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Solvothermal synthesis and characterization of α-Fe2O3 nanodiscs and Mn3O4 nanoparticles with 1,10-phenanthroline
Superlattices and Microstructures 52 (2012) 92–98
Contents lists available at SciVerse ScienceDirect
Superlattices and Microstructures journal homepage: www.elsevier.com/locate/superlattices
Solvothermal synthesis and characterization of a-Fe2O3 nanodiscs and Mn3O4 nanoparticles with 1,10-phenanthroline Robabeh Mehdizadeh ⇑, Lotf Ali Saghatforoush, Soheila Sanati Department of Chemistry, Payame Noor University, 19395-4697 Tehran, Iran
a r t i c l e
i n f o
Article history: Received 25 January 2012 Received in revised form 28 February 2012 Accepted 17 March 2012 Available online 23 March 2012 Keywords: a-Fe2O3 Nanodiscs 1,10-Phenanthroline Mn3O4 Nanoparticles
a b s t r a c t a-Fe2O3 nanodiscs and Mn3O4 nanoparticles have been prepared by the 1,10-phenanthroline as complexing agent in the presence of sodium hydroxide under hydrothermal conditions. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectra. The average diameter of a-Fe2O3 nanodiscs is of 2 lm. In the case of Mn3O4 sample, the Mn3O4 crystallites are nanoparticles with an average size of 34 nm. A formation mechanism for the a-Fe2O3 and Mn3O4 nanomaterials was proposed. Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction Nanostructures have attracted much attention because of their unique properties and potential applications [1–4]. However, it is still a big challenge to develop simple and reliable synthetic methods for hierarchically self assembled architectures with designed chemical components and controlled morphologies, which strongly affect the properties of nanomaterials. Hematite (a-Fe2O3) nanoparticles have potential applications in catalytic reactions, electronic devices (e.g., semiconductors and gas-sensitive), paint formulations, and rechargeable lithium batteries [5–7]. Various iron oxide structures, such as nanocrystals [8], particles [9,10], cubes [11], spindles [12], rods [13,14], wires [15], tubes [16], and flakes [17], have been successfully fabricated by a variety of methods [18]. Various methods exist for the synthesis a-Fe2O3 powder. Mechanical millings [19], decomposition of organic iron precursor, precipitation, sol–gel, combustion, solvent evaporation [20], are some of the methods. Most in
⇑ Corresponding author. Tel.: +98 4612349868; fax: +98 4612349566. E-mail address: [email protected] (R. Mehdizadeh). 0749-6036/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.spmi.2012.03.017
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this paper, a simple one step method is used to prepare single phase a-Fe2O3 nano-particles. In addition, the magnetic behaviors of c-Fe2O3 and a-Fe2O3 nanoparticles were also investigated [21]. Mn3O4 (Hausmannite, trimanganese tetraoxide) is one of the most stable oxides of manganese. Mn3O4 synthesis has gained significant attention due to its wide range of applications, such as high-density magnetic storage media, catalysts, ion exchange, molecular adsorption, electrochemical materials, varistors and solar energy transformation [22–25]. Mn3O4 has also been widely used as a main source of ferrite [26], which has extensive applications in electronics and information technology. Nanometer-sized Mn3O4 powders, with remarkably increased surface area and different morphologies, are expected to display better performance in all aspects of the above-mentioned applications. Various nanostructures of Mn3O4 with different morphologies such as, nanorods/nanowires [27,28], mesoporous/hollow spheres [29,30], nanofibers [31] and other structures have been synthesized by different routes, such as solid state reaction [32] and c-ray irradiation [33]. Synthesis of Mn3O4 by conventional high temperature and hydrothermal methods is very well known in the literature [34], but the conventional process leads to inconsistencies in the quality and stability of the product. There are reports on the synthesis of Mn3O4 by the sol–gel method [35], which also covers uniform heating and programmed cooling. The sol–gel method has been found to be more expensive, time consuming and polluting. Massive work has been reported on hydrothermal methods at various temperatures and for various times [36]. Synthesis of Mn3O4 nanoparticles with novel morphology (lozange) under hydrothermal treatment, using surfactant cetyltetramethylammonium bromide (CTAB) as a template agent has been reported by Dhaouadi and Madani [37]. Among the various techniques developed for the synthesis of Mn3O4 nanoparticles, thermal decomposition is a novel method to produce stable monodispersed products [38] and it is a rapidly developing research area. Metal complexes built from metal ions and polydentate organic ligands as complexing agent have been grown rapidly in recent years owing to their potential applications [39]. So far, however, the studies on the syntheses of nano- or microscaled structures with metal complexes as precursors have been less reported. In this study, a simple solvothermal route for fabricating a-Fe2O3 with disc-like morphology and Mn3O4 nanoparticles was developed without using hard or soft templates or surfactants. a-Fe2O3 nanodiscs and Mn3O4 nanoparticles have been prepared by the 1,10-phenanthroline as complexing agent in the presence of sodium hydroxide under hydrothermal conditions.
