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Bio-inspired green synthesis of Fe3O4 spherical magnetic nanoparticles using Syzygium cumini seed extract
Physica B ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Bio-inspired green synthesis of Fe3O4 spherical magnetic nanoparticles using Syzygium cumini seed extract Sada Venkateswarlu, B. Natesh Kumar, C.H. Prasad, P. Venkateswarlu, N.V.V. Jyothi n Analytical and Inorganic Division, Department of Chemistry, S.V. University, Tirupati 517502, India
art ic l e i nf o
a b s t r a c t
Article history: Received 24 February 2014 Received in revised form 24 March 2014 Accepted 16 April 2014
A novel and bio-inspired Fe3O4 spherical magnetic nanoparticles (SMNPs) were synthesized using Syzygium cumini (S. cumini) seed extract, which is a non-toxic ecofriendly fruit waste material. S. cumini seed extract acts as a green solvent, reducing and capping agent in which sodium acetate acts as electrostatic stabilizing agent. The green synthesized nanoparticles were characterized with the help of various techniques such as X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), Energy-dispersive spectroscopy (EDS), Vibrating sample magnetometer (VSM), FTIR spectroscopy and nitrogen adsorption and desorption analysis techniques. The XRD study divulged that the synthesized SMNPs have inverse spinel cubic structure. The hysteresis loop of Fe3O4 nanoparticles shows an excellent ferromagnetic behavior with saturation magnetization value of 13.6 emu/g. & 2014 Elsevier B.V. All rights reserved.
Keywords: S. cumini seed extract Spherical magnetic nanoparticles XRD TEM FTIR VSM
1. Introduction During the last few years, nanotechnology has been a boon for the scientific field owing to its typical size, surface area and shape and also show immense technological applications electrical, optical, magnetic and chemical fields, which cannot be achieved for their bulk counterparts [1]. In this context, especially Fe3O4 (magnetite) has generated great interest in the magnetic material field and has established its widespread current and promising applications such as magnetic resonance imaging (MRI) [2,3], spintronics [4,5], lithium ion battery field [6], optical [7], catalysis [8], environmental remediation [9,10], tissue-repair engineering [11] and targetted drug delivery [12–14]. A major advantage of magnetic drug targetting over conventional controlled release formulations is the possibility to turn off drug delivery rapidly by simply removing the external magnetic field. Moreover, the magnetic drug targetting employing nanoparticles act as carriers in promising cancer treatment and avoid the side effects of conventional chemotherapy [15]. Despite their technological importance, the Fe3O4 magnetic nanoparticles were synthesized by hard template directing technique [16], chemical co-precipitation [17,18], sol gel [19], microwave-assisted synthesis [20] and thermal methods [21,22]. Nevertheless, it is important to note that using organic solvents like sodium borohydride, hydrazine and carbon monoxide as reducing agents, all these chemicals are highly reactive and
potentially hazardous to environment. In this connection, there has been an increased emphasis on the topic of green chemistry. Utilization of innoxious chemicals and environmentally benign solvents are necessary. To the best of our knowledge, no reports are on synthesis of magnetic nanoparticles using S. cumini seed extraction. Herein, we report the first successful green synthesis of Fe3O4 SMNPs with S. cumini seed extract as the reducing material. The use of naturally available agricultural by-product material has not been hitherto investigated. S. cumini seeds are one of the classical examples for such applications. The S. cumini was native to the parts of South and Southeast Asia. It was widely available throughout India and the drier parts of Southeast Asia, Malaya, East Indies and tropical Africa. In the literature there were a few applications of these seeds [23,24]. S. cumini seed extracts have a potent antidiabetic and anti-HIV activities [25,26]. S. cumini is a rich source of polyphenols [27] and its biomolecules act as both reducing and capping agents in the synthesis of Fe3O4 SMNPs. The main advantage of this method was the relatively easy to handle and cost-effective, as well as environmentally benign. The obtained nanoparticles have been examined by using XRD, Raman spectroscopy, TEM, EDS, VSM, FT-IR and BET analysis.
2. Experimental 2.1. Extraction of S. cumini seed
n
Corresponding author. Tel.: þ 91 9912366219. E-mail address: [email protected] (N.V.V. Jyothi).
The collected seeds were thoroughly rinsed with double distilled water to remove dust particles. Later, S. cumini seeds were
http://dx.doi.org/10.1016/j.physb.2014.04.031 0921-4526/& 2014 Elsevier B.V. All rights reserved.
