Magnetic nanoparticles (MNPs) can be manipulated using an external magnetic field and are being researched for applications in catalysis, data storage, and biomedical fields. Various synthesis methods including co-precipitation, microemulsion, thermal decomposition, hydrothermal, and others affect the properties of MNPs, such as size and shape. MNPs have significant applications in enhancing MRI, drug delivery, magnetic storage, and more.

1. Magnetic Nanoparticles
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 Magnetic Nanoparticles(MNPs) are the type of nanoparticles that can be easily
tracked, manipulated and targeted by external magnetic field.
 The MNPs have been the focus of the research these days due to its properties which
could increase the potential use of Nanomaterial based catalysis, data storage and
optical fibers.
 Elements like Fe, Co, Ni and their oxides can form MNPs. Iron oxide NPs are
commonly used due to its high electrical resistivity, chemical stability, mechanical
hardness, magnetic properties in RF region
 The properties of MNPs depends on the synthesis methods and shapes of the
nanoparticles

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Preparation methods of Magnetic Nanoparticles
 There are many different ways to prepare Magnetic Nanoparticles
i. Co-precipitation method
ii. Micro-emulsion method
iii. Chemical vapor deposition method
iv. Thermal decomposition method
v. Solvothermal method /Hydrothermal
vi. Microwave assisted method.

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1. Co-PRECIPITATION METHOD:
 Co-precipitation is the most useful and proper method for controlled sizes
Magnetic Nanoparticles synthesis method.
 It is extensively used in the biomedical applications because of the ease of
application and harmless procedure.
 In this method, MNPs are prepared from aqueous salt solutions, by the addition of
a base under an inert atmosphere at room temperatures or at high temperature .
 The trouble with the synthesis of Nanoparticles by this method is the tendency of
particles to agglomerate because of the extremely small size which have high
surface area and surface energy.
Advantages Disadvantages
Low reaction temperature and
short reaction time
Uncontrollable shape and
irregular size distribution

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2. MICROEMULSION METHOD:
 Microemulsion is the thermodynamically stable isotropic dispersal of two
immiscible water and oil phases in the presence of a surfactant.
 The surfactant molecules can form a monolayer at the interface between the oil
and water, with the hydrophilic head groups in the aqueous phase and the
hydrophobic tails of the surfactant molecules dissolved in the oil phase .
 This method has series of advantages over other methods namely use of simple
equipment , controlled sized nanoparticles synthesis , particle with crystalline
structure and high surface area and simple experiment conditions.
 Particles produced by the microemulsion method are smaller in size and are
higher in saturation magnetization .
 The properties of NPs prepared by the microemulsion method depend on the
type and structure of the surfactant

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3. THERMAL DECOMPOSITION METHOD:
 The decomposition of metal precursors in the presence of hot organic
surfactants has yielded improved samples with good size control, narrow size
distribution, good crystallinity of individual and dispersible Nanoparticles.
 Nanoparticles with high level monodispersity and size controlled particles can
be produced by high temperature decomposition of organic surfactants.
 The nanoparticles produced by this method are crystalline in nature and can be
dispersed in Organic solvents.
 The size of the nanoparticles produced in this method varied with reaction
tempertature and time
Advantages Disadvantages
Controlled nanoparticle size can be
obtained
Small size (3-20nm) can be produced
High temperatures more than 900oC
Less useful for biological applications
due to involvement of organic solvents

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4. HYDROTHERMAL METHOD:
 This method is also known as solvothermal method. This technique is one of the
most successful ways to grow crystals of many different materials.
 The hydrothermal method contains various wet-chemical technologies of
crystallizing material in a sealed container, from aqueous solution at the high
temperature and at high vapor pressure.
 Despite the best method to produce monodisperse Nanocrystals, the method fails
to produce nanoparticles smaller than 10nm size.
 The residence time had a more significant impact on the average particle size than
the precursor concentration. Monodisperse particles were produced at short
residence times.
Advantages Disadvantages
Low reaction temperature,
short reaction time and low
experimental cost
Slow reaction kinetics at any
temperature. However it can
speed up by microwave
heating

