Content uploaded by Manoj Kumar
Author content
All content in this area was uploaded by Manoj Kumar on Jun 15, 2022
Content may be subject to copyright.
Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=tcph20
Contemporary Physics
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/tcph20
Synthesis and characterization of iron oxide
nanoparticles (Fe2O3, Fe3O4): a brief review
Sunil Kumar, Manoj Kumar & Amarjeet Singh
To cite this article: Sunil Kumar, Manoj Kumar & Amarjeet Singh (2022): Synthesis and
characterization of iron oxide nanoparticles (Fe2O3, Fe3O4): a brief review, Contemporary Physics,
DOI: 10.1080/00107514.2022.2080910
To link to this article: https://doi.org/10.1080/00107514.2022.2080910
Published online: 14 Jun 2022.
Submit your article to this journal
View related articles
View Crossmark data
CONTEMPORARY PHYSICS
https://doi.org/10.1080/00107514.2022.2080910
Synthesis and characterization of iron oxide nanoparticles (Fe2O3,Fe
3O4): a brief
review
Sunil Kumar, Manoj Kumar and Amarjeet Singh
Department of Physics, Himachal Pradesh University, Shimla, Himachal Pradesh, India
ABSTRACT
The iron oxides (Fe3O4,Fe
2O3, and their polymorphs) with nano dimensions have many interesting
applications in various fields, like biomedical, electronics, etc. This is due to the fact that nanoma-
terials have unique magnetic and physiological properties as compared to bulk materials. Synthesis
is the most important parameter in developing crystalline polymorphs of iron oxide with desirable
and distinctive properties that make them suitable for technological applications. In this review, we
have briefly discussed the methods of synthesis of iron oxide nanoparticles (chemical, physical and
biosynthesis techniques) with quite interesting outcomes reported in earlier literature. The different
characterization tools and concerns for iron oxide nanoparticles are also elaborated.
Abbreviations: AFM, atomic force microscopy; 3D, three dimensions; DLS, dynamic light scatter-
ing; FCS, fluorescence correlation spectroscopy; FTIR, Fourier transform infrared; IR, infrared; MS,
mass spectroscopy; NMs, nanomaterials; NMR, nuclear magnetic resonance; NPs, nanoparticles; SEM,
scanning electron microscopy; STM, scanning tunnelling microscopy; TEM, transmission electron
microscopy; XRD, X-ray diffraction.
ARTICLE HISTORY
Received 22 March 2022
Accepted 12 May 2022
KEYWORDS
Iron oxide; nanoparticles;
physical methods; chemical
methods; bio synthesis;
characterization tools
1. Introduction
Transition metal oxides are the centre of attraction
among scientic communities due to their unique char-
acteristics such as physical, electrical, magnetic, and opti-
cal properties at nanoscale dimensions (less than a few
hundred nanometers) compared to their bulk counter-
parts. This is due to the fact that the nanoparticles have
a high surface-to-volume ratio, a nite (surface) size
eect, and a quantum connement eect. Many transi-
tion metals and their oxides are used to synthesize mag-
netic nanoparticles [1]. Being a common compound and
its abundance; the iron and its oxides with oxygen are
serving in all human activities for the last about fty
years [2]. About sixteen iron oxides are identied [3].
Fewironoxidesarewidelyinvestigatedduetopotential
applications in various elds like electronics, biomedi-
cal and environmental processes [4,5].Inthelastfteen
years, magnetic iron oxide nanoparticles have not only
been investigated for their various technological appli-
cations but have an interesting scientic interest in var-
ious elds such as Magnetic hyperthermia, cancer ther-
apy, magnetic resonance imaging (MRI), photocatalyst,
biosensing and bioseparation, targeted drug delivery and
agriculture [3,6]asshowninFigure1. Bio applications
CONTACT Sunil Kumar sksunil004@gmail.com
based on magnetic nanoparticles have received attention
because these nanoparticles have unique properties like
biocompatibility, superior response to the magnetic eld,
catalytically more active, etc. as compared to other nano-
materials [1,7,8]. As magnetic iron oxides are low cost,
abundance in nature, low toxicity, physical and chemical
stability, biocompatible and eco-friendly [9–11]. Among
the various iron oxides, magnetite (Fe3O4), hematite (α-
Fe2O3), and maghemite (γ-Fe2O3) are mostly interesting
due to their unique structural and magnetic properties
[12,13].
1.1. Magnetite (Fe3O4)
This form of iron oxide has a face centred cubic spinel
structure based on the 32 O−2ions and is closed packed
along the [111] direction. Fe3O4has both divalent and
trivalent iron. In the cubic inverse spinel structure, the
Fe2+ions occupy half of the octahedral sites, and Fe3+
is randomly distributed between the remaining octahe-
dral and tetrahedral sites. In stoichiometric magnetite,
the Fe (II)/Fe(III) =1/2 and the other divalent ions (Co,
Mn, Zn, etc.) may be partly or fully replaced by the diva-
lent ion (Fe2+). The Fe3O4can act as both either n-type
© 2022 Informa UK Limited, trading as Taylor & FrancisGroup
2 S. KUMAR ET AL.
Figure 1. A schematic representation of Various major applica-
tions of Iron Oxide nanoparticles.
and p-type semiconductors. The low resistivity of Fe3O4
incomparisontootherironoxidesisduetothesmall
band (0.1 eV) [14]. The structure of magnetite is given
in Figure 2using VESTA software [15,16]. The mag-
netite form of iron oxide has ferrimagnetic behavior at
room temperature with a curie temperature of 928 K. The
magnetite particles show superparamagnetic behavior at
room temperature with dimensions of less than 6 nm.
Although the magnetic properties are mainly rely on the
methods of their synthesis.
1.2. Hematite (α-Fe2O3)
This is the most stable and known form of iron oxide.
It exists in nature as a mineral. It is an n-type semi-
conductor under surrounding conditions. This hematite
occurs in soil and rock. These can be starting materials
for magnetite (Fe3O4)andmaghemite(γ-Fe2O3), which
have numerous applications in biomedical elds, etc. The
hematites are low cost and have high resistance to cor-
rosion, which makes the hematite; a potential candidate
for catalysts, pigments, and gas sensors [2]. It has a
corundum Rhombohedral structure as shown in Figure 2
using VESTA software [15,17]. The Fe (III) ion occupied
two-thirds of the octahedral site that is restrained by the
hexagonal closed pack oxygen (O) lattice. The hematite
has an anti-ferromagnetic character at room tempera-
ture. Above 960 K (Neel temperature), it loses its weakly
ferromagnetic and anti-ferromagnetic characteristics to
become paramagnetic.
The hematite is a canted antiferromagnetic or weakly
ferromagnetic below 960 K and above the Morin tran-
sition occurs at 260 K. The magnetic moment vanishes
as the magnetic moment in sub-lattices becomes strictly
antiparallel to each other. The hematite has a bandgap
of 2.2 eV. In this type of semiconductor, the conduc-
tion band is composed of an empty d-orbital of Fe (III)
and the valence band consists of an occupied 3d crys-
tal eld orbital of Fe (III) with some admixture of O 2p
non-bonding orbital [2].
1.3. Maghemite (γ-Fe2O3)
This type of iron oxide is ferrimagnetic in nature and
a thermally unstable mineral. Maghemite has a similar
crystalline structure. At a suciently high temperature,
it transforms into a stable structure of iron oxide. It has
a cubic structure as shown in Figure 2using VESTA
software [15,18]; two-thirds of sites are lled with Fe
(III) ions arranged regularly with two lled sites being
Figure 2. Crystal structure and crystallographic data (cubic, Fd-3m), (Rhombohedral, R-3c), (Cubic, P4332)ofmagnetite,hematite,
maghemite respectively, (the black ball is Fe2+, the green ball is Fe3+and the red ball is O2−).
CONTEMPORARY PHYSICS 3
followedbyonevacantsite.Intheexternalmagnetic
eld, maghemite is easily magnetized and has a high
magnetic response. The γ-Fe2O3nanoparticles with sizes
less than 15 nm possess a superparamagnetic nature. Due
to its unique magnetic properties, maghemite is used
in various biomedical elds like MRI contrast agents,
drug delivery in cancer therapy and hyperthermia etc.
due to its unique magnetic properties. Maghemite is a
metastable oxide in an oxidative atmosphere, and it is
nally oxidized into alpha-Fe2O3when heated to a tem-
perature of 673K. γ-Fe2O3is an n-type semiconductor
with a bandgap of 2.0 eV [2].
Figure 3(a) shows the standard XRD pattern for α–
Fe2O3,Fe
3O4,andγ–Fe
2O3iron oxides in accordance
with standard JCPDS card as mentioned in graph. Simi-
larly, Figure 3(b) represents the standard XRD pattern for
β-Fe2O3and -Fe2O3according to the standard JCPDS
cards as given in each graph.From the standard XRD pat-
tern, we have seen that the crystal structures of Fe3O4
and γ–Fe
2O3are identical with little dierence in peak
Figure 3. (a) Standard powder diffraction pattern for α-Fe2O3γ-
Fe2O3and Fe3O4according to respective JCPDS data cards; (b)
Standard powder diffraction pattern for β-Fe2O3-Fe2O3accord-
ing to respective JCPDS data cards.
positions, which are shifting toward higher angles. The
dierent crystalline phases of iron oxides can be pre-
pared by heat treatment (annealing). The sequence of
phase transformation in iron oxides (Fe2O3) follows the
order as γ→ε→β→αreported by Sakurai et al.
[19].XRD analysis is a basic tool to identify the crystal
structure of iron oxide nanoparticles.
2. Magnetic aspects
Magnetism is a collective phenomenon that arises due
to the magnetic moment related to every electron. The
atom is the smallest unit of any material consisting of
electron contributing to the magnetic property of the
material. The magnetic moment of an electron arises
due to the spin motion and orbital motion around the
nucleus. According to the Faraday law of magnetic induc-
tion, the material is when placed in a magnetic eld, the
electrons present in the materials get aected by the mag-
netic forces. Sometimes, in an external magnetic eld,
the materials react dierently in the application of the
external magnetic eld. The response of materials on the
external magnetic eld is due to the atomic and molecular
structure of the materials and the total magnetic moment
associated with the atoms of materials. The main causes
of magnetic moment are electron orbital motion and spin
of electrons. If the electron occurs in a pair then magnetic
elds of opposite spin cancel each other. In some atoms,
the unpaired electron give rise to net magnetic moment
and in the presence of an external magnetic eld, they
react more.
The magnetic properties of iron oxide nanoparticles
are identied by the dependence of magnetic induc-
tion B on the applied eld H. The magnetic induction
(B) and applied eld (H) show the linear dependency
as, B =μH, where, μis the magnetic permeability of
magnetic materials. The value of μ>1, if the nanopar-
ticles are paramagnetic. The diamagnetism is shown by
the materials having μ<1. The magnetic susceptibility
(χ) is related to magnetic permeability μas: χ=μ−1.
Therefore, broadly, we have two groups; one side, dia-
magnetic materials have negative susceptibility (χ<0)
and repelled by the magnetic eld. One other side,
paramagnetic, ferromagnetic and ferromagnetic mate-
rialshavepositivesusceptibility(χ>0) and attracted
by the magnetic eld. Figure 4summarizes the dierent
magnetic materials according to their magnetic behavior
with varying magnetic permeability (μ)w.r.t. the v ac-
uum (μ0=1) [10,20]. Table 1also listed the dierent
magnetic materials with their atomic moment, magnetic
curve and magnetic susceptibility (χ). The ve basics
of magnetism found in magnetic materials are classied
4 S. KUMAR ET AL.
Figure 4. Different magnetic materials and their permeability (μ)
with reference to permeability in vacuum (free space) (μo=1),
Where His applied magnetic field. For instance,the magnetization
is weak and opposes the applied magnetic field, thus reducing the
magnetic flux density for diamagnetic material.
according to the response in the external applied mag-
netic eld as [21,22]:
2.1. Diamagnetism
Diamagnetism is observed in diamagnetic materials that
do not have any unpaired electrons in their orbital shells
or whose orbital shells are completely lled. So, they have
no net magnetic moment. This property of diamagnetic
materials was discovered by Michael Faraday in 1845.
