Rod-ShapedMagnetite Nano / Microparticles Synthesis at Ambient Temperature

Here, we reported room temperature synthesis of Fe3O4 rod-shaped nano/microparticles by chemical reductionmethod fromFeCl3 precursor and NaBH4 as the reducing agent in the presence of the pyrrole as a capping agent. e magnetic Fe3O4 particles were characterized by several methods, such as SEM, XRD, FTIR, and TGA. e average aspect ratio of Fe3O4 rod-shaped particles was ∼2.8. ese particles were redispersed in deionised water to form a colloidal solution and showed magnetic properties. is economical synthesis route is scalable, and Fe3O4 particles can be exploited for various applications such as MRI contrast enhancement, biodiseperations, Ni-Fe batteries, and as a catalyst.


Introduction
Recently, magnetic nano-and microparticles have become one of the most exciting and rapidly growing areas in material chemistry, separation technology, biology, and biomedicine, leading to a number of potential applications [1].Fe 3 O 4 has received major attention, as one of the most important transition magnetic metal oxides due to its extensive applications.It has been considered as an ideal material for magnetic data storage [2], a candidate for biological application such as a tag for sensing and imaging [3], and a drug-delivery carrier for antitumor therapy [4].Magnetite (Fe 3 O 4 ) is widely exploited due to its strong magnetic properties as well as extensive applications in biotechnology and medicine [5].Especially, the Fe 3 O 4 nanoor microspheres have smooth and large-surface areas which can be used for maximal protein, enzymes, antibodies, and anticancer agents binding [6].Ferrimagnetic iron oxide microparticles have been typically used for recording materials [7], but these particles are even used as tracers for investigating the behavior of air-borne matter in the human and animal respiratory tract [8] and the mechanical properties of living cells [9].As they are chemically stable, nontoxic, and noncarcinogenic [10], they permit clearance studies in the human lungs over time periods up to 1 year.Ferromagnetic and Ferrimagnetic particles can be detected in the human body by magnetopneumographic (MPG) methods [11].Ferrimagnetic particles were also used for measurements of macrophage functions and cellular integrity (viscoelasticity) in vivo and in vitro [9].Fe 3 O 4 particles in the micrometer size range can be produced by either a crystallization process [12] or by nebulization of a colloidal solution [13].Many techniques have been reported in the literature for chemical synthesis of these particles such as the sol-gel [14], microemulsion [15], sonochemical [16], ultrasonic spray pyrolysis [17], and microwave plasma [18].Each preparation method has its advantages and disadvantages, which primarily relate to particles size distribution, production scale, and cost.Wet chemical processes are capable from the economical perspective but consist of many steps.e gas-phase synthesis process is one-step process with relatively high production rate, but production costs are high.Two important synthesis routes are the thermal decomposition [19] and the chemical reduction [20] methods.A characteristic and serious problem is in assembling and stabilizing magnetic particles as it has high affinity to agglomerate, which is an obstacle to its application for magnetic storage.is barrier can be resolved if the particles are dispersed using proper dispersing agent.Various dispersing agents were reported earlier such as SDS, Triton-X, and PAA; however, this more or less resulted in ) were dissolved in 20 mL of deionised/conductivity water separately and mixed together (labeled as solution "A").e colour of the solution changes from yellow to orange.Separately, 0.75 gm of NaBH 4 was dissolved in 10 mL of conductivity water (labeled as solution B) followed by addition of solution "B" into "A" under vigorous magnetic stirring.Gradually, with an addition of solution B, entire solution becomes dark and eventually turns into completely black.

