synthesis of wo3 in nanoscale with the usage of sucrose ester

Radimana , M.A.bin Yarmob a School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia UKM, 43600 Bangi, Selangor Darul Ehsan, Malaysia b School of Chem

Synthesis of WO 3 in nanoscale with the usage of sucrose ester

microemulsion and CTAB micelle solution

N Asima,⁎ , S Radimana

, M.A.bin Yarmob a

School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM), 43600 Bangi, Selangor Darul Ehsan, Malaysia b

School of Chemical Science and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM),

43600 Bangi, Selangor Darul Ehsan, Malaysia Received 21 June 2006; accepted 9 October 2006 Available online 30 October 2006

Abstract

WO3nanoparticles were successfully prepared using first the low temperature hydrolysis method and second the chemical reaction method in water-in-oil sucrose ester microemulsion consisting of S1570, 1-butanol, tetradecane and aqueous phase In this study WO3nanoparticles also were prepared using the CTAB micelle solution The resultant WO3 nanoparticles have been investigated with X-ray diffraction (XRD), transmission electron microscopy (TEM), variable pressure scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS) The shape and particles size of the resultant WO3 nanoparticles from both methods in sucrose ester microemulsion show similar spherical shape and size range between 10 and 50 nm The WO3nanoparticles prepared with the CTAB micelle solution show spherical shape with the size range average of 25–50 nm

© 2006 Elsevier B.V All rights reserved

Keywords: WO 3 ; Nanoparticles; Sucrose ester microemulsion; X-ray techniques

1 Introduction

Tungsten trioxide is a simple compound in terms of

stoichiometry, but it is complex in terms of structure and phase

transitions Tungsten oxide is known as a photochromic and

electrochromic material since it changes color upon the

absorp-tion of light and in response to an electrically induced change in

oxidation state

WO3exhibits the electrochemical effect[1]and can be used

sensing[3] It can be operated reversibly and usually has stable

chemical and thermal properties over extended periods of use

Gas-sensitive resistors based on tungsten oxide are useful for

photocatalytic degradation of organic compounds, including a

purificatory ecomaterial suitable for application in energy renewal, energy storage and environmental cleanup In all of these applications, the morphological characteristics of the materials like grain size or shape are very important and depend strongly on the preparation method

In the last decade, there has been an increasing interest in the study of nanocrystalline materials owing to the different physical and chemical properties compared with conventional coarse-grained structures[7–10] The surface-to-bulk ratio for a nanocrystalline material is much greater than for a material with large grains, which yields a large interface between the solid and

a gaseous or liquid medium

Many different methods have been used for the production of nanometer particles Microemulsions that contain surfactant, oil, water and sometimes co-surfactant have been used widely for the synthesis of nanomaterials in the last two decades Sucrose esters are biodegradable surfactants that can be manufactured in various hydrophilic–lipophilic properties using different fatty acids varying in their lipophilic chain length Sucrose esters exist in a large variety of HLB values The physical properties of sucrose

⁎ Corresponding author Tel.: +60 3 89214131; fax: +60 3 89269470.

E-mail address: n_asim2001@yahoo.com (N Asim).

0167-577X/$ - see front matter © 2006 Elsevier B.V All rights reserved.

doi: 10.1016/j.matlet.2006.10.014

esters are somewhat unique Unlike the alkyl ethoxylates, the

sucrose esters do not significantly change their HLB with

in-creasing temperature Consequently, inin-creasing the temperature

does not induce a phase inversion in microemulsion systems based

on sucrose esters, as was observed in microemulsions based on

alkyl ethoxylates Temperature-insensitive sucrose ester-based

found in general that sucrose esters are not able to form

sucrose esters are hydrophilic it was not expected that these surfactants will form reverse micelles or w/o microemulsions However, Garti et al.[15]showed that the addition of a co-solvent/ co-emulsifier, such as short- or medium-chain alcohols, induces the formation of reverse micelles and the solubilization of

Fig 1 The VPSEM images of WO 3 nanoparticles prepared in this study.