Please cite this article as: S. Venkateswarlu, et al., Physica B (2014), http://dx.doi.org/10.1016/j.physb.2014.04.031i
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cut into small pieces and dried at room temperature for about 21 days under dust free condition. The dried pieces were grinded with mortar and pestle to convert into powder. An amount of 10 g of dried powder was blended with 100 ml double distilled water in to a 250 ml round bottom flask, and refluxed for 1 h at 70 1C until the color of aqueous solution changed from watery to light yellowish brown color. Then, the resultant extract was cooled to room temperature and filtered with a cheese cloth. The filtrate was stored at 4 1C in order to use for further experiments.
2.2. Green synthesis of Fe3O4 SMNPs Fe3O4 SMNPs were prepared through a simple and eco-friendly method. About 2.16 g of FeCl3 6H20 and 6.56 g of sodium acetate were dissolved in 40 ml of freshly prepared S. cumini seed extract. The resultant solution contains polysaccharides and other biomolecules and the mixture was stirred vigorously for 2 h at 65 1C in a 100 ml round bottom flask. After 2 h, the resulting solution turned into homogenous black color indicating the formation of Fe3O4 SMNPs. The obtained colloidal solution was cooled to room temperature and obtained black product was isolated by applying an external magnetic field. It was washed three times with ethanol and dried in a vacuum oven at 90 1C for overnight and finally stored in a stoppered bottle for further use. The following scheme shows the formation of Fe3O4 SMNPs.
2Fe3 þ þ CH3 COO þ 5H2 O-Fe2 OðCH3 COOÞðOHÞ3 H2 O þ 5H þ
3. Results and discussion 3.1. XRD-diffraction and Raman spectra characterization Fig. 1 reveals the XRD pattern of Fe3O4 magnetic nanoparticles obtained using S. cumini seed extract. The XRD patterns of the Fe3O4 magnetic nanoparticles display several relatively strong reflection peaks in the 2θ region of 5–901. It was found that all the reflection peaks at (1 1 1), (2 2 0), (3 1 1), (4 0 0), (4 2 2), (3 3 3), (4 4 0), (5 3 3) and (7 3 1) can be well indexed to the inverse spinel face-centered cubic structure of Fe3O4 magnetic nanoparticles (JCPDS card no.74-0748) according to the reflection peak positions and relative intensities which confirm that the nanoparticles synthesized in this study were the Fe3O4 magnetic nanoparticles. The crystallite size was determined by applying the Scherrer's equation D ¼0.89λ/β cos θ where D is the average particle size, λ is wave length of the Cu-Kα irradiation, β is the full width at half maximum intensity of the diffraction peak and θ is the diffraction angle for the (3 1 1) peak of SMNPs. The resulting mean crystallite size of Fe3O4 SMNPs was 14 nm was well coincided with the TEM result. In addition, the lattice parameter of cubic magnetite was also calculated by the formula: 1/d2 ¼1/ a2(h2 þk2 þ l2) where ‘a’ is lattice parameter, dhkl is the interplanar separation corresponding to Miller indices h, k, l and the calculated lattice constant was 8.381 Å. This indicates that Fe3O4 SMNPs can be obtained by eco-friendly method. Raman spectrum of green synthesized Fe3O4 SMNPs was shown in (Fig. 1a). The broad band
Δ
ð1Þ Fe2 OðCH3 COOÞðOHÞ3 H2 O-Fe2 O3 þ CH3 COOH þ 2H2 O
ð2Þ
3FeO3 þC 6 H12 O6 -2Fe3 O4 þ C 6 H12 O7
ð3Þ
Δ
Δ
In this green synthesis process, S. cumini seed extract, containing carbohydrates and polyphenols, can serve as reducing agents. In addition, sodium acetate acts as electrostatic stabilizing agent and also may serve as a ligand and form an intermediate complexation phase iron oxide acetate hydroxide hydrate (IOAHH) and is shown in Eq. (1). The Eq. (2) shows the brown color precipitate of Fe2O3 formation, and finally Eq. (3) shows the formation of Fe3O4 SMNPs. The carbohydrates here are converted into gluconic acid. The above equation proves the role of biofunctional group (carbohydrates) for the formation of Fe3O4 SMNPs. These bio-inspired nanoparticles might, in turn, find applications in removal of toxic metals from aqueous solution, biomedical fields and lithium ion battery field.
