- Email: [email protected]
O microemulsion
Materials Letters 65 (2011) 2820–2822
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
The preparation of iron (III) oxide nanoparticles using W/O microemulsion Kanda Wongwailikhit ⁎, Saranporn Horwongsakul Department of Chemistry, Faculty of Science, Rangsit University, Thailand
a r t i c l e
i n f o
Article history: Received 24 September 2010 Accepted 16 May 2011 Available online 19 May 2011 Keywords: W/O microemulsion Hematite Nanoparticle Fe2O3
a b s t r a c t Iron (III) oxide, Fe2O3, nanoparticles were prepared using W/O microemulsion as the reactor. W/O microemulsion was formed using n-heptane as oil phase, water and AOT as the surfactant under the specific composition. Iron (III) Chloride was used as a starting material and Ammonium hydroxide was a precipitating agent. Fe2O3, nanoparticles were then produced in situ the water core. Size of particles could be adjusted by the water content of the mixtures. The higher the water content, the bigger the particle size. The average size of the nanoparticles obtained was smaller than 100 nm. Moreover, Fe2O3 produced by this method was hematite with hexagonal in structure. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Aerosol-OT (AOT) is short for sodium bis(2-ethylhexyl) sulfosuccinate. It is the anionic surfactant which is slightly soluble in water because of two tails of C12 hydrophobic part. AOT has sulfonate head groups with sodium counterions that form the interface with the reverse micelle's water nanopool. In a continuous nonpolar organic phase, reverse micelle solution can be called water in oil microemulsion (W/O microemulsion). Reverse micelle solution formed by AOT are transparent, isotropic, thermodynamically stable where which aqueous phase is dispersed as nanosized droplets surrounded by a monolayer of surfactant molecules [1,2]. Inside the water nanopool core of water, the aqueous reaction can be incorporated and yield very fine particles. Therefore, W/O microemulsion are used in a numerous works to prepare a variety of nanoparticles of some metallic particles, Ag [3], metal oxide and sulfide catalysts, such as Fe3O4[4] TiO2[5] CdS [6,7] and some alloy nanoparticles for example Pt70Fe30[8]. Many advantages of the reverse micelle method are reported such as easily controllable process, and it is possible to obtain a narrow particle size distribution [9]. Hematite (α-Fe2O3) is one of the most used as electronic materials, pigments, cosmetics, coatings, abrasives, catalyze, etc. Many works has reported the preparation of monodispersed α-Fe2O3 in the shape of cubic, spherical, ellipsoidal, rod-like morphology and rectangular [10,11]. Electrothermal process [12] and hydrothermal process [10,11,13] are mostly used for synthesizing. Even of the excellent results from the methods above, it is found that the particle size is hardly controlled according to the some difficulty in the processes. Therefore, this study aims to find out if the reverse micelle reaction
scheme can minimize those drawbacks and be capable the favorable process for synthesizing very fine particle with a small size distribution of Fe2O3. 2. Experimental 2.1. Reagents The AOT was obtained from Fluka (purum, N98%) and used without further purification. The n-heptane solvent was of Fluka HPLC
H2O
20
40
0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.05.063
60
60
40
C B
80
20
A
AOT ⁎ Corresponding author at: Department of Chemistry, Faculty of Science, Rangsit University, 52/374 Muang-Ake Village, Phaholyothin Road, Patumtani 12000, Thailand. Tel.: + 66 2 9972220x1553, 3833; fax: + 66 2 9972220x1560. E-mail address: [email protected] (K. Wongwailikhit).
80
20
40
60
80
n-C7H16
Fig. 1. Pseudo-ternary phase diagram of n-heptane / AOT/ water microemulsion including the three different fractions of W/O microemulsion (A, B and C) chosen for studying in this work.