Thesematerialsareweaklyaectedbythemagneticeld.
The orbital angular moment induced by the applied eld
is in the opposite direction. Hence, the diamagnetic mate-
rials possessed a negative magnetic moment. Examples
of diamagnetic materials are water, acetone, copper, and
carbon dioxide. The value of magnetic susceptibility is
negative and the order of 10−5and permeability is less
than the one as shown in Figure 4.
2.2. Paramagnetism
Paramagnetism arises due to the magnetic forces on
unpaired electrons. The materials have a net magnetic
moment due to the electron spin associated with each
atom.Intheabsenceofanexternalmagneticeld,the
atomic magnetic moments are randomly oriented lead-
ingtozeromagnetization.Thesedipolesalignthemselves
in the direction of the applied magnetic eld, resulting
in net magnetization. The materials have small positive
susceptibility in the presence of a magnetic eld (approx-
imately between 10−5and 10−3)andthepermeability
is slightly greater than one as shown in Figure 4.The
materials like aluminium, calcium, Oxygen and alloy
of copper are paramagnetic in nature. The magnetic
susceptibility, χof the paramagnetic materials varies
with the temperature according to the Curie’s law as;
χ=C/T, where, C is the Curie constant and T is absolute
temperature.
2.3. Ferromagnetism
Ferromagnetic materials are a special class of param-
agnetic, but they are strongly aected by the applied
magnetic eld as magnetic moment points in the same
direction.Themagneticdipolesarealignedinparallelto
each other, strongly coupled to the neighbours by quan-
tum mechanical interaction called exchange interaction.
Duetoexchangeinteraction,largenumbersofatomic
dipoles get aligned in the same direction, giving rise to
net a magnetic moment. The magnetization is retained
in ferromagnetic materials in the absence of an applied
magnetic eld. Iron and its compounds, cobalt ferrites,
nickel, etc., have the properties of ferromagnetism. At
temperature when the ferromagnetic becomes paramag-
netic materials is called Curie temperature. Below this
Curie temperature, the ferromagnetic material has high
saturation magnetization. This is due to the reason that
ferromagnetic materials have small magnetized regions
called domains. The total magnetic moment of materi-
als is the vector sum of the magnetic moments of the
domains. In the absence of applied magnetic elds, these
domainsleadtohysteresiscurvesinsomematerials.The
value of magnetic susceptibility lies between 103and 105.
2.4. Antiferromagnetism
In this kind of magnetism, the spin moments are antipar-
allel inside the domains and the spin structure is assumed
to consist of two sub-lattices, one due to up spin and the
otherisduetodownspins.Themagneticmomentofeach
sub lattice is equal but in the opposite direction, which
results in zero magnetic moment. Above the Neel tem-
perature, the antiferromagentic becomes paramagnetic.
The value of magnetic susceptibility is small and posi-
tive. The magnetic permeability is slightly greater than
one. Salts of ions such as Mn+2,Fe
+3and Gd+3have an
antiferromagnetic nature.
2.5. Ferrimagnetism
This type of magnetism occurs mainly in magnetic
oxides like ferrites and magnetite. Where the magnetic
CONTEMPORARY PHYSICS 5
Tab le 1. The various magnetic parameters associated with different magnetic materials.
Materials nature Example
Absence of Magnetic
field/Atomic moment
Presence of magnetic
field/Magnetic susceptibility Magnetic curve
Diamagnetism Inert gases He, Ne, Ar, Kr, Xe,
Rn Metals as Cu, Ag, Au, Hg
Non-metals as B, P, S Ions as
Naþ, Cl_Molecules as H2,N
2,
H2O Organic compounds
No magnetic moment Small and negative
(∼10−6–10−5)
Paramagnetism Metals as Na, Al, Ca Ions as
transition metals and rare earth
metals Molecules O2Oxides as
rare earth elements
Randomly oriented
magnetic moment
Small and positive
(∼10−5–10−3)
Ferromagnetism Transitions metals as Fe, Co, Ni
Some alloys of Mn as MnBi,
Cu2MnAl
Parallel aligned Larger
Ferrimagnetism Magnetite (Fe3O4) Mixed oxides
of iron with other elements
such as Sr ferrite (SrFe12O19
(SrO·6Fe2O3))
Mixed parallel and
antiparallel aligned
magnetic moments
Large
Anti ferromagnetism Transition metals as Mn, Cr
Transition metals compound
as MnO, CoO, NiO, Cr2O3,MnS,
MnSe
Anti Parallel aligned Small and positive
(∼10−5,10−3)
moment has the opposite moment, similar to the anti-
ferromagnetic materials. But, the antiparallel magnetic
moments do not cancel out each other because the
magnetic moment has a parallel alignment and its mag-
netic moment is in an antiparallel arrangement with less
strength. Therefore, a spontaneous magnetization occurs
below a critical temperature called the Neel temperature.
The magnetic moment arrangement is shown in Figure 4.
The value of magnetic susceptibility is large and functions
as an applied eld.
2.6. Superparamagnetism
Frenkel and Doefan rst proposed the idea of super-
paramagnetism in magnetic materials in 1930. This kind
of magnetism is found in ferromagnetic and ferromag-
netic nanoparticles. The dimension of these nanoparti-
cles ranges from a few nanometers to a couple of tenths
of nanometers. The nanoparticles are single-domain
particlesandhavealargetotalmagneticmoment.This
is because the magnetization of these nanoparticles ran-
domly ips under the eect of temperature. The time
between two ips is called Neel relaxation time. In
the absence of an external magnetic eld, when the
time is used to predict the magnetization of nanos-
tructures that is longer than the Neel relaxation time.
Then the average value of magnetization emerges to
be zero and the nanoparticles are in a superparam-
agnetic state. In the multidomain system, the coerciv-
ity (Hc) increases with a decrease in particle size and
reachesamaximumvalueatsomecriticalvalueof
nanoparticle dimension (Ds). Furthermore, the decrease
in particle size in the single domain system is fol-
lowed by a decrease in Hc. Below the critical size Ds
the Hcbecomeszeroandthesingledomainparticle
becomes superparamagnetic. Superparamagnetic oxides
6 S. KUMAR ET AL.
like magnetite and maghemite are widely used in
biomedical elds [23].
2.7. Magnetic anisotropy
The exchange interactions are isotropic relative to
any externally xed spatial direction. In practice, the
exchange spherical symmetry is always broken because
of the interaction of electron orbitals with the poten-
tial created by the hosting crystal lattice. As a result, the
spin orientation along a certain spatial direction becomes
energetically favourable. Hence, the macroscopic behav-
ior of a magnetic material will eventually depend on
thespatialdirectioninwhichitismeasured.Sucha
phenomenon is called magnetic anisotropy. It describes
the dependence of the internal energy on the direc-
tion of the spontaneous magnetization. The dierence
between easy and hard axes results from two micro-
scopic interactions: (a) Spin–orbit interaction, which is
responsible for magnetocrystalline anisotropy, surface
anisotropy, and strain anisotropy. (b) Long range dipo-
lar coupling of magnetic moments, which are responsible
for shape anisotropy. In bulk materials, magnetocrys-
talline and magnetostatic energies are the main sources
of anisotropy, whereas in nanomaterials and thin lms,
shape and surface anisotropies are also relevant. The
abovestatedfourdierentcontributionstothemag-
netic anisotropy are magnetocrystalline anisotropy, sur-
face anisotropy, strain anisotropy, and shape anisotropy.
2.8. Core–shell structure for magnetic
nanoparticles
R.H. Kodama et al. presented a core shell model to
explain several unique magnetic features of ferromag-
netic nanoparticles, such as decreased magnetization,
lack of high eld magnetic saturation, and so on [24].
A magnetic nanoparticle, according to this model, is
made up of two parts: a centre part (known as the core)
andanexteriorpart(knownastheshell),asseenin
Figure 5. The bulk spin structure’s core spins are more
orderlythantheshellspinstructure’s.Becauseofthesur-
face spin canting and frustration eect, the shell spins are
disordered [23].
The decrease in magnetization in several ferromag-
netic and ferrimagnetic nanoparticles was explained
using the Kodama model. The magnetic enhancement
in antiferromagnetic nanoparticles is not described by
this model. Bhowmik et al. suggested a core–shell model
to successfully explain this. The centre of this model
is fundamentally antiferromagnetic, whereas the shell is
made up of frustrated spins. The surface spin canting is
the main cause of the increase in magnetic moment due
to the increase in the shell thickness as the nanoparti-
cles size decreases. So the spin canting increases, with
an increase in surface magnetism [25]. This is the main
reason for weak magnetism (canted ferromagnetism) in
antiferromagnetic substance (such as hematite).
3. Methods to synthesize the iron oxide
nanoparticles
There are numerous well-known methods for synthe-
sizing iron oxide nanoparticles. About 90% of chemical
methods are deploying the preparation of iron oxide
nanoparticles, whereas physical and biological methods
have 8% and 2%, respectively [3,7]. Furthermore, these
methods are divided into sub-categories as shown in
Figure 6, where we can easily observe the percentage
of methods to prepare iron oxide nanoparticles. Every
method has its advantages and disadvantages for syn-
thesizing iron oxide nanoparticles. The three kinds of
categories to synthesize the iron oxide nanoparticles are
physical methods, chemical and biological methods. A
Figure 5. Left–typical ferromagnetic domain in bulk materials, Right–spin alignment in nanosizedferromagnetic domain, forming Core-
shell structure of spins.
CONTEMPORARY PHYSICS 7
Figure 6. Basic methods of synthesizing iron oxides nanoparticles with the details subcategories modified from [3].
fewofthesemethodsarebrieydescribedinthenext
paragraph.
3.1. Sol–gel technique
This is a classical wet-chemical method widely used in
the eld of materials science and other engineering sec-
tors for the synthesis of iron oxide nanoparticles or other
transition metal oxides. In this process, the precursor
solution (colloidal solution) of nanoparticles is dried into
‘gelled’ by solvent removal until the three-dimensional
network of iron oxides is obtained [26,27]andthebasic
process of sol–gel is shown in Figure 7.Waterisusedas
asolvent,andprecursorscanalsobehydrolyzedbyacids
or bases. The size of the resulting spherical IONPs can
refrain between 15 and 50 nm [28]. The iron alkoxides
and iron salts (such as chlorides, nitrates, and acetates)
are the main precursors for the synthesis of iron oxide
nanoparticles via sol–gel process, which go through dif-
ferent kinds of hydrolysis and polycondensation reac-
tions [29]. In this method, iron oxide nanoparticles will
form through at least a two-step phase transformation:
Fe(OH)3→β-FeOOH→γ-Fe2O3[30]. These reactions
were performed at room temperature, and further heat
treatment is required for crystallization. The structure
formed during the sol stage in the sol–gel process is
very crucial for controlling the properties of iron oxide
nanoparticles. Lemine et al. reported that Fe3O4NPs
with an average particle size of 8nm were successfully
prepared by the sol–gel method. The saturated magneti-
zation could be up to 47 emu/g at room temperature, and
it was expected that these NPs were promising materials
for biomedical applications [31].
Qi et al. also reported the Fe3O4nanoparticles in
the range of 9−12 nm synthesized by the non-alkoxide
sol–gel technique. In this technique, sol–gel mate-
rials were prepared from the ethanolic solutions of
metal chlorides without the need for alkoxides, poly-
meric gel agents, or elaborate reaction schemes [33].