Fig 2 The TEM images of WO3 nanoparticles prepared in this study.

significant amounts of water into the micellar core to form

nanosize with different size ranges using sucrose ester and CTAB

surfactants and its chemical and physical properties were

investigated

2 Materials and methods

2.1 Materials

Nonionic surfactant of food grade sucrose fatty acid ester

(hereafter denoted as S1570 with HLB value = 15) and

tetradecane (99%) were supplied from Mitsubishi-Kagaku

Foods Corporation and TCI respectively Hexadecyl trimethyl

ammonium bromide (CTAB) (purity approx 99%) was

purchased from Sigma 1-butanol (N98% GC) and 1-hexanol

were purchased from Fluka

Tungsten (VI) chloride (99%) and ammonia solution (25%)

were purchased from Aldrich and BDH respectively Deionized

and double distilled water was used for microemulsion and

solution preparation All the chemicals and solvents were used

as received without further purifications

2.2 Determination of phase diagram for sucrose ester

diagram, alcohol, oil, sucrose ester mixtures were titrated with

water The behavior of the four-component system is described

in pseudo-ternary phase diagrams in which the weight ratio of

two components was fixed Usually, the oil:alcohol weight ratio

was held constant at 1:1 The construction of the phase diagram

was conducted in a thermostatic bath (37 ± 1 °C)

The weight ratio of tetradecane (oil phase) and 1-butanol (co-surfactant) was fixed at 1:1, whereas the surfactant phase consisted of sucrose ester (S1570) The sugar ester used is a commercial sucrose monoester of stearic acid (S1570, denoted as SES, HLB = 15, at least 70% monoester) in a mixture with di- and polyesters of stearic and palmitic acids The oil phase consists of a 1:1 weight ratio of tetradecane and l-butanol The addition of the co-solvent (l-butanol) to the oil phase turned the oil phase into a better solvent and allowed significant solubilization of the surfactant into the oil with the formation of inverse micelles

Fig 3 The XRD diffractogram for WO 3 (a) bulk, (b) sample 1, (c) sample 2 and

(d) sample 3, respectively.

Fig 4 The energy dispersive X-ray (EDX) results for WO nanoparticles.

The co-solvent is necessary because of the hydrophilicity of the

sucrose monostearate and hydrophobicity of the oil Upon

addition of 1-butanol to tetradecane , due to its amphiphilic

character it will redistribute into the interface and must therefore

be considered also as a co-surfactant and not just as a co-oil; i.e., it

has the ability to participate in the self-assembly with the

surfactant The microemulsion system used is solid at room

temperature, but liquefies and structures into a homogeneous

The typical microemulsion used in the present study has the following composition: 30 wt.% of S1570, 50 wt.% of

Fig 5 Peak-fitted W 4f , O 1s and C 1s signals of WO 3 nanoparticles (a) sample 1, (b) sample 2 and (c) sample 3 respectively.

tetradecane/1-butanol and 20 wt.% of aqueous solution.

Aqueous solutions containing of 4 wt.% and 14 wt.% of

tungsten (VI) chloride and ammonia solution respectively Two

with the use of sucrose ester microemulsion

In the first method, a w/o microemulsion with the

composition: 30 wt.% of S1570, 50 wt.% of

tetradecane/1-butanol and 20 wt.% of aqueous solution containing of 4 wt.%

tungsten (VI) chloride, was stirred vigorously for 2 h at about

45 °C Then this solution was kept in 60 °C for 4 days and were

washed several times with deionized water and absolute ethanol

in order to remove the surfactant, residual reactants and

byproducts All the precipitates were place in the furnace at

500 °C for 2 h (hereafter denoted as sample 1)

