Magnetic nanoparticles as heat-generating nanosources in hyperthermia treatment are still faced with many drawbacks for achieving sufficient clinical potential. In this context, increase in heating ...ability of magnetic nanoparticles in a biologically safe alternating magnetic field and also approach to a precise control on temperature rise are two challenging subjects so that a significant part of researchers’ efforts has been devoted to them. Since a deep understanding of Physics concepts of heat generation by magnetic nanoparticles is essential to develop hyperthermia as a cancer treatment with non-adverse side effects, this review focuses on different mechanisms responsible for heat dissipation in a radio frequency magnetic field. Moreover, particular attention is given to ferrite-based nanoparticles because of their suitability in radio frequency magnetic fields. Also, the key role of Curie temperature in suppressing undesired temperature rise is highlighted.
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•In MHT, the heat generated by MNPs is produced by independent mechanisms.•MHT demands MNPs with high heating efficiency in a safe alternating magnetic field.•Undesired temperature rise can be inhibited through Curie temperature of MNPs.•This review discusses about the Physics concepts involved in the above subjects.
Co–Ag granular films were grown using electrodeposition technique. Atomic percentage, crystalline structure, morphological characterizations and magnetic structure of Co–Ag films were studied. ...Results confirm the simultaneous deposition of fcc–Ag and fcc–Co in the samples. It was found that percentage of Co in the composition of the Co–Ag film increases with the deposition current density. The granular nature of the Co–Ag films is evident by AFM micrographs. Also, magnetic force microscopy images show that magnetic structure of the all samples is composed of regular and uniform domains. The results show the magnetoresistance increases with increasing the deposition current density. Moreover, results indicated that the long-range magnetic structure with largest domain dimensions for Co–Ag films which are electrodeposited at the lowest deposition current densities leads to the lowest GMR value. The maximum value of giant magnetoresistance (GMR) is found to be 5.25% for Co–Ag films electrodeposited under current density of 12 mA/cm
2
. Thus, deposition conditions (e.g., applied current density) allow improving the GMR in granular Co–Ag films. The lowest AMR value is detected in the films with the highest GMR as the smallest particles are present. A zero-field-cooled magnetization measurement suggests that the ferromagnetic particle sizes with various diameters are dispersed in the Ag matrix. The Co particle size decreases with increasing the current density so that the magnetoresistance also increases. An analysis of the magnetotransport features reveal a high superparamagnetic contribution in all films. Studying the magnetic characteristics confirmed that an increase in a current density reduces the coercivity and the magnetization. This result suggests that exchange softening effect works effectively by the enhancement of the current density.
Due to the increase of environmental pollution by various industries in recent decades, preparing drinking water has become one of the most vital issues for many countries. The organic pollutant, ...such as different azo dyes, is one of the most important issues. Using photocatalyst materials is considered to be an optimal solution to prevent environmental pollution. In this work, novel ternary catalysts of CoFe
2
O
4
/TiO
2
/Au were synthesized for the photocatalytic reduction of methyl orange (MO) under UV light illumination. The localized surface plasmon resonance (LSPR) property of Au nanoparticles is widely exploited for their photocatalytic activities. In this research, both CoFe
2
O
4
and TiO
2
nanoparticles (NPs) were prepared by sol–gel method. Hydrothermal treatment was also used to synthesize the nanocomposite. Au nanoparticles were successfully loaded on the CoFe
2
O
4
/TiO
2
surface to get CoFe
2
O
4
/TiO
2
/Au magnetic nanocomposites. To characterize the shape of the structure, morphology, purity, and particle size of the nanocomposite, scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Zeta potential analysis, dynamic light scattering (DLS), photoluminescence spectroscopy (PL), Brunauer–Emmett–Teller (BET), and Fourier transform infrared (FT-IR) spectroscopy were employed. Alternating gradient field magnetometer (AGFM) studies show the superparamagnetic properties of the CoFe
2
O
4
nanostructures. Finally, we investigated the catalytic performance and recyclability in reducing MO of synthesized nanocomposites by monitoring a UV–visible spectrophotometer. The composite catalysts can then be easily separated from the reaction solution using a magnet bar and ultimately reused. We used artificial neural network (ANN) to remove expensive experimental research and tried solving and predicting the novel phenomena with huge factors. Initially, information about the degradation of MO was gathered by experimental analyses. We then tried shaping and calculating the special algorithm that could find the best relation and high percentage of accuracy between input variables. The genetic algorithm as one of the most popular algorithms in an artificial world was selected to predict and train the model. In conclusion, the experimental results determined that the CoFe
2
O
4
/TiO
2
/Au magnetic nanocomposites were successfully synthesized and it exhibited a useful effect on the removal of azo dyes from the contaminated solutions. According to the prediction of removal efficiency of pollution by artificial neural network, the results show that using this algorithm has a high percentage of accuracy to investigate the experimental results of the current research.