K. Wongwailikhit, S. Horwongsakul / Materials Letters 65 (2011) 2820–2822 Table 1 Weight fractions (%) of the W/O emulsion system used in this study. Mixture
Weight fraction H2O : C7H16 : AOT
Fraction A Fraction B Fraction C
15.0 : 75.0 : 10.0 35.0 : 50.0 : 15.0 45.0 : 35.0 : 20.0
grade. All reagents were used as received. Water was double deionized and distilled. 3. Experimental The pseudo-ternary phase diagram for the system n-heptane/AOT/ H2O was reconstructed by titration method. The phase boundaries were established by observation of turbidity-to-transparency (or of transparency-to-turbidity) transitions. Based on the constructed phase diagram, the W/O microemulsion was prepared by mixing the required amount of H2O in a stock solution of AOT in n-heptane for reaching the specific ratio of microemulsion. The resulting clear solution was characterized by naked eye and turbidity meter and left overnight for reaching the equilibrium. Concentrated NH4OH and 1.0 M FeCl3 were used as the precursors for the reaction in the water core. Once FeCl3 and conc.NH4C l were dropped into the W/O microemulsion, Fe2O3 was
2821
then produced in situ the water core. The mixture was stirred over night for getting equilibrium. To remove Fe2O3 from the mixture, distilled water was added to destroy the microemulsion system where which the separation between two layer of organic solvent and aqueous phase was established. Suspended Fe2O3, was then filtered and washed with 95% ethanol many times. Fe2O3 particle was subjected to dry in the furnace at 300 °C for 3 h. Effect of water fractions in the W/O microemulsion was determined by repeating the procedures with three different fractions of W/O microemulsion system. Fe2O3 particle obtained were examined by Scanning electron microscope (JEOL model JSM 6301-F). X-ray diffraction analysis (XRay Diffractometer: Bruker AXS, Model D8 Advance) was also done using CuKαat 40 kV, 30 mA and1.54056 A o. Infrared Spectra in KBr pellets were recorded in the range of 4000–250 cm − 1 on Perkin Elmer, Model Spectrum 100 FTIR spectrometer. 4. Results and discussion 4.1. Phase behavior The pseudo-ternary phase diagram obtained by titration method is shown in Fig. 1 which is in excellent agreement with those published for the same system [8]. The region of continuous single phase microemulsion is determined as being permanent transparency and indicated in the diagram as region “I”. Above region I, permanent turbid is formed and labeled with “S” region.
Fig. 2. Fe2O3 synthesized in three different systems.
Fig. 3. SEM pictures of Fe2O3 synthesized from three different fractions W/O microemulsion.
K. Wongwailikhit, S. Horwongsakul / Materials Letters 65 (2011) 2820–2822
1010
220
208
018
214 300
024
113 202
006
012
116
110
104
2822
Fig. 4. X-ray diffraction pattern of Fe2O3 synthesized by this method.
4.2. The effect of water fraction Fe2O3 synthesized in the water core of the three different fractions W/O emulsion system (A, B and C) were examined. The component fractions used in this study is shown in Table 1 and Fig. 1. It should be mentioned here that the water fraction increased in the order of A B and C, respectively. In the process, the virtually results was observed. Just after FeCl3 and NH4OH, were droplet added into the mixture, the red–brown of Fe2O3 particles were formed and suspended without precipitation. After adding the distilled water, phase separation between lower aqueous phase and upper organic solvent phase was established. The particulate Fe2O3 of systems showed the distinguishable dispersion which was attributed to their particle sizes as shown in Fig. 2. Very fine particle, synthesized from fraction A (Fig. 2a) floated on top of the organic heptane layer while the bigger one, synthesized from fraction B (Fig. 2b), suspended in the heptane layer. The biggest one, from the fraction C (Fig. 2c), sank into the lower aqueous layer according to its weight. It was clearly shown that the particle size respectively increased from fraction A, B and C corresponding to the percent water content inside. This observation was confirmed by the result from Scanning Electron Microscope shown in Fig. 3 which showed that Fe2O3 from fraction A, Fig. 3(a), had a narrow and more uniform size distribution with an average diameter of 50 nm. In addition, the shape of Fe2O3 was approximately spherical. Fe2O3 yielded from fraction B and C, Fig. 3 (b) and (c), had larger size with some plate structures (arrow). This reflected that the water content in W/O microemulsion affected strongly to the size and shape of particulate. Therefore, the W/O microemulsion method could be an excellent method to control the particle size with the monodispersed and narrowly distribution. The XRD pattern is shown in Fig. 4. In this figure, the diffraction peak corresponded to the diffraction pattern of standard α-Fe2O3 given by the JCPDS-ICDD pattern and matched with the Fe2O3 produced by other methods [11,13]. The dominant bands of IR spectrum (at about 383, 480 and 574 cm − 1) in Fig. 5 are the characteristic of crystalline α-Fe2O3 [10,11]. Bands at 3420 and 1635 cm − 1 were ascribed to hydroxide group and water, respectively [11]. From above, the constituent of precipitate produced by this method was α-Fe2O3 with hematite in structure.