2.3. Characterization The crystal structure information was obtained using Seifert 3003 TT X-ray diffractometer with Cu Kα radiation with a wave length of 1.52 Å. Iron oxide phase was determined by LABRAM HR 800 micro Raman spectrometer, Morphology and size distribution of Fe3O4 SMNPs was determined with Jeol JEM-2100 transmission electron microscope (TEM). Quantitative elemental analyses were carried out with Oxford instrument Inca Penta FET 3 electron diffraction spectrum (EDS). The magnetization loops for magnetic nanoparticles were measured at room temperature using a Vibrating sample magnetometer (VSM, LKSM-7410). The specific surface area and pore diameter were determined using Brunauer, Emmett, Teller surface area analyzer Micromeritics ASAP 2020 V3.00H (BET). FTIR measurements of S. cumini seed extract and synthesized sample were carried out with Thermo Nicolet series-200.
Fig. 1. X-ray diffraction pattern of Fe3O4 SMNPs (a) Raman spectra of Fe3O4 SMNPs.
Please cite this article as: S. Venkateswarlu, et al., Physica B (2014), http://dx.doi.org/10.1016/j.physb.2014.04.031i
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observed at 670 cm 1 is assigned to the A1g modes of Fe3O4 [28]. In addition, the bands at 538 (T2g), 306 (Eg) and 194 cm 1 (T2g) were appeared which are characteristics of magnetite Fe3O4 [29]. No other characteristic iron oxide bands such as those for hematite (α Fe2O3) and maghemite (γ Fe2O3), are observed. This result proves that the synthesized iron oxide is Fe3O4.
3.2. TEM and EDS characterization Transmission electron microscope (TEM) studies of Fe3O4 SMNPs are carried out to understand the shape and size of the prepared particles. Fig. 2a shows representative transmission electron microscopy (TEM) with scale of 20 nm. It is apparent that the green synthesized Fe3O4 nanoparticles were spherical in shape and these particles were agglomerated because of hydroxyl form of extract. Fig. 2b shows the histogram for freshly prepared Fe3O4 SMNPs with the mean diameter of 9–20 nm. The spectrum was used to determine the distribution and composition and each nanoparticle of the nanocomposite was revealed by EDS analysis of the image is shown in Fig. 2c. To confirm the whole nanocomposite which contains iron and oxygen, no additional elements were observed.
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3.3. FT-IR analysis FTIR analysis was used for characterizing the synthesized Fe3O4 SMNPs and also for understanding the existence of surface functional groups in metal interactions. The S. cumini seed extract constituted by rich of polyphenols, flavanoides acid derivatives, proteins, lipids and fibers [30,31]. Fig. 3 represents the FT-IR spectra of S. cumini extract curve (a) and Fe3O4 curve (b). The two curves suggest that there was a variation in the intensity of peaks in different regions. A major peak was identified at 3635 cm 1 and corresponds to the O–H stretching vibrations (polyphenolic group), this peak shifted from 3635 to 3458 cm 1 which indicating the possible involvement of polyphenols in synthesis of nanoparticles. The other peak which shifts from 2922 to 2851 cm 1 is assigned to the C–H stretching vibration of methyl and methoxy groups and their role. The peak at 1730 cm 1 in curve (a) shifted to 1710 cm 1 in curve (b) and will reveal the involvement of C ¼O stretching vibration of acid derivatives and those 1623 cm 1 and 1310 cm 1 peaks were assigned to C¼ C of aromatic rings and amide groups. The curve (b) indicate the characteristic band of Fe–O at 579 cm 1 and is an indication of Fe3O4 [32]. The FT-IR results too indicate the presence of polyphenols, flavonoids other biomolecules in the S. cumini seed
Fig. 2. (a) TEM image, (b) histogram showing particle sizedistribution of Fe3O4 SMNPs and (c) EDS analysis of green synthesized Fe3O4 SMNPs.
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Fig. 3. FT-IR spectra of S. cumini extract (a), Fe3O4 SMNPs (b).
Fig. 5. Room-temperature magnetic hysteresis loops of Fe3O4 SMNPs.
3.5. Magnetic mersurments Fig. 5 shows the hysteresis loop demonstrates ferromagnetic behavior with the saturation magnetization (Ms) value about 13.6 emu/g, the coercive force (Hc) of 253.68 G and Magnetic remanence (Mr) is 2.25 emu/g. The inset up-left in Fig. 5 shows the behavior of magnetic nanoparticles before and after external magnetic field. These are easily dispersed in double distilled water and also could be drawn from the solution to the side wall of the vial by an external magnet and the black suspended aqueous solution turns into transparent within seconds when it is placed nearby suggesting that the obtained magnetic nanoparticles has an excellent magnetic responsivity. These magnetic properties will allow the nanocomposites which are to be used in biomedical applications such as targetted drug delivery and also extraction of toxic metals in environment and also possessing a good recyclable property.
