MINISTRY OF EDUCATION AND TRAINING
VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY
GRADATE UNIVERSIY OF SCIENCE AND TECHNOLOGY Pham Hong Nam STUDY OF MAGNETIC INDUCTION HEATING MECHANISMS
OF SPINEL FERRITE NANOPARTICLES
M1-xZnxFe2O4 (M = Mn, Co)
Major: Electronic materials
Code: 62.44.01.23
SUMMARY OF DOCTORAL THESIS IN MATERIAL SCIENCE
Ha Noi - 2018
This thesis was done at:
Laboratory of Biomedical Nanomaterials, Institute of Materials and Sciene,
Vietnam Academy of Science and Technology.
Supervisor: Assoc.Prof., Dr. Do Hung Manh
Assoc.Prof., Dr. Pham Thanh Phong
Reviewer 1: .....................................................
Reviewer 2: .....................................................
Reviewer 3: .....................................................
The dissertation will be defended at Graduate University of Science and Technology, 18
Hoang Quoc Viet street, Hanoi.
Time: .............,.............., 2018
This thesis could be found at National Library of Vietnam, Library of Graduate
University of Science and Technology, Library of Institute of Materials and Science,
Library of Vietnam Academy of Science and Technology.
INTRODUCTION
Currently, application of nanoparticle in magnetic hyperthermia has been
increasingly researched and developed, espescially mechanisms relating heat induced
process of nanoparticles. Studies mainly use Linear Respones Theory (LRT) to
calculate Specific Loss Power (SLP). However, this theory is not always suitable in
Magnetic Induction Heating (MIH). Accordingly, application of Stoner-Wohlfarth
(SW) model is necessary. The first study of Hert related to thermal mechanism
magnetic particles being distinguised between hysteresis loss and relaxation loss.
However, this distinction was not enough to establish a full theoretical model for
accurate calculation of SLP. A recent study demonstrated the effet of hysteresis to
heat induction by using numerical simulation. Although the obtained results were
suitable the authors have not established a full theoretical model for solving the SLP
issue. Some reports showed that physical factors such as size, shape, and content
effect on the SLP value. In which, the effective anisotropy constant (Keff) and size (D)
of magnetic particle play the most important effect.Carrery et.al demonstrated that
materials with different Keff s are consistent with theory models depending on the Keff
value. Materials with high Keff is consistent with the LRT model. In constrast, SW model materials with consistent with low the is Keff
Based on these theory models, the optimal SLP value is calculated by determining the
optimal values of Keff and D. These values depend on characteristics of nanoparticle
including content, synthesis condition and material structure. Therefore, how to select
theoretical model for calculating SLP of materials is very interesting.
In Vietnam, magnetic nanopartices for biomedical application are concerned
by a number of research groups at Institute of Materials Science (IMS), Institute for
Tropical Technology (ITT), Hanoi University of Science and Technology (HUST)...
However, only research group at IMS studies deeply about physical mechanisms
relating to hyperthermia. The research group not only focuses on fabircation of spinel
ferrite nanoparticles (Fe3O4, MnFe2O4, CoFe2O4), manganite nanoparticles (LSMO), alloy nanoparticles (CoPt, FeCo) but also figures out physical mechanisms through
experimental results and theoretical calculation. However, contribution of each
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physical mechanism in nanoparticles is not fully calculated .
Fe3O4 magnetic nanoparticle is alway the best selection for in-vitro and in-vivo
magnetic hyperthermia thanks to easy fabrication and excellent biocompatibility.
However, the Curie temperature (TC) of Fe3O4 (TC = 823K) is much higher than the
required temperature for killing cancer cell. Thus, the saturation heating temperature
is controlled by changing nanoparticle concentration and magnetic fied intensity. Recently, magnetic nanoparticles with suitable Curie temperature (TC = 42 - 46oC), high saturation magnetisation and good biocompatibility have been focusing. The
spinel- structured nanomaterial M1-xZnxFe2O4 (M= Mn, Co; 0,0 ≤x≤0.7) is high
potential because of good ability in controlling TC (or saturation heating temperature).
In addition, CoFe2O4 nanoparticle have attracted a great deal of attention thanks to
high anisotropy constant. Therefore, this material has high SLP value.
Based on the above reasons, we chose the research project for thesis, namely:
Study of Magnetic Induction Heating mechanisms of spinel ferrite nanoparticles
M1-xZnxFe2O4 (M=Mn, Co) Research object of the thesis:
Spinel ferrite nanoparticle M1-xZnxFe2O4 (M = Mn, Co; 0,0 ≤ x ≤ 0,7).
Research targets of the thesis:
Fabricating spinel ferrite nanoparticle M1-xZnxFe2O4 (M = Mn, Co; 0,0 ≤x≤0,7)
with controlled parameters affecting to Hc, TC and D.
Establishing semi-experimental models based on experimental results to
explain the correlation between SLP and (Keff, D) in order to figure out suitable
mechanisms for calculating SLP value of CoFe2O4 nanoparticle
Scientific and practical meaning of the thesis:
Applying 2 theoritical models (LRT and SW) to figure out physical
mechanisms contributing to the formation of SLP which helps to more clearly
understand about MIH in order to apply magnetic nanoparticle.