Fig. 5. Infrared spectrum of Fe2O3.
5. Conclusion α-Fe2O3 nanoparticle with hexagonal structure of hematite was successfully synthesized in situ the water cores of W/O microemulsion system of H2O n-heptane and AOT. A high degree of monodispersity and small size was obtained by using small water content. By increasing the water fraction in W/O microemulsion, the increase of particles size was obtained. Acknowledgement This research work was supported by Research Center, Rangsit University under the grant number RI 05/2008. References [1] Spry DB, Goun A, Glusac K, Moilanen DE, Fayer MD. Proton transport and the water environment in nafion fuel cell membranes and AOT reverse micelles. J Am Chem Soc 2007;129:8122–30. [2] Cassin G, Illy S, Pileni MP. Chemical modified proteins solubilized in AOT reverse micelles: Influence of proteins charges on intermicellar interactions. Chem Phys Lett 1994;21:205–12. [3] Dai Y, Deng T, Jia S, Jin L, Lu F. Preparation and characterization of fine silver powder with colloidal emulsion aphrons. J Membr Sci 2006;281:685–91. [4] Liu ZL, Wang X, Yao KL. Synthesis of magnetite nanopartices in W/O microemulsion. J Mater Sci Lett 2004;39:2633–6. [5] Hirai T, Sato H, Komasawa I. Mechanism of formation of titanium dioxide ultrafine particles in reverse micelles by hydrolysis of titanium tetrabutoxide. Ind Eng Chem Res 1993;32:3014–9. [6] Hirai T, Bando Y, Komasawa I. Immobilization of CdS nanoparticles formed in reverse micelles onto alumina particles and their photocatalytic properties. J Phys Chem B 2002;35:8967–70. [7] Pileni MP, Motte L, Petit C. Synthesis of cadmium sulfide in situ in reverse micelles: Influence of the preparation modes on size, polydispersity, and photochemical reactions. Chem Mater 1992;2:338–45. [8] Malheiro AR, Varanda LC, Perez J, Villullas HM. The aerosol OT + n-butanol + nheptane + water System: Phase behavior: Structure characterization and application to Pt70Fe30 nanoparticle synthesis. Langmuir 2007;23:11015–20. [9] Yuan S, Cai Z, Xu G, Jiang Y. Mesoscopic simulation study on phase diagram of system oil/water/aerosol OT. Chem Phys Lett 2002;365:347–53. [10] Wang X, Chen X, Ma X, Zheng H, Ji M, Zhang Z. Low temperature synthesis of αFe2O3 nanoparticles with a closed cage Structure. Chem Phys Lett 2004;384: 391–3. [11] Jing Z, Shihua W. Synthesis and characterization of monodisperse hematite nanoparticles modified by surfactants via hydrothermal approach. Mater Lett 2004;58:3637–40. [12] Katsuki H, Komarneni S. Role of α-Fe2O3 morphology on the color of red pigment for porcelain. J Am Ceram Soc 2003;86:183–5. [13] Avila-Garcia A, Carbajal-Franco G, Tiburcio-Silver A, Barrera-Calva E, AndradeIbarra E. α-Fe2O3 films grown by the spin-on sol-gel deposition method. Rev Mex Fis 2003;49:219–23.
