strong> 

different 

<strong>power</strong> (W) given by the operation and the ultrasound 

initial 

(W/cm 2 ) was determined by sonicator. <strong>The</strong> sonochemical 

intensity 

reaction was continued for 60 minutes and 

1. <strong>The</strong> samples synthesized at different <strong>sonication</strong> <strong>power</strong> 

Table 

50 o C at 

different conditions. 

under 

the sonochemical reaction, it was observed that 

During 

color <strong>of</strong> the slurry changed gradually from colorless 


the reaction) into white-lactic. <strong>The</strong>se changes <strong>of</strong> 

(before 

in the solution occurred as TiO 2 nanoparticles 

colors 

prepared. 

were 

precipitated particles were collected, filtered and 

Finally, 

carefully with methanol and double distilled water 

washed 

remove by-products. All the prepared samples were 

to 

in air at room temperature for 48 h. 

dried 

Characterization 

TiO 2 nanoparticles were characterized by different 


<strong>The</strong> evaluation <strong>of</strong> crystal structure and determination 

techniques. 

<strong>of</strong> crystallite size were by X-ray diffraction (XRD) 

(SIEMENS, D5000) with Cu-K α radiation source. 

patterns 

acceleration voltage <strong>of</strong> 30 kV with a 25 mA current 

An 

and an angular speed <strong>of</strong> 2 o /minute were used to record 

flux 

patterns in the 2θ range <strong>of</strong> 20 o -70 o . <strong>The</strong>rmogravimetry 


thermal analysis (TG-DTA) was simultaneously 

differential 

in air at a heating rate <strong>of</strong> 10 K·minute −1 (STA 1640). 

used 

morphology <strong>of</strong> the prepared samples was analyzed 


a transmission electron microscope (ZEISS, Germany). 

using 

samples were prepared by dispersing a few drops 

TEM 

TiO 2 on carbon films supported by copper grids. 


Diffraction analysis 

X-Ray 

1 shows the XRD patterns <strong>of</strong> TiO 2 nanoparticles 

Fig. 

via a sonochemical method. Fig. 1(a) shows 

prepared 

XRD pattern <strong>of</strong> TiO 2 nanoparticles prepared via a 


method at 50 o C. Fig. 1(b) and Fig. 1(c) show 

sonochemical 

XRD patterns <strong>of</strong> TiO 2 for samples (I, V) that were 


1. XRD patterns <strong>of</strong> TiO 2 nanoparticles prepared by a 

Fig. 

method at (a) 50 o C and (b) sample I calcined at 


300 Amir Hassanjani-Roshan, Seyed Mohammad Kazemzadeh, Mohammad Reza Vaezi and Ali Shokuhfar 

Experimental 

Results and Discussion 

calcined at 500 o C for 1 h. It is seen that anatase (JCPDS. 

ultrasound irradiation. 

different TiO 2 samples were prepared by this procedure 

V IV III II I Sample 

1 3 5 7 9 Initial <strong>sonication</strong> <strong>power</strong> (W) 

500 o for 1 h (c) sample V calcined at 500 o C for 1 h. 

9 15 24 33 48 Ultrasound intensity (W/cm 2 )

21-1272) and rutile (JCPDS. Pattern 21-1276) phases 

Pattern 

in the diffractograms. 

exist 

the X-ray diffractogram <strong>of</strong> all the samples, the characteristic 

In 

peaks <strong>of</strong> anatase and rutile at (2θ =25.2 o , 37.8 o , 

o , 48 o , 53.8 o , 55.0 o , 62.6 o , 64.1 o , 68.8 o ) and (2θ = 

38.5 o , 36.0 o , 39.2 o , 41.2 o , 44.1 o , 54.3 o , 69 o ) were observed, 

27.4 

Also, the present method has been shown to 

respectively. 

advantageous as it has been able to retain the anatase 

be 

rutile phases <strong>of</strong> TiO 2 even at 500 o C, while there are 

and 

that the anatase can be converted to the rutile phase 

reports 

temperatures higher than 450 o C [12]. 

at 

peak broadening <strong>of</strong> an XRD reflection can be used 


estimate the crystallite size based on Scherrer’s equation 

to 

follows [33]: 

as 

D is the crystallite size (nm), k is a shape-sensitive 

where 

(0.9, assuming spherical spheres), λ the wave- 

coefficient 

<strong>of</strong> the X-ray beam (λ = 0.15406 nm for Cu-K α 

length 

β the full width at half maximum (FWHM) 

radiation), 

the diffraction peak under consideration, and θ the 

for 

angle. 

diffraction 

average crystallite sizes <strong>of</strong> the rutile and anatase phases 


from Scherrer’s equation are about 8 nm. 

determined 

analysis 

TG-DTA 

XRD results showed that the initial product had 


characteristics. <strong>The</strong>rmogravimetric and differential 

amorphous 

thermal analysis (TG/DTA) was used to determine 

temperature and time <strong>of</strong> crystallization <strong>of</strong> TiO 2 nanoparticles. 


Fig. 2. Shows TG-DTA curves <strong>of</strong> TiO 2 nano- 

obtained from the suspension sonicated for 

particles 

h at 50 o C. 

