Magnetic NiFe2O4 Nanoparticles Research Articles

Adsorption Performance of Reactive Red 2BF onto Magnetic NiFe₂O₄ Nanoparticles Prepared via the Coprecipitation Process.

Magnetic NiFe₂O₄ nanoparticles were successfully prepared via the coprecipitation process with ferric nitrate, nickel nitrate, and sodium hydroxide as raw materials, and they were characterized by the scanning electron microscopy (SEM), the transmission electron microscope (TEM), the X-ray diffraction (XRD), the vibrating sample magnetometer (VSM), the energy dispersive spectroscopy (EDS) and the Brunauer-Emmett-Teller (BET). The magnetic NiFe₂O₄ nanoparticles were employed to research the adsorption performance of reactive red 2BF (RR-2BF) onto them, and they revealed very large adsorption capacity of RR-2BF. The adsorption kinetics data were evaluated with the pseudo first-order, the pseudo second-order and the intraparticle diffusion models, and the results showed that the pseudo second-order kinetics model was best fitted for the adsorption of RR-2BF onto magnetic NiFe₂O₄ nanoparticles. While, the adsorption isotherm experiments were carried out at room temperature, and the experimental data conformed to the Langmuir model, which suggested that the adsorption of RR-2BF onto magnetic NiFe₂O₄ nanoparticles was the monolayer adsorption process. The magnetic NiFe₂O₄ nanoparticles revealed good reusability, and the adsorption capacity was maintained over 80% of the initial capacity after being used for five cycles.

Synthesis of magnetic g-C3N4/NiFe2O4 nanocomposites for enhanced visible-light photocatalytic performance

A magnetically separable photocatalytic g-C3N4/NiFe2O4 nanocomposite was obtained via a two-step method. In the first step, the magnetic NiFe2O4 nanoparticles were acquired in a few minutes by ionic liquid self-combustion approach which significantly reduced the synthesis time of nanocomposites. Besides, the research of g-C3N4/NiFe2O4 nanocomposites for the visible-light-driven degradation of methylene blue in the absence of H2O2 was detailed. Compared with pure g-C3N4 and NiFe2O4, the as-prepared nanocomposites with NiFe2O4 doping of 12% manifested the enhanced photocatalytic activity and stability after three cycles for degrading methylene blue, and the photocatalytic process followed first-order reaction kinetics. Trapping experiments demonstrated that the H+ and OH• scavengers are the main active species and O2•− has a small effect for visible-light-driven degradation of methylene blue.

The underlying mechanisms of enhanced microwave absorption performance for the NiFe2O4-decorated Ti3C2Tx MXene

Incorporation of magnetic loss component is more favorable to high-performance microwave absorbing materials. In this paper, the NiFe2O4-decorated Ti3C2Tx MXene composites were synthesized by the in-situ chemical co-precipitation method. The magnetic NiFe2O4 nanoparticles were attached on the surfaces or inserted into the interlayers of Ti3C2Tx MXene. Interestingly, we reduced effectively complex permittivity and enhanced magnetic loss by increasing the NiFe2O4 content on Ti3C2Tx MXene. Stronger electromagnetic attenuation ability and preferable impedance matching property were achieved and considered to be responsible mainly for improving absorbing peaks as well as bandwidth of the NiFe2O4-Ti3C2Tx MXene composite. In particular, the NiFe2O4-Ti3C2Tx-20 sample exhibited an optimal effective absorption bandwidth (RL < −10 dB) of 7.68 GHz with the material thickness of only 1.5 mm. These findings are believed to pave the way of further promoting microwave absorption performance of Ti3C2Tx MXene from magnetic functionalized decoration of view.

Electrospun nanofibers of PVDF-HFP composites containing magnetic nickel ferrite for energy harvesting application

Nickel ferrite nanoparticles (NiFe2O4) synthesized by chemical co-precipitation method, are added to poly(vinylidene fluoride-co-hexafluoroproplyene) (PVDF-HFP) in specific concentrations (1, 2, and 3 wt%) and the composite nanofibers are fabricated by electrospinning. Structural investigation and morphology of the synthesized NiFe2O4 magnetic nanoparticles reveal its spinel nature. The crystalline behavior in addition to the ferroelectric properties of NiFe2O4 enhance the interfacial interaction with the polymer chains and creates better dipole alignment and phase transformations within the nanocomposite. The nanocomposite with 1 wt% NiFe2O4 shows the maximum dielectric constant of 118 at 1 Hz frequency, which is about 24 times higher than that of the neat polymer. At the typical concentration of 2 wt% NiFe2O4 in PVDF-HFP, the nanocomposite is capable to generate an output voltage of 4 V suggesting the possible use of those flexible and magnetic polymer nanocomposites in designing piezoelectric devices. The structural performance, dielectric properties and the energy harvesting performance of the PVDF-HFP/NiFe2O4 nanocomposites are demonstrated here based on the filler and polymer characteristics.