In the second method, two types of w/o microemulsion with

the composition: 30 wt.% of S1570, 50 wt.% of

tetradecane/1-butanol and 20 wt.% of aqueous solution (containing of 4 wt.%

and 14 wt.% of tungsten (VI) chloride and ammonia solution

respectively) have been prepared

After stirring and getting homogeny solutions, the

micro-emulsion containing ammonia solution was added to the other

microemulsion containing tungsten (VI) chloride The mixed

microemulsion was stirred for 3 h at about 45 °C Then the

mixed microemulsion was kept at room temperature for 3 days

in order to precipitate After washing several times with

deionized water and absolute ethanol in order to remove the

surfactant, residual reactants and byproducts, the precipitate

was kept in the furnace at 500 °C for 2 h (hereafter denoted as

sample 2) The CTAB micelle solution used in the present study

has a composition of 30 wt.% CTAB, 54 wt.% 1-hexanol and

16 wt.% of aqueous solution This chosen composition was

nanoparticles preparation, two micelle solutions with the

composition mentioned above with aqueous solutions

contain-ing of 3.1 wt.% and 12.5 wt.% of tungsten (VI) chloride and

ammonia solution respectively were prepared After stirring and

getting clear solutions, the micelle solution containing ammonia

solution was added to the other micelle solution containing

tungsten (VI) chloride The mixed micelle solution was stirred

for 4 h at about 50 °C Then the mixed micelle solution was kept

at room temperature for 3 days in order to precipitate After

washing several times with deionized water and absolute

ethanol in order to remove the surfactant, residual reactants and

byproducts, the precipitate was kept in the furnace at 500 °C for

2 h (hereafter denoted as sample 3)

The study of the morphology and composition of the

scanning electron microscope (VPSEM), (model Leo 1450, accelerating voltage at 30 kV) equipped with energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM) (model Phillips, CM12) operated at 100 kV The X-ray diffraction (XRD) measurements were performed by a Bruker D8 advance X-ray diffractometer with running step = 0.02° in the range of 20–65° 2-Theta, using a monochromatized Cu K α radiation (λ=0.154 nm)

The XPS analyses were performed using a XSAM-HS KRATOS X-ray photoelectron spectroscopy X-ray source type MgK was used with 10 mA current and 12 kV voltage to run XPS analysis for samples at 10− 9Torr pressure

The pass energy was set at 160 eV for the survey spectra and

at 40 eV for the high resolution spectra of all elements of interest Data processing was performed using the Kratos software after Shirley baseline subtraction and using Schofield sensitivity factors corrected for instrumentation transmission function

3 Results and discussion The morphologies and size of the prepared nanoparticles were studied

by variable pressure scanning electron microscope (VPSEM) and transmission electron microscopy (TEM) They give comparable informa-tion for morphology and size investigainforma-tions The VPSEM and TEM images are depicted in Figs 1 and 2 respectively and show that the WO3 nanoparticles prepared via sucrose ester microemulsion for both methods have spherical shape and approximately the same size range between 10 and 50 nm WO3nanoparticles prepared via CTAB microemulsion also have a spherical shape but with bigger size range between 25 and 50 nm The XRD patterns inFig 3shows that the WO3was in the form of orthorhombic lattice for all of the nanoparticles More evaluation of the composition and purity of prepared WO3nanoparticles has been done

by energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS) The calculated stoichiometry for the prepared nanoparticles taken from the atomic ratio data of EDX measurements (Fig 4) is WO3within the limits of the experimental error

The wide scan of XPS spectrum within the B.E range of 0–1100 eV and the narrow scan have been done for the WO3samples.Fig 5shows peak analysis of W4f 7/2, W4f 5/2, O1sand C1ssignals for WO3samples Both of the XPS and EDX patterns reveal the existence of W, O and

C in the nanoparticles The existence of C impurity in nanoparticles is believed to originate from environmental contamination and also the residual surfactants absorbed on the nanoparticles

The C1speak in the XPS results (Fig 5) is from carbon contamination that is very usual and in fact, it is often used to calibrate peak position and

in this case we assumed it comes from the residual surfactant and the environment The photoelectron peak of the W4fregion in all of WO3

samples shows a well-resolved double peak due to the 4f7/2and 4f5/2 components (spin orbit splitting) and reveals the W+ 6state and oxide form of tungsten in compound according to XPS handbook[20] The O1s band was deconvoluted in 3 components, the first one from right assumed

is terminal oxygen (_O) and the second one is linkage oxygen (–O–) and these peaks were associated to the O2−state, and the third one is

Table 1

Binding energy (eV) for relative peak of WO 3 samples (corrected using

C 1s = 285 eV as a reference)

Sample Particle size

(nm), shape

O 1s (1)

O 1s (2)

O 1s (3)

W 4f (1)

W 4f (2)

W 4f (3)

