Cobalt Iron Oxide Nanoparticles Research Articles

Magnetic heating of water dispersible and size-controlled superparamagnetic cobalt iron oxide nanoparticles

Magnetic nanoparticles have been of great interest for various biomedical applications due to their controllability in the distance. Monodisperse superparamagnetic CoFe2O4 (CFO) nanoparticles were synthesized by solvothermal method with oleic acid. The oleic acid ligands are exchanged with citric acid to obtain water-dispersible citric acid-coated CA (CFO–CA) nanoparticles. The M–H curve recorded at room temperature shows the superparamagnetic nature of CFO nanoparticles for both oleic- and citric-coated samples. The magnetic heating performance of CFO–CA shows an exciting dependence on the particle size and surface functionality. The hyperthermia efficiency of CFO–CA nanoparticles increases with increasing magnetic field strength and nanoparticle concentration. A specific absorption ratio value of 152.7 W/g obtained in this study is comparable to other investigations, demonstrating a great potential of CFO–CA nanoparticles for hyperthermia-based treatments. This controlled synthesis process can be applied to various functional biomedical nanoparticles to prepare nanoparticles with designed surface moieties for further potential applications.

Amorphous cobalt iron oxide nanoparticles with high magnetization intensity for spin conversion of hydrogen at 77K

Conversion of ortho-hydrogen (o-H2) to para-hydrogen (p-H2) is a necessary process in hydrogen liquefaction, and investigating the catalysts that accelerate conversion is significant. Herein we report the effect of Co/Fe ratio in cobalt iron oxide catalysts on conversion of o-H2 to p-H2 at 77 K, and use XRD, BET, and VSM to explore the influence of different Co/Fe ratios on internal crystal structure, pore size, and magnetization strength. It is concluded that the synergistic effect of crystal structure disorder (increase in active sites), small pores (decrease in distance between o-H2 and active sites), and high magnetization strength (larger torque upon) resulted in the optimal catalytic performance for CFO-3 [n(Co):n(Fe) = 3:10]. When the hydrogen flow is 100 mL min−1, the content of p-H2 in the converted hydrogen is 47.61%.

Polymer-Modified Cellulose Nanofibrils Cross-Linked with Cobalt Iron Oxide Nanoparticles as a Gel Ink for 3D Printing Objects with Magnetic and Electrochemical Properties

This paper presents a strategy to convert hydrophilic cellulose nanofibrils (CNF) into a highly cross-linked hydrophobic network with inorganic nanoparticles to develop a gel ink suitable for gel 3D printing. The CNF were chemically modified initially through a single-electron transfer-living radical polymerization (SET-LRP) of stearyl acrylate (SA) in the presence of the surface-modified cobalt iron oxide (CoFe2O4, CFO) nanoparticles. The modified CFO nanoparticles provide their multifunctional properties, such as magnetic and electrochemical, to the CNF hybrid network and, at the same time, act as cross-linking agents between the nanocellulose fibrils, while the grafted poly-stearyl acrylate (PSA) introduces a strong hydrophobicity in the network. A suitable gel ink form of this CNF–PSA–CFO material for gel 3D printing was achieved together with a certain solvent. Some test structure prints were directly obtained with the CNF–PSA–CFO gel and were used to evaluate the consolidation of such 3D objects through solvent exchange and freeze-drying while also keeping the magnetic and electrochemical properties of CFO in the CNF-based composite intact. The pristine CNF and CFO particles and the CNF–PSA–CFO were characterized by FTIR, SEM, XPS, TGA, VSM, and CV measurements.

Magnetohydrodynamic hybrid nanofluid flow with the effect of Darcy–Forchheimer theory and slip conditions over an exponential stretchable sheet

The characteristics of water-based hybrid nanofluid flow when passing over an exponentially stretchable sheet with velocity and thermal slip factors are presented. This article provides a concept for a hybridized fluid comprising copper and cobalt iron oxide nanoparticles (NPs) dispersed into a base fluid (water). In addition, physical observations of the heat absorption behavior, the Darcy effect, the thermal radiation, and viscous dissipation are also taken into account. Because of their strong thermophysical properties, copper and cobalt iron oxide NPs are used in a wide range of applications in the engineering and medical fields. To study the dynamics of these NPs, a system of partial differential equations (PDEs) has been generated that forms a highly nonlinear coupled model. The PDE system is converted into nondimensional ordinary differential equations (ODEs) with the aid of similarity replacements. The semi-analytical homotopy analysis method (HAM) is applied to the set of dimensionless ODEs obtained to find the solution. Two engineering parameters, the Nusselt number and the skin friction, are plotted versus various parameters of the hybridized fluid using bar charts. It was observed that the no-slip condition, the suction parameter, and the Darcy–Forchheimer medium enhanced the thermal profile of the hybridized fluid.

