The influence of synthesis parameters on one-step synthesized superparamagnetic cobalt ferrite nanoparticles with high saturation magnetization (original) (raw)
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Superparamagnetic Cobalt Ferrite Nanoparticles: Effect of Temperature and Base Concentration
Journal of Superconductivity and Novel Magnetism, 2014
Cobalt ferrite nanoparticles were coprecipitated in air medium using NH 3 , and the effects of temperature and base concentration on the properties were studied. X-ray diffraction (XRD) technique and Fourier transform infrared spectroscopy were used to investigate the structural properties of the samples. Particle sizes and shapes were determined by a transmission electron microscope (TEM). Magnetic measurements were done using vibrating sample magnetometer at room temperature. The proper reaction temperature was found to be 80°C for the synthesis of superparamagnetic cobalt ferrite nanoparticles. The effect of base concentration on the properties of the superparamagnetic nanoparticles was investigated under this temperature. The magnetization values of cobalt ferrite nanoparticles increased as the base concentration increased and reached to a value of 32.4 emu/g with zero coercivity. The particle sizes (d XRD , d TEM , and d VSM ) of cobalt ferrite nanoparticles were calculated from XRD patterns, TEM images, and magnetic data, respectively. It was observed that the d TEM and d VSM are similar to each other, and the d XRD are bigger than those with the similar trend of increase with the increase of base concentration.
Nanomaterials
Using magnetic nanoparticles for extracorporeal magnetic heating applications in bio-medical technology allows higher external field amplitudes and thereby the utilization of particles with higher coercivities (HC). In this study, we report the synthesis and characterization of high coercivity cobalt ferrite nanoparticles following a wet co-precipitation method. Particles are characterized with magnetometry, X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy (TEM) and calorimetric measurements for the determination of their specific absorption rate (SAR). In the first series, CoxFe3−xO4 particles were synthesized with x = 1 and a structured variation of synthesis conditions, including those of the used atmosphere (O2 or N2). In the second series, particles with x = 0 to 1 were synthesized to study the influence of the cobalt fraction on the resulting magnetic and structural properties. Crystallite sizes of the resulting particles ranged between 10 and 18 nm,...
Magnetic Hyperthermia Properties of Electrosynthesized Cobalt Ferrite Nanoparticles
The Journal of Physical Chemistry C, 2013
Using the electrochemical route, cobalt ferrite nanoparticles (NPs) with two different sizes were synthesized and stabilized in water by coating with citric acid. The specific absorption rate (SAR) values of aqueous suspensions of magnetic nanoparticles with crystal sizes of 13 and 28 nm were investigated in the frequency range 32−101 kHz and up to 51 mT. SAR values were higher for the larger NPs and reached 133 W/g. Numerical simulations are used for a quantitative analysis of hyperthermia experiments and seem to indicate that the larger NPs are multidomain. Cytotoxicity analysis was also performed in HeLa tumor cells; a null cytotoxicity of these nanoparticles in cell tissues were obtained.
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Magnetic nanoparticles such as cobalt ferrite are investigated under clinical hyperthermia conditions for the treatment of cancer. Cobalt ferrite nanoparticles (CFNPs) synthesized by the thermal decomposition method, using nonionic surfactant Triton-X100, possess hydrophilic polyethylene oxide chains acting as reducing agents for the cobalt and iron precursors. The monodispersed nanoparticles were of 10 nm size, as confirmed by high-resolution transmission electron microscopy (HR-TEM). The X-ray diffraction patterns of CFNPs prove the existence of cubic spinel cobalt ferrites. Cs-corrected scanning transmission electron microscopy–high-angle annular dark-field imaging (STEM–HAADF) of CFNPs confirmed their multi-twinned crystallinity due to the presence of atomic columns and defects in the nanostructure. Magnetic measurements proved that the CFNPs possess reduced remnant magnetization (MR/MS) (0.86), which justifies cubic anisotropy in the system. Microwave-based hyperthermia studies...