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
The preparation of iron (III) oxide nanoparticles using W/O microemulsion Kanda Wongwailikhit ⁎, Saranporn Horwongsakul Department of Chemistry, Faculty of Science, Rangsit University, Thailand
a r t i c l e
i n f o
Article history: Received 24 September 2010 Accepted 16 May 2011 Available online 19 May 2011 Keywords: W/O microemulsion Hematite Nanoparticle Fe2O3
a b s t r a c t Iron (III) oxide, Fe2O3, nanoparticles were prepared using W/O microemulsion as the reactor. W/O microemulsion was formed using n-heptane as oil phase, water and AOT as the surfactant under the specific composition. Iron (III) Chloride was used as a starting material and Ammonium hydroxide was a precipitating agent. Fe2O3, nanoparticles were then produced in situ the water core. Size of particles could be adjusted by the water content of the mixtures. The higher the water content, the bigger the particle size. The average size of the nanoparticles obtained was smaller than 100 nm. Moreover, Fe2O3 produced by this method was hematite with hexagonal in structure. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Aerosol-OT (AOT) is short for sodium bis(2-ethylhexyl) sulfosuccinate. It is the anionic surfactant which is slightly soluble in water because of two tails of C12 hydrophobic part. AOT has sulfonate head groups with sodium counterions that form the interface with the reverse micelle's water nanopool. In a continuous nonpolar organic phase, reverse micelle solution can be called water in oil microemulsion (W/O microemulsion). Reverse micelle solution formed by AOT are transparent, isotropic, thermodynamically stable where which aqueous phase is dispersed as nanosized droplets surrounded by a monolayer of surfactant molecules [1,2]. Inside the water nanopool core of water, the aqueous reaction can be incorporated and yield very fine particles. Therefore, W/O microemulsion are used in a numerous works to prepare a variety of nanoparticles of some metallic particles, Ag [3], metal oxide and sulfide catalysts, such as Fe3O4[4] TiO2[5] CdS [6,7] and some alloy nanoparticles for example Pt70Fe30[8]. Many advantages of the reverse micelle method are reported such as easily controllable process, and it is possible to obtain a narrow particle size distribution [9]. Hematite (α-Fe2O3) is one of the most used as electronic materials, pigments, cosmetics, coatings, abrasives, catalyze, etc. Many works has reported the preparation of monodispersed α-Fe2O3 in the shape of cubic, spherical, ellipsoidal, rod-like morphology and rectangular [10,11]. Electrothermal process [12] and hydrothermal process [10,11,13] are mostly used for synthesizing. Even of the excellent results from the methods above, it is found that the particle size is hardly controlled according to the some difficulty in the processes. Therefore, this study aims to find out if the reverse micelle reaction
scheme can minimize those drawbacks and be capable the favorable process for synthesizing very fine particle with a small size distribution of Fe2O3. 2. Experimental 2.1. Reagents The AOT was obtained from Fluka (purum, N98%) and used without further purification. The n-heptane solvent was of Fluka HPLC
H2O
20
40
0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.05.063
60
60
40
C B
80
20
A
AOT ⁎ Corresponding author at: Department of Chemistry, Faculty of Science, Rangsit University, 52/374 Muang-Ake Village, Phaholyothin Road, Patumtani 12000, Thailand. Tel.: + 66 2 9972220x1553, 3833; fax: + 66 2 9972220x1560. E-mail address: [email protected] (K. Wongwailikhit).
80
20
40
60
80
n-C7H16
Fig. 1. Pseudo-ternary phase diagram of n-heptane / AOT/ water microemulsion including the three different fractions of W/O microemulsion (A, B and C) chosen for studying in this work.