Recently, Suman et al. reported the formation of hematite
and maghemite nanostructures using the sol–gel tech-
nique, and the nanostructures obtained in this study
are highly capable catalysts for cleaning environmen-
tal pollution. The γ-Fe2O3nanocube exhibits maximum
8 S. KUMAR ET AL.
Figure 7. The basic schematic of the Sol-gel technique for the synthesis of desired iron oxide nanoparticles. Ferric nitrate is directly
dissolved in the ethylene glycol at 50°C. The resulting sol is then dried by heating to get the gel for desired IONPs. Modified from [7,28,32].
saturation magnetization with superior superparamag-
netic behaviour [34].
3.2. Co-precipitation method
This method is used widely to synthesize iron oxide
nanoparticles, which are engaged in biomedical applica-
tions because of their non-toxic nature [35]. The word
‘co-precipitation’ refers to the mechanisms by which a
precipitate can bring down one or more materials that are
normally soluble in those particular conditions through
nucleationandgraingrowth.Inthisconventionaltech-
nique, the magnetic nanoparticles are prepared in an
inert gas environment at room temperature by mix-
ing ferric and ferrous ions in a basic solution [36].
The molar ratio of both ions is 1:2 and the reaction
is as: Fe2++2Fe3++8OH−→
←Fe(OH)2+2Fe(OH)3→
Fe3O4↓+4H2O. The schematic given in Figure 8
shows the typical process for the synthesis of spheri-
cal iron oxide nanoparticles. The magnetic nanoparticles
obtained by this method are of sizes ranging from 5 to
40 nm. There are various parameters on which the shape,
size, and magnetic properties of obtained iron oxide
nanoparticles such as types of salts used, ionic strength,
and pH [37,38]. This method was widely deployed to pro-
duce iron oxides at a large scale (at gram scale) after the
revolutionary research on this method by Massart [39].
Variousco-precipitationtechniqueshavebeenmod-
ied and developed for the synthesis of iron oxide
nanoparticles [2]. Currently, the troubles of aggregation
and biocompatibility of IONPs possibly avert the pur-
posesinbiomedicalelds.Therefore,manysurfactants
and biomolecules are delivered immediately in the co-
precipitation process. For instance, Salavati-Niasari et al.
have suggested Fe3O4nanoparticles with a measurement
variationof25nmthathavebeenorganizedthrougha
Figure 8. Schematic of co-precipitation method for the synthesis of iron oxide nanoparticles modified from [7,40]. Fe3O4phase syn-
thesize in current example by mixing ferrous sulphate and ferric chloride in molar ratio of 1:2. Particle dimension and magnetic phase
controlled via changing Fe2+/Fe3+ratio, type of base, pH and temperature.
CONTEMPORARY PHYSICS 9
facile chemical co-precipitation method; the surfactant
octanoic acid is used to be existing in the response gad-
get to enhance the dispersity [41]. This technique can be
used to add a couple of functionalities, such as the addi-
tion of biomolecules after subsequent reactions. How-
ever, manipulation over particle size, morphology, and
composition in the co-precipitation route is conned as
particle kinetically managed growth [42]. Typically, small
dimensions lead to low magnetic properties; the above
eects conrm extended magnetic homes whilst main-
taining their small size. The size, form, and composition
of the IONPs rely on the experimental parameters, such
as the sorts of iron salts (chlorides, perchlorates, sul-
fates, nitrates, etc.), Fe(II)/Fe(III) ratio, pH cost, and ionic
energy of the medium [2]. Due to the stability, small
size, and large surface area of Fe3O4nanoparticles, they
have the characteristics of absorption and removal of
ions. For example, N. Shabani et al. reported the Fe3O4
nanoparticles synthesized using co-precipitation process.
The resultant nanoparticles (without any impurity size is
22–32 nm and a surface area of 99.6 m2/g with a pore of
an average diameter of 10.6 nm and saturation magneti-
zation of 66.21emu/g) can be used for turbidity reduc-
tion in the water treatment process [43]. Although the
co-precipitation technique is one of the successful and
classical strategies for synthesizing IONPs with excessive
saturation magnetization, extra attention has to be paid
to overcoming the shortcomings of this method, such
asthevastparticlesizedistributionofproductsandthe
utilization of a robust base in the reaction process.
3.3. Gas (aerosol) phase method
In this technique, the solution of ferric salts is sprayed
into the reactor in the presence of the reducing agent.
Thesolutecondenseswhilethesolventevaporates[44].
Finally, the dried left residue contained the nanoparti-
cles having size as the original one. By this method, spray
and laser pyrolysis are widely used to synthesize mag-
netic nanoparticles on a large scale [45]. From dierent
iron precursors, the maghemite nanoparticles were pre-
paredwithnumerousshapesandsizesrangingfrom5to
60 nm. One of the organometallic precursors must be in
the gaseous phase for laser pyrolysis of organometallic
precursors that depends on the reactant resonant inter-
action and sensitizer [46]. The combination of CO2laser
radiation is used to excite the sensitizer that transfers
energy absorbed to the reactants [47]. The mixture of
gasesisheatedwithaCO
2laser to meet the energy
requirement. Finally, the nucleation of particles occurs
when a threshold level of nuclei is achieved otherwise
chemical reactions carry on [48]. The nucleated particles
created at some stage in the response are entrained via the
gas stream and collected at the exit. The main demerit of
these techniques is the high cost related to them. The gas/
aerosol process produces high-quality nanoparticles with
a low yield. Further, the purity of the obtained product is
attained by decreasing gas impurities and controlling the
time of heating and concentration of gas. Recent study by
Hammad et al. shows the synthesis of iron oxide nanopar-
ticlesbygasphase.Thesenanoparticleshaveanimproved
magnetic property that makes them potential candidates
for hyperthermia [49].
3.4. High-temperature thermal decomposition
method
The co-precipitation technique has one major drawback
theparticlesizeandsizedistributionsarenotfullycon-
trollable due to the fast rate of formation of nanopar-
ticles. So thermal decomposition is one of the most
important techniques to overcome the mentioned draw-
back and produce narrow size magnetic nanoparticles
[2,50].Theparticle’smeandiameterisalsotunedby
this technique. The heating-up and heating-injection are
twomainapproachesbywhichthermaldecomposition
can be achieved [51,52]. In the heating-up approach, the
continuous heating of a premixed solution of precursor
materials, surfactant and solvent at a given temperature,
where nanoparticles start growing into clusters [52]. On
the other hand, in the hot-injection process, the precur-
sors are injected into the hot surfactant solution followed
by the controlled growth phase. High crystallinity and a
narrow size distribution of iron oxide nanoparticles can
be achieved by the high-temperature thermal decompo-
sition of organometallic or co-ordinate iron precursors in
organic solvents [53]. Argon gas plays a signicant role
by providing an inert environment. The most favourable
temperature range is 100–350°C and which results in
highly crystalline magnetic nanoparticles with a mean
diameter ranging from 4 to 30nm [50,54].
The crucial parameters are the time of reaction and
temperatureforcontrollingtheparticlesize.J.Parket
al. have reported a technique for synthesis of iron oxide
nanoparticles with monodisperse and reproducing the
nanoparticles with a tuned size. The nanoparticle can be
prepared by using non-toxic and low-cost iron chloride.
However, the nucleation of nanoparticles has aected
the shape of the obtained nanoparticles. The following
Figure 9shows the mono disperse nanoparticles formed
by this technique [55]
Moreover, the thermal decomposition method is often
used to prepare iron oxide with dierent shapes, such
as nanocubes and nanospheres. While this method has
been earlier proven to produce monodisperse magnetite
spheres,theuseofpreciseadditivesisdemonstratedto
10 S. KUMAR ET AL.
Figure 9. Metal–oleate precursors wereprepared from the reaction of metal chloride and sodium oleate. The monodisperse nanocrystals
were synthesized by thermal decomposition technique via metal–oleate precursors in the high boiling solvent. Modified from [55].
allow for the coaching of strongly faceted iron oxide
nanocrystals, with both cubic and octahedral shapes. In
addition, the usage of squalene or octadecene as the sol-
vent was discovered to set o the reduction of the iron
precursors and thereby lead to the formation of NPs
with core-shells (in the case of nanocubes) or island-
like buildings (in the case of octahedrons) of Fe0/iron
oxide [56].
Recently, T. Vangijzegem et al. reported the synthe-
sis of very small iron oxide nanoparticles proposed in
T1– weighted magnetic resonance imaging (MRI). The
impact of various factors like temperature, pressure, con-
centration/nature of surfactants, and residence time on
the thermal decomposition of Fe (III) acetylacetonate
in organic media was studied. The obtained very small
iron oxide nanoparticles have an almost constant average
diameter of ∼4 nm while varying the residence time.
The TEM micrographs of resulting very small iron oxide
nanoparticles are shown in Figure 10 [57].
3.5. Hydrothermal method
The hydrothermal (aqueous solution route) method is
used to produce a wide range of crystalline iron oxide
nanoparticles such as α-Fe2O3and Fe3O4and γ-Fe2O3.
Also, the γ-Fe2O3can be synthesized from the controlled
oxidation of Fe3O4or Fe3+mineralization. The various
wet-chemical techniques produce the crystalline materi-
als in a sealed vessel from high temperature (in the range
of 130–250°C) aqueous or non-aqueous solutions under
a high-pressure range from 0.3 to 4 MPa via hydrother-
mal or solvothermal methods [2,7,58]. Generally, in this
Figure 10. Transmission electron microscopy images of the very small iron oxides nanoparticles with an average small diameter of less
than 4 nm with different BPR of pressure (A) 3.73±0.77 nm at 40 psi, (B) 3.91±0.49 at 75 psi and (C) 3.82±0.46 at 100 psi adopted from
[57].
CONTEMPORARY PHYSICS 11
technique, the metal linoleate (solid), ethanol- linoleic
liquid phase, and water–ethanol solution are kept under
hydrothermal (means high temperature and high pres-
sure) conditions. The usual reaction temperature for the
hydrothermal process is around 220°C and pressure is
above 107Paandthetotalreactiontimeis72h[59].
Generally, a temperature gradient is created within a
Teon-lined stainless-steel autoclave whose cooler give
up will host the deposition of the mineral solute, sooner
or later, growing the desired crystal. Through this tech-
nique, the structure and size of the resulting NPs are gen-
erallyveryuniform,withtheopportunitytotuneNPsize
from a few nanometers to several hundred [58,60,61].
There are various parameters on which the particle size
and size distribution rely, like precursor concentration,
temperature for reaction, and total reaction time. This
method is also used to produce dislocation-fee single
crystal particles and grains formed in this process could
have superior crystallinity to those from other tech-
niques. The hydrothermal process is eco-friendly and
versatile as no organic solvent or post-treatments are
required [62].
Recently,Benhammadaetal.reportedasimpleand
direct hydrothermal process to synthesize the α-Fe2O3
nanoparticles using dierent precursors like iron chlo-
ride, iron nitrate, and iron sulphate. These nanopar-
ticleswerecharacterizedbyFTIR,XRD,SEM,DSC,
and Raman techniques. The major nding of this work
obtained α-Fe2O3prepared from iron chloride is the
best catalyst for nitrocellulose [63]. Another researcher
reported recently, the various nanostructures of iron
oxide prepared by the hydrothermal method with the
rhombohedral (α-phase) shape of Fe2O3.TheHRTEM
study reveals the size of nanostructures is around
12.3 nm, and the obtained nanostructures are helpful to
minimise environmental pollution [34].