W 4f (4)

WO 3 (bulk) 40 –120,

different shapes

530.3 532.1 533.5 35.7 37.8

WO 3 (sample 1) 10 –50,

spherical

530.6 532.2 533.6 36.0 38.0

WO 3 (sample 2) 10 –50,

spherical

530.5 532.3 533.8 35.9 38.1 37.3 39.7

WO 3 (sample 3) 25 –50,

spherical

530.7 532.4 533.6 36.1 38.2

assumed to come from different sources, probably coming from rooted

OH groups or from humidity in ambience (Table 1)[20] The binding

energies show the blue shift for nanomaterials prepared in this study

compared with the bulk one and the more study on XPS blue shift induced

in WO3nanoparticles are still in progress

4 Conclusion

Sucrose ester microemulsion and CTAB micelle solution

systems in the reverse micelle region have been used as

nanoparticles have been investigated with XRD, VPSEM, EDX

TEM and XPS methods and the results have shown and

nanoparticles obtained from using the one sucrose ester

microemulsion with heat aging process and using of the mixing

two sucrose ester microemulsions process In both methods

using sucrose ester microemulsion as a template the shapes are

spherical with the orthorhombic lattice and particles sizes are

approximately between 10 and 50 nm

have spherical shape with bigger size range between 25–50 nm

and orthorhombic lattice More work to optimize the reaction

conditions like precursors concentration and temperature for all

mentioned methods for preparing smaller size range with very

narrow size distribution is still in progress Finally this study

shows that the sucrose ester (biodegradable surfactants)

Acknowledgements

The author would like to thank the following UKM staff

namely: Mr Zaki, Mr Zailan, Ms Normala and Mr Syed for

helping with the use of VPSEM, XRD, TEM and XPS respectively

References

[1] S.K Deb, Philos Mag 27 (801) (1973).

[2] J.S.E.M Svensson, C.G Granqvist, Sol energy mater 12 (1985)

391 –402.

[3] H.T Sun, C Cantalini, L Lozzi, M Passacantando, S Santucci, M Pelino, Thin Solid Films 287 (1996) 258 –265.

[4] D.E Williams, Sens Actuators, B, Chem 57 (1999) 1 –16.

[5] S.R Aliwell, J.F Halsall, K.F.E Pratt, J O'Sullivan, R.L Jones, R.A Cox, S.R Utembe, G.M Hansford, D.E Williams, Meas Sci Technol 12 (2001) 684 –690.

[6] E Pelizzetti, Chemosphere 17 (1998) 499 –510.

[7] H Gleiter, Prog Mater Sci 33 (1989) 223.

[8] H Gleiter, Mat Sci Forum 67 (1995) 189 –190.

[9] R.W Siegel, Annu Rev Mater Sci 21 (1991) 559 –578.

[10] R.W Siegel, Mat Sci Forum 851 (1997) 235 –238.

[11] H Kunieda, N Ushio, A Nakano, M Miura, J Colloid Interface Sci 159 (1993) 37 –44.

[12] K Aramaki, H Kunieda, M Ishitobi, T Tagawa, Langmuir 13 (1997) 2266–2270.

[13] M.A Pes, K Aramaki, N Nakamura, H Kunieda, J Colloid Interface Sci.

178 (1996) 666 –672.

[14] M.A Thevenin, J.L Grossiord, M.C Poelman, Int J Pharmacol 137 (1996) 177 –186.

[15] N Garti, A Aserin, M.E Leser, V Clement, M Fanun, J Mol Liq 80 (1999) 253 –296.

[16] N Garti, V Clement, M Fanun, M.E Leser, J Agric Food Chem 48 (2000) 3945 –3956.

[17] N Garti, A Aserin, I Tiunova, M Fanun, J Colloids Surf., B Biointerfaces 170 (2000) 1 –18.

[18] O Glatter, D Orthhaber, A Stradner, J Colloid Interface Sci 241 (2001)

215 –225.

[19] P Ekwall, Advances in Liquid Crystals 1 (1975) 1 –142.

[20] J.F Moulder, W.F.S Tickle, Handbook of X-ray Photoelectron Spectros-copy, Perkin-Elmer corporation, 1992.