We present a study on the magnetic behavior of dextran-coated magnetite nanoparticles (DM NPs) with sizes between 3 and 19 nm, synthesized by hydrothermal-assisted co-precipitation method. The ...decrease of saturation magnetization (
M
s
) with decreasing particle size has been modeled by assuming the existence of a spin-disordered layer at the particle surface, which is magnetically dead. Based on this core–shell model and taking into account the weight contribution of non-magnetic coating layer (dextran) to the whole magnetization, the dead layer thickness (
t
) and saturation magnetization
M
s
of the magnetic cores in our samples were estimated to be
t
=
6.8 Å and
M
s
=
98.8
emu
/
g
, respectively. The data of
M
s
were analyzed using a law of approach to saturation, indicating an increase in effective magnetic anisotropy (
K
eff
) with decreasing the particle size as expected from the increased surface/volume ratio in small MNPs. The obtained
K
eff
values were successfully modeled by including an extra contribution of dipolar interactions due to the formation of chain-like clusters of MNPs. The surface magnetic anisotropy (
K
s
) was estimated to be about
K
s
=
1.04
×
10
5
J
/
m
3
. Our method provides a simple and accurate way to obtain the
M
s
core values in surface-disordered MNPs, a relevant parameter required for magnetic modeling in many applications.
Graphical abstract
Firstly nickel ferrite nanoparticles were synthesized via a simple precipitation method. Then mono-disperse platinum nanoparticles and NiFe2O4@TiO2/Pt nanocomposites were synthesized by a facile ...sol-gel procedure. The structure, phase and crystallite size of the magnetic and photo-catalyst products were characterized by X-ray diffraction pattern (XRD). The morphology and size of the nanostructures were surveyed by scanning electron microscopy (SEM). The purity of the samples was confirmed by Fourier transform infrared (FT-IR) spectroscopy. Vibrating sample magnetometer (VSM) illustrated that nickel ferrite nanoparticles have super paramagnetic behaviour. The photo catalytic behaviour of NiFe2O4@TiO2/Pt nanocomposites was approved using the fast degradation of two various azo dyes under visible and ultra violet light irradiation. The results show that nanocomposites have feasible magnetic feature for easy separation and effective photo catalytic properties for purification of organic dye contaminants. The antibacterial behaviour of NiFe2O4@TiO2/Pt nanocomposites was evaluated using degradation of E coli bacteria.
Keywords: Photo-catalyst; Nanostructures; Nanocomposite; Magnetic
•Magnetite nanoparticles were prepared by a simple precipitation method.•The influence of surfactant on the particle size of the products was investigated.•The effects of time, solvent and magnetic ...field on the morphology were examined.
Magnetite (Fe3O4) nanoparticles were prepared by a simple precipitation method between Fe(NO3)3·9H2O and FeCl2·4H2O. The effects of surfactant, temperature, time, solvent and magnetic field on the morphology and particle size of the products were investigated. The magnetic properties of the product were investigated using an alternating gradient force magnetometer (AGFM). The Fe3O4 nanoparticles exhibit ferrimagnetism behaviour at room temperature, with a saturation magnetization of 38.7emu/g and a coercivity of 0.78Oe. Such a low coercivity is attributed to superparamagnetic (which is a size dependent) behaviour of Fe3O4 in nanoparticle scale.