Fig. 4. N2 adsorption desorption isotherms, pore size distribution (inset) of the biogenic synthesized Fe3O4 SMNPs.
extract and these biomolecules may participate in the formation of Fe3O4 SMNPs.
3.4. BET analysis Nitrogen adsorption–desorption isotherm and the corresponding pore size distribution (inset) of the Fe3O4 SMNPs are revealed in Fig. 4. The Brunauer–Emmett and Teller (BET) surface area is determined to be 3.517 m2/g and the average pore size for the Fe3O4 is determined according to the single-point adsorption total volume at the relative pressure P/PO ¼0.9905 cm3/g. The pore size distribution is obtained from adsorption branch analysis by the Barret–Joyner and Halender (BJH) method. The pore size distribution (Fig. 4) (inset) indicates that most of the mesoporous is around 2 nm [33] in the sample. Eventually, the BET surface area and BHJ pore volume support the fact that the one-pot green synthesized Fe3O4 SMNPs have a mesoporous structure. These porous magnetic materials have tremendous application in catalysis, biomedical and separation technologies.
4. Conclusions In this investigation for the first time, we have successfully synthesized ferromagnetic Fe3O4 SMNPs by a green synthesis method utilizing nontoxic, inexpensive and environmentally benign agricultural by-product which was an alternate to the chemical methods. The TEM images showed the spherical shape and size of the sample. The FTIR, XRD and Raman spectroscopy characterized the molecular structure of Fe3O4 SMNPs. The specific surface area of the Fe3O4 particles is determined to be 3.517 m2/g and calculated from the linear part of the BET plot and the particles are mesoporous. Moreover, magnetic measurement was also an evident to ferromagnetic properties. This green synthesized ferromagnetic Fe3O4 SMNPs have promising application in bio-medicinal and separation field.
Acknowledgments The author Sada Venkateswarlu thank to UGC-BSR, New Delhi, Q2 India for providing financial support to carry out the present work. Also the authors thank to IIT-Madras and NEHU, Shillong for providing instrumental facilities.
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References [1] R.C. Ashoori, Nature 379 (1996) 413. [2] Y. Chen, H. Chen, D. Zeng, Y. Tian, F. Chen, J. Feng, J. Shi, ACS Nano 4 (2010) 6001. [3] W. Chen, P. Yi, Y. Zhang, L. Zhang, Z. Deng, Z. Zhang, ACS Appl. Mater. Interfaces 3 (2011) 4085. [4] Y.Q. Zhan, R. Zhao, Y.J. Lei, F.B. Meng, J.C. Zhong, X.B. Liu, J. Magn. Magn. Mater. 323 (2011) 1006. [5] D.H. Zhang, Z.Q. Liu, S. Han, et al., Nano Lett. 4 (2004) 2151. [6] M.L. Sanchez, A. Primo, H. Garcia, J. Mater. Chem. 22 (2012) 21373. [7] D.J. Hornbaker, S.J. Kahng, S. Misra, B.W. Smith, A.T. Johnson, E.J. Mele, D. E. Luzzi, A. Yazdani, Science 295 (2002) 828. [8] A.H. Lu, W. Schmidt, et al., Angew. Chem. Int. Ed. 43 (2004) 4303. [9] N. Zhang, H. Peng, B.I.N. Hu, Talanta 94 (2012) 278. [10] Q. Cheng, F. Qu, N.B. Li, H.Q. Luo, Anal. Chim. Acta 715 (2012) 113. [11] A.K. Gupta, M. Gupta, Biomaterials 26 (2005) 3995. [12] J. Jabera, E. Mohsen, Colloids Surf. B 102 (2013) 265. [13] C. Sun, J.S.H. Lee, M. Zhang, Adv. Drug Deliv. Rev. 60 (2008) 1252. [14] X. He, X. Wu, C.A.I. Xin, S. Lin, M. Xie, X. Zhu, D. Yan, Langmuir 28 (2012) 11929. [15] C. Alexiou., et al., Eur. Biophys. J. 35 (2006) 446. [16] J. Choi, G. Sauer, K. Nielsch, R.B. Wehrspohn, U. Gosele, Chem. Mater. 15 (2003) 776.