Cobalt-iron oxide nanoparticles anchored on carbon nanotube paper to accelerate polysulfide conversion for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries appear to be one of the most promising energy-storage devices owing to the unparalleled theoretical specific energy, relatively inexpensive price and abundant resources. Despite these attractive features, the practical performances of sulfur cathode still remain a lot of challenges, such as the electrical insulating nature of S and Li2S, huge volume change during cycling, notorious shuttle effect of lithium polysulfide intermediates (LiPSs), sluggish redox kinetics and construction of thick electrodes with high sulfur loading. Here, CoFe2O4 nanoparticles anchored on the carbon nanotube (CNT) paper is proposed as free-standing sulfur host to address the issues. The cross-linking CNT network can serve as conductive matrix and accommodate volume change upon cycling simultaneously. Meanwhile, the CoFe2O4 nanoparticles are capable of effectively anchoring LiPSs to suppress the shuttle effect and accelerating LiPSs conversion to boost redox kinetics. Moreover, the free-standing paper electrode without any binder is conducive to constructing stable cathode with high sulfur loading. In consequence, the well-designed S/CoFe2O4/CNT paper cathodes deliver impressive electrochemical performance, demonstrating an initial discharge capacity of 755.3 mAh g−1 and remaining a high reversible capacity of 642.6 mAh g−1 after 400 cycles at 2 C with an inconspicuous decay of 0.04% per cycle.

Rheological Model for Generalized Energy and Mass Transfer through Hybrid Nanofluid Flow Comprised of Magnetized Cobalt Ferrite Nanoparticles

The goal of the current research is to evaluate a 3D stagnation point flow of Darcy Forchheimer’s hybrid nanofluid (NF) through a heated wavy flexible cylinder under the influence of slip conditions and varying thickness. A numerical model is developed for the purpose to magnify the energy and mass transmission rate and maximize the efficiency and performance of thermal energy conduction for a variety of commercial and biological purposes through methanol‐based hybrid NF flow consisting of cobalt ferrite and copper nanoparticles. Due to their inclusive range of applications, copper and cobalt iron oxide nanoparticles are gaining a lot of attention in medical and technical research. The model has been articulated in the form of a set of PDEs, which are reduced by the resemblance substitutions to the system of ODEs. The obtained 1st‐order differential equations are further processed by the computational strategy PCM. For the sake of accuracy and credibility, the values are verified with the bvp4c package. The findings are physically exhibited and analyzed. It has been observed that the induced magnetic field lessens with the upshot of the magnetic term and enhances under the action of magnetic Prandtl number M. The energy profile declines due to the variation of thermal jump constraint and boosts with the absorption and generation term.

Green Synthesis of Iron-Doped Cobalt Oxide Nanoparticles from Palm Kernel Oil via Co-Precipitation and Structural Characterization.

In this study, a bio-derived precipitating agent/ligand, palm kernel oil, has been used as an alternative route for the green synthesis of nanoparticles of Fe-doped Co3O4 via the co-precipitation reaction. The palm oil was extracted from dried palm kernel seeds by crushing, squeezing and filtration. The reaction of the palm kernel oil with potassium hydroxide, under reflux, yielded a solution containing a mixture of potassium carboxylate and excess hydroxide ions, irrespective of the length of saponification. The as-obtained solution reacts with an aqueous solution containing iron and cobalt ions to yield the desired metallo-organic precursor, iron cobalt carboxylate. Characterization of the precursors by IR and gas chromatography (GC) attests to the presence of carboxylate fatty acids in good agreement with the proportion contained in the oil, and ICP confirms that the metallic ratios are in the proportion used during the synthesis. Analysis of the products thermally decomposed between 400 °C and 600 °C by XRD, EDX, TEM and ToF-SIMS, established that cobalt iron oxide nanoparticles (Co(1−x)Fex)3O4 were obtained for x ≤ 0.2 and a nanocomposite material (Co(1−x)Fex)3O4/Fe3O4 for x ≥ 0.2, with sizes between 22 and 9 nm. ToF-SIMS and XRD provided direct evidence of the progressive substitution of cobalt by iron in the Co3O4 crystal structure for x ≤ 0.2.