This study investigates the structure, morphological, and roughness properties of electrodeposited nickel thin films grown on different substrates, that is, silicon, copper, and gold. X‐ray ...diffraction analysis reveals that the Ni coatings exhibit a face‐centered‐cubic phase, regardless of the substrate used, although the texture is mainly influenced by the substrate. Atomic force microscopy images show that larger grains are obtained with gold substrates, while smaller ones are observed with copper and silicon substrates, in agreement with scanning electron microscopy. The results demonstrate that both topological and fractal characteristics of the Ni thin films are significantly influenced by the type of substrate. Statistical parameters are quantified to compare the surface morphology of the different samples. Fractal analysis reveals that the fractal dimensions of all surfaces range between 2 and 3, indicating self‐affinity. Fractal succolarity and lacunarity are measured to assess the penetration of a liquid into the surface and the distribution of gaps in the Ni film surfaces, respectively. Minkowski functionals are utilized for topological analysis to characterize the internal structure of the Ni thin films. The observed differences in roughness characteristics provide evidence that the type of substrate affects the nucleation and growth of surface features during electrodeposition.
The variation in surface spatial patterns of Ni films deposited using the electrodeposition technique on various substrates (Au, Si, and Cu) is studied. Statistical parameters, fractal geometry‐based methods, and Minkowski functionals are used to analyze the surfaces. Atomic force microscopy images show that larger grains are obtained with gold substrates, in agreement with scanning electron microscopy micrographs.
Hard magnetic BaFe12O19 (BaFe) nanoparticles were synthesized via a facile sonochemical-assisted reaction. BaFe nanoparticles were then added to acrylonitrile-butadiene-styrene (ABS) and cellulose ...acetate (CA) in order to make magnetic nanocomposites. Nanoparticles and nanocomposites were then characterized using X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The magnetic properties of the samples were also investigated using an alternating gradient force magnetometer. The barium ferrite nanoparticles exhibit ferrimagnetic behaviour at room temperature, with a saturation magnetization of 53 emu/g and a coercivity of 2430 Oe. Distribution of the BaFe12O19 nanoparticles into the polymeric matrixes increases the coercivity dramatically. KCI Citation Count: 16
At the first stage Fe3O4 and Fe nanoparticles were synthesized via a simple hydrothermal method. Then silver nanoparticles and Fe-Ag nanocomposites were synthesized in the presence of NaBH4. The ...prepared products were characterized by X-ray diffraction pattern, scanning electron microscopy, and Fourier transform infrared spectroscopy. Vibrating Sample magnetometer illustrated that Fe nanoparticles have super paramagnetic behaviour. The photo catalytic behaviour of Fe-Ag nanocomposites was investigated using the degradation of three various azo dyes under ultraviolet light irradiation. The results show that nanocomposites have feasible magnetic and photo catalytic properties.
•The scaling analysis showed that the surface growth of the Ag-Co thin films has an intrinsic anomalous scaling behavior.•The increase in the film thickness decreased coercivity and squareness while ...it increased local slope.•The XRD analyses showed that the Ag-Co films was single phase fcc Ag.•In-plan demagnetizing factor was also enhanced with the film thickness as a power-law and its results confirmed our dynamic scaling results.•Thin film growth mechanisms and surface roughness can have sturdy effect on magnetic features of thin films.
The effects of thickness on surface roughness and magnetic properties of Ag-Co thin films prepared by electrodeposition technique were studied. Crystalline structural of the films were discussed. The scaling analysis showed that the surface growth of the Ag-Co thin films has an intrinsic anomalous scaling behavior. Meanwhile, the increase in the film thickness decreased coercivity and squareness while it increased local slope. In-plan demagnetizing factor was also enhanced with the film thickness (growth time) as a power-law and its results confirmed our dynamic scaling results. It was found that thin film growth mechanisms and surface roughness can have sturdy effect on magnetic features of thin films.