Research methodology:
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The thesis was carried out by practical experimental combining with numerical data process. Random samples were fabricated by hydrothermal and thermal decomposition synthesis. Samples were characterized by electron microscopes (FESEM and TEM). Magnetic properties of material were investigated by Vibrating- Sample Magnetometer (VSM), PPSM, SQUID. FTIR, TGA were used to evaluate the
presence of functional groups on magnetic nanoparticles. DLS was used to determind the hydrodynamic diameter and stability of magnetic fluid. Magnetic Induction Heating was carried out on 2 equipments: RDO-HFI- 5 kW and UHF-20A- 20 kW.
Research contents of the thesis:
Investigating the effect of fabrication parameters (reaction time, temperature, Zn content) on structure and magnetic properties of M1-xZnxFe2O4 nanoparticles (M = Mn, Co; 0,0 ≤ x ≤ 0,7).
Investigating the effect of particle size on structure and magnetic properties of
CoFe2O4 nanoparticles
Investigating the correlation between D, Keff for SLP. Calculating and optimizing SLP based on particle size by numerical data process and experimental results. Using critical parameters of LRT and SW models to evaluate physical mechanisms in formation of SLP of nanoparticles with different sizes.
Evaluating toxicity of magnetic fluid for hyperthermia testing on cancer cells.
Layout of the thesis:
The contents of thesis were presented in 5 chapters. Chapter 1 is review of spinel ferrite materials. Chapter 2 is about physical mechanisms and theoretical models applying in magnetic induction heating (MIH). Chapter 3 presents experimental methods for fabricating nanoparticles. Chapter 4 is the results of fabrication of M1-xZnxFe2O4 (M=Mn, Co; 0,0 ≤ x ≤ 0,7) obtained by hydrothermal method. Chapter 5 is the results of fabrication of CoFe2O4 obtained by thermal decomposition method.
Research results of the thesis were published in 07 scientific reports including: 02 ISI reports, 03 national reports, 02 reports in national and international scientific workshop.
Main results of the thesis:
Investigated effect of fabrication paramters on structure and magnetic
properties of M1-xZnxFe2O4 (M=Mn, Co; 0,0 ≤ x ≤ 0,7).
Fabricated CoFe2O4 nanoparticles with different size. The effect of size on magnetic properties and SLP values was studied. Applying numerical data process to
find out the optimal size for magnetic induction heating. Using critical parameters of
LRT and SW models evaluate the mechanism contributing to formation of SLP.
Evaluated toxicity of magnetic fluid, carried hyperthermia experiment on
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cancer cell (Sarcoma 180).
Chapter 1. REVIEW OF SPINEL FERRITE MATERIALS
1.1. Structure and magnetic properties of spinel ferrite materials
1.1.1. Structure of spinel ferrite materials
Ferrite spinel is term of materials which have structure containing 2 crystal
lattices. The interaction between 2 crystal lacttices is ferromagnetic interaction. An unit cell of spinel ferrite crytal ( lattice constant – a ≈ 8,4 nm) is formed by 32 O2- , Zn2+, Co2+, Mn2+, Ni2+, Mg2+, Fe3+ and Gd3+). There are 96 atoms and 24 cations (Fe2+ positions for cations (64 octa-positions, 32 tetra-positions).
1.1.2. Magnetic property of spinel ferrite materials
Based on molecular field theory, the origin of magnetic property of spinel
ferrite material is the result of indirect interaction between metal ions (magnetic ions)
locating in two lattices A and B through oxygen ions
1.2. Effecting factors on magnetic property of spinel ferrite nanoparticles
Magnetic property of spinel ferrite nanoparticls is determined by factors
including size, shape and content.
1.3 . Dynamic state of magnetic nanoparticles
1.3.1. Non-interacting magnetic nanoparticles
s) for non-interacting
- 10-13
Based on classical theory, spin- reversed speed of particle through potential
energy depends on thermal energy and frequency according to Arrehenius law, calculating equation of relaxation time (τ0 ~ 10-9 magnetic nanoparticles.
1.3.2. Weakly interacting magnetic nanoparticles
Shtrikmann and Wohlfarth used mean field theory to establish the expression
of releaxtion time of weaky interacting magnetic nanoparticles under Vogel-Fulcher
law.
1.3.3. Strong interacting magnetic nanoparticles
By measuring the change of phase transition temperature by frequency in a
wide range, the state of material could be determined whether spin glass or not when
processing data by critical slowing down model.
1.4. Biomedical application of magnetic nanoparticle
Magnetic nanoparticle has been studying for 4 medical applications including
cell separation, drug delivery, MRI and magnetic hyperthermia
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Chapter 2. PHYSICAL MECHANISMS AND THEORETICAL MODELS
APPLIED IN MAGNETIC INDUCTION HEATING (MIH)
2.1. Induction heating mechanism of magnetic nanoparticls under AC magneitic
field
2.1.1. Relaxation mechanism (Néel and Brown)
In case of single domain size, anisotropic energy is smaller than heat energy,
spin of nanoparticle could rotate every direction even without magnetic field. If
roating spin while keeping particle in one direction then after a period of time, spin
will return to the original position. That is Néel relaxtion time.
Néel relaxation is rotation of moment of magnetic nanoparticle. Brown
relaxation is the movement of magnetic nanoparticls in liquid.
2.1.2. Hysteresis loss mechanism
Hysteresis loss is energy loss in a magnetism process, determined by the area
of hysteresis loop of material. This process strongly depends on magnetic field
intensity and intrinsic property of mangnetic nanoparticle.
2.1.3. Other mechanisms
Beside 2 above mechanisms, induction heating of magnetic nanoparticle
induces heat under AC magnetic field also happens by another mechanism. That is
the loss induced by friction in liquid.