3.6. Microwave irradiation (microwave-assisted
synthesis)
The magnetic iron oxide nanoparticles with tuned size
and shape are widely prepared using the microwave
assisted technique [64,65]. The microwave-assisted syn-
thesis has attracted chemist’s attention for a few years
due to its wide use in preparative chemistry and mate-
rials synthesis [66]. It is a well-known fact that molecules
get excited by electromagnetic radiation and this eect
is used in this synthesis. Then molecules begin aligning
their dipoles within the applied external eld. The strong
enough disturbance from the orientation of molecules
in the phase with external electrical eld causes extreme
internal heating. Therefore, this synthesis can reduce the
energy cost and processing time. This core heating of
materials is a consistent and careful approach [2]. Most of
the iron oxide nanoparticles are ellipsoid in shape and the
average diameter is less than 10nm when prepared using
this technique [67]. As compared to other techniques like
the thermal decomposition method, the stabilization of
the IONPs prepared by the microwave-assisted synthe-
sis route in organic solvents can be easily dispersed in
waterwithoutlaboriousligandexchangeorpurication
steps. Such characteristics can be considered attractive
for the fabrication of large-scale iron oxide nanoparti-
cles [68]. Recently, E.M. Kostyukhin et al. reported the
super paramagnetic magnetite nanoparticles coated with
water dispersible natural humate-polyanion synthesis via
microwaveassistedtechnique.Theobtainednanomate-
rials have an improved monodisperse smaller crystallite
with a grain size of about 8.2nm. The magnetization is
about 80 emu/g for the obtained nanoparticles [69].
3.7. Sonochemical method (sonolysis)
Figure 11 represents the general process of the sonoly-
sis method for the preparation of iron oxide nanoparti-
cles. In this technique, the organometallic precursors are
decomposed by sonolysis for the synthesis of nanopar-
ticles, and the growth of the nanoparticles is controlled
by the use of polymers, an organic capping agent, and
structural hosts [70]. This method is also known as the
sonochemical or ultrasound irradiation technique. The
ultrasonic irradiation results in acoustic cavitation in an
Figure 11. The basics schematic of the sonochemical method for
synthesis of iron oxides [3].
12 S. KUMAR ET AL.
aqueous medium and the growth, formation, and disin-
tegration of microbubbles takes place [71]. Many unusual
reactions occurred due to the temperature (∼5000 K)
and pressure (greater than 1800 KPa) created by the cavi-
tation [72,73]. The amorphous nanoparticles are formed
by ultrasonic induction, and thermal induction causes
the crystalline nanoparticles. Pinkas et al. investigates the
yttrium iron oxide nanoparticles of size 3 nm synthesized
by the sonochemical process [73].TEMandSEMstud-
ies show that globular agglomerates are embedded in the
acetate matrix. Thus, the desired integral ratio can be
obtained by changing the molar ratio of starting materials
(Y and Fe).
The sonochemical technique has some merits, such as
uniformity of blending and reduction in crystal growth,
which can also cause an acceleration eect in chemical
dynamics and reaction rate. However, the sonolysis tech-
niqueisnotsuitabletopreparetunedshapesofdispersed
iron oxide nanoparticles [2]. Recently, the importance of
thesonochemicaltechniqueforthepreparationofiron
oxide nanoparticles was discussed and explained in a
review article by Hooshmand et al. and Mostafa Yuse
et al. [74,75].
3.8. Biosynthesis
Biosynthesis of nanoparticles is a sort of granular
perspective where the primary response happening is
decrease/oxidation. The microbial chemicals or the plant
phytochemicals with hostile to oxidant or lessening
properties are normally answerable for a decrease of
metal mixtures in their nanoparticles [76–79]. The
obtained nanoparticles have good biocompatibility, and
this method is also an eco-friendly method for synthe-
sizing the nanoparticles. In the conventional biosynthe-
sis process, the iron oxide nanoparticles are prepared
by using dierent bacteria like magnetotactic bacteria,
and iron-reducing bacteria are used, such as Geobac-
termetallireducens, M. Gryphiswaldense [80]. Bharde et
al. reported a new kind of bacteria bacterium, Acti-
nobacter, for the preparation of iron oxide nanoparticles
(maghemite). The nanoparticle has a superparamagnetic
character as compared to the previously reported syn-
thesis of magnetic nanoparticles by magnetotactic bac-
teria and iron-reducing bacteria under anaerobic con-
ditions [81]. Protein-coated nano-sized magnetic iron
oxide nanoparticles/crystals are also prepared by using
magnetosomes [82,83]. The Fe3O4nanoparticles were
successfully synthesized by using the Bacillus subtilis
strainsisolatedfromtherhizospheresoilasreportedby
Sundaram et al. [84]. Control of the size, yield, and mag-
netic nanoparticle dispersion of nanoparticles during the
synthesis process is an issue that requires still more exper-
imental studies [58,85,86]. At present, many researchers
are interested in working on ferritin to produce the iron
oxide nanoparticle and other nanoparticles from ferritin
protein, which is found in every living species and plant
[4,25,79,87–94]. Recently, Sunil Kumar et al. reported the
iron oxide nanoparticle biomimetic synthesis by using
the ferritin molecular protein. The obtained nanopar-
ticles have an average diameter of ∼6nm from SEM
analysis and they are monodisperse [4]. The monodis-
persity of iron oxide nanoparticles is a crucial aspect of
technological applications [4,51]. The value of saturation
of magnetization is ∼15 emu/g with a corecivity of 0.125
KOe. The obtained results from this work are shown
in Figures 12(a,b). The annealing temperature range for
the synthesis of iron oxides nanoparticles (ferromagnetic
Fe2O3) is 400–500°C [4]. The current area of research is
also focused on the biosynthesis of iron oxide nanoparti-
cles because of the low cost and eco-friendly process. The
detailsreviewisreportedonthebiosynthesisofmagnetic
iron oxide nanoparticles by Jacinto et al. [95]. However,
this needs further studies to be fully functionalized in the
dierent elds of science and technology.
Although, discussed methods of synthesis of nanopar-
ticles have their importance in material science. But each
method of synthesis has its own merits and demerits.
Table 2listed the pros and cons of various methods of
synthesis of iron oxide nanomaterials.
4. Characterization of iron oxide nanoparticles
There are various techniques that can be used to explore
the physiochemical properties, spatial distribution of
thefunctionalgroupsandadeeperunderstandingof
the magnetic properties of the iron oxide nanoparticles
[3,10,85,112]. These techniques are broadly divided into
spectroscopic, microscopic, and magneto metric tech-
niques. A few basic techniques fall under these men-
tioned techniques are X-ray diraction (XRD), Scan-
ning electron microscopy (SEM), transmission electron
microscopy (TEM), Atomic force microscopy (AFM),
Infrared spectroscopy (IR), X-ray photoelectron spec-
troscopy (XPS), Fourier transform infrared spectroscopy
(FTIR), Electrophoresis, Zeta potential measurement,
Thermal gravimetric analysis (TGA), Dierential scan-
ning calorimetry (DSC), Extended X-ray absorption ne
structure spectroscopy (EXAFS), vibrating sample mag-
netometer measurement (VSM), Superconducting quan-
tum interface device (SQUID), Mossbauer spectroscopy,
Ultraviolet–visiblespectroscopy(UV-VIS)andmany
more [77,78,113].
Figure 13 is a simple schematic showing the funda-
mental techniques to study iron oxide nanoparticles. The
CONTEMPORARY PHYSICS 13
Figure 12. (a) SEM images of obtained Fe2O3finely dispersed nanoparticles from ferritin solution annealed at 430°C with inset shows
particle size histogram; (b) The magnetization curve for Fe2O3finely dispersed nanoparticles from ferritin solution annealed at different
temperatures; the right-hand bottom graph shows the magnetization and coercivity as a function of annealing temperature. (Reprint
with permission from S. Kumar, A. Thakur, S. K. Gupta, P. Rajput, and A. Singh, J. Supercond. Nov. Magn. 33, 3841 (2020). Copyright 2020,
Springer Nature).
iron oxide nanoparticles are characterized by many spec-
troscopic techniques. Table 3listed the details of eval-
uated properties with advantages and limitations of the
basic characterization tools [3]. The very basic tool to
investigate any nanomaterial is XRD. X-ray diraction
wasusedtoinvestigatethecrystallinestructureandsize
of nanoparticles. The sharp peaks in the XRD pattern are
used to nd the size of the nanoparticles through Scher-
rer’sequation[114]. For the noncrystalline nanoparti-
cles,sizecannotbepredictedeasilyduetothebroad
peaks [85]. TEM/HRTEM is used to study the shape
and size distribution of nanoparticles suspended in the
liquid. SEM/FESEM and AFM are used to investigate
the morphology and size of iron oxide nanoparticles.
From the obtained images, we have some clues about
the shape and size (diameter estimation). The electron
phase shift, determination of crystallinity, aggregation
state of nanoparticles, and lattice spacing are estimated
from the TEM analysis [115]. The AFM tool is help-
ful in nding the surface roughness, step height, and
position of distributed particles [3,7]. FTIR spectroscopy
is used to collect information about structure char-
acterization and functional group determinations [85].
The molecules present in nanoparticles absorb light in
the region with wave numbers of 4000 cm−1–660 cm−1
(2.5–15 μm) [116,117]. The thermal stability of iron oxide
14 S. KUMAR ET AL.
Tab le 2. Various kinds of synthesis techniques of iron oxides nanoparticles with advantages and disadvantages.
Synthesis Techniques Advantages Disadvantages References
Sol-gel Low cost of processing, high yield efficiency,
energy efficient and quick output
Expansive, inadequate efficiency [86,96,97]
Microwave assisted synthesis Higher yields, short reaction time, excellent
reproducibility and easy handling
Unsuitable for scale-up and reaction
monitoring
[98,99]
Chemical vapour condensation Suitable for preparing small quantities to
demonstrate desired properties in the
laboratory
Low production, difficult to control size and
particle size distribution
[100]
Spray pyrolysis Finely dispersed particles of predictable size,
shape and variable composition
Aggregated particles, Expensive [45,101,102]
Thermal decomposition Producing highly monodispersed par ticles
with a narrow size distribution
High cost, long-time synthesis reaction, high
temperature
[103–105]
Polyol Uniform size particles can be prepared, easy to
scale-up
Needs high temperature, long time [45,106]
Co-precipitation well-situated technique, simple and rapid
preparative method, easy control of particle
size and composition
Extensive agglomeration, poor morphology
and particle size distribution
[107,108]
Microemulsion Monodispersed nanoparticles with various
morphology can be produced
Not very efficient and difficult to scale up [7,103]
Sonochemical Simple, low cost, eco-friendly safe, absence of
many reactants
Very small concentration of prepared NPs,
particle agglomeration is very narrow
[70,109]
Bio-synthesis using protein,
plants and bacteria
Mono dispersity, Selectivity and precision
for nanoparticle formation, cost-effective,
eco-friendly
Limited knowledge, difficulty in controlling
size and properties
[4,85,110,111]
Figure 13. The basics characterization tools to investigate the
various aspects of iron oxide nanoparticles.
nanoparticles can be investigated by Thermogravimetry
analysis [118]. The NMR technique is used to study the
structure of compounds, and NMR provides the specic
bonding structure information and stereochemistry of
molecules. Therefore, NMR is a very powerful tool to
determine structural information [119].
The studies of concentration eects, molecular dif-
fusion, and chemical kinetics of nanoparticles are via
uorescence correlation spectroscopy (using visible and
UV radiation). Raman spectroscopy is helpful in collect-
ing structural conformation directly from the aqueous
solution without any specic sample preparation [3,120].
Other spectroscopic techniques like dynamic light scat-
tering (DLS) determine the size of the nanoparticles
andtheirdistribution.TheDynamicLightScattering
(DLS) technique is mainly used to nd the hydrody-
namicdiameterandsurfaceareaofironoxidenanopar-
ticles (typically ranging from 30 nm to 190 nm) via the
Stokes–Einstein equation [121]. While the surface charge
on nanoparticles is determined by the Zeta potential
measurement, and the polymer coating helps to mod-
ify the zeta potential [122,123]. Because the zeta poten-
tial is crucial for predicting the colloidal stability of the
charged nanoparticles, and also helps to understand the
performance of nanoparticles in dierent conditions.
