Advanced Materials Research Vol. 584 (2012) pp 272-275 Online available since 2012/Oct/22 at www.scientific.net © (2012) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.584.272
Electrocatalytic property of nano-Fe3O4 modified glassy carbon electrode R. Suresh1a, K. Giribabu1b, R. Manigandan1c, L. Vijayalakshmi2d, A. Stephen3e and V. Narayanan1f* 1
Department of Inorganic Chemistry, University of Madras, Guindy Maraimalai Campus, Chennai 600025, Tamil Nadu, India 2 CSI Ewart Women’s Christian College, Melrosapuram, Kancheepuram 603204 Tamil Nadu, India 3 Department of Nuclear Physics, University of Madras, Guindy Maraimalai Campus, Chennai 600025, Tamil Nadu, India a
[email protected],
[email protected],
[email protected], d
[email protected],
[email protected], f*
[email protected]
Keywords: Fe3O4, agglomerates, electrocatalyst, uric acid.
Abstract We have synthesized Fe3O4 nanoparticles by simple hydrothermal method. The synthesized material was characterized by XRD, FT-IR and FE-SEM etc., The FT-IR spectrum confirms the formation of Fe3O4. XRD confirms the structure and phase purity of the Fe3O4 nanoparticles. The morphological property was characterized by FE-SEM. The synthesized Fe3O4 nanoparticles were used to modify the glassy carbon electrode (GCE) and the modified electrode (n-Fe3O4/GCE) was found to exhibit electrocatalytic activity for the oxidation of uric acid (UA). It shows that the Fe3O4 nanopowder exhibits promising applications in the development of bio-sensors. 1. Introduction Magnetite (Fe3O4) is a common ferrite that has a cubic inverse spinel structure. It exhibits unique magnetic and electric properties based on the transfer of electrons between Fe2+ and Fe3+ in the octahedral sites. As an important magnetic material, Fe3O4 nanoparticles have been widely used in MR contrast agents, biosensors, protein separation, cancer therapy, and recovery of metal irons [1-3], etc., Several methods have been reported in the literature for the preparation of Fe3O4 nanoparticles, such as hydrothermal process, thermal decomposition and microwave-synthesis [4-6] etc., In this work, Fe3O4 nanoparticles were successfully prepared by the hydrothermal method. Further, the prepared nanoparticles have been used to modify the GCE and remarkable shift in anodic peak potential is observed for the electrochemical oxidation of UA than the bare electrode. 2. Experimental 2.1 Materials and physical measurements Ferric chloride, ferrous ammonium sulphate (FAS), sodium hydroxide, sodium acetate, sodium dihydrogen phosphate and disodium hydrogen phosphate were purchased from Qualigens and used without further purification. Uric acid was purchased from Sigma and used as received. Doubly distilled water and ethanol were used as the solvent. The sample was studied by FTIR spectroscopy using a Schimadzu FT-IR 8300 series instrument. The phase and structure of the sample was analyzed by a Rich Siefert 3000 diffractometer with Cu-Kα1 radiation (λ = 1.5406 Å). The morphology of the sample was analyzed by FE-SEM using a HITACHI SU6600 field emission-scanning electron microscopy. The electrochemical experiments were performed on a CHI 600A electrochemical instrument using the as-modified electrode and bare GCE as working electrode, a platinum wire was the counter electrode, and saturated calomel electrode (SCE) was the reference electrode. The modifying process of the electrode was followed by literature method [7]. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 14.139.186.162-22/11/12,12:10:12)
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2.2 Sample preparation In order to prepare Fe3O4 nanoparticles, the mixture of FeCl3.6H2O (2 mmol, 1.621 g in 50 mL of water) and FAS (1 mmol, 1.9607 g in 50 mL of water) were taken in the round bottom flask under constant stirring. To the resulting solutions, 3 mmol of CH3COONa (in 20 ml of water) was added slowly. After the addition of sodium acetate, required amount of 0.1 M NaOH was added to increase the pH up to 10-12. The above mixture kept stirring for 30 min to get uniform precipitation. The obtained nanoparticles was filtered, washed with ethanol three times and dried at room temperature. 3. Results and discussion 3.1 Structure and morphology Fig. 1 depicts the XRD pattern of Fe3O4 nanoparticles. In Fig. 1, the diffraction peaks at 30.26 , 35.67o, 43.21o, 53.63o, 57.34o and 62.88o are in accordance with standard XRD card of Fe3O4 [8]. The peak at 2θ = 35.60o corresponds to the spinel phase of Fe3O4. There was no indication of any other additional phases, except Fe3O4 in the XRD pattern. It was observed that the XRD peaks of Fe3O4 shows broadening, indicating the ultra fine nature of the particles. According to the β value of the Fe3O4 (35.67o) peak, the calculated average crystallite size (using the Scherrer’s equation) of the Fe3O4 is shown found to be 28 nm. Fig. 2 shows the FT-IR spectrum of Fe3O4 nanoparticles. It shows the absorption in the regions of 3407, 1624, 535 and 460 cm-1. The general range of 3600-3100 cm-1 is related to anti-symmetrical and symmetrical O-H stretching vibrations and is also indicative of the presence of some amount of ferric hydroxide in Fe3O4 [9]. Hydrates also absorb in the region of 1670-1600 cm-1 which is related to O-H broadening. The broad peak at 3407 cm-1 and 1624 cm-1 are due to the presence of lattice water molecule in the corresponding samples. The simultaneous presence of these two bands indicates that the water of crystallization is likely to be present in the samples. The two distinct absorption peaks at 535 and 460 cm-1 are attributed to the vibrations of Fe2+–O2- and Fe3+–O2- respectively [10]. The sharp and high intense peak appears at 535 cm-1 demonstrates the high degree of crystallinity of the Fe3O4 nanoparticles. The characteristic absorption bands in the spectrum confirm the presence of spinel structure of Fe3O4. o
Fig. 1 XRD pattern of Fe3O4
Fig. 2 FT-IR spectrum of Fe3O4
The FE-SEM image and EDS of Fe3O4 nanoparticles are given in Fig 3a and b respectively. The FE-SEM image of Fe3O4 shows the particles are agglomerated by irregular shaped particles. However, the size of the particle is in the nm range. Fig. 3b shows the sample contains only Fe and oxygen which confirms the formation of Fe3O4 and there is no other impurity present in the sample. The Al present in the spectrum arises from the aluminium foil.