2.2. Theoretical models
2.2.1. Stoner-Wohlfarth (SW) model
The SW model is a theoretical model use calculating the area energy of the
delay of material when it magnetized to saturated. LRT model is not suitable for
materials without supperparamagnetism. Accordingly, SW model is used.
Theoretically, some authors calculated magnetic resistance force by following
[
] (2.16)
equation:
2.2.2. LRT model
LRT model describes the linear reponse of magnetic moments under magnetic
field. The simulation result of magnetism process by magnetic field shows the
linearity with magnetic field at < 1. This is the condition for application of LRT
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model.
2.3. Calculation methods of Specific Loss Power (SLP)
2.3.1. Theoretical calculation of SLP
For non-interacting superparamagnetic nanoparticle under AC magnetic field,
(2.21) maximum SLP is calculated by following equation:
2.3.2. Experimental calculation of SLP
a) Heat measurement method
This is the most common method for determining heat induction capacity of
magnetic liquid. SPL value is calculated by the rate of increasing temperature:
(2.24)
b) Hysteresis loop measurement method
SLP is calculated from hysteresis loop corresponding to applied magnetic field:
∮
(2.27)
2.4. State of art of Magnetic Heat Induction study
Studies of MHI used many materials such as single nanoparticle, exchange-
coupled materials, core-shell materials. Supperparamagnetic nanoparticles, Fe3O4 and γ-Fe2O3, are most common studied thanks to good biocompatibility, specially success in MRI apllication.
Chapter 3. EXPERIMENTAL METHODS
3.1. Fabrication of M1-xZnxFe2O4 (M = Mn, Co; 0,0 ≤ x ≤ 0,7) nanoparticle by hydrothermal method
M1-xZnxFe2O4 (M = Mn, Co; 0,0 ≤ x ≤ 0,7) nanoparticles were fabricated by
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hydrothermal method described in the following diagram (Figure 3.1.)
Figure 3.1. Fabrication process of M1-xZnxFe2O4 (M = Mn, Co; 0,0 ≤ x ≤ 0,7) nanoparticles.
3.2. Fabrication of CoFe2O4@OA/OLA nanoparticles by thermal decomposition method
CoFe2O4@OA/OLA nanoparticles were fabricated by thermal decomposition
method described in the following diagram (Figure 3.2.) :
Figure 3.2. Fabrication process of Figure 3.2. PMAO encaosulation
process. CoFe2O4 @OA/OLA nanoparticles
3.2.3. Phase transition of magnetic nanoparticle from organic solvent to water
Phase transition process of magnetic nanoparticle from organic solvent to
water was performed in the following diagram (Figure 3.5.)
3.3. Characterization methods
Samples were characterized by electron microscopes (FESEM and TEM).
Magnetic properties of material were investigated by Vibrating-Sample Magnetometer
(VSM), PPSM, SQUID. FTIR, TGA were used to evaluate the presence of functional
groups on magnetic nanoparticles. DLS was used to determind the hydrodynamic
diameter and stability of magnetic fluid. Magnetic Induction Heating was carried out
on 2 equipments: RDO-HFI- 5 kW and UHF-20A- 20 kMaterial structure was studied
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by X-ray diffraction, electron microscopy.
3.4. Toxicity evaluation of magnetic fluid on cancer cell
Evaluating cancer cell killing ability of magnetic fluid on cancer cell.
3.5. Magnetic hyperthermia of magnetic fluid on cancer cell
Evaluating death ratio of cancer cell after magnetic hyperthermia by changing
temperature and magnetic fied application time.
Chapter 4. STRUCTURE, MAGNETIC PROPERTY AND MAGNETIC
INDUCTION HEATING OF M1-xZnxFe2O4 (M = Mn, Co; 0,0 ≤ x ≤ 0,7)
NANOPARTICLES FABRICATED BY HYDROTHERMAL METHOD
4.1. Effect of reaction temperature on structure and magnetic property
4.1.1. Effect of reaction temperature on structure
Figure 4.1. X-ray diffraction of samples: MnFe2O4 (a) and CoFe2O4 (b) at different
temperatures in 12 hours.
Figure 4.1a and 4.1b are the X-ray diffraction of MnFe2O4 and CoFe2O4
nanoparticles fabricated by hydrothermal method at different temperatures, coded: 120oC (MnFe1, CoFe1), 140oC (MnFe2, CoFe2), 160oC (MnFe3, CoFe3) and 180oC
(MnFe4, CoFe4) with reaction time of 12 hours. It was showed that both kinds of
sample are single crystal expressed at characteristic peaks (220), (311), (222), (440),
(442), (511), (440). When increasing temperature reaction, particle size of two kinds
of sample increases.
4.1.2. Effect of reaction temperature on magnetic property
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Saturation magnetism Ms increases from 31,1 emu/g (MnZn1) to 66,7 emu/g (MnZn4) (Figure 4.4a) and from 59,3 emu/g (CoZn1) to 68,8 emu/g (CoZn4) when changing reaction temperature from 120oC to 180oC (Figure 4.4b).
Figure 4.4. Hysteresis loop of MnFe2O4 (a) và CoFe2O4 (b) nanoparticles fabricated at different temperature. Smaller figures are hysteresis loops at low magnetic field.