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[17] D. Shan, Y. Shi, S. Duan, Y. Wei, Q. Cai, X. Yang, Mater. Sci. Eng. C 33 (2013) 3498. [18] L. Sun, C. Huang, T. Gong, S. Zhou, Mater. Sci. Eng. C 30 (2010) 583. [19] W. Wu, X. Xiao, S. Zhang, H. Li, X. Zhou, C. Jiang, Nanoscale Res. Lett 4 (2009) 926. [20] S. Yin, Z. Luo, J. Xia, H. Li, J. Phys. Chem. Solids 71 (2010) 1785. [21] J.X. Wan, X.Y. Chen, Z.H. Wang, X.G. Yang, Y.T. Qian, J. Cryst. Growth 276 (2005) 571. [22] H. Zhang, G. Zhu, Appl. Surf. Sci. 258 (2012) 4952. [23] V. Kumar, S.C. Yadav, S.K. Yadav, J. Chem. Technol. Biotechnol. 85 (2010) 1301. [24] B. Joyita, R.T. Narendhirakannan, Dig. J. Nanomater. Biostruct. 6 (2011) 961. [25] M. Chandrasekaran, V. Venkatesalu, J. Ethnopharmacol. 91 (2004) 105. [26] M. Ayyanar, P.S. Babu, Asian Pac. J. Trop. Biomed. 2 (2012) 240. [27] M. Bajpai, A. Pande, S.K. Tewari, D. Prakesh, Int. J. Food Sci. Nutr. 56 (2005) 287. [28] Y.S. Li, J.S. Church, A.L. Woodhead, J. Magn. Magn. Mater. 324 (2012) 1543. [29] L. Slavov, M.V. Abrashev, et al., J. Magn. Magn. Mater. 322 (2010) 1904. [30] S. Hossain, A. Rahaman, et al., Orient. Pharm. Exp. Med. 12 (2012) 59. [31] P. Bigoniya, C.S. Singh, B. Srivastava, Asian Pac. J. Trop. Biomed. 2 (2012) S290. [32] X. Sun, C. Zheng, F. Zhang, Y. Yang, G. Wu, A. Yu, N. Guan, J. Phys. Chem. C 113 (2009) 16002. [33] K. Sing, D. Everett, R. Haul, L. Moscou, R. Pierotti, J. Rouquerol, T. Siemieniewska, Pure Appl. Chem. 57 (1985) 603. Q3
Please cite this article as: S. Venkateswarlu, et al., Physica B (2014), http://dx.doi.org/10.1016/j.physb.2014.04.031i
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Contents lists available at ScienceDirect
Physica B journal homepage: www.elsevier.com/locate/physb
Bio-inspired green synthesis of Fe3O4 spherical magnetic nanoparticles using Syzygium cumini seed extract Sada Venkateswarlu, B. Natesh Kumar, C.H. Prasad, P. Venkateswarlu, N.V.V. Jyothi n Analytical and Inorganic Division, Department of Chemistry, S.V. University, Tirupati 517502, India
art ic l e i nf o
a b s t r a c t
Article history: Received 24 February 2014 Received in revised form 24 March 2014 Accepted 16 April 2014
A novel and bio-inspired Fe3O4 spherical magnetic nanoparticles (SMNPs) were synthesized using Syzygium cumini (S. cumini) seed extract, which is a non-toxic ecofriendly fruit waste material. S. cumini seed extract acts as a green solvent, reducing and capping agent in which sodium acetate acts as electrostatic stabilizing agent. The green synthesized nanoparticles were characterized with the help of various techniques such as X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), Energy-dispersive spectroscopy (EDS), Vibrating sample magnetometer (VSM), FTIR spectroscopy and nitrogen adsorption and desorption analysis techniques. The XRD study divulged that the synthesized SMNPs have inverse spinel cubic structure. The hysteresis loop of Fe3O4 nanoparticles shows an excellent ferromagnetic behavior with saturation magnetization value of 13.6 emu/g. & 2014 Elsevier B.V. All rights reserved.