2. Experimental 2.1. a-Fe2O3 nanodiscs synthesis In a typical experiment, 2 mmol of Fe(NO3)39H2O and 6 mmol of phen were dissolved into the mixed distilled water and ethanol then NaOH aqueous solution (2 M) added under magnetic stirring. This alkaline solution was transferred into a Teflon-lined autoclave with about 80% capacity. The autoclave was then sealed and maintained at 160 °C for 24 h. After cooling to room temperature, the red precipitates were filtered, washed with distilled water and absolute ethanol for several times. Finally, the resulting product was dried at 50 °C (Scheme 1).
+ Fe(NO3)3.9H2O N
1) NaOH [Fe(phen)3 ] 3+
N
+ N
C2H5OH/H2O
N
MnCl2
C2H5OH/H2O
2) hydrothermal
1) NaOH [Mn(phen)2 ] 2+
2) hydrothermal
Scheme 1. Illustration of the formation mechanism of nanostructures.
Fe2O3 nanodiscs
Mn3O4 nanoparticles
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2.2. Mn3O4 nanoparticles synthesis In a typical experiment, 3 mmol of MnCl2 and 6 mmol of phen were dissolved into the mixed distilled water and ethanol then NaOH aqueous solution (2 M) added under magnetic stirring. This alkaline solution was transferred into a Teflon-lined autoclave with about 80% capacity. The autoclave was then sealed and maintained at 160 °C for 24 h. After cooling to room temperature, the black precipitates were filtered, washed with distilled water and absolute ethanol for several times. Finally, the resulting product was dried at 50 °C (Scheme 1).
2.3. Materials and physical measurements All chemical reagents in this experiment were of analytical grade and used without further purification. Fourier transform infrared (FT-IR) spectra were recorded using KBr disks on a Shimadzu FT-IR model Prestige 21 spectrometer. The morphologies of products were observed with scanning electron microscopy (Philips XL-30). X-ray powder diffraction (XRD) measurements were performed using a Philips diffractometer manufactured by X’pert with monochromatized CuKa radiation.
3. Results and discussion In the FT-IR spectrum of the a-Fe2O3 nanostructures (Fig. 1), absorption bands around 529 and 454 and 639 cm 1 was observed, which is related to the Fe–O stretching vibration. In the FT-IR spectrum of the Mn3O4 nanostructures (Fig. 2), strong bands around 629 and 524 cm 1 was observed, which is related to the Mn–O stretching vibration. The broad peak at ca. 3425 cm 1 in (Fig. 2) is for hydroxyl group (–OH). The H–OH bending vibration appears at 1635 cm 1. Also, there is a tiny dip in the spectra at 2362 cm 1 due to the presence of atmospheric CO2. These absorption peaks may be associated with the coupling modes between the Mn and O stretching modes of tetrahedral and octahedral sites [40]. In the region from 500 to 400 cm 1, the absorption peak at 410 cm 1 was observed for the Mn3O4.
Fig. 1. FT-IR spectra of the a-Fe2O3 nanodiscs.
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Fig. 2. FT-IR spectra of the Mn3O4 nanoparticles.
