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Synthesis of three-dimensional hierarchical BaCrO4 dendrites
Materials Letters 65 (2011) 3618–3620
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
Synthesis of three-dimensional hierarchical BaCrO4 dendrites Young-Sik Cho, Young-Duk Huh ⁎ Department of Chemistry, Institute of Nanosensor and Biotechnology, Dankook University, Gyeonggi-Do 448-701, Republic of Korea
a r t i c l e
i n f o
Article history: Received 28 May 2011 Accepted 18 July 2011 Available online 22 July 2011 Keywords: Crystal growth Microstructure Hierarchical dendrite BaCrO4
a b s t r a c t 3-D hierarchical superstructures of BaCrO4 were prepared by a hydrothermal reaction of Ba(NO3)2 and Na2CrO4 in an aqueous-hexane bilayer system. A surfactant mixture of oleylamine and oleic acid was used to form hydrophobic barium oleate micelles. During the hydrothermal process, aqueous CrO42− anions reacted at the interface with Ba2+ cations in the hexane phase to form BaCrO4 crystals. 3-D hierarchical dendritic BaCrO4 formed with a trunk and aligned, cruciform series of branches perpendicular to it. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) confirmed that both trunk and branches preferentially grew in the b 001N direction. The dendrites formed through epitaxial growth. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved.
1. Introduction The hierarchical self-assembly of three-dimensional (3-D) superstructures has attracted considerable interest because of their complex arrangements, including hyperbranches, snowflakes, and dendrites [1–5], and their potential applications. A material with various morphologies of BaCrO4 was used as a useful oxidation catalyst and photocatalyst [6,7]. It has been formed as, for example, rods, colloidal spheres, and flower-shapes, depending on the synthetic method [8–10]. 3-D hierarchical superstructures of BaCrO4 have been prepared by surfactant-based microemulsion methods, e.g. tree- and funnel-like particles, linear chains of prismatic particles, and dendrites [11–15]. This work reports a novel addition to the variety of BaCrO4 structures prepared by a hydrothermal reaction: 3-D dendrites comprising a trunk (long axis) with aligned, cruciform series of branches (short axes) perpendicular to the trunk. Their crystal growth mechanism is also reported.
ethanol, and dried at 60 °C for 12 h. Reaction temperatures of 100 °C and 140 °C were also tested with other conditions unchanged. The resulting BaCrO4 was characterized by powder X-ray diffraction (XRD, PANalytical, X'pert-pro MPD), field-emission scanning electron microscopy (FESEM, Hitachi S-4300) and high-resolution transmission electron microscopy (HRTEM, JEOL JEM-3010). 3. Result and discussion Fig. 1 shows the XRD pattern of BaCrO4 obtained from a hydrothermal method at 100 °C. All peaks correspond to orthorhombic BaCrO4, matching reported data for this system (JCPDS 15-0376, a = 0.9105 nm, b = 0.5541 nm, and c = 0.7343 nm). The presence of
2. Experimental Ba(NO3)2 (Aldrich), Na2CrO4 (Aldrich), sodium oleate (TCI), oleic acid (Aldrich) and oleylamine (TCI) were used as received. In a typical synthesis, 1.22 g sodium oleate, 5 mL oleic acid, 5 mL oleylamine and 40 mL hexane were added to 0.2 M Ba(NO3)2 in 10 mL water with vigorous stirring at room temperature for 1 h. Then 0.2 M Na2CrO4 in 10 mL water was added and the mixture was heated at 90 °C for 1 h in a 100 mL Teflon-lined autoclave. The autoclave was cooled in ice– water. BaCrO4 precipitate was washed several times with hexane and
⁎ Corresponding author. Tel.: + 82 31 80053154; fax: + 82 31 80053148. E-mail address: [email protected] (Y.-D. Huh).
Fig. 1. XRD pattern of BaCrO4 from a hydrothermal process at 100 °C.
0167-577X/$ – see front matter. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.07.055
Y.-S. Cho, Y.-D. Huh / Materials Letters 65 (2011) 3618–3620
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Fig. 2. (a, c and e) Low-magnification and (b, d and f) high-magnification FESEM images of BaCrO4 prepared at (a, b) 90 °C, (c, d) 100 °C, and (e, f) 140 °C.
no other peaks indicates BaCrO4 free from impurities. The BaCrO4 was synthesized using oleylamine and oleic acid capping surfactants, which formed deprotonated oleic acid and protonated oleylamine due
to the acid–base chemical equilibrium [16]. The deprotonated oleic acid could interact with Ba 2+ ions to form barium oleate, Ba (OA)2. This was stabilized by the protonated oleylamine, forming micelles with
Fig. 3. (a) TEM image of an individual BaCrO4 dendrite. HRTEM images of the (b) trunk and (c) branch. Insets show FFT patterns of the HRTEM images.