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Fig. 3a FE-SEM image of Fe3O4
Fig. 3b EDS spectrum of Fe3O4
3.2 Electrocatalytic property Fig. 4a and b depict the cyclic voltammogram (CV) of bare and n-Fe3O4/GCE in the blank 0.1 M PBS respectively. It can be seen that no redox peak was observed at the n-Fe3O4/GCE in blank 0.1 M PBS indicates that the n-Fe3O4/GCE is not electroactive in that potential. In Fig. 5, the voltammogram (a) corresponds to the oxidation of 2.5 mM UA at the bare GCE (anodic peak potential: +0.35 V) and the voltammogram (b) corresponds to the oxidation of 2.5 mM UA at the nFe3O4/GCE (anodic peak potential: +0.33 V), respectively. It can be seen that the n-Fe3O4/GCE shows shift in potential with slightly less in peak current than the bare GCE indicates the electrocatalytic ability of the modified electrode. This electrocatalytic effect was attributed to the larger available surface area of the modifying layer due to the nanometer size of the sample [11].
Fig. 4 Cyclic voltammogram of (a) bare and Fig. 5 Cyclic voltammogram of (a) bare and -1 (b) n-Fe3O4/GCE in 0.1 M PBS at 10 mV s (b) n-Fe3O4/GCE in 2.5 mM UA at 10 mV s-1 4. Conclusion The Fe3O4 nanoparticles were successfully prepared by hydrothermal method. The FT-IR confirms the formation of Fe-O bond in the Fe3O4. The XRD confirms the structure and phase purity of the sample. The FE-SEM of Fe3O4 shows the particles are agglomerated by irregular shaped particles. The electrochemical detection of UA by Fe3O4 nanoparticles was investigated by CV. The results suggest that the Fe3O4 nanoparticles have higher electrocatalytic activity for the detection of UA and we think that the Fe3O4 nanoparticles may be a great potential for UA determination.
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Acknowledgment: One of the author (RS) acknowledges the University of Madras for the financial assistance in the form of Dr Kalaignar M. Karunanidhi Endowment Scholarship and NCNSNT, University of Madras for recording FE-SEM image. References [1] E.H. Kim, H.S. Lee, B.K. Kwak, B.K. Kim, Synthesis of ferrofluid with magnetic nanoparticles by sonochemical method for MRI contrast agent, J. Magn. Magn. Mater., 289 (2005) 328-330. [2] S. Dubus, J.F. Gravel, B.L. Drogoff, P. Nobert, T. Veres, D. Boudreau, PCR-Free DNA Detection Using a Magnetic Bead-Supported Polymeric Transducer and Microelectromagnetic Traps, Anal. Chem.78 (2006) 4457-4464. [3] Y.C. Chang, D.H. Chen, Preparation and adsorption properties of monodisperse chitosan-bound Fe3O4 magnetic nanoparticles for removal of Cu(II) ions, J. Colloid Interface Sci., 283 (2005) 446-451. [4] C.Q. Hu, Z.H. Gao, X.R. Yang, Fabrication and magnetic properties of Fe3O4 octahedra, Chem. Phys. Lett., 429 (2006) 513-517. [5] F.Q. Hu, Z. Li, C.F. Tu, M.Y. Gao, Preparation of magnetite nanocrystals with surface reactive moieties by one-pot reaction, J. Colloid Interface Sci., 311 (2007) 469-474. [6] R.Y. Hong, T.T. Pan, H.Z. Li, Microwave synthesis of magnetic Fe3O4 nanoparticles used as a precursor of nanocomposites and ferrofluids, J. Magn. Magn. Mater., 303 (2006) 60-68. [7] R. Suresh, R. Prabu, A. Vijayaraj, K. Giribabu, A. Stephen, V. Narayanan, Fabrication of αFe2O3 nanoparticles for the electrochemical detection of uric acid, Synth. React. Inorg. MetalOrg. nano-Met. Chem., 42 (2012), 303–307. [8] R. Boistelle, J.P. Astier, Crystallization mechanisms in solution, J. Cryst Growth, 90 (1988) 1430. [9] X. Chen, Y. Wang, J. Zhou, W. Yan, X. Li, J.J. Hu, Electrochemical Impedance Immunosensor Based on Three-Dimensionally Ordered Macroporous Gold Film, Anal. Chem., 80 (2008) 2133-2140. [10] A. Kaushik, R. Khan, P.R. Solanki, P. Pandey, J. Alam, S. Ahmad, B.D. Malhotra, Iron oxide nanoparticles–chitosan composite based glucose biosensor, Biosens. Bioelectron., 24 (2008) 676-683. [11] S. Reddy, B.E. Kumara Swamy, U.B. Chandra, S. Sherigara, H. Jayadevappa, Synthesis of CdO nanoparticles and their modified carbon park electrodes for determination of dopamine and ascorbic acid by using cyclic voltammetry technique, Int. J. Electrochem. Sci., 5 (2010)1017
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Electrocatalytic Property of Nano-Fe3O4 Modified Glassy Carbon Electrode 10.4028/www.scientific.net/AMR.584.272