Preparation and physical characterization of cobalt iron oxide magnetic nanoparticles loaded polyvinyl alcohol

A solvent thermal method which depends on a thermal process under critical temperature and pressure was used to prepare cobalt iron oxide magnetic nanoparticles with a molar ratio 2. The prepared particles were in the form of nanoparticles with diameter ranging from 5 to 10 nm and with amorphous structure. Magnetic hysteresis behavior with saturation magnetization 36.31 emu/g and coercivity 4 Oe were observed for the nanoparticles. Polyvinyl alcohol was loaded with different concentrations of cobalt iron oxide nanoparticles using casting technique. Hysteresis loops for the polymer films were observed and both the saturation magnetization and coercivity were increased from 0.36 to 16.03 emu/g and 115 to 293 Oe for samples containing 5 and 20 wt% of nanoparticles, respectively. The elastic modulus of films was increased from 2.7 to 4.9 GPa for unloaded and loaded samples with 20 wt%, respectively. The storage modulus of the polymer films was found to obey the percolation behavior.

Characterization and Nanofluid Stability of CoFe2O4-APTES and CoFe2O4-PVA Nanoparticles

Nanofluid contains nanoparticles that enhanced the property of the base fluid. However, the separating layer between the nanoparticles and base fluids may interfere the nanofluids performance. Studies have been made that surface modification of nanoparticles may improve the dispersion of nanoparticles in base fluids. This paper reports the study of the colloidal stability of surface modified nanoparticles using a polymer and an amino-silane. The nanoparticles were prepared by one-step and two-step methods using cobalt iron oxide nanoparticles with brine solution and deionized water as the base fluids. Functionalization by surface modification of the nanoparticles to enhance the nanofluids stability was carried out using (3-aminopropyl) triethoxysilane (APTES) and polyvinyl alcohol (PVA). Characterization using Fourier Transform Infrared (FTIR), Field Emission Scanning Electron Microscope (FESEM) and X-ray Powder Diffraction (XRD) were performed to study the functionality and morphology of the synthesized nanoparticles. The extra IR peaks such as Si-O-Si at 1063 cm-1 for CoFe2O4-APTES and C=O at 1742 cm-1 for CoFe2O4-PVA showed that there are additional elements in the cobalt ferrite due to functionalization. The size of synthesized CoFe2O4-APTES ranged between 15.99 nm to 26.89 nm while CoFe2O4-PVA is from 25.70 nm to 54.16 nm. The stability of the nanofluid were determined via zeta potential measurements. CoFe2O4-APTES nanofluid has zeta potential of -35.7 mV compared to CoFe2O4-PVA at -15.5 mV.

Boosting oxygen evolution reaction performance by nickel substituted cobalt-iron oxide nanoparticles embedded over reduced graphene oxide

Designing non-precious-metal (NPM) electrocatalysts for oxygen evolution reaction (OER) from alkaline water is of paramount importance for clean, sustainable and conversion technologies. Herein, we report a facile, scalable and rapid microwave assisted synthesis to produce Ni substituted cobalt-iron oxides Co1-xNixFe2O4 (x = 0, 0.10, 0.25, 0.50, 0.75 and 1) supported over conductive reduced graphene oxide (rGO) and successfully employing them as electrode materials for OER in alkaline medium. Interestingly, by tuning Ni amount in cobalt-iron oxide has a profound influence on the OER activity i.e., Co0.75Ni0.25Fe2O4/rGO exhibits the best OER performance with an overpotential of 440 mV at 10 mA cm−2 and considerable electrochemical stability over 1000 cycles and even up to 10 h in 0.1 M KOH solution.