K. Wongwailikhit, S. Horwongsakul / Materials Letters 65 (2011) 2820–2822 Table 1 Weight fractions (%) of the W/O emulsion system used in this study. Mixture
Weight fraction H2O : C7H16 : AOT
Fraction A Fraction B Fraction C
15.0 : 75.0 : 10.0 35.0 : 50.0 : 15.0 45.0 : 35.0 : 20.0
grade. All reagents were used as received. Water was double deionized and distilled. 3. Experimental The pseudo-ternary phase diagram for the system n-heptane/AOT/ H2O was reconstructed by titration method. The phase boundaries were established by observation of turbidity-to-transparency (or of transparency-to-turbidity) transitions. Based on the constructed phase diagram, the W/O microemulsion was prepared by mixing the required amount of H2O in a stock solution of AOT in n-heptane for reaching the specific ratio of microemulsion. The resulting clear solution was characterized by naked eye and turbidity meter and left overnight for reaching the equilibrium. Concentrated NH4OH and 1.0 M FeCl3 were used as the precursors for the reaction in the water core. Once FeCl3 and conc.NH4C l were dropped into the W/O microemulsion, Fe2O3 was
2821
then produced in situ the water core. The mixture was stirred over night for getting equilibrium. To remove Fe2O3 from the mixture, distilled water was added to destroy the microemulsion system where which the separation between two layer of organic solvent and aqueous phase was established. Suspended Fe2O3, was then filtered and washed with 95% ethanol many times. Fe2O3 particle was subjected to dry in the furnace at 300 °C for 3 h. Effect of water fractions in the W/O microemulsion was determined by repeating the procedures with three different fractions of W/O microemulsion system. Fe2O3 particle obtained were examined by Scanning electron microscope (JEOL model JSM 6301-F). X-ray diffraction analysis (XRay Diffractometer: Bruker AXS, Model D8 Advance) was also done using CuKαat 40 kV, 30 mA and1.54056 A o. Infrared Spectra in KBr pellets were recorded in the range of 4000–250 cm − 1 on Perkin Elmer, Model Spectrum 100 FTIR spectrometer. 4. Results and discussion 4.1. Phase behavior The pseudo-ternary phase diagram obtained by titration method is shown in Fig. 1 which is in excellent agreement with those published for the same system [8]. The region of continuous single phase microemulsion is determined as being permanent transparency and indicated in the diagram as region “I”. Above region I, permanent turbid is formed and labeled with “S” region.
Fig. 2. Fe2O3 synthesized in three different systems.
Fig. 3. SEM pictures of Fe2O3 synthesized from three different fractions W/O microemulsion.
K. Wongwailikhit, S. Horwongsakul / Materials Letters 65 (2011) 2820–2822
1010
220
208
018
214 300
024
113 202
006
012
116
110
104
2822
Fig. 4. X-ray diffraction pattern of Fe2O3 synthesized by this method.
4.2. The effect of water fraction Fe2O3 synthesized in the water core of the three different fractions W/O emulsion system (A, B and C) were examined. The component fractions used in this study is shown in Table 1 and Fig. 1. It should be mentioned here that the water fraction increased in the order of A B and C, respectively. In the process, the virtually results was observed. Just after FeCl3 and NH4OH, were droplet added into the mixture, the red–brown of Fe2O3 particles were formed and suspended without precipitation. After adding the distilled water, phase separation between lower aqueous phase and upper organic solvent phase was established. The particulate Fe2O3 of systems showed the distinguishable dispersion which was attributed to their particle sizes as shown in Fig. 2. Very fine particle, synthesized from fraction A (Fig. 2a) floated on top of the organic heptane layer while the bigger one, synthesized from fraction B (Fig. 2b), suspended in the heptane layer. The biggest one, from the fraction C (Fig. 2c), sank into the lower aqueous layer according to its weight. It was clearly shown that the particle size respectively increased from fraction A, B and C corresponding to the percent water content inside. This observation was confirmed by the result from Scanning Electron Microscope shown in Fig. 3 which showed that Fe2O3 from fraction A, Fig. 3(a), had a narrow and more uniform size distribution with an average diameter of 50 nm. In addition, the shape of Fe2O3 was approximately spherical. Fe2O3 yielded from fraction B and C, Fig. 3 (b) and (c), had larger size with some plate structures (arrow). This reflected that the water content in W/O microemulsion affected strongly to the size and shape of particulate. Therefore, the W/O microemulsion method could be an excellent method to control the particle size with the monodispersed and narrowly distribution. The XRD pattern is shown in Fig. 4. In this figure, the diffraction peak corresponded to the diffraction pattern of standard α-Fe2O3 given by the JCPDS-ICDD pattern and matched with the Fe2O3 produced by other methods [11,13]. The dominant bands of IR spectrum (at about 383, 480 and 574 cm − 1) in Fig. 5 are the characteristic of crystalline α-Fe2O3 [10,11]. Bands at 3420 and 1635 cm − 1 were ascribed to hydroxide group and water, respectively [11]. From above, the constituent of precipitate produced by this method was α-Fe2O3 with hematite in structure.