Characterization of Fe
3 O 4 Nano/Microparticles. e characterization study was carried out using Bruker, D8-Advance X-ray Diffractometer between 2 values 30 ∘ to 70 ∘ with low-angle scan.e thermal analysis of TGA and DTA was obtained at DTG-60H and DSC at DSC-60 instrument.e IR spectrum was obtained with a Shimadzu 8400 spectrophotometer. .e reaction was accompanied by generation of numerous bubbles.e reaction was supposed to be complete once bubble formation ceased and completed aer 24 hours under continuous magnetic stirring [21].e pH of the solution was observed to be 9.9.To separate the Fe 3 O 4 particles, a strong magnet was used as shown in Figures 1(B Chen et al. [22] earlier reported that in this approach, the Fe 3 O 4 spherical nanoparticles were treated with FeCl 3 solution.Because of common ion effect, Fe 3+ ions were absorbed onto the surface of Fe 3 O 4 nanoparticles, and Fe 3 O 4 particles were then surrounded by positively charged (Fe 3+ ) shells to prevent their aggregation.is scheme does support our formation processes of pyrrole-coated rod-shaped Fe 3 O 4 nano/microparticles as shown in Figure 2.Moreover, in this scheme [22], the formed Fe 3+ ion shell was also served as the oxidant to polymerize pyrrole monomers which may lead to rod formation over the template of polymer.One more supportive model to prevent the aggregation of nanoparticles has also been proposed by Zhao and Nan [23].As per their paper, the steric stabilization effect arises from the fact that polymers coating on the surface of particles occupy a certain amount of space.us, the space becomes compressed when nanoparticles are brought too close together.An associated repulsive force makes separate nanoparticles from each other and restrains the aggregation of nanoparticles.

Results and Discussion
e length and width of Fe 3 O 4 particles were observed in the range between 555.55 nm and 1555.55 nm; 333.33 nm and 444.44 nm, respectively.e average aspect ratio that is, length divided by width, was found to be ∼2.8 (Table 1).
Figure 3(a), spectrum 1 represents the spectra of the surfactant or dispersing agent, that is, pyrrole.Pyrrole contains secondary amine which shows characteristic peak at 3500-3300 cm −1 due to N-H stretching vibrations.Spectrum 2 represents the spectra of the as-prepared Fe 3 O 4 particles.In this spectra, the wavelength is shied, that is, 3432 to 3001 cm −1 ; it shows broad peak due to the coating of cationic surfactant, (pyrrole) which indicates the presence of surfactant that is, pyrrole coated on the surface of Fe 3 O 4 particles.ese wavelengths are shied due to the attachment of secondary amine.e nitrogen group is attached to the carbon which is having lone pair of electrons.e peak at 1040 cm −1 shows that carbon is attached to nitrogen atom [24].Spectrum 3 represents the spectra of the Fe 3 O 4 particles aer thermal analysis.Due to the decomposition of pyrrole and possible phase transition of iron, the wavelength was changed.On TGA analysis of a sample, removal of the water molecule and other impurities from Fe 3 O 4 nano/microparticles takes place.e removal of impurities is exhibited by the weak bands at wavelengths 3186 to

Pyrrole
Pyrrole-coated 2Fe + + 21H 2 + 6B(OH) 3 + 6NaCl [21] is first formed on the surface [   3498 cm −1 as a result of the shi in a wavelength [25].At wavelengths 1341, 1365 and 1467 cm −1 , C-H stretching was observed due to methyl group.e peaks at 1547 and 1464 cm −1 can be assigned to C=C and C-N stretching vibrations, respectively.e peaks at 1182 and 901 cm −1 indicate the C-H in-plane bending and ring deformation, respectively.e peaks observed at 457 to 430 cm −1 are the characteristic peaks of Fe-O stretching vibrations [26].Similar patterns were also observed in pyrrole-Fe [OH] microcomposites.e obvious spectral differences between pure pyrrole and the composites indicate that pyrrole exhibits a different chain structure, and there are physical interactions between particles and pyrrole.e presence of Fe To determine the degree of oxidation of the Fe 3 O 4 particles, TGA analysis was performed, and the result is shown in Figure 3(c), curve 1.When the Fe 3 O 4 particles were heated in air up to 750 ∘ C at 10 ∘ C min −1 , a signi�cant weight loss was observed, which can be attributed to the oxidation of the Fe 3 O 4 core [19].e thermal stability of Fe 3 O 4 particles was investigated by TGA measurements.e black particles were observed to turn red upon test completion, a characteristic of Fe 3 O 4 rather than black carbon, indicating the complete loss of pyrrole.e weight loss at temperatures lower than 592.56 ∘ C is due to loss of moisture, while the major loss at temperatures higher than 700.39 ∘ C is due to the decomposition of pyrrole.e difference in the residue re�ects the different amount of Fe 3 O 4 particles present.e thermal stability increases slightly with increasing particles loading, which is believed to be due to both the lower mobility of the polymer chains when the polymer chains are bound to the particles and stronger chemical interaction [19].Figure 3(c) curve 2-represents differential thermogram analysis (DTA) of Fe 3 O 4 particles from this �gure, it is clear that endothermic reaction takes place.e �rst broad peak was observed at 77.77 ∘ C and; a second at 647.40 ∘ C due to the decomposition of pyrrole and the possible phase transition of Fe 3 O 4 , respectively.As compared with no obvious phase transition in the pure Fe 3 O 4 particles, the observed phase transition is likely due to an intermediate product of pyrrole.is cheap method of Fe 3 O 4 synthesis is scalable and can be exploited for various applications such as MRI contrast enhancement, catalyst for carbon nanotubes growth and, is currently being pursued.

