Synthesis, characterization and magnetic properties of iron oxide nanoparticles from reverse chemical co-precipitation method

Studying magnetic characteristics of iron oxide nanoparticles was highlighted as a key step in creating potential powder nanomaterials. The occurrence of electron spins parallel to the crystallographic orientations and single domain nanopartilces are the recognized causes of superparamagnetism in bulk magnetite. Nanoparticles whose size could be tuned exhibit this superparamagnetism effect. The reverse co-precipitation process is used to create the current magnetite nanoparticles. The iron oxide nanoparticles were synthesized by reverse chemical coprecipitation method and were confirmed based on XRD data. The room temperature magnetic property was studied and the tiny levels of coercivity and remanence indicate that the samples may exhibit superparamagnetic nature.


Introduction:
Nanotechnology has been regarded as one of the most significant contemporary advances in science and technology.Nanoparticles are a key building component in the production and development of nanomaterials [1].As a result, the nanoparticle has sparked widespread attention among academics due to unique properties such as form, size, and dispersion, which might be used in a variety of applications.Nanoparticles of iron oxide have an important role in many chemical, physical, and material sciences [2].
Due to their abundance, quick reaction, super-paramagnetic nature, high competence, nontoxicity, improved stability, and effectiveness in the chemical and physical adsorption of organic and inorganic pollutants, including heavy metals from contaminated waters, iron magnetic nanoparticles have drawn the most attention among nanoparticles [3].Fe3O4-NPs' special qualities enable their widespread usage in a variety of applications, including targeted drug delivery [8], environmental treatment [6], magnetic resonance imaging (MRI) [7], catalysis [4], magnetic storage media [5], and environmental treatment [6].The size distributions and particle sizes of nanoparticles can be used to fit their magnetic characteristics.The synthesis path sequentially affects the magnetic nanoparticle sizes and size distributions.
IOP Publishing doi:10.1088/1742-6596/2765/1/012024 2 For these purposes, numerous synthesis techniques have been created to generate magnetic iron oxide nanoparticles with the desired properties [9], as reported in other papers, including gas-phase deposition and mechanical techniques (physical methods) [10], green synthesis (biological method) [11], coprecipitation method [12], microwave assisted synthesis [13], and chemical methods.Fe3O4 nanoparticles are most frequently prepared via the chemical technique.Comparatively speaking, chemical preparation techniques used less energy than physical ones.One may choose pick the reaction medium, as well as the physical parameters of the reaction (precursors, reactant concentration, base (NaOH and ammonium hydroxide), temperature, and pH) to regulate the size and shape of the nanoparticles.The biological approach is an excellent production methodology because to its high yield, cheap prices, and minimal energy consumption, however the process of fermenting takes a long period.[14].In other study describes the synthesis of various forms of Fe3O4 nanoparticles as spherical, plate, and nano flowers by chemical approach by solving thermal method aided by microwave radiation, utilizing FeSO4⋅(NH4)2SO4⋅6H2O as an iron precursor, ethanol and NaOH [15].In this study, the production and characterisation of Fe3O4 nanoparticles is done with inexpensive raw materials such as ferrous sulphate hexahydrate and ammonium hydroxide utilizing the reverse co-precipitation technique.

Materials:
Every component utilized in the manufacture of Fe3O4 was analytical grade and did not require additional purification.Sigma supplied Ferrous Sulphate hexahydrate (98%), and ammonium hydroxide [NH4OH] (98%), which were utilized without purification.

The Procedure of Fe3O4 Synthesis[16]:
In this process initially a 0.05M ferrous sulphate solution was made by mixing 0.695g FeSO4.7H2O with deionized water under ultrasonication for 15 mins.The process is continued until the salt dissolved completely.Meanwhile in another 250 mL beaker, mix 50 mL of ammonia and 50 mL of water until the solution turned to pH 13.To this base solution add the iron precursor solution at once and stirring was continued under 600 rpm for one hour.After completion of the reaction, the solution turned to dark color and it can be washed three times with deionized water to remove the traces of the base.

Characterization:
The specification and characteristics of nano Fe3O4 were measured using a variety of characterisation methods.A Shimadzu 6000 (Japan) was used for XRD analysis at ambient temperature, with a CuKα radiation Nickel filter (λ= 1.5418A°) at a rate of 0.5° between 2 and 80° 2θ.

X-Ray Diffraction (XRD):
XRD study was used to verify crystalline structure of synthesized iron oxide nanoparticles and they have followed the required pattern.The results of XRD were presented in Figure 1.From the figure, it was noticed that the produced nano Fe3O4 X-ray diffraction pattern is about equivalent to the typical lattice spacing and angle.From the XRD data the size of the nanoparticles are calculated by using debye scherrers equation ‫ܦ‬ = ఒ ఉைௌ where D is the nanoparticles crystalline size, K represents the Scherrer constant (0.98), λ denotes the wavelength (1.54), β denotes the full width at half maximum (FWHM).The size of the nanoparticles was determined to be 29.6 nm using this equation.

TEM studies
Fe3O4 nanoparticles exhibited a spherical shape with uneven or non-uniform distribution.Similarly, the nanomaterials were found to be crystalline in form, with sharp edges in a spherical shape (the crystal planes were also seen in the materials).The Fe3O4 nanoparticles are formed as core-shell nanoparticles with spherical shapes.The mean diameter was used to calculate the grain size and which is the same value as the particle size calculated from the XRD data.

M-H Studies:
In order to create potential nanocomposite powders, the magnetic properties of iron oxide nanoparticles were the focus of the investigation.Figure 4 displays the magnetic characteristics of the produced nanoparticles, while Table 1 displays the magnetic data.It can be shown from figure 5 that the samples behave super-paramagnetically at normal temperature.It is commonly known that single domain nanopartilces and the electron spins that are parallel to the crystallographic orientations cause bulk magnetite's super-paramagnetic behavior.It's possible that super-paramagnetism relaxation prevents the temperature from falling.This effect is often seen in particles smaller than 10 nm.XRD data indicates that the iron oxide (Fe3O4) nanoparticles are 29.6 nm in size.The magnetic qualities are supported by this value.The tiny remanence and coercivity values in Figure 5 indicate that the samples are super-paramagnetic.There are possible uses for these kinds of low coercive materials in magnetic hyperthermia.The development of magnetite nanomaterials employing Reverse co-precipitation method in a open vessel process.The structural characterization of the iron oxide nanoparticles was in coincidence with literature reports.The average particle size was 29.6 nm and the result was in accordance with TEM reports.The particles were in spherical in shape and were not agglomerated.Further, the magnetic studies of the iron oxide nanoparticles were studied at room temperature.The results showed that super-paramagnetic nature in the prepared sample due to small remanence and coercivity values.This type of low coercive materials is found to have potential applications in magnetic hyper thermia.

Fig 2 :
Fig 2: SEM images of surface of Fe3O4 nanoparticles

Figure 3 :
Figure 3: Transmission electron micrographs of the Fe3O4 nanoparticles.The bar marker represents 200 nm

Table 1 :
Magnetic characteristics of the produced nanocomposites