These absorption peaks were attributed to the band stretching modes of the octahedral sites; displacement of the Mn2+ ions in the tetrahedral sites was negligible [40]. Figs. 3 and 4 shows X-ray diffraction patterns of a-Fe2O3 and Mn3O4 nano-crystals. It can be observed from Fig. 3 that the all diffraction peaks are consistent with the a-Fe2O3 crystallite. The diffraction peaks in the XRD pattern can be readily indexed to crystalline bulk a-Fe2O3. The lattice constants (a = 5.035, c = 13.726, Z = 2 Å) calculated from this XRD pattern correspond well to the values given in the standard card (JCPDS card No. 80-2377). The results indicated that the products are consisted of pure phases. Fig. 4 shows the XRD pattern of the obtained Mn3O4 via solvothermal treatment. As could be seen from Fig. 4, product displayed the similar XRD pattern corresponding to the tetragonal cell of Mn3O4 (Hausmannite). The lattice parameters obtained by refinement of the XRD data were a = 5.75, c = 9.42, Z = 4 Å for the Mn3O4 which were also consistent with those of Mn3O4 reported in the JCPDF card (File No. 1-1127). No impurity peaks are found, suggesting a high purity of the as-synthesized products. Moreover, the observed peaks are sharper and higher in intensity which confirmed the well-crystallization of the obtained a-Fe2O3 and Mn3O4 structures. The broadening of the peaks indicated that the particles were of nanometer scale. The morphology, structure and size of the samples are investigated by scanning electron microscopy (SEM). Fig. 5a and b shows the SEM micrograph of a-Fe2O3 nanostructures. As shown in Fig. 5a and b the morphology of the a-Fe2O3 sample is a disc-like nanomaterial with an average size of 2 lm in diameter. In the case of Mn3O4 sample, the Mn3O4 crystallites are nanoparticles with an average size of 34 nm which show in Fig. 5c and d. Estimated from the Scherrer formula, D = 0.891k/bcosh, where, D is the average grain size, k is the X-ray wavelength (0.15405 nm), and h and b are the diffraction angle and full-width at half maximum of an observed peak, respectively. The average size of the a-Fe2O3 nanodiscs and Mn3O4 nanoparticles is calculated were about 56.2 nm for a-Fe2O3 by using the strongest peak (1 0 4) at 2h = 33.18 and 41 nm for Mn3O4 by using the strongest peak (2 1 1) at 2h = 36.14. Based on the experimental results, the possible formation mechanism of the nanomaterials was illustrated in Scheme 1. In the beginning, formed complex decomposed and released a small quantity of Fe(III) and Mn(II) ions. The process of decomposition was a controlling step, because complex did
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Fig. 3. XRD of the a-Fe2O3 nanodiscs.
Fig. 4. XRD of the Mn3O4 nanoparticles.
not decompose as quickly as other Fe or Mn-containing inorganic salts, which may provide enough time and opportunity for the growth of a-Fe2O3 and Mn3O4 nanomaterial. Under the condition of heavy alkaline solution, [Fe3(OH)4]5+ and [Mn(OH)4]2 ions were first formed. Then [Fe3(OH)4]5+ and
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Fig. 5. SEM of the (a and b) a-Fe2O3 nanodiscs, (c and d) Mn3O4 nanoparticles.
[Mn(OH)4]2 ions were dehydrated under hydrothermal conditions and they in situ generated a bit of a-Fe2O3 and Mn3O4 nuclei which acted as the seeds for the growth of a-Fe2O3 and Mn3O4. The surface of a-Fe2O3 and Mn3O4 nuclei is either positively charged or negatively charged. In either case the surface will selectively adsorb ions of opposite charges (OH or Fe3+ for a-Fe2O3 and OH or Mn2+ for Mn3O4) on it, and the new surface covered with ions will in turn adsorb ions with opposite charges to cover the surface next. In the heavy alkaline synthetic system, more OH may neutralize positive charges on the surface of a-Fe2O3 and Mn3O4, preventing them from possible crystallite aggregation. Thus, a-Fe2O3 and Mn3O4 nuclei slowly grew along reaction, resulting in the disc-like and nanoparticle structure of the samples. 4. Conclusions In summary, iron oxide and manganese oxide nanostructures has been successfully prepared with the assistance of 1,10-phenanthroline as complexing agent by a simple low-temperature solvothermal method. This approach using both coordination complex and mixed solvents of water/ethanol may be applied to synthesize other inorganic materials with abundant morphologies. The properties of nanostructures were studied by SEM, XRD, and FT-IR. The solvothermal method is very fast and does not need any additives and surfactants during the reactions. Comparing with other methods such as sonochemical and sol–gel methods (that requires high temperature, expensive equipment and long aging times); this procedure does not require pressure controlling and high temperature. In comparison to other similar works, the current method is simple and can be scaled-up. Acknowledgment We are grateful to Payame Noor University for financial support of this work.