Anionic azo dyes removal from water using amine-functionalized cobalt-iron oxide nanoparticles: a comparative time-dependent study and structural optimization towards the removal mechanism.

The current study is aimed at synthesizing and characterizing magnetic cobalt–iron oxide nanoparticles (CoFeNPs) functionalized with two different amino reagents, hydrazine and dodecylamine, resulting in CoFeNPs1 and CoFeNPs2, respectively. Both types of cobalt–ferrite nanoparticles were investigated for the removal of six different negatively charged azoic dyes (Amaranth, Acid Orange 7, Naphthol Blue Black, Reactive Orange 16, Acid Orange 52 and Reactive Red-P2B) from water, and their removal efficiency was compared as a function of different factors such as time, type of anchored amine, size of CoFeNPs and structure of the dye. CoFeNPs were successfully characterized by FT-IR spectra, AFM, SEM-EDS, surface charge (ζ-potential) and thermal analysis. CoFeNPs1 revealed 44.5–82.1% dye removal at equilibrium (attained within 28–115 min) with an adsorptive capacity (qe) of 5.4–13.5 mg g−1 observed under unoptimized conditions (temp. 30 °C, adsorbent dose 0.67 g L−1, pH 6, dye concentration 20 μmol L−1). Use of CoFeNPs2 significantly enhanced the removal of each dye (percent dye removal 68.0–98.9%, qe 6.6–23.5 mg g−1) compared to CoFeNPs1 under similar conditions. From a comparative structural study, a larger size, more complex structure, hydrophobic character and greater number of phenyl SO3− groups among the tested dyes facilitated their removal by CoFeNPs2, while all of these structural factors were negatively related to dye removal by CoFeNPs1. CoFeNPs2 showed some dye aggregation along with adsorption, while in the case of CoFeNPs1, only adsorption was observed as confirmed by FT-IR and UV-visible spectral studies. Dye removal data in all cases was in best compliance with pseudo-second order kinetics in comparison to pseudo-first order or the Elovich model, where film diffusion was a dominant phenomenon compared to intra-particle diffusion. Adsorption isotherms, thermodynamics and reusability of the CoFeNPs were studied selecting Reactive Orange 16. Adsorption equilibrium was best fitted to the Langmuir isotherm. ΔG° and ΔH° indicated spontaneous and exothermic adsorption. Amine-functionalized CoFeNPs are recommended as potential cost-effective adsorbents with excellent reusability that could be applied efficiently for rapid and selective dye removal from textile effluents considering the size, structure, charge and number of S atoms in the target azo dyes.

An iron oxide -copper bismuth oxide photoelectrochemical cell for spontaneous water splitting

Highly efficient water splitting reaction on hematite photoelectrode has been encumbered by its low photovoltage and photocurrent in a water splitting cell. In this work, a nanostructured hematite photoanode was prepared via a hydrothermal method, and its water oxidation activity was greatly enhanced by the synergetic application of uniform in-situ cobalt-doping and surface modification with fine cobalt iron oxide nanoparticles electrocatalyst. As a result, its remarkable low onset potential of 0.55 VRHE for water oxidation allows the construction of tandem cell with a novel metal oxide photocathode CuBi2O4, which has already proven reasonably robust photoactivity for water reduction reaction. The photocurrent and long-term stability of this metal oxides based device in alkaline electrolyte for unassisted overall water splitting reaction were investigated. A solar to hydrogen efficiency of 0.15% was measured accordingly on this spontaneous hydrogen production device, without the involvement of precious metal components.

Electrochemical study of magnetic nanogel designed for controlled release of chlorhexidine gluconate