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5. CHEMICAL VAPOUR DEPOSITION METHOD:
 In vapor deposition method, the vapor phase mixture is thermodynamically
unstable than the generation of solid material.
 This method has wonderful flexibility in production of wide range of materials
Advantages Disadvantages
Easy to work on,
different shaped
nanoparticles
low yield, existence of
complex phase and
difficult to separate
nanoparticles

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6. SOL-GEL METHOD:
 This method is one of the most important methods for the preparation of
Inorganic Oxides.
 This method is based on the hydroxylation and condensation of molecular
precursor in solution.
 It is a wet chemical method involving both physical and chemical processes
like drying, hydrolysis , polymerization etc..
 The name “sol-gel” is given to the process due to the distinctive increase in
viscosity in a certain stage of the process producing a sol of nanoparticles.
 This method has an advantage to produce homogenous powders with good
control of particle size. The nanostructures can be varied by changing the
experimental conditions.

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TYPES OF MAGNETIC NANOPARTICLES
1. Ferrites:
 Iron Oxides or Ferrites are the most explored nanoparticles.
 They can exhibit super paramagnetism below 128nm which prevents self
agglomeration since they exhibit magnetic nature when only magnetic field
applied.
Bin Zhao, ‡a Kevin M. Ryan, b Emmet O'Reillyb and Conor McCarthy*a: RSC Adv., 2017, 7, 26328

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2. Ferrites with a shell:
 The surface of ferrite nanoparticles are inert . The reactivity can be improved by
coating around them with other compound.
 These have several advantages including high chemical stability, narrow size
distribution, magnetic moment can be tuned with nuclear cluster size, higher
colloidal stability.
 The studies on spinel ferrites have increased rapidly as they provide better
understanding and controlled superparamagnetism properties. Components like
SiO2 and TiO2 can be coated on spinel ferrites to obtain even more properties.
TEM image of Magnetite
Nanoparticle with silica shellCore-shell-shell Nanoparticle formation
https://commons.wikimedia.org/wiki/Fi
le:Maghemite_silica_nanoparticle_clust
er.jpg
Hesham Hamad,*ab Mona Abd El-Latif,a Abd El-Hady Kashyout,c Wagih
Sadikd and Mohamed Feteha : New J. Chem., 2015, 39, 3116

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3. Metallic with a shell:
 The metallic core of nanoparticles may be passivated by oxidation, surfactants or
metals.
 Nanoparticles with magnetic core consisting either of elementary iron or cobalt
with a shell of other metals like Au/Ag.
Fig 2 shows the
microscope images of
nanoparticles in the
relative order as Fig 1
https://www.ineffableisland.com/2010/09/gold-boom-in-nanotechnology-
continues.html

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4. Polymeric nanocomposties:
 Magnetic polymers can be defined as the substances composed of
inorganic magnetic component in the form of fibers, particles of nanosize
embedded in organic polymer or vice versa.
 The polymer can play many roles such as
• As a template to control size and shape
• As a coating protects from environment or separator from the medium
• Endowing the material with mechanical properties and process ability of
the polymers.
• As a functional component adding its own optical, electrical or chemical
properties enhances the magnetic properties of the material.

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APPLICATIONS OF MAGNETIC NANOPARTICLES
 Enhances the Magnetic Resonance Imaging(MRI) scan
 Effective Drug delivery
 Biomedical applications and sensors.
 High density magnetic storage devices
 Catalyst in organic dye removal and water splitting reactions
 Magnetic separation or sensing the contaminants in various
aqueous systems.
 Enhances the solar cell power conversion efficiency
 Cell and gene therapy
 Polymeric solar cells

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Idea to work on
There are several publications have been reported on spinel magnetic
nanoparticles so far.
 α-Fe2O3 Nanoparticles in different shapes with change in concentration
dx.doi.org/10.1021/jp5
02087h | J. Phys.
Chem. C 2014, 118,
10903−10910
 NiFe2O4 nanoparticles
Ying Zhang et al 2018 Mater. Res. Express 5 025023 doi:10.1088/2053-1591/aaacde

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 CoFe2O4 nanoparticles coated with MnFe2O4
http://dx.doi.org/10.22180/na171
CoFe2O4 @MnFe2O4 material Co, Fe, Mn mapping image

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