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Y.-S. Cho, Y.-D. Huh / Materials Letters 65 (2011) 3618–3620
first-order branches (Fig. 2e and f). Fig. 3 shows a TEM image of an individual BaCrO4 dendrite, with HRTEM images and fast Fourier transform (FFT) patterns of its trunk and branches. The fringe patterns of the trunk and branch were both uniform with fringe spaces of 0.36 nm, corresponding to the (002) plane. The 3-D hierarchical BaCrO4 dendrites were composed of a main trunk with first- and second-order branches. Because of preferential growth in the b001N direction, the trunk formed first, with first-order branches following, perpendicular to it. Second-order branches then emerged perpendicular to the first-order branches. The branches grew via epitaxial growth [3]. Fig. 4 outlines the proposed crystal growth mechanism for the 3-D hierarchical dendritic BaCrO4. 4. Conclusions
Fig. 4. Proposed crystal growth mechanism for 3-D hierarchical dendritic BaCrO4.
hydrophobic outer parts stable in non-polar solvents such as toluene. When aqueous Na2CrO4 was added to the hexane solution, bilayer phases formed at room temperature. During the hydrothermal process, Ba 2+ cations reacted with CrO42− anions at the interface of the hexane and water phases, allowing nucleation of BaCrO4. Subsequent crystallization formed 3-D hierarchical dendrites of BaCrO4. The BaCrO4 was examined by field-emission scanning electron microscopy (FESEM). Fig. 2a shows a low-magnification SEM image of BaCrO4 prepared at 90 °C. The dendritic BaCrO4 comprised a trunk (long axis) with a series of short branches (short axes) (Fig. 2b). With a reaction temperature of 100 °C, 3-D dendrite structures were also formed, though with longer branches (Fig. 2c and d). Aligned, cruciform series of branches were formed perpendicular to the trunk. The trunks had ca. 10 μm mean length and cruciform cross sections. When the reaction temperature was 140 °C, a hyperbranch structure emerged with second-order branches perpendicular to the
3-D hierarchical dendrites of BaCrO4 were synthesized at a hexanewater interface by a hydrothermal reaction. Oleylamine and oleic acid capping surfactants were important in the preparation of the dendrites. Each dendrite comprised a trunk with aligned, cruciform series of branches perpendicular to it. During the reaction, the trunk formed first, then first-order branches perpendicular to the trunk, with second-order branches emerging perpendicular to the first-order branches. Branch grew via epitaxial growth. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
Wang D, Qian F, Yang C, Zhong Z, Lieber CM. Nano Lett 2004;4:871–4. Lu Q, Gao F, Komarneni S. J Am Chem Soc 2004;126:54–5. Cao H, Gong Q, Qian X, Wang HW, Zai J, Zhu Z. Cryst Growth Des 2007;7:425–9. Kuang D, Xu A, Fang Y, Liu H, Frommen C, Fenske D. Adv Mater 2003;15:1747–50. Sun G, Dong B, Cao M, Wei B, Hu C. Chem Mater 2011;23:1587–93. Economy J, Meloon DT, Ostrozynski RL. J Catal 1965;4:446–53. Yin J, Zou Z, Ye J. Chem Phys Lett 2003;378:24–8. Mao Y, Wong SS. J Am Chem Soc 2004;126:15,245–52. Bai MH, Wang D, Huo Z, Chen W, Liu L, Liang X, et al. Angew Chem Int Ed 2007;46: 6650–3. Liu S, Yu J, Cheng B, Zhang Q. Chem Lett 2005;34:564–5. Shi H, Qi L, Ma J, Cheng H, Zhu B. Adv Mater 2003;15:1647–51. Yu SH, Antoniettí M, Cölfen H, Hartmann J. Nano Lett 2003;3:379–82. Johnson CJ, Li M, Mann S. Adv Funct Mater 2004;14:1233–9. Li Z, Zhang J, Du J, Han B, Mu T, Gao Y, et al. Mater Chem Phys 2005;91:40–3. Yan Y, Wu QS, Li L, Ding YP. Cryst Growth Des 2006;6:769–73. Bu W, Chen Z, Chen F, Shi J. J Phys Chem C 2009;113:12,176–85.