Keywords: S. cumini seed extract Spherical magnetic nanoparticles XRD TEM FTIR VSM
1. Introduction During the last few years, nanotechnology has been a boon for the scientific field owing to its typical size, surface area and shape and also show immense technological applications electrical, optical, magnetic and chemical fields, which cannot be achieved for their bulk counterparts [1]. In this context, especially Fe3O4 (magnetite) has generated great interest in the magnetic material field and has established its widespread current and promising applications such as magnetic resonance imaging (MRI) [2,3], spintronics [4,5], lithium ion battery field [6], optical [7], catalysis [8], environmental remediation [9,10], tissue-repair engineering [11] and targetted drug delivery [12–14]. A major advantage of magnetic drug targetting over conventional controlled release formulations is the possibility to turn off drug delivery rapidly by simply removing the external magnetic field. Moreover, the magnetic drug targetting employing nanoparticles act as carriers in promising cancer treatment and avoid the side effects of conventional chemotherapy [15]. Despite their technological importance, the Fe3O4 magnetic nanoparticles were synthesized by hard template directing technique [16], chemical co-precipitation [17,18], sol gel [19], microwave-assisted synthesis [20] and thermal methods [21,22]. Nevertheless, it is important to note that using organic solvents like sodium borohydride, hydrazine and carbon monoxide as reducing agents, all these chemicals are highly reactive and
potentially hazardous to environment. In this connection, there has been an increased emphasis on the topic of green chemistry. Utilization of innoxious chemicals and environmentally benign solvents are necessary. To the best of our knowledge, no reports are on synthesis of magnetic nanoparticles using S. cumini seed extraction. Herein, we report the first successful green synthesis of Fe3O4 SMNPs with S. cumini seed extract as the reducing material. The use of naturally available agricultural by-product material has not been hitherto investigated. S. cumini seeds are one of the classical examples for such applications. The S. cumini was native to the parts of South and Southeast Asia. It was widely available throughout India and the drier parts of Southeast Asia, Malaya, East Indies and tropical Africa. In the literature there were a few applications of these seeds [23,24]. S. cumini seed extracts have a potent antidiabetic and anti-HIV activities [25,26]. S. cumini is a rich source of polyphenols [27] and its biomolecules act as both reducing and capping agents in the synthesis of Fe3O4 SMNPs. The main advantage of this method was the relatively easy to handle and cost-effective, as well as environmentally benign. The obtained nanoparticles have been examined by using XRD, Raman spectroscopy, TEM, EDS, VSM, FT-IR and BET analysis.
2. Experimental 2.1. Extraction of S. cumini seed
n
Corresponding author. Tel.: þ 91 9912366219. E-mail address: [email protected] (N.V.V. Jyothi).
The collected seeds were thoroughly rinsed with double distilled water to remove dust particles. Later, S. cumini seeds were
http://dx.doi.org/10.1016/j.physb.2014.04.031 0921-4526/& 2014 Elsevier B.V. All rights reserved.
Please cite this article as: S. Venkateswarlu, et al., Physica B (2014), http://dx.doi.org/10.1016/j.physb.2014.04.031i
S. Venkateswarlu et al. / Physica B ∎ (∎∎∎∎) ∎∎∎–∎∎∎
2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66
cut into small pieces and dried at room temperature for about 21 days under dust free condition. The dried pieces were grinded with mortar and pestle to convert into powder. An amount of 10 g of dried powder was blended with 100 ml double distilled water in to a 250 ml round bottom flask, and refluxed for 1 h at 70 1C until the color of aqueous solution changed from watery to light yellowish brown color. Then, the resultant extract was cooled to room temperature and filtered with a cheese cloth. The filtrate was stored at 4 1C in order to use for further experiments.
2.2. Green synthesis of Fe3O4 SMNPs Fe3O4 SMNPs were prepared through a simple and eco-friendly method. About 2.16 g of FeCl3 6H20 and 6.56 g of sodium acetate were dissolved in 40 ml of freshly prepared S. cumini seed extract. The resultant solution contains polysaccharides and other biomolecules and the mixture was stirred vigorously for 2 h at 65 1C in a 100 ml round bottom flask. After 2 h, the resulting solution turned into homogenous black color indicating the formation of Fe3O4 SMNPs. The obtained colloidal solution was cooled to room temperature and obtained black product was isolated by applying an external magnetic field. It was washed three times with ethanol and dried in a vacuum oven at 90 1C for overnight and finally stored in a stoppered bottle for further use. The following scheme shows the formation of Fe3O4 SMNPs.