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Contents lists available at SciVerse ScienceDirect
Superlattices and Microstructures journal homepage: www.elsevier.com/locate/superlattices
Solvothermal synthesis and characterization of a-Fe2O3 nanodiscs and Mn3O4 nanoparticles with 1,10-phenanthroline Robabeh Mehdizadeh ⇑, Lotf Ali Saghatforoush, Soheila Sanati Department of Chemistry, Payame Noor University, 19395-4697 Tehran, Iran
a r t i c l e
i n f o
Article history: Received 25 January 2012 Received in revised form 28 February 2012 Accepted 17 March 2012 Available online 23 March 2012 Keywords: a-Fe2O3 Nanodiscs 1,10-Phenanthroline Mn3O4 Nanoparticles
a b s t r a c t a-Fe2O3 nanodiscs and Mn3O4 nanoparticles have been prepared by the 1,10-phenanthroline as complexing agent in the presence of sodium hydroxide under hydrothermal conditions. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectra. The average diameter of a-Fe2O3 nanodiscs is of 2 lm. In the case of Mn3O4 sample, the Mn3O4 crystallites are nanoparticles with an average size of 34 nm. A formation mechanism for the a-Fe2O3 and Mn3O4 nanomaterials was proposed. Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction Nanostructures have attracted much attention because of their unique properties and potential applications [1–4]. However, it is still a big challenge to develop simple and reliable synthetic methods for hierarchically self assembled architectures with designed chemical components and controlled morphologies, which strongly affect the properties of nanomaterials. Hematite (a-Fe2O3) nanoparticles have potential applications in catalytic reactions, electronic devices (e.g., semiconductors and gas-sensitive), paint formulations, and rechargeable lithium batteries [5–7]. Various iron oxide structures, such as nanocrystals [8], particles [9,10], cubes [11], spindles [12], rods [13,14], wires [15], tubes [16], and flakes [17], have been successfully fabricated by a variety of methods [18]. Various methods exist for the synthesis a-Fe2O3 powder. Mechanical millings [19], decomposition of organic iron precursor, precipitation, sol–gel, combustion, solvent evaporation [20], are some of the methods. Most in
⇑ Corresponding author. Tel.: +98 4612349868; fax: +98 4612349566. E-mail address: [email protected] (R. Mehdizadeh). 0749-6036/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.spmi.2012.03.017
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this paper, a simple one step method is used to prepare single phase a-Fe2O3 nano-particles. In addition, the magnetic behaviors of c-Fe2O3 and a-Fe2O3 nanoparticles were also investigated [21]. Mn3O4 (Hausmannite, trimanganese tetraoxide) is one of the most stable oxides of manganese. Mn3O4 synthesis has gained significant attention due to its wide range of applications, such as high-density magnetic storage media, catalysts, ion exchange, molecular adsorption, electrochemical materials, varistors and solar energy transformation [22–25]. Mn3O4 has also been widely used as a main source of ferrite [26], which has extensive applications in electronics and information technology. Nanometer-sized Mn3O4 powders, with remarkably increased surface area and different morphologies, are expected to display better performance in all aspects of the above-mentioned applications. Various nanostructures of Mn3O4 with different morphologies such as, nanorods/nanowires [27,28], mesoporous/hollow spheres [29,30], nanofibers [31] and other structures have been synthesized by different routes, such as solid state reaction [32] and c-ray irradiation [33]. Synthesis of Mn3O4 by conventional high temperature and hydrothermal methods is very well known in the literature [34], but the conventional process leads to inconsistencies in the quality and stability of the product. There are reports on the synthesis of Mn3O4 by the sol–gel method [35], which also covers uniform heating and programmed cooling. The sol–gel method has been found to be more expensive, time consuming and polluting. Massive work has been reported on hydrothermal methods at various temperatures and for various times [36]. Synthesis of Mn3O4 nanoparticles with novel morphology (lozange) under hydrothermal treatment, using surfactant cetyltetramethylammonium bromide (CTAB) as a template agent has been reported by Dhaouadi and Madani [37]. Among the various techniques developed for the synthesis of Mn3O4 nanoparticles, thermal decomposition is a novel method to produce stable monodispersed products [38] and it is a rapidly developing research area. Metal complexes built from metal ions and polydentate organic ligands as complexing agent have been grown rapidly in recent years owing to their potential applications [39]. So far, however, the studies on the syntheses of nano- or microscaled structures with metal complexes as precursors have been less reported. In this study, a simple solvothermal route for fabricating a-Fe2O3 with disc-like morphology and Mn3O4 nanoparticles was developed without using hard or soft templates or surfactants. a-Fe2O3 nanodiscs and Mn3O4 nanoparticles have been prepared by the 1,10-phenanthroline as complexing agent in the presence of sodium hydroxide under hydrothermal conditions.