4.2. Effect of reaction time on structure and magnetic property
4.2.1. Effect of reaction time on structure
Changing reaction time: 6h, 8h, 10h, 12h at reaction temperature 180oC for
fabrication of MnFe2O4 và CoFe2O4 nanoparticles coded: (MnFe7, CoFe7); (MnFe6, CoFe6); (MnFe5, CoFe5) và (MnFe4, CoFe4), all sample are single crystal with
ferrite spinel structure. Reaction time increasing led to increasing diffraction peak
intensity, decreasing peak wide which determine the decrease of particle size.
4.2.2. Effect of reaction time on magnetic property
Figure 4.8. Hysteresis loops of MnFe2O4 (a) and CoFe2O4 (b) fabricated at different
reaction times. Smaller figures are hysteresis loops at low magnetic field
Figure 4.8 are hysteresis loops of MnFe2O4 and CoFe2O4 nanoparticles
measured under mangetic field from -11 kOe to 11 kOe. In both kinds of sample,
decreasing reaction time from 12h to 6h led to reduction of Ms. Magnetic resistance 9
force Hc for both kinds of samples changed but it did not follow the law of Herzer
which is that Hc decreases when particle size decreases only in single domain size
range. 4.3. Effect of Zn2+ content on structure and magnetic property 4.3.1. Effect of Zn2+ content on structure
With the aim of fabricating materials possessing Curie temperature lower than 42oC-46oC (temperature kills cancer cell), we studied effect of Zn2+ on structure and
magnetic property of Mn1-xZnxFe2O4 và Co1-xZnxFe2O4 (x = 0,0; 0,1; 0,3; 0,5 và 0,7)
nanoparticles, coded: MnZn0, MnZn1, MnZn3, MnZn5 và MnZn7; CoZn0, CoZn1, CoZn3, CoZn5 và CoZn7. All samples were fabricated at 180oC in 12h. X-ray
diffraction in figure 4.9 show that both kinds of sample are single phase spinel
xZnxFe2O4, meaning that the size of Mn1-xZnxFe2O4 nanoparticle is bigger than that of Co1-xZnxFe2O4 nanoparticle. In one kind of sample, increasing Zn2+ leads to decreasing intensity of diffraction peaks showing that the particle size decreases.
structure. However, diffraction peaks of Mn1-xZnxFe2O4 are sharper than that of Co1-
Figure 4.9. X-ray diffractions of Mn1-xZnxFe2O4 nanoparticles (x = 0,0; 0,1; 0,3; 0,5
and 0,7) (a) and Co1-xZnxFe2O4 nanoparticles (x = 0,0; 0,1; 0,3; 0,5 và 0,7) (b).
4.3.2. Effect of Zn2+ content on magnetic property
Figure 4.14 shows hysteresis loops of Mn1-xZnxFe2O4 nanoparticles (x = 0,0;
0,1; 0,3; 0,5 và 0,7) measured at room temperature. Compared to MnZn0 sample
without Zn, Ms achieved the highest values at 66,7 emu/g and gradualy decreased when increased Zn2+ content. MnZn7 sample had the lowest value at 29,8 emu/g.
Temperature dependence of magnetism of samples measured at 100 Oe, in Field
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Cooled manner was showed in figure 4.15. Samples exhibited the ferromagnetic-
paramagnetic phase transition at differrent TC. TC values of MnZn0, MnZn1, MnZn3,
MnZn5 và MnZn7 were 620 K, 560 K, 440 K, 350 K và 330 K.
Figure 4.14. Hysteresis loops of Figure 4.15. Temperature
dependence of magnetism of Mn1-xZnxFe2O4 (x = 0,0; 0,1; 0,3; 0,5
and 0,7). Smaller figure is hysteresis
loop at low magnetic field. Mn1-xZnxFe2O4 (x = 0,0; 0,1; 0,3; 0,5 and 0,7) measured at 100 Oe.
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For Co1-xZnxFe2O4 nanoparticles (x = 0,0; 0,1; 0,3; 0,5 and 0,7), the change of Ms was similar to Mn1-xZnxFe2O4 nanoparticles. Ms decreased when increasing Zn2+ content, achieving the highest value at 68,8 emu/g at x = 0,0. The reduction of saturation magnetism of Co1-xZnxFe2O4 nanoparticels could be explained by core- shell structure. In this structure, the core has magnetism, shell is considered as non- magnetism because of that spin on the surface of shell arrange disorderly. Temperature dependence of magnetism of Co1-xZnxFe2O4 (x = 0,0; 0,1; 0,3; 0,5 and 0,7) measured in FC and ZFC (Zero Field Cooled - ZFC) manners at 100 Oe was showed in figure 4.17. From the results, TC and Blocking temperaute (TB) were determined. Below TB , randomly orriented spins are “locked” at non-stable state. This state is gradually lost when temperature increase to TB. Under magnetic field, spins are oriented in the direction of magnetic field. Thus, magnetism value measured in FC manner is higher than that in ZFC manner and little changes at T < TB .