2Fe3 þ þ CH3 COO þ 5H2 O-Fe2 OðCH3 COOÞðOHÞ3 H2 O þ 5H þ
3. Results and discussion 3.1. XRD-diffraction and Raman spectra characterization Fig. 1 reveals the XRD pattern of Fe3O4 magnetic nanoparticles obtained using S. cumini seed extract. The XRD patterns of the Fe3O4 magnetic nanoparticles display several relatively strong reflection peaks in the 2θ region of 5–901. It was found that all the reflection peaks at (1 1 1), (2 2 0), (3 1 1), (4 0 0), (4 2 2), (3 3 3), (4 4 0), (5 3 3) and (7 3 1) can be well indexed to the inverse spinel face-centered cubic structure of Fe3O4 magnetic nanoparticles (JCPDS card no.74-0748) according to the reflection peak positions and relative intensities which confirm that the nanoparticles synthesized in this study were the Fe3O4 magnetic nanoparticles. The crystallite size was determined by applying the Scherrer's equation D ¼0.89λ/β cos θ where D is the average particle size, λ is wave length of the Cu-Kα irradiation, β is the full width at half maximum intensity of the diffraction peak and θ is the diffraction angle for the (3 1 1) peak of SMNPs. The resulting mean crystallite size of Fe3O4 SMNPs was 14 nm was well coincided with the TEM result. In addition, the lattice parameter of cubic magnetite was also calculated by the formula: 1/d2 ¼1/ a2(h2 þk2 þ l2) where ‘a’ is lattice parameter, dhkl is the interplanar separation corresponding to Miller indices h, k, l and the calculated lattice constant was 8.381 Å. This indicates that Fe3O4 SMNPs can be obtained by eco-friendly method. Raman spectrum of green synthesized Fe3O4 SMNPs was shown in (Fig. 1a). The broad band
Δ
ð1Þ Fe2 OðCH3 COOÞðOHÞ3 H2 O-Fe2 O3 þ CH3 COOH þ 2H2 O
ð2Þ
3FeO3 þC 6 H12 O6 -2Fe3 O4 þ C 6 H12 O7
ð3Þ
Δ
Δ
In this green synthesis process, S. cumini seed extract, containing carbohydrates and polyphenols, can serve as reducing agents. In addition, sodium acetate acts as electrostatic stabilizing agent and also may serve as a ligand and form an intermediate complexation phase iron oxide acetate hydroxide hydrate (IOAHH) and is shown in Eq. (1). The Eq. (2) shows the brown color precipitate of Fe2O3 formation, and finally Eq. (3) shows the formation of Fe3O4 SMNPs. The carbohydrates here are converted into gluconic acid. The above equation proves the role of biofunctional group (carbohydrates) for the formation of Fe3O4 SMNPs. These bio-inspired nanoparticles might, in turn, find applications in removal of toxic metals from aqueous solution, biomedical fields and lithium ion battery field.
2.3. Characterization The crystal structure information was obtained using Seifert 3003 TT X-ray diffractometer with Cu Kα radiation with a wave length of 1.52 Å. Iron oxide phase was determined by LABRAM HR 800 micro Raman spectrometer, Morphology and size distribution of Fe3O4 SMNPs was determined with Jeol JEM-2100 transmission electron microscope (TEM). Quantitative elemental analyses were carried out with Oxford instrument Inca Penta FET 3 electron diffraction spectrum (EDS). The magnetization loops for magnetic nanoparticles were measured at room temperature using a Vibrating sample magnetometer (VSM, LKSM-7410). The specific surface area and pore diameter were determined using Brunauer, Emmett, Teller surface area analyzer Micromeritics ASAP 2020 V3.00H (BET). FTIR measurements of S. cumini seed extract and synthesized sample were carried out with Thermo Nicolet series-200.
Fig. 1. X-ray diffraction pattern of Fe3O4 SMNPs (a) Raman spectra of Fe3O4 SMNPs.
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observed at 670 cm 1 is assigned to the A1g modes of Fe3O4 [28]. In addition, the bands at 538 (T2g), 306 (Eg) and 194 cm 1 (T2g) were appeared which are characteristics of magnetite Fe3O4 [29]. No other characteristic iron oxide bands such as those for hematite (α Fe2O3) and maghemite (γ Fe2O3), are observed. This result proves that the synthesized iron oxide is Fe3O4.
3.2. TEM and EDS characterization Transmission electron microscope (TEM) studies of Fe3O4 SMNPs are carried out to understand the shape and size of the prepared particles. Fig. 2a shows representative transmission electron microscopy (TEM) with scale of 20 nm. It is apparent that the green synthesized Fe3O4 nanoparticles were spherical in shape and these particles were agglomerated because of hydroxyl form of extract. Fig. 2b shows the histogram for freshly prepared Fe3O4 SMNPs with the mean diameter of 9–20 nm. The spectrum was used to determine the distribution and composition and each nanoparticle of the nanocomposite was revealed by EDS analysis of the image is shown in Fig. 2c. To confirm the whole nanocomposite which contains iron and oxygen, no additional elements were observed.