1.5 

to Fig. 2, the samples were heat treated at 

According o C for 1.5 hour to obtain the crystalline titanium 

500 

nanoparticles. A main exothermic peak at around 

dioxide o C is detected in the TG-DTA curve. <strong>The</strong> exothermic 

500 

2. TG-DTA curves <strong>of</strong> the nanopowders synthesized by 

Fig. 

irradiation for 1.5 h at 50 o C. 

ultrasound 

the amorphous particles and the formation <strong>of</strong> TiO 2 phase 


in this process. <strong>The</strong> TG-DTA curve shows that the 

occurs 

loss is about 15%. <strong>The</strong> weight loss remains constant 

weight 

the DTA curve decreases with an increase in the 

while 

because this weight loss depends on the intrinsic 

temperature 

<strong>of</strong> the material and is realized in a special temperature 

value 

analysis 

TEM 

3. shows TEM images <strong>of</strong> TiO 2 nanoparticles prepared 

Fig. 

different intensities <strong>of</strong> ultrasound waves. <strong>The</strong> particle 

with 

<strong>of</strong> TiO 2 from the TEM images are listed in Table 2. 

sizes 

average size <strong>of</strong> TiO 2 nanoparticles was increased from 


to 30 nm when the intensity <strong>of</strong> the ultrasound waves was 

12 

from 48 W/cm 2 to 9 W/cm 2 in this process 

decreased 

4). (Fig. 

study <strong>of</strong> the morphology <strong>of</strong> nanoparticles in this 

A 

process showed that with different ultrasound 


the morphology <strong>of</strong> TiO 2 nanoparticles is nearly 

intensity, 

and semi spherical with a smooth geometry. From 

spherical 

images <strong>of</strong> these nanoparticles, it can be clearly seen 

TEM 

the nanoparticles have some aggregation. Also, the 

that 

proved that the TiO 2 nanoparticles were agglomerated 

images 

some places. 

in 

3. Transmission electron microscopy (TEM) images <strong>of</strong> TiO 2 

Fig. 

calcined at 500 o C and synthesized at (a) 48 W/cm 2 

nanoparticles 

Table 2. Particle sizes <strong>of</strong> synthesized samples from TEM images 

<strong>The</strong> <strong>effect</strong> <strong>of</strong> <strong>sonication</strong> <strong>power</strong> on the sonochemical synthesis <strong>of</strong> titania nanoparticles 301 

range and is independent <strong>of</strong> an increase in the temperature. 

k.λ 

D 

β.Cosθ 

(1) 

= ---------------- 

peak at around 500 o C shows the crystallization temperature 

(b) 33 W/cm 2 (c) 24 W/cm 2 (d) 15 W/cm 2 (e) 9 W/cm 2 . 

Sample 

Particles Size(nm) 

I 12 

II 18 

III 23 

IV 28 

V 30

Fig. 4. Variation <strong>of</strong> particles size vs. the ultrasound intensity. 

output <strong>power</strong>) 

(<strong>sonication</strong> 

results obtained in this section show that the ultrasound 


plays very important roles in the morphological 

intensity 

dimensional properties <strong>of</strong> titanium dioxide nanoparticles. 

and 

in this process, the ultrasound intensity plays two 

Also, 

roles. 1) the dispersion <strong>of</strong> TiO 2 nanoparticles 

different 

2) the production <strong>of</strong> TiO 2 nanoparticles with broken 

and 

bonds. 

chemical 

the case <strong>of</strong> ultrasound intensity, increasing the ultrasound 

In 

increases the cavitations phenomenon so the 

intensity 

cavity in the solution creates a shockwave and 

collapsed 

the particles size is decreased. Also, the shockwaves 

hence 

the surface are known to create a localized erosion 

on 

is responsible for many sonochemical <strong>effect</strong>s on 

which 

reactions [34]. Moreover, the shockwaves 

heterogeneous 

by homogeneous cavitations can create high velocity 

created 

collisions [34-36]. 

inter-particle 

final results indicate that the sonochemical method 


be easily controlled and is expected to be applicable 

can 

fabrication <strong>of</strong> other nanosized particles. 

for 

this paper, TiO 2 nanopowders were synthsized via 

In 

sonochemical method successfully. <strong>The</strong> processing con- 

a 

have important <strong>effect</strong>s on the morphology, particle 

ditions 

and the formation <strong>of</strong> a stable phase. Also, increasing 

size 

ultrasound intensity decreases the particle size <strong>of</strong> the 


2 . With an increase in the calcination temperature about 

TiO 

o C, the anatase phase can be converted to the rutile phase. 

450 

to the results, the median size <strong>of</strong> the particles 

According 

about 12-30 nm and the average size <strong>of</strong> the crystallite 

is 

two stable phases (anatase and rutile) in this process 

for 

about 8 nm. <strong>The</strong> morphology <strong>of</strong> particles is spherical 

is 

semi spherical. 

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<strong>The</strong> <strong>effect</strong> <strong>of</strong> <strong>sonication</strong> <strong>power</strong> on the sonochemical synthesis <strong>of</strong> titania nanoparticles 303

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