NiFe2O4 coated sand as a nano-adsorbent for removal of Pb (II) from aqueous solutions

In this study, NiFe2O4 magnetic nanoparticles as an adsorbent for lead (Pb) removal were coated on sand particles. Adsorption studies were conducted to investigate the efficacy of contact time, pH, adsorbent dosage and initial lead ion concentration on the removal efficiency. To choose the most fitting kinetic model, the pseudo-first order and pseudo-second order models were compared and the most suitable kinetic model was selected by the pseudo-second order. Langmuir and Freundlich isotherms were evaluated and the most suitable isotherm was observed as the Freundlich model. In addition, the NiFe2O4 coated sand can simply be removed by an ordinary filtration process.

Preconcentration/Extraction of Phthalate Esters in Milk Samples Using MFe2O4-Based Magnetic Ionic Liquid Effervescent Tablets Consisting of Accessory Functional Fillers

Magnetic effervescent tablet-based (MEFTs) microextraction has recently gained much attention because it requires no physical energy inputs or dispersive solvent. A prominent shortcoming of MEFTs results from the short tablet storage period owing to rapid absorption of moisture, thereby making it impracticable for field use. Physico-chemical properties of MEFTs were greatly improved by the addition of water-soluble starch, such as hygroscopicity, storage/stability period, adherence, effervescent time, and intensity. MEFTs were used in a MFe2O4-based magnetic ionic liquid effervescent tablet microextraction (MMIL-ETM) for preconcentration/extraction of trace phthalate esters (PAEs) in milk matrices. This MMIL-ETM method provided three distinct advantages: (1) MEFTs integrate water-soluble starch as a functional filler, leading to longer tablet storage/stability; (2) combined effervescent dispersion and rapid retrieval of NiFe2O4 magnetic nanoparticles (MNPs) result in substantial time saving; and (3) integration of ionic liquid-based extraction with MNP adsorption produces high PAEs extraction recoveries. Optimized experimental parameters were as follows: 0.77 g mixture of Na2CO3 and water-soluble starch, 7 mg NiFe2O4 (30 nm), 50 μL [HMIM]NTf2, solution pH 2.3, and 300 μL acetonitrile as elution solvent. Under optimized conditions, extraction recoveries for four PAEs reached as high as 94.8–105.6%, LODs were as low as 0.042 μg L−1, and RSDs were < 5.4% for intra- and inter-day precisions. Due to the longer stable storage period and rapid dispersion without additional physical energy inputs, the proposed MMIL-ETM method shows great potential application for routine food monitoring under field conditions.

Efficiency of glucose oxidase immobilized on tannin modified NiFe2O4 nanoparticles on decolorization of dye in the Fenton and photo-biocatalytic processes

Immobilized enzymes are significantly studied both environmental and textile industries. In this work, glucose oxidase was immobilized on the tannin coated NiFe2O4 magnetic nanoparticles for decolorization of indigo carmin. The as-synthesized all magnetic nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, UV–vis spectroscopy, Thermogravimetric analysis, Vibrating sample magnetometer and Scanning electron microscopy. The activity of the free and immobilized glucose oxidase in various temperature and pH values was investigated. Finally, the produced immobilized glucose oxidase was applied for decolorization of indigo carmine due to production of H2O2. The decolorization yields of indigo carmine are 98.6% and 37.6% of the glucose oxidase immobilized on tannin modified NiFe2O4 in presence of the both of UV-light and iron(II)chloride for 90 min, respectively. The results exude that the obtained photocatalysts exhibit excellent both photocatalytic efficiency and easy separation from dye solution by an external magnet.

Effects of Solution Concentration on Magnetic NiFe2O4 Nanomaterials Prepared via the Rapid Combustion Process

A rapid combustion process for the preparation of magnetic NiFe₂O₄ nanomaterials was introduced. The experimental results showed that the solution concentration of ferric nitrate was a key factor to control the structure and the properties of magnetic NiFe₂O₄ nanomaterials: the magnetic NiFe₂O₄ nanorods with the diameter of about 15 nm, the length of approximately 100 nm and the saturation magnetization of 18.4-25.3 emu/g could be formed when the solution concentration of ferric nitrate was equal or greater than 1.68 mol/L; the magnetic NiFe₂O₄ nanoparticles with the average particle sizes of 20-32 nm and the saturation magnetization of 10.0-31.8 emu/g could be formed when the solution concentration of ferric nitrate was lower than 1.12 mol/L.