Thesynthesisprocesshasasignicantimpacton
magnetic properties. The nanoparticles have numerous
dimensions ranging from micro to nanometer, show-
ing superparamagnetic behaviour [85]. The other char-
acterizationtechniques,whicharedeployedtoexplore
the magnetic properties of iron oxide nanoparticles, are
well known as magneto-metric techniques. The vibrat-
ing sample magnetometer (VSM) is a direct magnetic
measurement tool, where magnetization of the samples
is observed. In the 1950s, Foner developed the vibrat-
ing sample magnetometer technique. This is easy and
accurate. Furthermore, in the magnetometry tools, the
superconducting quantum interface device (SQUID) has
fundamental techniques to evaluate the various crucial
magnetic parameters for magnetic nanoparticles like sat-
uration magnetization, coercive eld and remnant mag-
netization [124,125]. In the SQUID technique, we can
investigate dierent sample types like crystal, powder, liq-
uid, gases, and thin lms and sensitivity of about 10−10
emu [126]. The behavior of nanoparticles was studied
CONTEMPORARY PHYSICS 15
Tab le 3. Details of analyzed properties from characterization tools for iron oxides nanoparticles with advantages and constraints.
Characterization
tools
Evaluation/analysed physical and
chemical properties Advantages Constraints
XRD Crystal structure, average grain
size, preferred crystal orientation
and other structural parameters
Quick phase identification, Ease of
sample preparation, ease of access for
amorphous materials and liquid samples
The Resolution is comparatively low. No
information about chemical nature
SEM Morphology, sample composition,
Dispersion
Larger depth of focus, High resolution
(below to subnanometer) in natural state
visualization of biomolecules supplied
by the usage of ESEM (Environmental
SEM) technique
Conducting sample or coating conductive
materials required in conventional SEM, Need
of dry samples. Heterogeneous samples are
required. Costly apparatus. For numerous NP
bioconjugates, cryogenic method is needed.
ESEM resolution is reduced
TEM Crystallinity, size distribution,
composition
With higher spatial resolution than
SEM, direct measurement of the size
transportation and shape of NMs
occurs. For investigation of chemical
composition and electronic structure of
NMs. A lot of analytical techniques are
paired off with TEM
Ultrathin samples are needed. Requirement of
samples in nonphysiological states. Damage or
variations in sample. Sampling is insufficient.
Equipment is expensive. Expertise required
AFM High resolution nanoscale, Shape
heterogeneity, study of local
sites in air or liquid surroundings
Mapping of 3D sample surface resolution
of sub-nanoscaled topographic samples.
Direct measurement in dry state, ambient,
or aqueous environment
Lateral dimensions over description
Sampling is poor and time-consuming
The exterior of NM analysis is generally restricted
DLS Hydrodynamic diameter Constructive way for rapid and more
consistent measurement. Measures in
some liquid media, solvent of interest
for monodisperse, hydrodynamic sizes
are exactly determined
Moderate expenses on equipment
With a particular composition, unresponsive
correlation of size fractions. Effect of small
numbers of large particles in polydisperse
sample
Size restrictions
Restricted size determination
Thermal analysis
DSC, TGA
Surface coverage, thermal
stability, nature of surface
functionalization, carrier-drug
interaction
No need for sample preparation, Easy and
accurate information provided, low cost
Liquid samples are difficult to study and non-
homogeneous materials cannot be tested, very
sensitive to heating rate
Raman
Spectroscopy
Chemical finger prints, electronic
characteristics
No need of sample preparation Compared to Rayleigh scattering, there is
comparatively a weak single restricted spatial
resolution, enormously minute cross-section.
Disturbance of fluorescence irreproducible
measurement
Fluorescence
correlation
spectroscopy
Dimension, binding kinetics
of hydrodynamics, reaction
kinetics, molecular interaction
High temporal and spatial magnification
Uptake-sample is low
The deficiency of proper methods, causes
limitation in fluorophore species and restriction
inusage and inaccuracy
For studying concentration effect,
molecular diffusion, chemical kinetics,
and conformation dynamics are
specifically performed via fluorescent
probes methods
NMR Structure conformation, purity of
sample, phase changes
Non-invasive and constructive procedure.
Minute or less sample preparation
required
Sensitivity is low
Time consuming
Comparatively large amount of sample needed
VSM, SQUID Magnetic properties at room
temperature and with
temperature
Easy to use and sensitive Expansive equipment
STM Shape heterogeneity, size and local
structure at atomic scale
high, spatial resolution takes place Cannot use in ultrahigh vacuum, Conductive
surfaces needed, clean and stable surfaces
IR Nature of functionalization,
molecular structure
Rapid and cheap measurement Sample preparation is complex intervention and
efficient absorbance of water
Mass spectroscopy Mass to charge ratio of ions,
Molecular weight
High accuracy and precision in
measurement
High sensitivity to detection (a very small
amount of sample required)
Expensive equipment
Lack of complete databases for the identification
of molecular species. Limited application to
date in studying NM bioconjugates
Zeta potential
measurement
Surface charge on nanoparticles Concurrent measurement of numerous
particles
Electro-osmotic effect deficiency of accurate and
repetition measurement
Circular dichroism Structural aspects of optically
active chiral media in solution
Quick and easy, Molecules of any size can
be studied
Does not provide atomic level structure analysis
UV/VIS
Spectroscopy
Optical aspects of NMs that
are sensitive to size, shape,
concentrations
Low cost and easy Less applicable in complex mixtures of samples
under the broadly dened range of applied magnetic
elds between −15 KOe and +15 KOe [4]inVSMmea-
surement with a sensitivity of 10−6emu [126]. So far,
those measurements constitute a crucial characterization
step, due to the interaction between magnetic nanoparti-
cles and the external magnetic elds hired for magnetic-
driven nanocarriers as benecial techniques for several
biomedical packages [127]. The PPMS (physical property
16 S. KUMAR ET AL.
measurement system) is an additional tool to nd the
magnetic property of iron oxide nanoparticles with tem-
perature [128]. The oxidation state, magnetic character,
structural and bonding aspects of iron oxide nanoparti-
cles are predicted from Mossbauer spectroscopy and the
VSM estimate of the shell’s eect on the magnetization
saturation of obtained iron oxide nanoparticles [129].
5. Challenges with iron oxides nanoparticles
Newmaterialscanbedevelopedbytuningtheproper-
ties of existing materials like controlling the atoms or
molecules, crystallinity, and purity [130,131]. Similarly,
the basic challenges in fabricating the nanoparticles are
uniform size distribution, tuned shape and size, scalabil-
ity and construction of complex nanostructures, toxicity
and biocompatibility [7,85,132]. The reproducible prepa-
ration of iron oxide nanoparticles with the preferred
aspects is still an issue at present [106,133] These issues
must be addressed while synthesizing nanoparticles for
any technological applications [85]. It is a well-known
fact that prices decrease if the production cost decrease.
So, nanoparticles of iron oxide prepared are costly and
need a method of preparation of iron oxide nanoparticles,
that is low-cost and eco-friendly [85,131,134]. And also
produces iron oxide nanoparticles on a large scale. Still, a
lot of investigation and comprehension study is required
to understand the properties of nanoparticles of iron
oxides such as morphology, shape, size, structure, com-
position, and make them more useful in various areas of
interest for a better future. Table 4listed some of the con-
cerns which directly or indirectly aect humankind and
agriculture [3,135–137].
Tab le 4. Concerns of iron oxides nanoparticles (IONPs) related to
human and agriculture.
Sources Effects
Effect on human
health
Skin absorption
Orally inhaled or ingested
Catalysis
Absorptioninmicrobes
Skin cancer, irritation
Harmful side effect, lung cancer
Illness, death, speed up reaction
Toxic effect upon ingestion or
inhalation, kills useful microbes
and nonbacterial cells
Environmental Flying nanoparticles affect plants,
loss of soil fertility
Agriculture
Agrichemicals Seed germination and growth,
affect soil nutrients, harm
bacteria important for plant
growth
Cosmetic industry Pollution in solid waste from
sewage treatment, and are used
as organic fertilizers
Nanoparticles, cerium oxides Complete inhibition of the plants
ability to fix nitrogen in the roots
6. Conclusions and outlook
This work provides a brief concept of iron oxide nanopar-
ticles (Fe2O3and Fe3O4) and their most interesting poly-
morphs. The crystalline Fe2O3has dierent polymorphs
like α,β,and γ-Fe2O3. Also, discuss the magnetism
and classication of magnetic materials (nanoparticles)
in accordance with the response to external applied
magnetic eld. Dierent methods of synthesis of iron
oxide nanoparticles via physical, chemical, and biotech-
niques are described with the latest updates. The chem-
ical methods are widely used methods to prepare iron
oxide nanoparticles with various improved properties
like uniform size, shape, composition, and crystallinity.
The synthesis processes have a great impact on the phys-
ical and magnetic properties. The monodispersity of
iron oxide nanoparticles synthesized through various
processes is highly required for technological applica-
tions.Fewresearchersprovideevidencerelatedtothe
production of the iron oxide nanoparticle via biosyn-
thesis methods because of limited knowledge. Recently,
biosynthesis has gained popularity due to the low cost
and monodispersity of obtained nanoparticles. We still
need more work to overcome the issues related to iron
oxide nanoparticles, such as lack of crystallinity and uni-
formity in shape and size. There is a need for a new
strategy of synthesis or hybrid methods to synthesize
the desired iron oxide nanoparticles with no or mini-
mum toxicity for biomedical applications and other areas.
The magnetic response of iron oxide nanoparticles is
explained by the saturation of magnetization of uncoated
and functionalized magnetic nanoparticles. The satura-
tion of magnetization decreases the stabilization of iron
oxide nanoparticles. But they show an enhancement in
the saturation of magnetization on the agglomeration of
the nanoparticles. Although, there are other parameters
that aect the magnetic properties. The interaction of
iron oxides nanoparticles with an external magnetic eld
is understood by a deeper understanding of magnetic
characterization. The superparamagnetic properties are
evolving; making the iron oxide nanoparticles potential
candidates for many elds, especially in the biomedi-
cal area. Also, give brief concepts to understand the few
crucial characterization tools and instruments to inves-
tigate the iron oxide nanoparticles prepared by dierent
methods. The concerns related to the iron oxide nanopar-
ticles associated with human kind and agriculture are
presented in this review. This review is helpful to those
who are interesting in entering and exploring the world
of iron oxide nanoparticles. The science community must
address some challenges (reproducibility, control over
size, monodispersity, and toxicity) associated with the
synthesis of the iron oxide nanoparticle for a clean and
green tomorrow.
CONTEMPORARY PHYSICS 17
Acknowledgements
The author S.K. grateful to the University Grant Commission
for the nancial support as a fellowship (Lett. No. F1-17.1/
2016-17/RGNF-2015-17-SC-HIM-18502/(SA-III/Website)).
SK is also thankful to Dr. Subhash Chand and Mukul Kumar
forvaluablediscussionsandmotivations.
Disclosure statement
No potential conict of interest was reported by the author(s).
Data availability statement
The data are available from the original research articles
that are cited in this review.
Notes on contributors
Sunil Kumar obtained his Master of Philosophy, Master of
Science in Physics from HPU Shimla, India. Currently he is
pursuinghisresearchinsoftcondensedmatterPhysics(experi-
mental) from same institute for Doctor of Philosophy. His main
focusofresearchistostudythenanomaterialssynthesizedfrom
Ferritin.
Manoj Kumar received his M. Phil & M. Sc in Physics from
HimachalPradeshUniversity,Shimla,India.Currently,heis
pursuing Ph. D under the mentorship of Dr. Amarjeet Singh
from same University. His main research activities are in the
eld of polymeric organic semiconductor with special focus on
internal morphology of the bulk hetero junction.