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
Synthesis of three-dimensional hierarchical BaCrO4 dendrites Young-Sik Cho, Young-Duk Huh ⁎ Department of Chemistry, Institute of Nanosensor and Biotechnology, Dankook University, Gyeonggi-Do 448-701, Republic of Korea
a r t i c l e
i n f o
Article history: Received 28 May 2011 Accepted 18 July 2011 Available online 22 July 2011 Keywords: Crystal growth Microstructure Hierarchical dendrite BaCrO4
a b s t r a c t 3-D hierarchical superstructures of BaCrO4 were prepared by a hydrothermal reaction of Ba(NO3)2 and Na2CrO4 in an aqueous-hexane bilayer system. A surfactant mixture of oleylamine and oleic acid was used to form hydrophobic barium oleate micelles. During the hydrothermal process, aqueous CrO42− anions reacted at the interface with Ba2+ cations in the hexane phase to form BaCrO4 crystals. 3-D hierarchical dendritic BaCrO4 formed with a trunk and aligned, cruciform series of branches perpendicular to it. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) confirmed that both trunk and branches preferentially grew in the b 001N direction. The dendrites formed through epitaxial growth. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved.
1. Introduction The hierarchical self-assembly of three-dimensional (3-D) superstructures has attracted considerable interest because of their complex arrangements, including hyperbranches, snowflakes, and dendrites [1–5], and their potential applications. A material with various morphologies of BaCrO4 was used as a useful oxidation catalyst and photocatalyst [6,7]. It has been formed as, for example, rods, colloidal spheres, and flower-shapes, depending on the synthetic method [8–10]. 3-D hierarchical superstructures of BaCrO4 have been prepared by surfactant-based microemulsion methods, e.g. tree- and funnel-like particles, linear chains of prismatic particles, and dendrites [11–15]. This work reports a novel addition to the variety of BaCrO4 structures prepared by a hydrothermal reaction: 3-D dendrites comprising a trunk (long axis) with aligned, cruciform series of branches (short axes) perpendicular to the trunk. Their crystal growth mechanism is also reported.
ethanol, and dried at 60 °C for 12 h. Reaction temperatures of 100 °C and 140 °C were also tested with other conditions unchanged. The resulting BaCrO4 was characterized by powder X-ray diffraction (XRD, PANalytical, X'pert-pro MPD), field-emission scanning electron microscopy (FESEM, Hitachi S-4300) and high-resolution transmission electron microscopy (HRTEM, JEOL JEM-3010). 3. Result and discussion Fig. 1 shows the XRD pattern of BaCrO4 obtained from a hydrothermal method at 100 °C. All peaks correspond to orthorhombic BaCrO4, matching reported data for this system (JCPDS 15-0376, a = 0.9105 nm, b = 0.5541 nm, and c = 0.7343 nm). The presence of
2. Experimental Ba(NO3)2 (Aldrich), Na2CrO4 (Aldrich), sodium oleate (TCI), oleic acid (Aldrich) and oleylamine (TCI) were used as received. In a typical synthesis, 1.22 g sodium oleate, 5 mL oleic acid, 5 mL oleylamine and 40 mL hexane were added to 0.2 M Ba(NO3)2 in 10 mL water with vigorous stirring at room temperature for 1 h. Then 0.2 M Na2CrO4 in 10 mL water was added and the mixture was heated at 90 °C for 1 h in a 100 mL Teflon-lined autoclave. The autoclave was cooled in ice– water. BaCrO4 precipitate was washed several times with hexane and
⁎ Corresponding author. Tel.: + 82 31 80053154; fax: + 82 31 80053148. E-mail address: [email protected] (Y.-D. Huh).
Fig. 1. XRD pattern of BaCrO4 from a hydrothermal process at 100 °C.
0167-577X/$ – see front matter. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.07.055
Y.-S. Cho, Y.-D. Huh / Materials Letters 65 (2011) 3618–3620
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Fig. 2. (a, c and e) Low-magnification and (b, d and f) high-magnification FESEM images of BaCrO4 prepared at (a, b) 90 °C, (c, d) 100 °C, and (e, f) 140 °C.
no other peaks indicates BaCrO4 free from impurities. The BaCrO4 was synthesized using oleylamine and oleic acid capping surfactants, which formed deprotonated oleic acid and protonated oleylamine due
to the acid–base chemical equilibrium [16]. The deprotonated oleic acid could interact with Ba 2+ ions to form barium oleate, Ba (OA)2. This was stabilized by the protonated oleylamine, forming micelles with
Fig. 3. (a) TEM image of an individual BaCrO4 dendrite. HRTEM images of the (b) trunk and (c) branch. Insets show FFT patterns of the HRTEM images.