IEEE Transactions on Magnetics, 2000
Cobalt ferrite (CoFe 2 O 4) is an engineering material which is used for applications such as magnetic cores, magnetic switches, hyperthermia based tumor treatment, and as contrast agents for magnetic resonance imaging. Utility of ferrites nanoparticles hinges on its size, dispersibility in solutions, and synthetic control over its coercivity. In this work, we establish correlations between room temperature co-precipitation conditions, and these crucial materials parameters. Furthermore post-synthesis annealing conditions are correlated with morphology, changes in crystal structure and magnetic properties. We disclose the synthesis and process conditions helpful in obtaining easily sinterable CoFe 2 O 4 nanoparticles with coercive magnetic flux density (H c) in the range 5.5-31.9 kA/m and M s in the range 47.9-84.9 A.m 2 Kg-1. At a grain size of ~54±2 nm (corresponding to 1073 K sintering temperature), multi-domain behavior sets in, which is indicated by a decrease in H c. In addition, we observe an increase in lattice constant with respect to grain size, which is the inverse of what is expected of in ferrites. Our results suggest that oxygen deficiency plays a crucial role in explaining this inverse trend. We expect the method disclosed here to be a viable and scalable alternative to thermal decomposition based CoFe 2 O 4 synthesis. The magnetic trends reported will aid in the optimization of functional CoFe 2 O 4 nanoparticles.
Langmuir, 2007
Monodisperse and stable cobalt ferrite (CoFe2O4) nanoparticles (5.4 nm) have been produced, coated with monoand difunctional phosphonic and hydroxamic acids, and fully characterized (using thermogravimetric analysis (TGA), dynamic light scattering (DLS), IR spectroscopy, transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) measurements). Cobalt leakage of the coated nanoparticles has been also studied. Magnetic measurements show the possible applications in hyperthermia at low frequencies, and for this reason, water-soluble coated CoFe2O4 can be seen as a first step toward the obtainment of novel systems for biomagnetic applications.
International Journal for Innovation Education and Research, 2021
In this study we report on the synthesis and characterization of cobalt ferrite (CoFe2O4) nanoparticles (NPs), synthesized by chemical co-precipitation in alkaline medium. Two samples were synthesized at two different temperatures, 35 and 90 oC. Both samples were characterized by Transmission Electron Microscopy (TEM), x-ray diffraction (XRD), and room-temperature (RT) magnetization. Two samples showed superparamagnetic behavior (SPM) at RT. TEM reveals morphological mean diameter increasing 5.8 nm to 10.4 nm, with the increase of the co-precipitation temperature. XRD confirm the inverse cubic spinel structure. The RT magnetization curves were analyzed by the first-order Langevin function averaged out by a lognormal distribution function of magnetic moments. This analysis showed saturation magnetization and magnetic moment increases from 60.2 to 74.8 emu/g and from 3.9 x 103 to 8.2 x 103 mB, respectively.
Cobalt ferrite nanoparticles: Achieving the superparamagnetic limit by chemical reduction
2006
An unanticipated superparamagnetic response has been observed in cobalt ferrite materials after thermal treatment under inert atmosphere. Cobalt ferrite particles were prepared via normal micelle precipitation that typically yields Co x Fe 3−x O 4 nanoparticles ͑x = 0.6− 1.0͒. While samples thermally treated under oxygen show majority spinel phase formation, annealing in nitrogen gas yields materials consisting of Co-Fe alloy, FeS, and CoFe 2 O 4 spinel. After thermal treatment, thermomagnetic studies reveal composition-insensitive, but highly treatment-sensitive, saturation magnetization, coercivity, blocking temperature, and Verwey transition temperature dependence. Extremely high saturation magnetization ͑159 emu/g͒ with low coercivity ͑31 Oe͒ was observed for one of the treated compositions, which drastically deviates from prototypical cobalt ferrite with large magnetocrystalline anisotropy. We attribute such unique magnetic response to Co-Fe alloy coexisting with FeS and CoFe 2 O 4 spinel where the diameter of the metallic phase is below the superparamagnetic limit. While thermal treatment in nitrogen was not anticipated to yield Co-Fe alloy, chemisorbed surfactant molecules ͑i.e., sodium dodecylsulfate͒ are postulated to act as reducing agents in the present scenario.
Materials Today: Proceedings, 2019
The magnetic cobalt ferrite nanoparticles (CoFe 2 O 4) were synthesized by sol-gel combustion technique and encapsulated with polyethylene glycol (PEG). The phase formation and crystalline nature were confirmed by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The microstructure and elemental composition were characterized using Scanning Electron Microscopy (SEM). Magnetic characteristics of the synthesized sample were studied at room temperature using Vibrating Sample Magnetometer (VSM) and its low coercivity value indicates that these nanoparticles are near the superparamagnetic limit. Hyperthermic behavior and cell biocompatibility characteristics with human leucocyte culture were analyzed and results signify that synthesized cobalt ferrite (CoFe 2 O 4) nanoparticles encapsulated with Polyethylene glycol (PEG) are one of the potential candidates for hyperthermia, targeted drug delivery and various other biomedical applications.