Synthesis and Characterization of Multishapes of Fe 3 O 4 Nanoparticle by Solve-Hydrothermal Method Using Microwave Radiation

Iron oxide(Fe3O4) nanoparticles of different sizes and shapes were synthesized by solve-hydrothermal reaction assisted by microwave irradiation using ferrous ammonium sulfate as a metal precursor, oleic acid as dispersing agent, ethanol as reducing agent and NaOH as precipitating agent at pH=12. The synthesized Fe3O4 nano particles were characterized by X-ray diffraction (XRD), FTIR and thermal analysis TG-DTG. Sizes and shapes of Fe3O4 nanoparticles were characterized by Scanning Electron Microscopy (SEM), and atomic force microscopy (AFM).


Instruments:
FT-IR spectra were recorded on Shimadzu 8400 S FT-IR spectrophotometer using KBr pellet.Scanning electron microscope (SEM) analyses were acquired using type SEM TE SCAN VEGA 2 Cheech.A few drops of nanoparticle suspension were applied on a carbon coated copper grid followed by vacuum drying.Atomic force microscope images AFM were acquired using AFM model AA 3000 SPM 220V Angstrom Advanced INC.USA.Samples were prepared by applying few drops of nanoparticles dispersed in acetone by sonication for 20 min, on a glass slide followed by vacuum drying at room temperature.Thermal gravimetric analyses (TGA) were performed using Perkin Elmer TGA 4000 thermo gravimetric analyzer in a synthetic N 2 atmosphere at heating range 30°-900°C and heating rate of 20 °C/min.X-ray diffraction analyses (XRD) were recorded using SHIMADZU 6000 X-Ray Diffract meter with a high-intensity Cu K α radiation (λ=1.54180Å) and a graphite monochromatic source.Magnetic susceptibility of the prepared oxide was measured by using a magnetic balance Model MSB-MK I. Preparation of Fe 3 O 4 nanoparticles by microwave irradiation was performed in a domestic microwave oven (mode LG, MS2042X frequency 2.450 MHz, maximum power 1000 W), fixed with a wireless camera to watch capsulate reactor.

Preparation of Fe 3 O 4 by solvehydrothermal microwave method
Fan Zhang, et al [33] e).The product was collected and separated by permanent magnet which took more than 20 min, washed several times with distilled deionized water (DDW), followed by ethanol, then vacuum dried at 80°C for 10 h and stored under nitrogen atmosphere for characterization by XRD, FTIR, SEM, AFM, and TG analyses.Five main diffraction peaks were observed at 2Ɵ =30°, 35.6°, 43.3°, 54°, 57.1°, correspond respectively to the planes (220, 311, 400, 422, and 511 respectively) of Fe 3 O 4 nanostructures which came in agreement with the card (space group: JCPDS Nos.26-1136) Xray diffract meter with a high-intensity Cu K α radiation (α=1.54056Å) and a graphite monochromatic a.The results indicated a cubic structure of Fe 3 O 4 with lattice parameters a=b=c=8.0903A° and α = β= γ = 90° and agreed with the structure of an inverse spinel type oxide [2,35,37,38].Crystallite size measurements were determined from the full-width at half maximum (FWHM) of the strongest peaks assigned to the reflection planes ( 220), ( 311), ( 400) and (511) (Table ( 1)) using the Debye-Scherer approximation [39]

D =
Where (D) is crystallite diameter, (K) = 0.9 is the constant, wavelength of the X-rays, (β) is the peak breadth of the XRD peak, and θ is the Bragg angle (in radians or degrees).The calculated crystal average size is (25.5)nm.

FT-IR Spectrophotometry
Figure 3 shows the FT-IR spectrum of the prepared Fe 3 O 4 coated with oleic acid (OA).The spectrum displayed an absorption band at 3006 cm -1 which was assigned to the stretch vibration of vinylic =C-H group [40,41].The broad peak at 3122 cm -1 can be assigned to surface and bulk OH groups in magnetite [40].Two absorption sharp peaks were observed at 2923.8 and 2852.5 cm −1 were attributed to the CH 2 and CH 3 stretching vibrations [41].The intense peak at 1701 cm -1 was assigned to the C = O stretching vibration of carboxylate anion [42].The two new bands at 1639 and 1541 cm -1 were assigned to the asymmetric (COO -) and symmetric (COO -) stretching vibrations.This indicates that the carboxylate group is present as both mono and bidentate bonding group i.e. oleic acid has been both physically and coordinatively adsorbed on the surface of magnetite nanoparticles.The bands observed at 1454.2 and 900 cm -1 were attributed to the O-H in-plane and outof-plane vibrations respectively.The absorption peak observed at 584 cm −1 corresponds to the Fe-O stretching vibration related to the magnetite phase [40] ,

Conclusion:
Iron oxide (Fe 3 O 4 ) nano particles of different sizes and shapes were synthesized by solve-hydrothermal reaction assisted by microwave irradiation using ferrous ammonium sulfate as a metal precursor, oleic acid as dispersing agent, ethanol as reducing agent and NaOH as precipitating agent at pH=12.XRD analysis supported the inverse spinel structure.The FTIR and thermogravimetric analyses supported the conjugation of Fe 3 O 4 with oleic acid through the carboxyl group which behaved as mono and bidentate ligand

Fig.( 3
Fig.(3): FTIR Fe 3 O 4 synthesized by solve-hydrothermal microwave Scanning electron microscopy (SEM) The SEM micrographs of Fe 3 O 4 reveal the presence of three types of morphology like spherical, sheets and flowers nanostructures as is shown in Figures 4a and b and the average particle sizes of spherical Fe 3 O 4 nanoparticles are (50-200nm).The thickness of thorns in flower shaped nanostructures are about (8-10nm) while the diameter and length of nanosheets are 0.8-1µm and 1-2µm respectively.The same morphology of copper oxide nanoparticles was reported by Volanti et.al using the same method [1].

Fig.(
Fig.(4a): SEM micrograph and particle size distribution of solve-hydrothermally synthesized Fe 3 O 4 nanoparticles under microwave radiation showing different sizes of nanospheres, nanosheets, and flower shaped nanostructures.

Fig.( 5
Fig.(5): AFM 2D, 3D views and particle size distribution of Fe 3 O 4 nanoparticles synthesized by solve hydrothermal microwave method NH 4 ) 2 SO 4 ⋅6H 2 O (0.352g, 0.898 mmol) with vigorous stirring.The final pH of the reaction mixture was adjusted to 12.A dark green precipitate appeared immediately.After stirring for further 30 minutes under continuous argon flow, the mixture turned brown.The resultant suspension was then transferred into a homemade 30 mL Teflon autoclave which was sealed, and heated in the microwave domestic oven (second level, 6 second ON and 16 second OFF) at 190 ° C for 15 min.The system was then allowed to cool naturally to room temperature.The color of the mixture was black.The steps of separation of the product are illustrated in Figures (1a