Fig. 5. Infrared spectrum of Fe2O3.
5. Conclusion α-Fe2O3 nanoparticle with hexagonal structure of hematite was successfully synthesized in situ the water cores of W/O microemulsion system of H2O n-heptane and AOT. A high degree of monodispersity and small size was obtained by using small water content. By increasing the water fraction in W/O microemulsion, the increase of particles size was obtained. Acknowledgement This research work was supported by Research Center, Rangsit University under the grant number RI 05/2008. References [1] Spry DB, Goun A, Glusac K, Moilanen DE, Fayer MD. Proton transport and the water environment in nafion fuel cell membranes and AOT reverse micelles. J Am Chem Soc 2007;129:8122–30. [2] Cassin G, Illy S, Pileni MP. Chemical modified proteins solubilized in AOT reverse micelles: Influence of proteins charges on intermicellar interactions. Chem Phys Lett 1994;21:205–12. [3] Dai Y, Deng T, Jia S, Jin L, Lu F. Preparation and characterization of fine silver powder with colloidal emulsion aphrons. J Membr Sci 2006;281:685–91. [4] Liu ZL, Wang X, Yao KL. Synthesis of magnetite nanopartices in W/O microemulsion. J Mater Sci Lett 2004;39:2633–6. [5] Hirai T, Sato H, Komasawa I. Mechanism of formation of titanium dioxide ultrafine particles in reverse micelles by hydrolysis of titanium tetrabutoxide. Ind Eng Chem Res 1993;32:3014–9. [6] Hirai T, Bando Y, Komasawa I. Immobilization of CdS nanoparticles formed in reverse micelles onto alumina particles and their photocatalytic properties. J Phys Chem B 2002;35:8967–70. [7] Pileni MP, Motte L, Petit C. Synthesis of cadmium sulfide in situ in reverse micelles: Influence of the preparation modes on size, polydispersity, and photochemical reactions. Chem Mater 1992;2:338–45. [8] Malheiro AR, Varanda LC, Perez J, Villullas HM. The aerosol OT + n-butanol + nheptane + water System: Phase behavior: Structure characterization and application to Pt70Fe30 nanoparticle synthesis. Langmuir 2007;23:11015–20. [9] Yuan S, Cai Z, Xu G, Jiang Y. Mesoscopic simulation study on phase diagram of system oil/water/aerosol OT. Chem Phys Lett 2002;365:347–53. [10] Wang X, Chen X, Ma X, Zheng H, Ji M, Zhang Z. Low temperature synthesis of αFe2O3 nanoparticles with a closed cage Structure. Chem Phys Lett 2004;384: 391–3. [11] Jing Z, Shihua W. Synthesis and characterization of monodisperse hematite nanoparticles modified by surfactants via hydrothermal approach. Mater Lett 2004;58:3637–40. [12] Katsuki H, Komarneni S. Role of α-Fe2O3 morphology on the color of red pigment for porcelain. J Am Ceram Soc 2003;86:183–5. [13] Avila-Garcia A, Carbajal-Franco G, Tiburcio-Silver A, Barrera-Calva E, AndradeIbarra E. α-Fe2O3 films grown by the spin-on sol-gel deposition method. Rev Mex Fis 2003;49:219–23.