2. Experimental 2.1. a-Fe2O3 nanodiscs synthesis In a typical experiment, 2 mmol of Fe(NO3)39H2O and 6 mmol of phen were dissolved into the mixed distilled water and ethanol then NaOH aqueous solution (2 M) added under magnetic stirring. This alkaline solution was transferred into a Teflon-lined autoclave with about 80% capacity. The autoclave was then sealed and maintained at 160 °C for 24 h. After cooling to room temperature, the red precipitates were filtered, washed with distilled water and absolute ethanol for several times. Finally, the resulting product was dried at 50 °C (Scheme 1).
+ Fe(NO3)3.9H2O N
1) NaOH [Fe(phen)3 ] 3+
N
+ N
C2H5OH/H2O
N
MnCl2
C2H5OH/H2O
2) hydrothermal
1) NaOH [Mn(phen)2 ] 2+
2) hydrothermal
Scheme 1. Illustration of the formation mechanism of nanostructures.
Fe2O3 nanodiscs
Mn3O4 nanoparticles
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2.2. Mn3O4 nanoparticles synthesis In a typical experiment, 3 mmol of MnCl2 and 6 mmol of phen were dissolved into the mixed distilled water and ethanol then NaOH aqueous solution (2 M) added under magnetic stirring. This alkaline solution was transferred into a Teflon-lined autoclave with about 80% capacity. The autoclave was then sealed and maintained at 160 °C for 24 h. After cooling to room temperature, the black precipitates were filtered, washed with distilled water and absolute ethanol for several times. Finally, the resulting product was dried at 50 °C (Scheme 1).
2.3. Materials and physical measurements All chemical reagents in this experiment were of analytical grade and used without further purification. Fourier transform infrared (FT-IR) spectra were recorded using KBr disks on a Shimadzu FT-IR model Prestige 21 spectrometer. The morphologies of products were observed with scanning electron microscopy (Philips XL-30). X-ray powder diffraction (XRD) measurements were performed using a Philips diffractometer manufactured by X’pert with monochromatized CuKa radiation.
3. Results and discussion In the FT-IR spectrum of the a-Fe2O3 nanostructures (Fig. 1), absorption bands around 529 and 454 and 639 cm 1 was observed, which is related to the Fe–O stretching vibration. In the FT-IR spectrum of the Mn3O4 nanostructures (Fig. 2), strong bands around 629 and 524 cm 1 was observed, which is related to the Mn–O stretching vibration. The broad peak at ca. 3425 cm 1 in (Fig. 2) is for hydroxyl group (–OH). The H–OH bending vibration appears at 1635 cm 1. Also, there is a tiny dip in the spectra at 2362 cm 1 due to the presence of atmospheric CO2. These absorption peaks may be associated with the coupling modes between the Mn and O stretching modes of tetrahedral and octahedral sites [40]. In the region from 500 to 400 cm 1, the absorption peak at 410 cm 1 was observed for the Mn3O4.
Fig. 1. FT-IR spectra of the a-Fe2O3 nanodiscs.
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Fig. 2. FT-IR spectra of the Mn3O4 nanoparticles.