Interaction betwwen magnetic
4.4. nanoparticles
Some studies demonstrated that at nano scale, materials have some differents properties compared to bulk materials. When the size of than the critical size material is smaller
⁄ (
(magnitude
Figure 4.17. Temperature dependence of Co1-xZnxFe2O4 nanoparticles (x = 0,0; 0,1; 0,3; 0,5 and 0,7) measured in FC and ZFC manners at 100 Oe.
of exchange interaction, K- anisotropy constant, M- Spontaneous magnetism), each nanoparticle is single domain with spin about 104 Bohr magneton and called “super spin”. There are 2 kinds of super spin: non/weakly interacting super spin (inducing superparamagnetim) and strongly interacting super spin (inducing spin glass state). Both cases are not same and verry difficult to distinguish. There are some measurements and theoretical models to study intrinsic magnetic property of nanoparticles. In case of strongly interacting magnetic nanoparticles, critical slow model is the best to study this case. In case of non interacting magnetic nanoparticles, Néel-Brown model is suitable for studying experimental data. In other way, if there is interaction between nanoparticles but not enough to induce spin glass state, Vogel-Fulcher model will be used to study the magnetic property. Based on these information, we chose these theoretical models along with our experimental data to figure out magnetic interaction of MnZn7 and MnZn5 samples. The obtained results showed that these samples fit the critical slow model.
4.5. Self-regulated Magnetic Induction Heating 4.5.1. MnZn7 and MnZn5 nanoparticles
Figure 4.31 is the magnetic induction heating of MnZn7 nanoparticle at different concentrations: 3 mg/ml, 5 mg/ml, 10 mg/ml và 15 mg/ml under different magnetic fields (50-80 Oe, 236 kHz). It was showed that the magnenetic induction heating increases along with the increase of magnetic field. Temperature increases linearly at the fist stage from bigining to 250s. After that temperature increases slower and reaches almost saturation at 1500s. Moreover, Tb at 1500s are alway lower than 48oC and TC (55oC) when increasing both magnetic field intensity and 12
concentration of magnetic nanoparticles. This could be explained by the escapse of a part of heat to outside. Therefore, Tb in all experimental conditons are alway smaller than TC.
Figure 4.31. Magnetic induction heating of MnZn7 at different magnetic field
intensities,236 kHz,
concentrations: 3mg/ml (a), 5 mg/ml (b), 10 mg/ml (c) and 15 mg/ml (d).
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The fast increase of temperature at the first stage is the result of hysteresis loss, relaxation loss (Néel, Brown) and vortex current loss. Other way, superparamagnetic state at room temperature was obseverd on MnZn7 sample. Therefore, the Magnetic induction heating of MnZn7 is the result of relaxation loss (Néel, Brown). H2 dependence of SLP at different concentrations is showed in figure 4.32. SLP depends linearly with H2 at determined concentrations. Therefore, the obtained results fit with LRT model, meaning that the obtained SLP is only the result of relaxation mechanism (Néel, Brown). Calculated SLP of MnZn5 shows that when concentration of magnetic nanoparticles increases from 3mg/ml to 7 mg/ml, SLP decreases from 28,38 W/g to 25,52 W/g at 80 Oe. The increase of magnetic
nanoparticle concentration increases the aggregation of nanoparticles in liquid leading to the increase of dipole-dipole interaction and the reduction of inducting heat. The result demonstrated that concentration increase is not the reason for high SLP.
4.5.2. CoZn7 and CoZn5 nanoparticles
increases linearly
Figure 4.36 is the magnetic induction heating of CoZn7 and CoZn5 at different the magnetic fields from 50-80 Oe with mangnetic concentrations of 1 mg/ml and 3 mg/ml. At the first stage from the beginning to 350s, in all temperature experimental conditions. Figure 4.32. H2 denpendence of SLP at different concentrations of magnetic nanoparticles
Figure 4.36. Magnetic induction heating of CoZn7 at concentrations of 1 mg/ml (a),
3 mg/ml (b); CoZn5 at concentrations of 1 mg/ml (c), 3 mg/ml (d), measured under
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different magnetic fields from 50 to 80 Oe, frequency 178 kHz.
After the first stage, temperature increases slower and reaches almost
saturation at 1500s. Induced heat depends on magnetic field intensity at the same
frequency (178 kHz). Increasing magnetic field intensity leads to increase of Tb. In addition, (ΔT) of CoZn7 and CoZn5 at different concentrations at the beginning to the
end of applying magnetic field increases when increasing magnetic field intensity
from 50 to 80 Oe. It is showed that when increasing magnetic field intensity, SLP of
CoZn7 increases for both concentrations (1 mg/ml and 3 mg/ml). SLP of CoZn7 (1
mg/ml) are 20,48 W/g (50 Oe) and 64,37 W/g (80 Oe). Obtained experimental SLP was fit by SLP Hα law with α > 2 at different concentrations. Therefore, SLP does not fit with LRT model (SLP H2).
4.5.3. Comparition of SLP between experimental data and LRT model using size
distribution
In theoretical study, size (D) of nanoparticle is often used with σ = 0. In fact,
for any synthesis method, size of obtained nanoparticle always has σ > 0. The
obtained results showed that MnZn5 and MnZn7 is suitable with LRT model,
meaning that the mechanism of formation of SLP is only (Neél and Brown)
relaxation loss. In contrast, for CoZn5 and CnZn7 samples, SLPHC is higher than SLPLRT. It is said that hysteresis loss happens in these two samples. This result fits with experimental data (SLP does not fit with LRT model (SLP H2)).
In conclusion, changing temperature, time and Zn2+ content lead to change of size and magnetic property. Study of magnetic induction heating of MnZn7, MnZn5,
CoZn7, CoZn5 nanoparticles shows that SLP increases when increasing magnetic
field intensity and decreases when increasing magnetic nanoparticle concentration. In case of MnZn7 and MnZn5 samples, SLP depends linearly with H and follows H2 law. However, in case of CoZn7 and CoZn5 samples, SLP depends linearly with H bit does not follow H2 law with α > 2.
