Short communication
Characterization of ZnFe2O4 Nanoparticles Obtained by the Thermal Decomposition
of ZnFe2(cin)3(N2H4)3
Kalpanadevi Kalimuthu, Sinduja C. Rangasamy and Manimekalai Rakkiyasamy*
Department of Chemistry, Kongunadu Arts and Science College, Coimbatore, Tamilnadu, India * Corresponding author: E-mail: manimekalair@ymail.com
Received: 06-09-2013
Abstract
ZnFe2O4 nanoparticles have been obtained from the inorganic precursor ZnFe2(cin)3(N2H4)3 via thermal decomposition route. The precursor prepared by a simple precipitation method, was characterised by hydrazine and metal analyses, infrared spectral analysis and thermo gravimetric analysis. Using appropriate annealing conditions, ZnFe2O4 na-noparticles of average size around 9 nm were synthesised by the thermal treatment of the precursor. The nanoparticles were characterised for their size and structure using X-Ray Diffraction (XRD), High Resolution Transmission Electron Microscopic (HRTEM), Selected Area Electron Diffraction (SAED) and Scanning Electron Microscopic (SEM) techniques.
Keywords: ZnFe2O4 nanoparticles, XRD, HRTEM, SAED, SEM
1. Introduction
Nano-sized spinel ferrites have been extensively investigated in the recent past for their valuable electrical and magnetic properties, and applications in several important technological fields such as ferrofluids,1 electronic gadgets, information storage, magnetic resonance imaging (MRI), drug-delivery technology and catalysis.2 Zinc ferrite (ZnFe2O4), an important spinel ferrite, is a commercially important material and has been widely used as magnetic materials,3 gas sensor,4 catalysts,5 pho-tocatalysts,6 absorbent materials,7 magneto caloric pumps,8 etc.
Various methods have been developed to synthesize nanocrystalline ZnFe2O4 such as mechanical allo-ying,9 pulsed wire discharge,10 sol-gel method,11 microe-mulsion,12 thermal transformation process,13 hydrothermal methods,14 etc. Among these established methods, thermal treatment has attracted immense interest owing to its simple process, cost-effectiveness and crystallization as well as the control of the morphologies, sizes and phase transformation. In the present study, we report the synthesis of nanocrystalline ZnFe2O4 by a simple thermal decomposition method at a relatively low cost and low time.
2. Experimental
2. 1. Preparation of Zinc Ferrous Cinnamate Hydrazinate ZnFe2(cin)3(N2H4)3
This was prepared by the addition of an aqueous solution (50 mL) of hydrazine hydrate (1 mL, 0.02 mol) and cinnamic acid (1.18 g, 0.0079 mol) to the corresponding aqueous solution (50 mL) of zinc nitrate hexahydrate (0.058 g, 0.0019 mol) and ferrous sulphate hepta-hydrate (2.22 g, 0.0079 mol). The brown orange product formed immediately was kept aside for an hour for digestion, then filtered and washed with water, alcohol followed by diethylether and air dried.
2. 2. Preparation of Zinc Ferrite Nanoparticles
Zinc ferrite nanoparticles were obtained from the autocatalytic decomposition of the precursor. In this method, the dried precursor was transferred to a silica crucible and heated to red hot condition in an ordinary atmosphere for about 45 minutes. The precursor started decomposing violently. The total decomposition of ZnFe2(cin)3(N2H4)3 led to the formation of ZnFe2O4, which are quenched to room temperature, ground well and stored.
3. Results and Discussion:
3. 3. Thermal Analysis of the Precursor
3. 1. Chemical Formula Determination of the Precursor
The hydrazine content in the precursor was determined by titration using KIO3 as the titrant, by volumetric analysis under Andrew's condition.15 The percentage of zinc and iron in the precursor was estimated by gravi-metry as given in the Vogel's textbook,15 which was then confirmed by EDX analysis. Of the total composition of the precursor, the percentage remaining belongs to cinna-mate, which was then confirmed by elemental analysis. Based on the observed percentage of hydrazine (13.38), zinc (26.84) and iron (45.99) which are found to match closely with the calculated values (13.52), (26.97) and (46.62) for hydrazine, zinc and iron respectively, the chemical formula ZnFe2(cin)3(N2H4)3 has been tentatively assigned to the precursor, zinc ferrous cinnamate hydra-zinate.