Dr. Amarjeet Singh is currently Assistant Professor at the
Department of Physics, Himachal Pradesh University Shimla in
India. Dr. Amarjeet Singh pursued his Ph.D. from Saha Insti-
tute of Nuclear Physics in Kolkata in Physics discipline in the
eldofstructureofpolymericthinlmsandroleofinterfacesin
governing structure and dynamics of macromolecules conned
in thin lms.
ORCID
Amarjeet Singh http://orcid.org/0000-0001-9384-6029
References
[1]KeppelerM,ShenN,NageswaranS,etal.Synthe-
sis of α-Fe2O3/carbon nanocomposites as high capac-
ity electrodes for next generation lithium ion batteries:
a review. J Mater Chem A. 2016;4(47):18223–18239.
DOI:10.1039/c6ta08456g.
[2] WuW,WuZ,YuT,etal.Recentprogressonmagnetic
iron oxide nanoparticles: synthesis, surface functional
strategies and biomedical applications. Sci Technol Adv
Mater. 2015;16(2). DOI:10.1088/1468-6996/16/2/023
501.
[3]AliA,ZafarH,ZiaM,etal.Synthesis,charac-
terization, applications, and challenges of iron oxide
nanoparticles. Nanotechnol, Sci Appl. 2016;9:49–67.
DOI:10.2147/NSA.S99986.
[4] Kumar S, Thakur A, Gupta SK, et al. Afacile route to syn-
thesis of ferromagnetic and antiferromagnetic phases of
iron oxide nanoparticles by controlled heat treatment of
ferritin. J Supercond Novel Magn. 2020;33:3841–3852.
DOI:10.1007/s10948-020-05649-1.
[5] Tong S, Quinto CA, Zhang L, et al. Size-dependent
heatingofmagneticironoxidenanoparticles.ACS
Nano. 2017;11(7):6808–6816. DOI:10.1021/acsnano.7b0
1762.
[6] GulS, KhanSB, RehmanIU, et al. A comprehensive
review of magnetic nanomaterials modern day theranos-
tics. Frontiers in Materials. 2019;6(July):1–15. DOI:10.
3389/fmats.2019.00179.
[7] Ansari SAMK, Ficiarà E, Runatti FA, et al. Mag-
netic iron oxide nanoparticles: synthesis, characteriza-
tion and functionalization for biomedical applications in
the central nervous system. Materials (Basel).2019;12(3).
DOI:10.3390/ma12030465.
[8] Bhattacharya P, Du D, Lin Y. Bioinspired nanoscale
materials for biomedical and energy applications. J
RSocInterface.2014;11(95). DOI:10.1098/rsif.2013.
1067.
[9]WheelerDA,WangG,LingY,etal.Nanostructured
hematite: synthesis, characterization, charge carrier
dynamics, and photoelectrochemical properties. Energy
and Environmental Science. 2012;5(5):6682–6702. DOI:
10.1039/c2ee00001f.
[10]Al-HakkaniMF,GoudaGA,HassanSHA.Areview
of green methods for phyto-fabrication of hematite
(α-Fe2O3) nanoparticles and their characterization,
properties, and applications. Heliyon. 2021;7(1):e05806.
DOI:10.1016/j.heliyon.2020.e05806.
[11] Sharma P, Dhiman S, Kumari S, et al. Revisiting the phys-
iochemical properties of hematite (-Fe2O3) nanopar-
ticle and exploring its bio-environmental application.
Mater Res Express. 2019;6(9). DOI:10.1088/2053-1591/
ab30ef.
[12] Cannas C, Concas G, Gatteschi D, et al. Superpara-
magnetic behaviour of γ-Fe2O3nanoparticles dis-
persed in a silica matrix. Phys Chem Chem Phys.
2001;3(5):832–838. DOI:10.1039/b008645m.
[13] CotinG,PiantS,MertzD.Ironoxidenanoparticlesfor
biomedical applications. Synt Funct Appl. 2018, 43–88.
[14] Boxall C, Kelsall G, Zhang Z. Photoelectrophoresis of
colloidal iron oxides. Part 2 – magnetite (Fe3O4). J Chem
Soc Faraday Trans. 1996;92(5):791–802. DOI:10.1039/
FT9969200791.
[15] Momma K, Izumi F. VESTA3 for three-dimensional
visualization of crystal, volumetric and morphology
data. J Appl Crystallogr. 2011;44(6):1272–1276. DOI:10.
1107/S0021889811038970.
[16] ElMendiliY,AbdesselamA,andJ-F.BardeauJF.“Insight
into the mechanism of carbon steel corrosion under
aerobic and anaerobic conditions.” Physical Chemistry
Chemical Physics. 2013;15.23: 9197–9204.
[17] El Mendili Y, Bardeau JF, Randrianantoandro N, et al.
Insights into the mechanism related to the phase tran-
sition from γ-Fe2O3 to a-Fe2O3 nanoparticles induced
by thermal treatment and laser irradiation. The Jour-
nal of Physical Chemistry C. 2012;116(44): 23785–
23792.
[18] Solano E, Frontera C, Puig T, et al. Neutron and X-
ray diraction study of ferrite nanocrystals obtained
18 S. KUMAR ET AL.
by microwave-assisted growth. A structural compari-
son with the thermal synthetic route. Journal of Applied
Crystallography. 2014;47(1): 414–42.
[19] Saku rai S, Namai A, Hashimoto K, et al. First obser vation
of phase transformation of all four Fe2O3phases (γf
f f r-phase). J Am Chem Soc. 2009;29(29):18299–18303.
DOI:10.1021/ja9046069
[20] Chen C. Magnetism and metallurgy of soft magnetic
materials. New York: Dover publications; 1986.
[21] Kittel C. Introduction to solid state physics. 7th ed.
Delhi:JohnWiley&Sons;1999.
[22] B.D, C.; C.D, G. Introduction to magnetic materials. 2nd
ed.; 2009.
[23] Kittel C. Introduction to solid state physics. 8th ed. New
York:Wiley&Sons;2004.
[24] KodamaRH,BerkowitzAE,McNiJr,EJ,etal.Sur-
face spin disorder in NiFe 2 O 4 nanoparticles. Physical
Review Letters. 1996; 77(2): 394.
[25] Bhowmik RN, Sarvanan A. Surface magnetism, morin
transition, and magnetic dynamics in antiferromagnetic
α-Fe2O3(hematite) nanograins. J Appl Phys. 2010;107.
DOI:10.1063/1.3327433
[26] Hasany SF, Ahmed IJR, Rehman A. Systematic review
of the preparation techniques of iron oxide magnetic
nanoparticles. Nanosci Nanotechnol. 2012;2(6):148–158.
DOI:10.5923/j.nn.20120206.01.
[27] Riaz S, Shah SZH, Kayani ZN, et al. Magnetic and
structural phase transition in ironoxide nanostruc-
tures. Mater Today. 2015;2(10, Part B):5280–5287.
DOI:10.1016/j.matpr.2015.11.036.
[28] Mathevula LE, Noto LL, Mothudi BM, et al. Struc-
tural and optical properties of sol-gel derived α-Fe2O3
nanoparticles. J Lumin.2017;192:879–887. DOI:10.1016/
j.jlumin.2017.07.055.
[29] Pandey S, Mishra SB. Sol–gel derived organic–inorganic
hybrid materials: synthesis, characterizations and appli-
cations. J Sol-Gel Sci Technol. 2011;59(1):73–94. DOI:
10.1007/s10971-011-2465-0.
[30] Dong W, Zhu C. Use of ethylene oxide in the sol-gel
synthesis of α-Fe2O3nanoparticles from Fe(III) salts. J
Mater Chem. 2002;12(6):1676–1683. DOI:10.1039/b200
773h.
[31] Lemine OM, Omri K, Zhang B, et al. Sol–gel syn-
thesis of 8nm magnetite (Fe3O4) nanoparticles and
their magnetic properties. Superlattices Microstruct.
2012;52(4):793–799. DOI:10.1016/j.spmi.2012.07.009.
[32] Raja K, Mary Jaculine M, Jose M, et al. Sol–gel synthesis
and characterization of α-Fe2O3nanoparticles. Super-
lattices Microstruct. 2015;86:306–312. DOI:10.1016/j.
spmi.2015.07.044.
[33] QiH,YanB,LuW,etal.ANon-alkoxidesol-gelmethod
for the preparation of magnetite (Fe3O4)nano-particles.
Curr Nanosci. 2011: 381–388. DOI:10.2174/1573413
11795542426
[34] Suman Devi S, Sharma V, Chahal S, et al. Phase transfor-
mation and structural evolution in iron oxide nanostruc-
tures. Mater Sci Eng. 2021;272:115329. DOI:10.1016/j.
mseb.2021.115329.
[35] Osial M, Rybicka P, Pękała M, et al. Easy synthesis and
characterization of holmium-doped SPIONs. Nanoma-
terials. 2018;8(6). DOI:10.3390/nano8060430.
[36] Bhandari R, Gupta P, Dziubla T, et al. Single step
synthesis, characterization and applications of cur-
cumin Functionalized iron oxide magnetic nanoparti-
cles. Mater Sci Eng C Mater Biol Appl. 2016;67:59–64.
DOI:10.1016/j.msec.2016.04.093.
[37] Gruskiene R, Krivorotova T, Staneviciene R, et al. Prepa-
ration and characterization of iron oxide magnetic
nanoparticles functionalized by nisin. Colloids Surf B.
2018;169:126–134. DOI:10.1016/j.colsur.2018.05.017.
[38] Lassoued A, Dkhil B, Gadri A, et al. Control of the
shape and size of iron oxide (α-Fe2O3) nanoparticles
synthesized through the chemical precipitation method.
Results Phys. 2017: 3007–3015. DOI:10.1016/j.rinp.
2017.07.066.
[39] Massart R. Preparation of aqueous magnetic liquids in
alkaline and acidic media. IEEE Trans Magn.1981;17(2):
1247–1248. DOI:10.1109/TMAG.1981.1061188.
[40] Fatima H, K KS. Iron-based magnetic nanoparticles
for magnetic resonance imaging. Adv Powder Technol.
2018;29(11):2678–2685. DOI:10.1016/j.apt.2018.07.017.
[41] Salavati-Niasari M, Mahmoudi T, Amiri O. Easy syn-
thesis of magnetite nanocrystals via coprecipitation
method. J Cluster Sci. 2012;23:597–602. DOI:10.1007/
s10876-012-0451-5
[42] Slimani S, Meneghini C, Abdolrahimi M, et al. Spinel
iron oxide by the Co-precipitation method: eect of
the reaction atmosphere. Appl Sci. 2021;11(12). DOI:
10.3390/app11125433.
[43] Shabani N, Javadi A, Jafarizadeh-Malmiri H, et al.
Potential application of iron oxide nanoparticles syn-
thesized by co-precipitation technology as a coagulant
for water treatment in settling tanks. Min Metal Explor.
2021;38(1):269–276. DOI:10.1007/s42461-020-00338-y.
[44] González-Carreño T, Morales MP, Gracia M, et al. Prepa-
ration of uniform γ-Fe2O3particles with nanometer
size by spray pyrolysis. Mater Lett. 1993;18(3):151–155.
DOI:10.1016/0167-577X(93)90116-F.
[45] Hasany FS, Abdurahman HN, Sunarti R, et al. mag-
netic iron oxide nanoparticles: chemical synthesis
and applications review. Curr Nanosci. 2013:561–575.
DOI:10.2174/15734137113099990085
[46] Dumitrache F, Morjan I, Alexandrescu R, et al. Iron–iron
oxide core–shell nanoparticles synthesized by laser
pyrolysisfollowedbysupercialoxidation.ApplSurfSci.
2005;247(1):25–31. DOI:10.1016/j.apsusc.2005.01.037.
[47] Tartaj P, Morales MP, González-Carreño T, et al.