Chapter 5. MAGNETIC INDUCTION HEATING, TOXICITY AND CANCER
HYPERTHERMIA OF MANGNETIC NANOPARTICLE (
CoFe2O4@OA/OLA-PMAO) FABRICATED BY THERMAL DECOMPOSITION
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5.1. Structure and magnetic property of CoFe2O4@OA/OLA nanoparticle 5.1.1. Structure and morphology of CoFe2O4@OA/OLA nanoparticle
Figure 5.1 shows X-ray diffraction of CF1, CF2, CF3 and CF4 samples
fabricated by thermal decomposition
method. All samples are single phase
spinel structure with the mean size of
6,3 nm, 8,6 nm, 10,6 nm và 20,6 nm,
standard deviations calculated by
LogNormal are ± 0,8 nm (12,6%), ± 1,3
nm (15%), ± 1,5 nm (15%) và ± 2,4 nm
(11,2%).
Hình 5.1. Giản đồ nhiễu xạ tia X của mẫu
5.1.2. Magnetic property of
CF1, CF2, CF3 và CF4 được tổng hợp
CoFe2O4@OA/OLA nanoparticles
bằng phương pháp phân hủy nhiệt.
Figure 5.3 shows hysteresis loops
of samples measured at 300 K. CF4 sample has highest saturation magnetism of 70
emu/g, (smaller than saturation magnetism of bulk material: 80 emu/g). Sizes of CF1
and CF2 samples are smaller than 10 nm and their Hcs are nearly zero, meaning that
they exhibit superparamagnetic state at room temperature.
Figure 5.3. Hysteresis loops o CF1, Figure 5.4. Temperature dependene
CF2, CF3 and CF4 samples. Smaller of magnetism of CF1, CF2, CF3 and
figure is hysteresis loop at low CF4 samples measured in FC-ZFC
magnetic field manner under mangetic field of 100
Oe.
Ferromagnetism is exhibited on CF3 (Hc = 40 Oe) and CF4 (Hc = 480 Oe) and
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particle size beyond the critical size range of superparamagnetism. Both Ms and Hc
increases when particle size increases. Ms is low with small size and reaches highest
value at size of 20,6 nm. Figure 5.4 shows temperature denpendence of magnetism
measured in FC and ZFC manners under 100 Oe. CF1, CF2 and CF3 samples have
maximum points (TB) on ZFC line.
5.2. Phase transfer of CoFe2O4@OA/OLA nanoparticle using PMAO
For biomedical applications, one of essential requirements is aqueous
dispersion. Figure 5.7 is the images of CF3 sample before and after encapsulation of
PMAO (which is an amphiphilic polymer) in hexan and water. It is seen that before
encapsulation of PMAO, the nanoparticles is well-dispersed in hexan and absolutely
can not disperssed in water (Figure 5.7a and 5.7b). After encapslutated by PMAO,
surface of CoFe2O4 becomes hydrophylicity and well-dispersed in water (figure 5.7c and 5.7d). Furthermore, magentic nanparticles after encapsulated by PMAO still have
strong magnetism (figure 5.7e).
Hình 5.7. CoFe2O4 nanoparticle before and after encapsulating PMAO in hexane (a)
in in mixture of hexane and water (b); CoFe2O4 nanoparticle encapsulated by PMAO
in water (c) and in mixture of hexane and water (d).CoFe2O4 encapsulated by PMAO
in mixture of hexane and water under application of magnet (e). For mixture of
hexane and water, the upper part is hexane,the under part is water.
5.3. Magnetic induction heating of CoFe2O4@OA/OLA-PMAO nanoparticle
5.3.1. Heat inducing capacity of o CoFe2O4@OA/OLA-PMAO nanoparticle
To understand effect of magnetic field parameters (H,f) to heat inducing
process of magnetic liquid (CF1, CF2, CF3, and CF4 transfered to aqueous
environment with the magnetic nanoparticle concentration of 1 mg/ml, magnetic
induction heating was carried out at H (100-300 Oe) and f (290-450 kHz) with the 17
rule that when H changes, f is fixed and reverse. Based on experimental data, SLP
value was calculated. The obtained results showed that there are changes at different
H and f for all samples. This trend demonstrated that the temperature changing
process at the beginning stage of magnetic induction heating process in fist 300s.
From the calculated results, maximum SLP (297,4 W/g, 300 Oe, 450 kHz) was
reached at particle size of 10,6 nm.
5.3.2. Contributing mechansims and Specific Loss Power, Neél and Brown
Figure 5.22. SLPhys, SLPB, SLPN and SLP depend on magnetic field of different magnetic liquids
Early studies suggested that SLP of superparamagnetic nanoparticle only
depends on Néel and Brown relaxation. The interference of two processes depends on
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anisotropic constant Keff and particle volume V. Néel relaxation time τN depends on (eα) of Keff and V, meanwhile, Brown relaxation time (τB ) changes linearly with V and viscosity (η) of solvent. Suggesting that viscosity of magnetic nanoparticle is similar to water η =1,01x10-3 Pa.s = 1,01x10-3 kg.m-1.s-1 Neél and Brown relaxation
time will be calculated. When two losses happen at the same time, sorter relaxation
time will predominate.