Conclusion
We synthesized Fe 3 O 4 rod-shaped nano/microparticles by chemical reduction of Fe 3+ ions using NaBH 4 reducing agent and pyrrole as a surfactant.e X-ray diffraction pattern concluded that the particles are mainly composed of Fe 3 O 4 crystals.e SEM images con�rm rod shape of Fe 3 O 4 particles.e average aspect ratio of the stated particles was ∼2.8.TGA analysis revealed that the surfaces of particles were oxidized containing about 5% weight loss of iron oxide.e FTIR spectra of Fe 3 O 4 rod-shaped particles clearly indicated that the particles were coated by dispersing agent pyrrole.e colloidal solution of Fe 3 O 4 particles exhibited magnetic properties.is synthesis route is economical and convenient method to fabricate Fe 3 O 4 particles, which could be suitable for various applications such as MRI contrast enhancement, biodiseperations, Ni-Fe batteries, and as a catalyst.
e well-dispersed Fe 3 O 4 particles in water (Figure 1(A)) were collected by external magnet as shown in Figure 1(B) from as-prepared solution (inset of Figure 1(B))

F 1 :
In (A) and (C) are represented the colloidal solution and calcinated powder of Fe 3 O 4 particles, exhibiting their magnetic properties using external magnet (�) and (�), respecti�ely.In (�) is represented lower magni�cation and in (F) higher magni�cation S�� image of Fe 3 O 4 particles.

F 2 :
Schematic diagram of the formation processes of pyrrole-coated rod-shaped Fe 3 O 4 nano/microparticles.
T 1: is shows length, width, and aspect ratio of Fe 3 O 4 nano/microrods from Figure1(F).
2.2.Synthesis of Fe3 O 4 Nano/Microparticles. 0.27 gm ferric chloride (FeCl 3 ) and 0.55 gm of pyrrole (C 4 H 5 N [21]icles, dispersing agents were added during synthesis.Several commonly used dispersing agents were evaluated in this work including poly(vinylpyrrolidone), (PVP; average molecular weight 10000), poly(acrylic acid), and sodium dodecyl-benzenesulfonate (SDS, 80%).esesurfactants were resulted in agglomeration.Nevertheless, we obtained Fe 3 O 4 particles without agglomeration using pyrrole as a surfactant.Other surfactants used such as SDS, Triton-X, and PAA, however, resulted in agglomeration of particles and settled down immediately in the solution.isproblemwassolvedbyusingpyrrole as a surfactant or dispersing agent.Pyrrole was well coated to the surface of the Fe 3 O 4 particles[21].Figures1(E) and 1(F) show SEM images of Fe 3 O 4 rodlike particles.eplausiblemechanism of synthesis is as given on the next page[21].