Intensive care is required for patient with higher degree of burns as they are prone to sepsis mortality. Topical antimicrobials/antiseptics are the conventional treatment of choice with each having its limitation in terms of toxicity and effectiveness. Magnetic nanogel have long been studied for in vivo drug delivery in cancer treatment. Inspired by fact that incorporation of magnetic nanoparticles will enhance the antimicrobial properties of nanogel, we developed a chitosan-gelatin based polymer with dispersed magnetic Cobalt iron oxide nanoparticles for controlled release of chlorhexidine gluconate. MNPs were synthesized by co-precipitation method and confirmation of CoFe2O4 phase was done with XRD analysis. Nanogel was fabricated by solution casting method and further characterization to determine drug interaction with polymer and MNPs was performed using Fourier Transformed Infra-Red Spectroscopy, Scanning Electron Microscopy, and Electroanalytical methods including Cyclic Voltammetry, Square Wave Voltammetry and Electrochemical Impedance Spectroscopy. Results of the study indicate that electrochemical nature of nanogel is pH dependent and the drug release can be induced at pH ranging from 6 to 7. Findings of this study highlight potential of the synthesized nanogel in developing burn care treatment that enables on demand drug release in response to sepsis with changing pH and can be integrated with detection system due to the presence of MNPs in it.

Microemulsion-based synthesis of strontium hexaferrite cobalt iron oxide nanoparticles and their biocompatibility in albino mice

A number of strontium-based iron oxides are available for the industrial use. Among them, strontium hexaferrite cobalt iron oxide (Sr2Co2Fe12O22) is preferred over others due to its better magnetic and electrical properties than others. This material is also extensively used for the absorption of microwave radiations. This study was conducted to account for the synthesis and characterization of Sr2Co2Fe12O22 nanoparticles and to report their biocompatibility in albino mice. Nanoparticles were synthesised by normal microemulsion, XRD analysis confirmed the single and scanning electron microscopy (SEM) revealed average particle size ranged between 30 and 50 nm. Nine-week-old male mice were intraperitoneally administered with 50 mg/mL of solvent/kg body weight of strontium hexaferrite cobalt iron oxide nanoparticles for 22 days. Control group was maintained in parallel. A series of neurological tests (rota rod, light and dark box, open field and Morris water maze) were conducted in both groups. Blood samples were collected from direct cardiac puncture, and parameters of complete blood count, serum biochemical parameters and antioxidant were determined in liver and brain tissues of all subjects. Analysis of result revealed that all studied neurological test performances varied nonsignificantly (P > 0.05) between the two treatments except clockwise rotations during open field test that were significantly reduced (P = 0.05) in Strontium hexaferrite Cobalt Iron Oxide nanoparticle-treated male albino mice than in the control group. All studied complete blood count and serum parameters varied nonsignificantly (P > 0.05) between two treatments. It was observed that superoxide dismutase concentration was significantly higher (P = 0.05) in the liver of nanoparticle-treated male mice. In conclusion, we are reporting that applied dose of strontium hexaferrite cobalt iron oxide nanoparticles is affecting the exploratory behaviour and antioxidant metabolites of male albino mice.

Cobalt iron oxide nanoparticles induce cytotoxicity and regulate the apoptotic genes through ROS in human liver cells (HepG2)

Cobalt iron oxide (CoFe2O4) nanoparticles (CIO NPs) have been one of the most widely explored magnetic NPs because of their excellent chemical stability, mechanical hardness and heat generating potential. However, there is limited information concerning the interaction of CIO NPs with biological systems. In this study, we investigated the reactive oxygen species (ROS) mediated cytotoxicity and apoptotic response of CIO NPs in human liver cells (HepG2). Diameter of crystalline CIO NPs was found to be 23nm with a band gap of 1.97eV. CIO NPs induced cell viability reduction and membrane damage, and degree of induction was dose- and time-dependent. CIO NPs were also found to induce oxidative stress revealed by induction of ROS, depletion of glutathione and lower activity of superoxide dismutase enzyme. Real-time PCR data has shown that mRNA level of tumor suppressor gene p53 and apoptotic genes (bax, CASP3 and CASP9) were higher, while the expression level of anti-apoptotic gene bcl-2 was lower in cells following exposure to CIO NPs. Activity of caspase-3 and caspase-9 enzymes was also higher in CIO NPs exposed cells. Furthermore, co-exposure of N-acetyl-cysteine (ROS scavenger) efficiently abrogated the modulation of apoptotic genes along with the prevention of cytotoxicity caused by CIO NPs. Overall, we observed that CIO NPs induced cytotoxicity and apoptosis in HepG2 cells through ROS via p53 pathway. This study suggests that toxicity mechanisms of CIO NPs should be further investigated in animal models.