In magnetic induction heating, there are 3 main mechanisms including
hysteresis loss (SLPhys), Neél relaxation loss (SLPN) and Brown relaxation loss
(SLPB). The constribution of each mechanism on the formation of SLP is different
depending on Keff and D. Therefore, the estimation of each mechanism on SLP is very difficult. For estimating Brown relaxation, 1mg/ml of CF1, CF2, CF3 and CF4
encapsulated by PMAO were dispersed in agar solution (2%), SLPhys of samples are
showed in figure 5.22.
5.3.3. Theoretical and experimental optimal size
LRT model was used to optimize experimental paramters in magnetic
induction heating. In this model, optimal particle volume (Vopt) is determinded by
⁄ (5.3)
)
(
J.m-3 and 14 nm, Keff = 1,8x105
kB – Boltzmann constant (1,38 x 10-23 J.K-1), T - (300 K), f -frequency (kHz), τo J.m-3), – standard relaxation time (10-9 s), Keff –anisotropic constant ((1,8-3,0) x 105 μoHmax – applied magnetic field (4 x 10-7 H.m-1 x μoHmax A.m-1) and Ms –saturation magnetism (336 kA.m-1). f = 450 kHz, Hmax = 24 kA.m-1, Dopt = [6x(V/)]1/3 = 8 nm, J.m-3. For this calculation, optimal size Keff = 3,0x105 is in the range of 8 nm - 14 nm.
following equation:
5.3.4. SW and LRT theoretically model
Theoretically, SLP is an important parameter to evaluate heat inducing
capacity of magnetic liquid and determined by the following equation:
(5.5)
A3 is calculated by quation 5.6 or 5.7 depeding on = KeffV/kBT (ratio of
anisotropic energy and heat energy):
* + (5.6)
or
* + (5.7)
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is a multivariable function. It is difficult to calculate SLP of material. To understand clearly the effect of anistropic constant on SLP, LRT model was used to
calculate SLP of CF1, CF2, CF3 and CF4 by using experimental data in case of
with:
(5.8)
Other way, SW model showed good results for multi domain nanoparticles
when k < 0,7:
(
) (5.9)
To determine which model is the most suitable, experimental data was used to
calculate. The obtained results showed that CF1, CF2 and CF3 have < 1, k > 0,7,
CF4 has , not suitable with LRT model.
5.4. Stability and toxicity of CoFe2O4@OA/OLA-PMAO magnetic fluid. fluid Stability of magnetic in
physiological environment is an important
requirement for biomedical application. In
body, salt concentration is in the range of
165 ÷ 180 mM, pH 7,5. Therefore, the
stability of magnetic fluid was examinded in
aqueous solution with the salt concentrations
of 165 mM, 180 mM, 200 mM, 220 mM và
Figure 5.32. Proliferation of 250 mM and pH: 1, 2, 4, 5, 7, 9 and 11. The
Sarcoma 180 cell at different results showed that magnetic fluid
magnetic nanoparticle concentration is
containing CoFe2O4@OA/OLA-PMAO stable enough for biomedical application.
CF3 sample was test toxicity on cancer cell (Sarcoma 180). Cells were cultured
in 96-well plate with density of 2000 cells/well before adding CF3 magnetic
nanoparticle at concentrations of 100 µg/ml (C1), 50 µg/ml (C2), 25 µg/ml (C3), 12,5
µg/ml (C4), 6,25 µg/ml (C5), 3,125 µg/ml (C6) và 1,56 µg/ml (C7). The proliferation of Sacroma 180 cell was different at different concentrations of CF3 (Fiugre 5.32).
The results showed that CF3 magnetic fluid is not toxic on Sacroma 180 at studied
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concentrations.
5.5. Hyperthermia on Sacomar 180 cell.
CF3 magnetic fluid with the
concentration of 100 µg/ml
(corresponding to 0,04 ng/cell) was
selected for hyperthermia experiment on
Sacomar 180 cell. Two hyperthermia
methods were carried out: method 1:
appling magnetic field to induce heat
from magnetic nanoparticle, method 2:
Figure 5.37. Cell death (%) at different using magnetic stirrer to heat the sample
experimental conditions. (MHT). Figure 5.37 shows the cell death
at different experimental conditions (EHT): T1: cancer cell control, cell death: 9,3%;
T2: magnetic nanoparticle control, cell death: 10,6%; T3: magnetic field control, cell death: 10,4%; T4: magnetic hyperthermia at 40oC, 10 min, cell death: 10,5%; T5: magnetic hyperthermia at 42oC, 1 min, cell death: 14,8%; T6: magnetic hyperthermia at 42oC, 3 min, cell death 73,5%; T7: magnetic hyperthermia at 42oC, 5 min, cell death: 93,7%; Exogenous heating at 42oC, 1 min, cell death 17,1%; T9: Exogenous heating at 42oC, 3 min, cell death 19,4%; T10: Exogenous heating at 42oC, 5 min, tế
cell death 23,2%; T11: cell death, after 15 minutes (at T7), cell death 98,7%. Magnetic hyperthermia induced 90% cell death at 42oC in 5 min.
In conclusion, SLP value of CoFe2O4 magnetic fluid increases linearly with H
and f. CF1, CF2, CF3 sample is suitable with LRT model, SW model is suitable for
CF4 sample. Toxicity of magnetic fluid was evaluated on Sacomar 180 cancer cell.
The result showed that at the highest concentration of 100 µg/ml, cell death is smaller
than 50%, meaning safety to cell. For hyperthermia experiment, MHT method induced 90% cell death at 42oC in 5 min, meanwhile, at the same condition, EHT
induced only 23,7% cell death. This result demonstrated the efficacy of magnetic
hyperthermia method.