These absorption peaks were attributed to the band stretching modes of the octahedral sites; displacement of the Mn2+ ions in the tetrahedral sites was negligible [40]. Figs. 3 and 4 shows X-ray diffraction patterns of a-Fe2O3 and Mn3O4 nano-crystals. It can be observed from Fig. 3 that the all diffraction peaks are consistent with the a-Fe2O3 crystallite. The diffraction peaks in the XRD pattern can be readily indexed to crystalline bulk a-Fe2O3. The lattice constants (a = 5.035, c = 13.726, Z = 2 Å) calculated from this XRD pattern correspond well to the values given in the standard card (JCPDS card No. 80-2377). The results indicated that the products are consisted of pure phases. Fig. 4 shows the XRD pattern of the obtained Mn3O4 via solvothermal treatment. As could be seen from Fig. 4, product displayed the similar XRD pattern corresponding to the tetragonal cell of Mn3O4 (Hausmannite). The lattice parameters obtained by refinement of the XRD data were a = 5.75, c = 9.42, Z = 4 Å for the Mn3O4 which were also consistent with those of Mn3O4 reported in the JCPDF card (File No. 1-1127). No impurity peaks are found, suggesting a high purity of the as-synthesized products. Moreover, the observed peaks are sharper and higher in intensity which confirmed the well-crystallization of the obtained a-Fe2O3 and Mn3O4 structures. The broadening of the peaks indicated that the particles were of nanometer scale. The morphology, structure and size of the samples are investigated by scanning electron microscopy (SEM). Fig. 5a and b shows the SEM micrograph of a-Fe2O3 nanostructures. As shown in Fig. 5a and b the morphology of the a-Fe2O3 sample is a disc-like nanomaterial with an average size of 2 lm in diameter. In the case of Mn3O4 sample, the Mn3O4 crystallites are nanoparticles with an average size of 34 nm which show in Fig. 5c and d. Estimated from the Scherrer formula, D = 0.891k/bcosh, where, D is the average grain size, k is the X-ray wavelength (0.15405 nm), and h and b are the diffraction angle and full-width at half maximum of an observed peak, respectively. The average size of the a-Fe2O3 nanodiscs and Mn3O4 nanoparticles is calculated were about 56.2 nm for a-Fe2O3 by using the strongest peak (1 0 4) at 2h = 33.18 and 41 nm for Mn3O4 by using the strongest peak (2 1 1) at 2h = 36.14. Based on the experimental results, the possible formation mechanism of the nanomaterials was illustrated in Scheme 1. In the beginning, formed complex decomposed and released a small quantity of Fe(III) and Mn(II) ions. The process of decomposition was a controlling step, because complex did
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Fig. 3. XRD of the a-Fe2O3 nanodiscs.
Fig. 4. XRD of the Mn3O4 nanoparticles.
not decompose as quickly as other Fe or Mn-containing inorganic salts, which may provide enough time and opportunity for the growth of a-Fe2O3 and Mn3O4 nanomaterial. Under the condition of heavy alkaline solution, [Fe3(OH)4]5+ and [Mn(OH)4]2 ions were first formed. Then [Fe3(OH)4]5+ and
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Fig. 5. SEM of the (a and b) a-Fe2O3 nanodiscs, (c and d) Mn3O4 nanoparticles.
[Mn(OH)4]2 ions were dehydrated under hydrothermal conditions and they in situ generated a bit of a-Fe2O3 and Mn3O4 nuclei which acted as the seeds for the growth of a-Fe2O3 and Mn3O4. The surface of a-Fe2O3 and Mn3O4 nuclei is either positively charged or negatively charged. In either case the surface will selectively adsorb ions of opposite charges (OH or Fe3+ for a-Fe2O3 and OH or Mn2+ for Mn3O4) on it, and the new surface covered with ions will in turn adsorb ions with opposite charges to cover the surface next. In the heavy alkaline synthetic system, more OH may neutralize positive charges on the surface of a-Fe2O3 and Mn3O4, preventing them from possible crystallite aggregation. Thus, a-Fe2O3 and Mn3O4 nuclei slowly grew along reaction, resulting in the disc-like and nanoparticle structure of the samples. 4. Conclusions In summary, iron oxide and manganese oxide nanostructures has been successfully prepared with the assistance of 1,10-phenanthroline as complexing agent by a simple low-temperature solvothermal method. This approach using both coordination complex and mixed solvents of water/ethanol may be applied to synthesize other inorganic materials with abundant morphologies. The properties of nanostructures were studied by SEM, XRD, and FT-IR. The solvothermal method is very fast and does not need any additives and surfactants during the reactions. Comparing with other methods such as sonochemical and sol–gel methods (that requires high temperature, expensive equipment and long aging times); this procedure does not require pressure controlling and high temperature. In comparison to other similar works, the current method is simple and can be scaled-up. Acknowledgment We are grateful to Payame Noor University for financial support of this work.
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