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3.3. FT-IR analysis FTIR analysis was used for characterizing the synthesized Fe3O4 SMNPs and also for understanding the existence of surface functional groups in metal interactions. The S. cumini seed extract constituted by rich of polyphenols, flavanoides acid derivatives, proteins, lipids and fibers [30,31]. Fig. 3 represents the FT-IR spectra of S. cumini extract curve (a) and Fe3O4 curve (b). The two curves suggest that there was a variation in the intensity of peaks in different regions. A major peak was identified at 3635 cm 1 and corresponds to the O–H stretching vibrations (polyphenolic group), this peak shifted from 3635 to 3458 cm 1 which indicating the possible involvement of polyphenols in synthesis of nanoparticles. The other peak which shifts from 2922 to 2851 cm 1 is assigned to the C–H stretching vibration of methyl and methoxy groups and their role. The peak at 1730 cm 1 in curve (a) shifted to 1710 cm 1 in curve (b) and will reveal the involvement of C ¼O stretching vibration of acid derivatives and those 1623 cm 1 and 1310 cm 1 peaks were assigned to C¼ C of aromatic rings and amide groups. The curve (b) indicate the characteristic band of Fe–O at 579 cm 1 and is an indication of Fe3O4 [32]. The FT-IR results too indicate the presence of polyphenols, flavonoids other biomolecules in the S. cumini seed
Fig. 2. (a) TEM image, (b) histogram showing particle sizedistribution of Fe3O4 SMNPs and (c) EDS analysis of green synthesized Fe3O4 SMNPs.
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Fig. 3. FT-IR spectra of S. cumini extract (a), Fe3O4 SMNPs (b).
Fig. 5. Room-temperature magnetic hysteresis loops of Fe3O4 SMNPs.
3.5. Magnetic mersurments Fig. 5 shows the hysteresis loop demonstrates ferromagnetic behavior with the saturation magnetization (Ms) value about 13.6 emu/g, the coercive force (Hc) of 253.68 G and Magnetic remanence (Mr) is 2.25 emu/g. The inset up-left in Fig. 5 shows the behavior of magnetic nanoparticles before and after external magnetic field. These are easily dispersed in double distilled water and also could be drawn from the solution to the side wall of the vial by an external magnet and the black suspended aqueous solution turns into transparent within seconds when it is placed nearby suggesting that the obtained magnetic nanoparticles has an excellent magnetic responsivity. These magnetic properties will allow the nanocomposites which are to be used in biomedical applications such as targetted drug delivery and also extraction of toxic metals in environment and also possessing a good recyclable property.
Fig. 4. N2 adsorption desorption isotherms, pore size distribution (inset) of the biogenic synthesized Fe3O4 SMNPs.
extract and these biomolecules may participate in the formation of Fe3O4 SMNPs.
3.4. BET analysis Nitrogen adsorption–desorption isotherm and the corresponding pore size distribution (inset) of the Fe3O4 SMNPs are revealed in Fig. 4. The Brunauer–Emmett and Teller (BET) surface area is determined to be 3.517 m2/g and the average pore size for the Fe3O4 is determined according to the single-point adsorption total volume at the relative pressure P/PO ¼0.9905 cm3/g. The pore size distribution is obtained from adsorption branch analysis by the Barret–Joyner and Halender (BJH) method. The pore size distribution (Fig. 4) (inset) indicates that most of the mesoporous is around 2 nm [33] in the sample. Eventually, the BET surface area and BHJ pore volume support the fact that the one-pot green synthesized Fe3O4 SMNPs have a mesoporous structure. These porous magnetic materials have tremendous application in catalysis, biomedical and separation technologies.
4. Conclusions In this investigation for the first time, we have successfully synthesized ferromagnetic Fe3O4 SMNPs by a green synthesis method utilizing nontoxic, inexpensive and environmentally benign agricultural by-product which was an alternate to the chemical methods. The TEM images showed the spherical shape and size of the sample. The FTIR, XRD and Raman spectroscopy characterized the molecular structure of Fe3O4 SMNPs. The specific surface area of the Fe3O4 particles is determined to be 3.517 m2/g and calculated from the linear part of the BET plot and the particles are mesoporous. Moreover, magnetic measurement was also an evident to ferromagnetic properties. This green synthesized ferromagnetic Fe3O4 SMNPs have promising application in bio-medicinal and separation field.
Acknowledgments The author Sada Venkateswarlu thank to UGC-BSR, New Delhi, Q2 India for providing financial support to carry out the present work. Also the authors thank to IIT-Madras and NEHU, Shillong for providing instrumental facilities.
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Please cite this article as: S. Venkateswarlu, et al., Physica B (2014), http://dx.doi.org/10.1016/j.physb.2014.04.031i