Advances in magnetic nanoparticles for biotechnol-
ogy applications. J Magn Magn Mater. 2005: 290–291.
DOI:10.1016/j.jmmm.2004.11.155.
[48] Tartaj P, del Puerto Morales M, Veintemillas-Verdaguer
S, et al. The preparation of magnetic nanoparticles
for applications in biomedicine. J Phys D Appl Phys.
2003;36(13):R182–R197. DOI:10.1088/0022-3727/36/
13/202.
[49] Hammad M, Hardt S, Mues B, et al. Gas-phase syn-
thesis of iron oxide nanoparticles for improved mag-
netic hyperthermia performance. J Alloys Compd.
2020;824:153814. DOI:10.1016/j.jallcom.2020.153814.
[50] Belaïd S, Stanicki D, Vander Elst L, et al. Inuence
of experimental parameters on iron oxide nanoparti-
cle properties synthesized by thermal decomposition:
CONTEMPORARY PHYSICS 19
size and nuclear magnetic resonance studies. Nanotech-
nology. 2018;29(16):165603. DOI:10.1088/1361-6528/
aaae59.
[51] Frey NA, Peng S, Cheng K, et al. Magnetic nanopar-
ticles: synthesis, functionalization, and applications in
bioimagingandmagneticenergystorage.ChemSocRev.
2009;38(9):2532–2542. DOI:10.1039/B815548H.
[52] Glasgow W, Fellows B, Qi B, et al. Continuous syn-
thesis of iron oxide (Fe3O4) nanoparticles via ther-
mal decomposition. Particuology. 2016;26(C):47–53.
DOI:10.1016/j.partic.2015.09.011.
[53] Eenberger FB, Couto RA, Kiyohara PK, et al. Econom-
ically attractive route for the Preparation of high quality
magnetic nanoparticles by the thermal decomposition of
iron(III) acetylacetonate. Nanotechnology. 2017;28(11).
DOI:10.1088/1361-6528/aa5ab0.
[54] Jović Orsini N, Babić-Stojić B, Spasojević V, et al. Mag-
netic and power absorption measurements on iron oxide
nanoparticles synthesized by thermal decomposition
of Fe(Acac)3. J Magn Magn Mater. 2018;449:286–296.
DOI:10.1016/j.jmmm.2017.10.053.
[55] Park J, An K, Hwang Y, et al. Ultra-large-scale syntheses
of monodisperse nanocrystals. Nat Mater. 2004;3(12):
891–895. DOI:10.1038/nmat1251.
[56] Shavel A, Liz-Marzán LM. Shape control of iron oxide
nanoparticles. Phys Chem Chem Phys. 2009;11(19):
3762–3766. DOI:10.1039/B822733K.
[57] Vangijzegem T, Stanicki D, Panepinto A, et al. Inuence
of experimental parameters of a continuous ow process
on the properties of very small iron oxide nanopar-
ticles (VSION) designed for T1-weighted magnetic
resonance imaging (MRI). Nanomaterials. 2020;10(4).
DOI:10.3390/nano10040757.
[58] Lu A-H, Salabas EL, Schüth F. Magnetic nanoparti-
cles: synthesis, protection, functionalization, and appli-
cation. Angew Chem, Int Ed. 2007;46(8):1222–1244.
DOI:10.1002/anie.200602866.
[59] Biehl P, der Lühe M, Dutz S, et al. Synthesis, charac-
terization, and applications of magnetic nanoparticles
featuring polyzwitterionic coatings. Polymers (Basel).
2018;10(1). DOI:10.3390/polym10010091.
[60] Nejati K, Zabihi R. Preparation and magnetic proper-
ties of nano size nickel ferrite particles using hydrother-
mal method. Chem Cent J. 2012;6(1):23), DOI:10.1186/
1752-153X-6-23.
[61] Lassoued A, Lassoued MS, Dkhil B, et al. Synthesis,
photoluminescence and magnetic properties of iron
oxide (α-Fe2O3) nanoparticles through precipitation or
hydrothermal methods. Physica E. 2018;101:212–219.
DOI:10.1016/j.physe.2018.04.009.
[62]WegmannM,ScharrM.Chapter8–synthesisof
magnetic ironoxide nanoparticles. In: Deigner H-P,
Kohl M, editor. In precision medicine. Academic Press;
2018. p. 145–181. DOI:10.1016/B978-0-12-805364-5.
00008-1.
[63] Benhammada A, Trache D, Kesraoui M, et al. Synthe-
sis and characterization of α-Fe2O3nanoparticles from
dierent precursors and their catalytic eect on the ther-
mal decomposition of nitrocellulose. Thermochim Acta.
2020;686:178570. DOI:10.1016/j.tca.2020.178570.
[64] HuX,YuJC,GongJ,etal.α-Fe2O3nanorings prepared
by a microwave-assisted hydrothermal process and their
sensing properties. Adv Mater. 2007;19(17):2324–2329.
DOI:10.1002/adma.200602176.
[65] Qiu G, Huang H, Genuino H, et al. Microwave-assisted
hydrothermal synthesis of nanosized α-Fe2O3for cat-
alysts and adsorbents. J Phys Chem C. 2011;115(40):
19626–19631. DOI:10.1021/jp2067217.
[66] Kijima N, Yoshinaga M, Awaka J, et al. Microwave
synthesis, characterization, and electrochemical prop-
erties of α-Fe2O3nanoparticles. Solid State Ionics.
2011;192(1):293–297. DOI:10.1016/j.ssi.2010.07.012.
[67] Parsons JG, Luna C, Botez CE, et al. Microwave-assisted
synthesis of iron(III) oxyhydroxides/oxides character-
ized using transmission electron microscopy, X-ray
diraction, and X-ray absorption spectroscopy. J Phys
Chem Solids. 2009;70(3):555–560. DOI:10.1016/j.jpcs.
2008.12.017.
[68] Pascu O, Carenza E, Gich M, et al. Surface reactiv-
ity of iron oxide nanoparticles by microwave-assisted
synthesis; comparison with the thermal decomposi-
tion route. J Phys Chem C. 2012;116(28):15108–15116.
DOI:10.1021/jp303204d.
[69] Kostyukhin EM, Nissenbaum VD, Abkhalimov EV, Kus-
tov AL, Ershov BG, Kustov LM. Microwave-assisted
synthesis of water-dispersible humate-coated magnetite
nanoparticles: relation of coating process parame-
ters to the properties of nanoparticles. Nanomaterials.
2020;10(8). DOI:10.3390/nano10081558.
[70] Hassanjani-Roshan A, Vaezi MR, Shokuhfar A, et al.
Synthesis of iron oxide nanoparticles via sonochem-
ical method and their characterization. Particuology.
2011;9(1):95–99. DOI:10.1016/j.partic.2010.05.013.
[71] Ashokkumar M, Lee J, Kentish S, et al. Bubbles in
an acoustic eld: an overview. Ultrason Sonochem.
2007;14(4):470–475. DOI:10.1016/j.ultsonch.2006.09.
016.
[72] Xu H, Zeiger BW, Suslick KS. Sonochemical synthesis
of nanomaterials. Chem Soc Rev. 2013;42(7):2555–2567.
DOI:10.1039/C2CS35282F.
[73] PinkasJ,ReichlovaV,ZborilR,etal.Sonochemicalsyn-
thesis of amorphous nanoscopic iron(III) oxide from
Fe(Acac)3. Ultrason Sonochem. 2008;15(3):257–264.
DOI:10.1016/j.ultsonch.2007.03.009.
[74] Hooshmand S, Hayat SMG, Ghorbani A, et al. Prepa-
ration and applications of superparamagnetic iron
oxide nanoparticles in novel drug delivery systems: An
overview article. Curr Med Chem. 2020.DOI:10.2174/
0929867327666200123152006-a.
[75] Yuse M, Shameli K, Jumaat AF. Preparation and prop-
erties of magnetic iron oxide nanoparticles for biomed-
ical applications: a brief review. J Adv Res Mater Sci.
2020;75(10–18). DOI:10.37934/arms.75.1.1018.
[76] Harshiny M, Iswarya CN, Matheswaran M. Biogenic
synthesisofironnanoparticlesusingamaranthusdubius
leaf extract as a reducing agent. Powder Technol. 2015;
286(C):744–749. DOI:10.1016/j.powtec.2015.09.021.
[77] Saddik MS, Alsharif FM, El-Mokhtar MA, et al. Biosyn-
thesis, characterization, and wound-healing activity of
phenytoin-loaded copper nanoparticles. AAPS Pharm-
SciTech. 2020;21(5):175), DOI:10.1208/s12249-020-01
700-5.
[78] Hassanien R, Husein DZ, Al-Hakkani MF. Biosyn-
thesis of copper nanoparticles using aqueous tilia
20 S. KUMAR ET AL.
extract: antimicrobial and anticancer activities. Heliyon.
2018;4(12):e01077), DOI:10.1016/j.heliyon.2018.e01
077.
[79] JutzG,VanRijnP,SantosMirandaB,etal.Ferritin:aver-
satile building block for bionanotechnology. Chem Rev.
2015;115(4):1653–1701. DOI:10.1021/cr400011b.
[80]BazylinskiDA,FrankelRB.Magnetosomeformation
in prokaryotes. Nat Rev Microbiol. 2004;2(3):217–230.
DOI:10.1038/nrmicro842.
[81] Bharde AA, Parikh RY, Baidakova M, et al. Bacteria-
mediated precursor-dependent biosynthesis of super-
paramagnetic iron oxide and iron sulde nanoparticles.
Langmuir. 2008;24(11):5787–5794. DOI:10.1021/la7040
19p.
[82] Alphandéry E. Bio-synthesized iron oxide nanoparti-
cles for cancer treatment. Int J Pharm. 2020;586:119472.
DOI:10.1016/j.ijpharm.2020.119472.
[83] Amaliyah S, Pangesti DP, Masruri M, et al. Green
synthesis and characterization of copper nanoparti-
cles using piper retrofractum vahl extract as biore-
ductor and capping agent. Heliyon. 2020;6(8):e04636.
DOI:10.1016/j.heliyon.2020.e04636.
[84] Sundaram PA, Augustine R, Kannan M. Extracellular
biosynthesis of iron oxide nanoparticles by bacillus sub-
tilis strains isolated from rhizosphere soil. Biotechnol
Bioprocess Eng. 2012;17(4):835–840. DOI:10.1007/s122
57-011-0582-9.
[85] AALI,ShahT,UllahR,etal.Reviewonrecentprogress
in magnetic nanoparticles: synthesis, characterization,
and diverse applications. Front Chem. 2021;9(July):548.
DOI:10.3389/FCHEM.2021.629054.
[86] Duan M, Shapter JG, Qi W, et al. Recent progress in
magnetic nanoparticles: synthesis, properties, and appli-
cations. Nanotechnology. 2018;29(45):452001. DOI:10.
1088/1361-6528/aadcec.
[87] Kumar S, Gupta SK, Singh A. Determination of opti-
cal properties of γ-Fe2O3crystalline phase synthesized
from ferritin using UV-VIS absorption spectrum. AIP
Conf Proc. 2021;2352(1):20067. DOI:10.1063/5.0052
995.
[88] Volatron J, Carn F, Kolosnjaj-Tabi J, et al. Ferritin pro-
tein regulates the degradation of iron oxide nanoparti-
cles. Small. 2017;13(2):1–13. DOI:10.1002/smll.201602
030.
[89] LuY,YinY,MayersBT,etal.Modifyingthesurface
properties of superparamagnetic iron oxide nanoparti-
cles through a sol-gel approach. Nano Lett. 2002;2(3):
183–186. DOI:10.1021/nl015681q.
[90] Gupta AK, Gupta M. Synthesis and surface engi-
neering of iron oxide nanoparticles for biomedi-
cal applications. Biomaterials. 2005;26(18):3995–4021.