3. 2. FT-IR Analysis of the Precursor
The infrared spectrum of the solid precursor sample was recorded by the KBr disc technique using a Shimadzu spectrophotometer. From the IR spectrum of ZnFe2(cin)3(N2H4)3, it is observed that the N-N stretching frequency is seen at 975 cm1, which unambiguously proves the bidentate bridging nature of the hydra-zine ligand.16 The asymmetric and symmetric stretching frequencies of the carboxylate ions are seen at 1639 and 1411 cm -1, respectively with the Au (Uasymm_ usym) separation of 228 cm1, which indicate the mono-dentate linkage of the carboxylate groups. The N-H stretching is observed at 3371 cm1. The IR data thus confirms the formation of zinc ferrous cinnamate hydrazinate.
The simultaneous TGA-DSC study was carried out in Universal V4.5A TA Instrument in a nitrogen atmosphere from room temperature to 700 °C. As can be observed from Figure 1, the precursor loses weight in two particular steps. The first step is the dehydrazination of the two hydrazine molecules between room temperature and 175 °C with a weight loss of 9%. The corresponding peak in DSC is observed as an exotherm. The major weight loss of 60% on the TG curve from 175 to 430 °C is attributed to the second step involving the dehydrazina-tion of the remaining one hydrazine molecule and decar-boxylation of the precursor, which gives ZnFe2O4 as the final residue.
3. 4. Characterization of ZnFe2O4 Nanoparticles
3. 4. 1. XRD Analysis
XRD pattern of ZnFe2O4 nanoparticles recorded using an X-ray diffractometer (X'per PRO model) using Cu-Ka radiation, at 40 keV in the 2h range of 10-80 is shown in Figure 2. Six characteristic peaks can be indexed as the cubic structure ZnFe2O4, which is accorded with the reported data (JCPDS File No 73-1963). The peaks with 29 values of 30.416, 35.609, 43.600, 53.500, 56.860, 62.759 correspond to the crystal planes (220), (311), (400), (422), (511), (440) of crystalline ZnFe2O4 respectively, with lattice constant a = 0.835 nm. The average crystallite size was calculated using Debye-Scherrer formula, D = KA/ P cos9, where, 9 is Bragg diffraction angle, K is Blank's constant, A is the source wavelength (1.54), and P is the width of the XRD peak at half maximum height. The calculated average crystallite size of the ZnFe2O4 was found to be around 9
Fig.1. TG-DSC curve of ZnFe2(cin)3(N2H4)3
Fig. 2. XRD pattern of ZnFe2O4 nanoparticles
nm. No characteristic peaks for other impurities were detected, confirming that the product obtained is phase pure.
3. 4. 2. HRTEM Analysis
The HRTEM technique is used to visualize the shape and size of the ZnFe2O4 nanoparticles, formed in different sizes, ranging from polydispersed small spherical to large spherical shapes. HRTEM micrographs of ZnFe2O4, recorded on Jeol Jem 2100 advanced analytical electron microscope, which are shown in Figures 3a and 3b. The presence
Fig. 3a. HRTEM image of ZnFe2O4 nanoparticles
Fig.4. SAED pattern of ZnFe2O4 nanoparticles
of some bigger particles should be attributed to be the aggregation or overlapping of some small particles. The average grain size observed from the micrograph is about 9 nm, which is in agreement with the calculation using Scher-rer's equation. Figure 4 shows the selected area electron diffraction (SAED) pattern indicating sharp rings, which reveal the polycrystalline nature of the nanoparticles.
3. 4. 3. SEM Analysis
The morphology of ZnFe2O4 was characterised by scanning electron microscope performed with a HITACHI Model S-3000H. The SEM pictures in Figures 5 a and 5 b clearly show randomly distributed grains with very smaller size and agglomeration of particles.
r*, * .
' « ^
20kV ^X30,000 0.5pm	12 28SEI
Fig. 3b. HRTEM image of ZnFe2O4 nanoparticles
Fig. 5a. SEM image of ZnFe2O4 nanoparticles
Fig. 5b. SEM image of ZnFe2O4 nanoparticles
The composition of the sample is given in table 1. EDX spectrum of ZnFe2O4 nanoparticles is presented in Figure 6, which furnishes the chemical compositional analysis of the nanoscale ZnFe2O4
Compound	Zinc (%)	Iron (%)
	Obs. Calc.	Obs. Calc.