Preparation of an activated carbon from hazelnut shells and its hybrids with magnetic NiFe2O4 nanoparticles

Preparation of an activated carbon from hazelnut shells and its hybrids with magnetic NiFe2O4 nanoparticles

NiFe2O4 as a magnetically recoverable nanocatalyst for odourless C–S bond formation via the cleavage of C–O bond in the presence of S8 under mild and green conditions

We present green methodologies for one‐pot and odourless syntheses of unsymmetric and symmetric diaryl sulfides via C─O bond activation using NiFe2O4 magnetic nanoparticles as a reusable heterogeneous nanocatalyst. The synthesis of unsymmetric sulfides is performed using the cross‐coupling reaction of phenolic esters such as acetates, triflates and tosylates with arylboronic acid/S8 or triphenyltin chloride/S8 as thiolating agents in the presence of base and NiFe2O4 magnetic nanoparticles as a catalyst in poly(ethylene glycol) as solvent at 60–85°C. Also, the synthesis of symmetric diaryl sulfides from phenolic compounds using S8 as the sulfur source and NiFe2O4 as catalyst in dimethylformamide at 120°C is described. Using these protocols, the syntheses of various unsymmetric and symmetric sulfides become easier than using the available protocols due to the use of a magnetically reusable bimetallic nanocatalyst and avoiding the use of thiols and aryl halides.

Papain Immobilization on NiFe2O4 Magnetic Nanoparticles Functionalized with Gallic Acid and Microwave Assisted Digestion of Bovine Serum Albumin

NiFe2O4 magnetic nanoparticles were solvothermally prepared. NiFe2O4 magnetic nanoparticles were functionalized with gallic acid and then papain immobilized on NiFe2O4 functionalized with gallic acid. The obtained samples were characterized and the activities of free and immobilized papain were studied. Immobilized papain showed higher and more effective activity than free papain. This immobilized papain retained about 75.5% of its initial activity after 8 weeks of storage at 4 °C in sodium phosphate buffer (0.1 M, pH 6.5), while the free trypsin protected 30.5% of its initial activity during the same condition. Furthermore, the immobilized papain protected approximately 51% of its initial activity following the times of ten sequential reuse. Finally, the microwave assisted digestion of bovine serum albumin was carried out for 15 s with matrix-assisted laser desorption/ionization mass spectrometry by using free and immobilized papain.

Preparation of an activated carbon from hazelnut shells and its hybrids with magnetic NiFe2O4 nanoparticles

A low cost activated carbon was prepared from hazelnut shells by chemical activation with sodium hydroxide at 600 °C in a N2 atmosphere and then combined with magnetic NiFe2O4 nanoparticles by hydrothermal and co-precipitation methods. Samples were characterized by FESEM, TEM, XRD, FT-IR, nitrogen adsorption and magnetic measurements. Results indicated that the NiFe2O4 nanoparticles synthesized by the hydrothermal method had a higher saturation magnetization and smaller average particle size than those produced by the co-precipitation method. The specific surface area and total pore volume of the activated carbon decreased from 314 to 288 m2/g and 0.3639 to 0.3338 cm3/g, respectively by forming a hybrid with the magnetic NiFe2O4 nanoparticles synthesized by the hydrothermal method. NiFe2O4 nanoparticles were mainly distributed on the surface, although a few were inside the pores of the activated carbon. Their sizes were the same as those of the original ones. The saturation magnetization of the hybrids was lower than those of the original NiFe2O4 nanoparticles due to the existence of the activated carbon. They showed superparamagnetic behavior at room temperature and were easily separated from solutions by an external magnet.

Removal of Zn(II) from Aqueous Solutions Using NiFe2O4 Coated Sand as an Efficient and Low Cost Adsorbent: Adsorption Isotherm, Kinetic and Thermodynamic Studies

In this study, NiFe2O4 magnetic nanoparticles as adsorbent for zinc (Zn) were coated on sand particles. Adsorption studies were conducted to investigate the efficacy of contact time, pH, adsorbent dosage, initial zinc ion concentration and temperature on removal efficiency. To decide the most fitting kinetic model, the suitability of pseudo-first order and pseudo-second order model was compared and the most appropriate kinetic model was determined to be pseudo-second-order. Langmuir, Freundlich and Dubinin–Radushkevich isotherms were assessed and the most suitable isotherm was observed to be Langmuir model. The maximum adsorption capacity obtained from Langmuir model was 57.14 mg/g. The calculated thermodynamic parameters indicated the endothermic and spontaneous character of the adsorption process. In addition, the adsorbent can easily be removed by a simple filtration process.