Kinetic and equilibrium investigation of Cu(II) removal by Co(II)-doped iron oxide nanoparticle-immobilized in PVA–alginate recyclable adsorbent under dark and photo condition

Magnetic nanoparticles of cobalt(II)-doped iron oxide (Co-Fe2O3) were synthesized by co-precipitation method using stable ferric and cobalt salts coated with different surfactants (citrate, acetate and polyetheylene glycol (PEG)) and water as the carrier. X-ray diffraction (XRD) and transmission electron microscope (TEM) confirmed the formation of single phase cobalt iron oxide nanoparticles while Fourier transform infrared (FTIR) was performed so as to ensure successful coating process. The nanoparticles were then immobilized in polyvinyl alcohol (PVA)-alginate gel matrix for the removal of Cu(II). X-ray photoelectron spectroscopy (XPS) was then used to validate the Cu(II) removal mechanism under photo condition. Langmuir equation was used to simulate the adsorption isotherms while Weber–Morris model and Langmuir–Hinshelwood model were then used to describe diffusion and adsorption kinetics. Adsorption–desorption results depicted that the PEG coated Co-Fe2O3 PVA–alginate adsorbent experienced only a 2.7% drop in removal efficiency after 5 cycles which made it a potential photoadsorbent to be used for Cu(II) removal.

Magneto-responsive hybrid materials based on cellulose nanocrystals

We fabricated self-standing films of cellulose nanocrystals (CNC) and electrospun composite fibers with CNC and polyvinyl alcohol both with magnetic properties arising from cobalt iron oxide nanoparticles in the CNC matrix. Aqueous dispersions of cobalt-iron oxide nanoparticles (10–80 nm diameter) and CNCs (ca. 150 nm length) were used as precursor systems for the films and composite fibers. The properties of the hybrid material were determined by electron and atomic force microscopy, X-ray diffraction, thermogravimetry and magnetometry. The CNC-inorganic system was ferromagnetic, with a saturation magnetization of ca. 20 emu g−1 of the magnetic phase. We demonstrate potential applications of the precursor dispersions, including magnetic fluid hyperthermia and highlight possible uses of the CNC-based magneto-responsive systems in biomedical and magneto-optical components.

Fabrication and Characterization of Cobalt Iron Oxide Nanoparticles by a Reverse Micelle Process

The preparation of CoFe2O4 nanoparticles in Igepal CO-520-cyclohexane-water reverse micelle solutions has been studied. Transmission electron microscopy and X-ray diffraction pattern analyses revealed the resultant particles to be CoFe2O4. The average size and distribution of synthesized particles calcined at 6000C for 2 hrs were in the range of 30 to 70 nm and broaden, respectively. The phase of synthesized particles was crystalline. The magnetic behavior of the synthesized particles was ferromagnetism. The effects of synthesis parameters, such as the molar ratio of water to surfactant and calcination temperature, are discussed.

Magnetic and elastic properties of CoFe2O4- polydimethylsiloxane magnetically oriented elastomer nanocomposites

Magnetic elastic structured composites were prepared by using CoFe2O4 ferromagnetic and superparamagnetic nanoparticles as fillers in polydimethylsiloxane (PDMS) matrixes, which were cured in the presence of a uniform magnetic field. Cobalt-iron oxide nanoparticles of three different average sizes (between 2 and 12 nm) were synthesized and characterized. The smallest nanoparticles presented superparamagnetic behavior, with a blocking temperature of approximately 75 K, while larger particles are already blocked at room temperature. Macroscopically structured-anisotropic PDMS-CoFe2O4 composites were obtained when curing the dispersion of the nanoparticles in the presence of a uniform magnetic field (0.3 T). The formation of the particle’s chains (needles) orientated in the direction of the magnetic field was observed only when loading with the larger magnetically blocked nanoparticles. The SEM images show that the needles are formed by groups of nanoparticles which retain their original average size. The Young’s moduli of the structured composites are four times larger when measured along the oriented needles than in the perpendicular direction. Magnetization (VSM) and ferromagnetic resonance curves of the structured composites were determined as a function of the relative orientation between the needles and the probe field. The remanence magnetization was 30% higher when measured parallel to the needles, while the coercive field remains isotropic. These observations are discussed in terms of the individual nanoparticle’s properties and its aggregation in the composites.