DOI:10.1016/j.biomaterials.2004.10.012.
[91] CondeJ,DoriaG,BaptistaP.Noblemetalnanoparti-
cles applications in cancer. J Drug Deliv. 2012: 1–12.
DOI:10.1155/2012/751075.
[92] He D, Marles-Wright J. Ferritin family proteins and their
use in bionanotechnology. New Biotechnol. 2015;32(6):
651–657. DOI:10.1016/j.nbt.2014.12.006.
[93] Kim JW, Choi SH, Lillehei PT, et al. Electrochem-
ically controlled reconstitution of immobilized fer-
ritins for bioelectronic applications. J Electroanal Chem.
2007;601(1–2):8–16. DOI:10.1016/j.jelechem.2006.10.
018.
[94] ParkCW,ParkHJ,KimJH,etal.Immobilizationand
characterization of ferritin on gold electrode. Ultrami-
croscopy. 2009;109(8):1001–1005. DOI:10.1016/j.ultra
mic.2009.03.002.
[95] Jacinto MJ, Silva VC, Valladão DMS, et al. Biosynthesis
of magnetic iron oxide nanoparticles: a review. Biotech-
nol Lett. 2021;43(1):1–12. DOI:10.1007/s10529-020-030
47-0.
[96] Takai ZI, Mustafa MK, Asman S, et al. Preparation
and characterization of magnetite (Fe3O4) nanopar-
ticles by sol-gel method. Int J Nanoelectron Mater.
2019;12(1):37–46.
[97] Rasheed RT, Al-Algawi SD, Kareem HH, et al. Prepa-
ration and characterization of hematite iron oxide (α-
Fe2O3)bysol-gelmethod.ChemSciJ.2018;09(04):2–7.
DOI:10.4172/2150-3494.1000197.
[98] Morán-Lázaro JP, Guillen-López ES, López-Urias F, et al.
SynthesisofZnMn
2O4nanoparticles by a microwave-
assisted colloidal method and their evaluation as a
gassensorofpropaneandcarbonmonoxide.Sensors.
2018;18(3). DOI:10.3390/s18030701.
[99] AmbroŽiČ G, Orel ZC, Žigon M. Microwave-assisted
non-aqueous synthesis of ZnO nanoparticles. Materiali
in Tehnologije. 2011;45(3):173–177.
[100] Dong XL, Choi CJ, Kim BK. Structural and mag-
netic characterization of Fe nanoparticles synthesized
by chemical vapor condensation process. J Appl Phys.
2002;92(9):5380–5385. DOI:10.1063/1.1510168.
[101] Eslamian M, Ahmed M, Ashgriz N. Modelling of
nanoparticle formation during spray pyrolysis. Nan-
otechnolog y. 2006;17(6):1674–1685. D OI:10.1088/0957-
4484/17/6/023.
[102] Jung DS, Ko YN, Kang YC, et al. Recent progress
in electrode materials produced by spray pyrolysis
for next-generation lithium ion batteries. Adv Pow-
der Technol. 2014;25(1):18–31. DOI:10.1016/j.apt.2014.
01.012.
[103] Wu W, He Q, Jiang C. Magnetic iron oxide nanoparti-
cles: synthesis and surface functionalization strategies.
Nanoscale Res Lett. 2008;3(11):397–415. DOI:10.1007/
s11671-008-9174-9.
[104] Singamaneni S, Bliznyuk VN, Binek C, et al. Mag-
netic nanoparticles: recent advances in synthesis, self-
assembly and applications. J Mater Chem. 2011;21(42):
16819–16845. DOI:10.1039/C1JM11845E.
[105] Campanini M, Ciprian R, Bedogni E, et al. Lorentz
microscopy sheds light on the role of dipolar interac-
tionsinmagnetichyperthermia.Nanoscale.2015;7(17):
7717–7725. DOI:10.1039/C5NR00273G.
[106] Nene AG, Takahashi M, Wakita K, et al. Size con-
trolled synthesis of Fe3O4nanoparticles by ascorbic acid
mediated reduction of Fe(Acac)3without using capping
agent. J Nano Res. 2016;40:8–19. DOI:10.4028/www.sci
entic.net/JNanoR.40.8.
[107] Kumar H, Sangwan P. Synthesis and characterization of
MnO2nanoparticles using co-precipitation technique.
Int J Chem Chem Eng. 2013;3(3):155–160.
[108] Wang B, Wei Q, Qu S. Synthesis and characterization
of uniform and crystalline magnetite nanoparticles via
CONTEMPORARY PHYSICS 21
oxidation-precipitation and modied co-precipitation
methods. Int J Electrochem Sci. 2013;8(3):3786–3793.
[109] Umer A, Naveed S, Ramzan N, et al. Selection of a suit-
able method for the Synthesis of copper nanoparticles.
Nano. 2012;7(5). DOI:10.1142/S1793292012300058.
[110] Singh P, Kim Y-J, Zhang D, et al. Biological synthesis of
nanoparticles from plants and microorganisms. Trends
Biotechnol. 2016;34(7):588–599. DOI:10.1016/j.tibtech.
2016.02.006.
[111] Varshney R, Bhadauria S, Gaur MS. A review: biolog-
ical synthesis of silver and copper nanoparticles. Nano
Biomed Eng. 2012;4(2):99–106. DOI:10.5101/nbe.v4i2.
p99-106.
[112] Hyeon T. Chemical synthesis of magnetic nanoparticles.
Chem Commun2003;(8):927–934. DOI:10.1039/B20
7789B.
[113] Xu J, Sun J, Wang Y, et al. Application of iron magnetic
nanoparticles in protein immobilization. Molecules
(Basel, Switzerland). 2014;19(8):11465–11486. DOI:10.
3390/molecules190811465.
[114] Patterson AL. The Scherrer formula for X-ray parti-
cle size determination. Phys Rev. 1939;56(10):978–982.
DOI:10.1103/PhysRev.56.978.
[115] Chekli L, Bayatsarmadi B, Sekine R, et al. Analyti-
cal characterisation of nanoscale zero-valent iron: a
methodological review. Anal Chim Acta. 2016;903:
13–35. DOI:10.1016/j.aca.2015.10.040.
[116] Gopal SV, Mini R, Jothy VB, et al. Synthesis and char-
acterization of iron oxide nanoparticles using DMSO
as a stabilizer. Mater Today. 2015;2(3):1051–1055.
DOI:10.1016/j.matpr.2015.06.036.
[117] Nosrati H, Salehiabar M, Bagheri Z, et al. Prepara-
tion, characterization, and evaluation of amino acid
modied magnetic nanoparticles: drug delivery and
MRI contrast agent applications. Pharm Dev Technol.
2018;23(10):1156–1167. DOI:10.1080/10837450.2018.
1536995.
[118] Das B, Kusz J, Reddy VR, et al. Solventless synthe-
sis, morphology, structure and magnetic properties of
iron oxide nanoparticles. Solid State Sci. 2017;74:62–69.
DOI:10.1016/j.solidstatesciences.2017.10.010.
[119] Babić-Stojić B, Jokanović V, Milivojević D, et al. Ultra-
small iron oxide nanoparticles: magnetic and NMR
relaxometric properties. Curr Appl Phys. 2018;18(2):
141–149. DOI:10.1016/j.cap.2017.11.017.
[120] Reddy LH, Arias JL, Nicolas J, et al. Magnetic nanopar-
ticles: design and characterization, toxicity and biocom-
patibility, pharmaceutical and biomedical applications.
Chem Rev. 2012;112(11):5818–5878. DOI:10.1021/
cr300068p.
[121] Lim J, Yeap SP, Che HX, et al. Characterization of
magnetic nanoparticle by dynamic light scattering.
Nanoscale Res Lett. 2013;8(1):381), DOI:10.1186/1556-
276X-8-381.
[122] Di Bona KR, Xu Y, Ramirez PA, et al. Surface charge
and dosage Dependent potential developmental toxic-
ity and biodistribution of iron oxide nanoparticles in
pregnant CD-1 mice. Reprod Toxicol. 2014;50:36–42.
DOI:10.1016/j.reprotox.2014.09.010.
[123] Roca AG, Gutiérrez L, Gavilán H, et al. Design
strategies for shape-controlled magnetic iron oxide
nanoparticles. Adv Drug Delivery Rev. 2019;138:68–104.
DOI:10.1016/j.addr.2018.12.008.
[124] Foner S. Versatile and sensitive vibrating-sample magne-
tometer. Rev Sci Instrum. 1959;30(7):548–557. DOI:10.
1063/1.1716679.
[125] Kashe MRGM, Shams SF, Jaafari MR. Perspective of
Fe3O4nanoparticles role in biomedical applications.
Biochem Res Int. 2016;1:1–32.
[126] Zahid M, Nadeem N, Hanif MA, et al. Metal fer-
rites and their graphene-based nanocomposites: syn-
thesis, characterization, and applications in wastewater
treatment. In: Abd-Elsalam K, Mohamed MPR, edi-
tor. In magnetic nanostructures. Nanotechnology in
thelifesciences.Cham:Springer;2019. p. 181–212.
DOI:10.1007/978-3-030-16439-3_10.
[127] Krzyminiewski R, Dobosz B, Schroeder G, et al. Focus-
ing of Fe3O4nanoparticles using a rotating mag-
netic eld in various environments. Phys Lett A.
2018;382(44):3192–3196. DOI:10.1016/j.physleta.2018.
07.051.
[128] Singh AK, Srivastava ON, Singh K. Shape and size-
dependent magnetic properties of Fe3O4nanoparti-
cles synthesized using piperidine. Nanoscale Res Lett.
2017;12(1):298, DOI:10.1186/s11671-017-2039-3.
[129] Faraji M, Yamini Y, Rezaee M. Magnetic nanoparticles:
synthesis, stabilization, functionalization, characteriza-
tion, and applications. J Iran Chem Soc. 2010;7(1):1–37.
DOI:10.1007/BF03245856.
[130] Roco MC, Harthorn B, Guston DSP. Innovative and
responsible governance of nanotechnology for societal
development. In Nanotechnology research directions
for societal needs in 2020. Dordrecht: Springer; 2011.
p. 561–617. DOI:10.1007/978-94-007-1168-6_14.
[131] Ajinkya N, Yu X, Kaithal P, et al. Magnetic iron
oxide nanoparticle (Ionp) synthesis to applications:
present and future. Materials (Basel). 2020;13(20):1–35.
DOI:10.3390/ma13204644.
[132] Lee J-H, Huh Y-M, Jun Y, et al. Articially engi-
neered magnetic nanoparticles for ultra-sensitive molec-
ular imaging. Nat Med. 2007;13(1):95–99. DOI:10.1038/
nm1467.
[133] Huang P-H, Zhao S, Bachman H, et al. Acoustou-
idic synthesis of particulate nanomaterials. Adv Sci.
2019;6(19):1900913, DOI:10.1002/advs.201900
913.
[134] Buzea C, Pacheco II, Robbie K. Nanomaterials and
nanoparticles: sources and toxicity. Biointerphases.
2007;2(4):MR17–MR71. DOI:10.1116/1.2815690.
[135] Hlaing H, Lu X, Hofmann T, et al. Nanoimprint-
induced molecular orientation in semiconducting poly-
mer nanostructures. ACS Nano. 2011;5(9):7532–7538.
DOI:10.1021/nn202515z.
[136] Patil AG, Kounaina K, Aishwarya S, et al. Myco-
nanotechnology for sustainable agriculture: challenges
andopportunities.InRecenttrendsinmycological
research. Cham: Springer; 2021. p. 457–479. DOI:10.
1007/978-3-030-60659-6_20.
[137] Geppert M, Himly M. Iron oxide nanoparticles in
bioimaging – an immune perspective. Front Immunol.
2021;12(June):688927. DOI:10.3389/mmu.2021.688
927.