ZnFe2O4	26.84 26.97	45.00 46.32
6000
5000
2000
1000
Fig. 6. EDX spectrum of ZnFe2O4 nanoparticles
4.	Conclusion
ZnFe2O4 nanoparticles were effectively synthesised through a simple and novel thermal decomposition method from the corresponding inorganic precursor, ZnFe2(cin)3 (N2H4)3 and characterised by XRD, TEM, SAED and SEM techniques. The average particle size of ZnFe2O4 nanoparticles determined from XRD and TEM is about 9 nm. The present method is uncomplicated and commercially viable. It is also efficient in terms of time and equipment. Hence this method is a potential and facile route for the large scale industrial production of ZnFe2O4 nanoparticles.
5.	References
1.	J. Sun, Sh. Zhou, P. Hou, Y. Yang, J. Weng, X. Li, M. Li, J. Biomedica. Mat. Res. A, 2007, 83, 333-341.
2.	L. J. Ma, L. S. Chen, S. Y. Chen, J Phys Chem Solids, 2007, 68, 1330-1335.
3.	H. Deng, X. Li, Q. Peng, X. Wang, J. Chen, Y. Li, Angew. Chem., Int. Ed. Engl., 2005, 44, 2782-2785.
4.	X. Niu, W. Du, W. Du, Sens. Actuators, B, Chem., 2004, 99, 405-409.
5.	J. A. Toledo-Antonio, N. Nava, M. Martínez, X. Bokhimi, Appl. Catal, A Gen., 2002, 234, 137-144.
6.	J. Qiu, C. Wang, M. Gu, Mater. Sci. Eng., B, Solid-State Mater. Adv. Technol., 2004, 112, 1-4.
7.	F. Tomás-Alonso, J. M. Palacios Latasa, Fuel Process. Technol., 2004, 86, 191-203.
8.	L. J. Love, J. F. Jansen, T. E. McKnight, Y. Roh, T. J. Phelps, L. W. Yeary, G. T. Cunningham, T. IEEE, Mechatronics, 2005, 10, 68-76.
9.	Y. Shi, J. Ding, S. L. H. Tan, Z. Hu, J Magn Magn Mater, 2003, 256, 13-19.
10.	Y. Kinemuchi, K. Ishizaka, H. Suematsu, W. Jiang, K. Yatsui, Thin Solid Films, 2002, 407, 109-113.
11.	D. H. Chen, X. R. He, Mater Res Bull. 2001, 36, 1369-1377.
12.	C. Liu, B. Zou, A. J. Rondinone, Z. J. Zhang, J Phys Chem., 2000, B104, 1141-1145.
13.	H. M. Fan, J. B. Yi, Y. Yang, K. W. Kho, H. R. Tan, Z. X. Shen, et al., ACS Nano, 2009, 3, 2798-2808.
14.	H. Li, H. Z. Wu, G. X. Xiao, Powder Technol., 2010, 198, 157-166.
15.	I. Vogel, "A Textbook of Quantitative Inorganic Analysis", 4th Ed., (Longman, UK, 1985).
16.	A. Braibanti, F. Dallavalle, M. A. Pellinghelli, E. Leporati, Inorg. Chem. 1968, 7, 1430-1433.
Povzetek
Nanodelce ZnFe2O4 smo pripravili s termičnim razpadom prekurzorja ZnFe2(cin)3(N2H4)3. Prekurzor smo sintetizirali z metodo obarjanja, mu določili vsebnosti hidrazina in kovine ter ga karakterizirali z infraredčo spektroskopijo in ter-mogravimetrično analizo. Z izbiro primernih pogojev termičnega razpade smo pripravili nanodelce ZnFe2O4 s povprečno velikostjo 9 nm, ki smo jih nadalje karakterizirali z različnimi tehnikami: rentgensko praškovno difrakcijo (XRD), z visokoločljivostnim transmisijskim elektronskim mikroskopom (HRTEM), elektronsko difrakcijo (SEAD) in z vrstičnim elektronskim mikroskopom (SEM).