Thermophysical Investigations of Ultrasonically Assisted Magnetic Nanofluids for Heat Transfer

The NiFe2O4 magnetic nanoparticles synthesized and used to prepare stable water-based magnetic nanofluids of various concentrations by ultrasonically assisted two-step techniques. Thermophysical investigations are made on the nanofluids at different temperatures ranging from 20 to 80 °C. The measurements revealed that the thermal conductivity of nanofluids significantly enhances with an increase in the percentage of nanoparticle volume fraction. The thermal conductivity measurements showed that the maximum enhancement is 32.65% achieved at 1% nanoparticle volume fraction and at 80 °C. Specific heat of nanofluids was decreased with increasing nanoparticle volume fractions, and it augments with increasing temperature. Viscosity measurements showed that nanofluid had a Newtonian behavior at all nanoparticle volume fractions and temperatures considered. The viscosity of the nanofluid increased with increasing nanoparticle concentration and decreasing temperature. Experimental results revealed that the viscosity sensitivity to temperature variation is minor, while it is more sensitive to the variations of nanoparticle volume fraction. The density of nanofluids was increased with increasing nanoparticle volume fractions and decreased with increasing temperature. Lastly, efforts were made to provide a precise correlation to estimate the thermal conductivity, as well as other thermophysical properties at various temperatures and volume fractions of nanoparticles. The comparison between the results and the correlation results showed a good agreement.

Effects of surfactant on the structural and magnetic properties of hydrothermally synthesized NiFe2O4 nanoparticles

A simple and effective hydrothermal route is adopted where glycerol and NaOH are used as surfactant and precipitating agents respectively, for the synthesis of NiFe2O4 (NFO) magnetic nanoparticles. The structure and morphology of the as prepared NFO are characterized by X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM) techniques. The formation of phase-pure NFO is evident from the XRD studies. The crystallite size calculated using the Scherer equation are in the range of 22–38 nm. A mixed morphology of spherical and octahedral shape are found in FESEM images depending on the concentrations of glycerol as surfactant. The increase in Curie temperature (Tc) from 805 to 815 K is observed, when the surfactant concentration is increased from 10 to 20% w/v. However with an increase in surfactant concentration to 40% w/v, the Tc decreases to 790 K. The NFO nanoparticles prepared at 10% w/v surfactant concentration show a high saturation magnetization (Ms) of 42 emu/g which increases to 53 emu/g at 20% w/v of surfactant. Very small change in Ms (decrease of 1–2 emu/g) is noticed with further increase in surfactant to 40% w/v. The possible explanations are hypothesized for such observed phenomena. A linear dependence of coercivity (Hc) and remanence (Mr) with surfactant concentrations is found for NFO nanoparticles, where both Hc and Mr decrease with increase in surfactant concentrations. It is found that glycerol, which is economical and eco-friendly, is an effective surfactant to prepare NFO nanoparticles with desirable magnetic properties and controllable particle size.

Synthesis of diaryl sulfides via nickel ferrite‐catalysed C─S bond formation in green media

NiFe2O4 magnetic nanoparticles (MNPs) were synthesized, characterized and applied as an air‐stable, inexpensive and magnetically separable nanocatalyst for the synthesis of structurally diverse sulfides. Efficient methodologies were developed for the synthesis of unsymmetric diaryl sulfides via odourless and one‐pot reactions of triphenyltin chloride/S8 or arylboronic acid/S8 as thiolating agents with aryl halides or nitroarenes as starting materials in the presence of base (K2CO3 or NaOH) and NiFe2O4 MNPs as a catalyst in water or poly (ethylene glycol) as solvent at 80–110 °C. Free from ligand and the unpleasant smell of thiols and with the use of magnetically reusable nanocatalyst, green solvents and commercially available and cheap sulfur source and starting materials, these methods are more eco‐friendly and practical than available protocols for the synthesis of sulfides.

Synthesis of NiFe2O4 nanoparticles for energy and environment applications

Magnetic nanoparticles are of great interest due to their applications in energy and environment. In this work, we developed a chemical solution based method to synthesize NiFe2O4 (NFO) nanoparticles with different sizes and structures by organic ligands and studied their applications in magnetic electrolyte concentration cells and waste water treatment. NFO nanoparticle growth is controlled by the organic passivating ligand ratios, reaction temperatures, and reaction solution concentrations to achieve the control of NFO nanoparticle size ranging from 25 nm to 160 nm. The NFO growth mechanism is controlled by aggregation related mechanism, leading to tunable magnetic properties and concentration cell device performance. Magnetic biochar consisting of biochar/NFO composite was also obtained based on the developed method. Waste water containing Rhodamine B was tested by the synthesized magnetic biochar. We believe the method developed in this work about magnetic NFO nanoparticles and magnetic biochar will shed light on the application of magnetic nanoparticles in energy and environment.