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CONCLUSION
1. Success in fabrication of M1-xZnxFe2O4 (M = Mn, Co; 0,0 ≤ x ≤ 0,7) with single
phase spinel structure, spherical shape by hydrothermal method. Optimal
fabricating conditions for maximum saturation magnetism are: reaction temperature- 180oC, reaction time- 12h.
xZnxFe2O4. MnZn7 has TC = 330 K, CoZn7 has TC = 380 K. Although these
2. Increase of Zn2+ content leads to decrease of Ms, Hc, TC of Mn1-xZnxFe2O4, Co1-
values are higher than temperature killing cancer cell, magnetic resistance force
Hc achieves requirement for hyperthermia.
3. Specific Loss Power (SLP) of MnZn7, MnZn5, CoZn7, CoZn5 and CoFe2O4
nanoparticles increases when increasing magnetic field intensity and decreases
when increasing nanoparticle concentration. For MnZn7 and MnZn5, SLP is proportional to H2. However, SLP of CoZn7 and CoZn5 increases with increase of H but is not proportional to H2.
4. CoFe2O4 fabricated by thermal decomposition method was transferred to aqueous
phase by using PMAO. The obtained samples are very stable in different salt
concentrations and pHs with zeta potential in range of - 60 mV to 60 mV. CF3
sample is stable at pH ≥ 2 and salt concentration ≤ 230 mM
5. Magnetic induction heating was examined under different magnetic field (100-
300 Oe and 290-450 kHz). SLP increases linearly with H and f. In case of CF3,
maximum SLP is 297,4 (W/g) under 300 Oe, 450 kHz. For CF and CF2, Neél
mechasnim contributes mainly to the formation of SLP. For CF3 and CF4, which
mechanism for the formation of SLP is not clearly understood. Size of maximum
SLP of CF3 is 10,6 nm. Heat inducing mechanism of CF1, CF2, CF3 magnetic
fluid is in good agreement with LRT model, meanwhile, SW model is suitable for
CF4.
6. Toxicity of magnetic fluid was evaluated on Sacomar 180 cell. At the highest
concentration of 100 µg/ml, cell proliferates above 50%. Therefore, the magnetic
22
fluid does not induce toxicity on cancer cell.
7. MHT and EHT are two methods applied for cancer hyperthermia. In case of MHT,there is 90% cell death at 42oC in 5 min. Meanwhile, in case of EHT, at the
23
same conditions, there is only 23,7% cell death.
PUBLISHED REPORTS USED IN THIS THESIS
1. Pham Thanh Phong, P.H. Nam, Do Hung Manh, D.K. Tung, In-Ja Lee & N.X. Phuc, Studies of the Magnetic Properties and Specific Absorption of Mn0.3Zn0.7Fe2O4 Nanoparticles, Journal of Electronic Materials, 44 (2015) 287- 294.
2. P.T. Phong, P.H. Nam*, D.H. Manh, In-Ja Lee, Mn0.5Zn0.5Fe2O4 nanoparticles with high intrinsic loss power for hyperthermia therapy, Journal of Magnetism and Magnetic Materials, 433 (2017) 76-83.
3. Phạm Hồng Nam, Trần Đại Lâm, Nguyễn Xuân Phúc, Đỗ Hùng Mạnh, Ảnh hưởng của nồng độ Zn tới tính chất từ và đốt nóng cảm ứng từ của hệ hạt nano Mn1- XZnXFe2O4, Tạp chí Khoa học và Công nghệ 52 (3B) (2014) 136-143.
4. Phạm Hồng Nam, Phạm Thanh Phong, Đỗ Hùng Mạnh, Nghiên cứu cấu trúc và tính chất từ của hệ hạt nano Co1-xZnxFe2O4 (x = 0-0,7) chế tạo bằng phương pháp phân hủy nhiệt, Tạp chí Khoa học và Công nghệ 54 (1A) (2016) 25-32.
5. P.H. Nam, L. T. Lu, V.T.K. Oanh, D.K.Tung, D.H. Manh, P.T. Phong, N.X. Phuc, Magnetic heating of monodisperse CoFe2O4 nanoparticles encapsulated by poly(maleic anhydride-alt-1-octadecene), Proceedings of The 8th International Workshop on Advanced Materials Science and Nanotechnology, Ha Long City, Vietnam, 8-12 November (2016) 171-182.
6. Phạm Hồng Nam, Nguyễn Thị Thảo Ngân, Đỗ Hùng Mạnh, Lê Trọng Lư, Phan Mạnh Hưởng, Phạm Thành Phong, Nguyễn Xuân Phúc, Nghiên cứu so sánh công suất tổn hao riêng xác định từ đường cong từ trễ trong từ trường xoay chiều và lý thuyết đáp ứng tuyến tính, Tuyển tập báo cáo Hội nghị vật lý chất rắn toàn quốc lần thứ X, TP. Huế, Việt Nam, 19-21, tháng 10 (2017), 64-67.
7. Pham Hong Nam, Luong Le Uyen, Doan Minh Thuy, Do Hung Manh, Pham Thanh Phong, Nguyen Xuan Phuc, Dynamic effects of dipolar interactions on the specific loss power of Mn0.7Zn0.3Fe2O4, Vietnam Journal of Science and Technology 56 (1A) (2018) 50-58.