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Y.-S. Cho, Y.-D. Huh / Materials Letters 65 (2011) 3618–3620
first-order branches (Fig. 2e and f). Fig. 3 shows a TEM image of an individual BaCrO4 dendrite, with HRTEM images and fast Fourier transform (FFT) patterns of its trunk and branches. The fringe patterns of the trunk and branch were both uniform with fringe spaces of 0.36 nm, corresponding to the (002) plane. The 3-D hierarchical BaCrO4 dendrites were composed of a main trunk with first- and second-order branches. Because of preferential growth in the b001N direction, the trunk formed first, with first-order branches following, perpendicular to it. Second-order branches then emerged perpendicular to the first-order branches. The branches grew via epitaxial growth [3]. Fig. 4 outlines the proposed crystal growth mechanism for the 3-D hierarchical dendritic BaCrO4. 4. Conclusions
Fig. 4. Proposed crystal growth mechanism for 3-D hierarchical dendritic BaCrO4.
hydrophobic outer parts stable in non-polar solvents such as toluene. When aqueous Na2CrO4 was added to the hexane solution, bilayer phases formed at room temperature. During the hydrothermal process, Ba 2+ cations reacted with CrO42− anions at the interface of the hexane and water phases, allowing nucleation of BaCrO4. Subsequent crystallization formed 3-D hierarchical dendrites of BaCrO4. The BaCrO4 was examined by field-emission scanning electron microscopy (FESEM). Fig. 2a shows a low-magnification SEM image of BaCrO4 prepared at 90 °C. The dendritic BaCrO4 comprised a trunk (long axis) with a series of short branches (short axes) (Fig. 2b). With a reaction temperature of 100 °C, 3-D dendrite structures were also formed, though with longer branches (Fig. 2c and d). Aligned, cruciform series of branches were formed perpendicular to the trunk. The trunks had ca. 10 μm mean length and cruciform cross sections. When the reaction temperature was 140 °C, a hyperbranch structure emerged with second-order branches perpendicular to the
3-D hierarchical dendrites of BaCrO4 were synthesized at a hexanewater interface by a hydrothermal reaction. Oleylamine and oleic acid capping surfactants were important in the preparation of the dendrites. Each dendrite comprised a trunk with aligned, cruciform series of branches perpendicular to it. During the reaction, the trunk formed first, then first-order branches perpendicular to the trunk, with second-order branches emerging perpendicular to the first-order branches. Branch grew via epitaxial growth. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
Wang D, Qian F, Yang C, Zhong Z, Lieber CM. Nano Lett 2004;4:871–4. Lu Q, Gao F, Komarneni S. J Am Chem Soc 2004;126:54–5. Cao H, Gong Q, Qian X, Wang HW, Zai J, Zhu Z. Cryst Growth Des 2007;7:425–9. Kuang D, Xu A, Fang Y, Liu H, Frommen C, Fenske D. Adv Mater 2003;15:1747–50. Sun G, Dong B, Cao M, Wei B, Hu C. Chem Mater 2011;23:1587–93. Economy J, Meloon DT, Ostrozynski RL. J Catal 1965;4:446–53. Yin J, Zou Z, Ye J. Chem Phys Lett 2003;378:24–8. Mao Y, Wong SS. J Am Chem Soc 2004;126:15,245–52. Bai MH, Wang D, Huo Z, Chen W, Liu L, Liang X, et al. Angew Chem Int Ed 2007;46: 6650–3. Liu S, Yu J, Cheng B, Zhang Q. Chem Lett 2005;34:564–5. Shi H, Qi L, Ma J, Cheng H, Zhu B. Adv Mater 2003;15:1647–51. Yu SH, Antoniettí M, Cölfen H, Hartmann J. Nano Lett 2003;3:379–82. Johnson CJ, Li M, Mann S. Adv Funct Mater 2004;14:1233–9. Li Z, Zhang J, Du J, Han B, Mu T, Gao Y, et al. Mater Chem Phys 2005;91:40–3. Yan Y, Wu QS, Li L, Ding YP. Cryst Growth Des 2006;6:769–73. Bu W, Chen Z, Chen F, Shi J. J Phys Chem C 2009;113:12,176–85.