Tailoring the Structural, Optical and Magnetic Properties of NiFe2O4 by Varying Annealing Temperature

Magnetic nanocrystalline NiFe2O4 nanoparticles of size ranging between 13 and 19 nm were synthesized by the hydrothermal method using polyethylene glycol (PEG) as surfactant. The role of annealing on phase, crystallite size, and morphology was determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Energy-dispersive X-ray spectroscopy (EDX) was used for qualitative analysis. X-ray diffraction confirmed the single phase of as-obtained particles. TEM revealed a spherical morphology having an average particle size of 13.73 nm at 523 K and rises to 14.89, 16.42, and 21.14 nm at 623, 723, and 823 K respectively, which is approximately the same as the crystallite size determined from XRD. EDX results confirmed that elemental ratios were in stoichiometry. Fourier transform infrared (FTIR) spectral analysis demonstrates the formation of M-O bond in NiFe2O4 nanoparticles. The optical spectra obtained from UV-visible spectroscopy revealed that nanoparticles have direct allowed energy band gap of 2.34, 2.47, 2.70, and 2.20 eV at 523, 623, 723, and 823 K respectively. A vibrating sample magnetometer (VSM) was used at room temperature for magnetic measurements which further showed ferromagnetic behavior of as-synthesized material. In addition, it was found that saturation magnetization increases with an increase of annealing temperature while coercivity decreases with temperature.

Constructing magnetic catalysts with in-situ solid-liquid interfacial photo-Fenton-like reaction over Ag3PO4@NiFe2O4 composites

A high-performance photocatalyst should be superior not only in light absorption and charge transfer but also surface catalytic reaction. Here we report a green and simple strategy for evenly decorating Ag3PO4 particles using magnetic NiFe2O4 nanoparticles (NPs). The NiFe2O4 NPs could act as a magnetic support material for recycling the photocatalysts, as well as in situ catalytically decompose the H2O2 produced on the surface of Ag3PO4 into O2− and OH radicals via a photo-Fenton process. The catalytic decomposition of H2O2 could produce strong oxidative capacity O2− and OH radicals for the organic pollutants degradation and reduce host semiconductor holes (h+(Ag3PO4)) consumption by these produced H2O2. Thus, the photocatalytic activities of Ag3PO4@NiFe2O4 composites were greatly enhanced. Taking the photocatalytic degradation of Methyl orange (MO), hardly decomposed colorless phenol compounds bisphenol A (BPA) and killing Escherichia coli (E. coli) as mode photocatalytic reactions, this system exhibited superior photocatalytic performances than that of pristine Ag3PO4. Electron spin resonance (ESR) spectroscopy and sacrificial-reagent incorporated photocatalytic characterizations indicated that the in situ eliminating/active decomposition of H2O2 produced by Ag3PO4 was the main reason for the enhanced photocatalytic activities.

Layer by layer coating of NH2-silicate/polycarboxylic acid polymer saturated by Ni2+ onto the super magnetic NiFe2O4 nanoparticles for sensitive and bio-valuable separation of His-tagged proteins

Magnetic nanoparticles NiFe2O4 was synthesized and covered in the silicate lattice of (3-Aminopropyl) triethoxysilane (APS) by the sol-gel process. Subsequently, the EDTA-dianhydride was attached to the amino surface of magnetic nanoparticles (MNPs) during the nucleophilic attack. This polycarboxylic layer trapped the high level of nickel ions for selective bonding to the His-tagged recombinant protein. The surface of MNPs was investigated by TEM, XRD, SEM (EDSA), VSM, BET, FT-IR and zeta potential analysis which characterized the size, chemical lattice, morphology, magnetic strength, specific surface area, functional groups and charge of the surface of nanoparticles. The performance and validity of the nanoparticles were studied by the purification of His-tagged green fluorescence protein (His-GFP). Also, the safety of proposed Ni-MNPs in the purification procedure of His-tagged proteins for pharmaceutical applications was proved by the determination of the nickel leakage level in the purified final protein using atomic absorption spectroscopy. In vitro cytotoxicity of Ni-MNPs and trace metal ions was investigated by the MTS assay technique. In addition, the comparison of biological activity in purified protein (GM-CSF) and commercial sample did not show any toxic effect.