Alternating Gradient Force Magnetometer Research Articles

Modification of Magnetic Graphene Oxide by an Earth-Friendly Deep Eutectic Solvent to Preconcentrate Ultratrac Amounts of Pb(II) and Cd(II) in Legume Samples

A novel magnetic solid-phase extraction adsorbent using deep eutectic solvent-coated magnetic graphene oxide (EgLiCl-mGO) was proposed for simultaneous preconcentration of Pb(II) and Cd(II). The nanocomposite was characterized by Fourier Transform Infrared Spectroscopy, X-ray diffractometry, and alternative gradient force magnetometer. Parameters that could affect the preconcentration recoveries of the target ions were investigated via the one-factor-at-a-time method. The optimum conditions are pH of 4 ± 0.5, EgLiCl-mGO amount of 1.0 × 10−2 g, adsorption time of 5 min, eluent of HNO3 (1 mL, 2 mol L−1), and desorption time of one minute. The swelling property of the adsorbent versus pH was studied. The linearity of the dynamic range for Pb(II) (5.0 × 10−6–4.0 × 10−4 g L−1) and Cd(II) (5.0 × 10−6–15 × 10−5 g L−1) was recorded. The limits of detection were Pb(II): 1.2 × 10−6 g L−1 and Cd(II): 47 × 10−8 g L−1. The preconcentration factor of 50 was calculated for both ions and the relative standard deviations were 1.27% for Pb(II) and 0.94% for Cd(II). Reusability, effect of interference ions, selectivity, isotherm adsorption, kinetic adsorption, and thermodynamic adsorption were established. The adsorbent was successful at preconcentrating the ions in legumes.

Applicability of an eco-friendly deep eutectic solvent loaded onto magnetic graphene oxide to preconcentrate trace amount of indigotin blue dye

This article investigates the applicability of an environmentally friendly and energy efficient deep eutectic solvents (DES) for indigotin blue dye (IBD) preconcentration prior to its quantification by a UV–Visible spectrophotometer. The adsorbent (UT-mGO) is made of Fe3O4, graphene oxide, urea and tetramethylammonium chloride. It was prepared via dispersing magnetic graphene oxide in a DES. The adsorbent was prepared fast and easy, without consumption of dangerous reagents. X-ray diffraction patterns show pure structures of components. FT-IR spectra show strong interaction between DES and mGO. In addition, a scanning electron microscope confirms that DES covered the surface of mGO homogeneously. Magnetic amount and surface property were characterized by an alternating gradient force magnetometer and Brunauer-Emmett-Teller, respectively. High surface area and enough magnetic property, as well as π-π and electrostatic interactions among analyte and adsorbent propose UT-mGO as a qualified candidate to preconcentrate IBD. Effective parameters including pH, adsorbent amount, adsorption time, eluent and desorption time were optimized. Under the optimized conditions, the method has the following figures of merit: (a) limit of detection of 1.5 × 10-6 g L-1, (b) relative standard deviation (n = 7) of 3.49%, (c) preconcentration factor of 50 and (d) linearity of dynamic range of 1.0 × 10-5 to 45 × 10-5 g L-1. The adsorbent is not reusable but durable in six months. Isotherm model of Langmuir and kinetic model of pseudo-second-order fitted for the system. ΔH (-13.2 × 103 J mol−1), ΔS (5.38 J K−1 mol−1) and ΔG (-3.69 × 103 - +10.9 × 103 J mol−1) were calculated as thermodynamic parameters. The method was successfully applied for IBD preconcentration from three samples of fruit juices and three samples of jelly powders.

β-Cyclodextrin-grafted magnetic graphene oxide nanocomposites in ultrasound-assisted dispersive magnetic solid-phase extraction for simultaneous preconcentration of lead and cadmium ions

This article presents an ultrasound-assisted dispersive magnetic solid-phase extraction method (USA-DMSPE) to preconcentration Cd(II) and Pb(II) simultaneously. The adsorbent (mGO-βCD) was synthesized through three steps with consumption of environmentally friendly materials at room temperature. First graphene oxide (GO) was prepared via modified Hummer’s method and then magnetized by Fe3O4 precipitation (mGO). Finally, β-cyclodextrin was covalently immobilized onto the surface of mGO. X-ray diffraction patterns established pure crystallinity of the materials. Homogenous distribution of magnetic nanoparticles onto GO sheets was confirmed by scanning electron microscopy and transmission electron microscopy. FT-IR spectra proved successful modification of mGO by β-CD. Alternating gradient force magnetometer characterized magnetic property. Brunauer–Emmett–Teller showed porous structure of mGO-βCD and having high surface area. pH (7 ± 0.2), adsorption time (2 min), adsorbent amount (20 mg), eluent kind (HNO3 (3 ml of 2.0 mol L−1)) and desorption time (one minute) were optimum conditions. Sonication disperses adsorbent in sample solution, which accelerates mass transfer, as well as decreasing adsorption time and adsorbent usage amount. Applicability of the method was investigated according to preconcentration factor (Pb(II): 200 and Cd(II): 167), linearity of dynamic range (Pb(II): (2–410) and Cd(II) (3–400 μg L−1), limit of detection (Pb(II): 0.64 and Cd (II): 0.9 μg L−1), relative standard deviation (Pb(II): 1.68% and Cd(II): 2.51%) and adsorption capacity (Pb(II): 188.68 and Cd(II): 78.12). mGO-βCD was reusable for ten times and durable in six months. Selectivity and effect of interference ions were reported. Obtained recoveries for real samples verified the satisfactory performance of the method.

Adsorption/desorption of acid violet-7 onto magnetic MnO2 prior to its quantification by UV–visible spectroscopy: optimized by fractional factorial design

A highly efficient magnetic adsorbent is presented to preconcentrate acid violet-7 (AV-7) prior quantifying by UV–visible spectroscopy (λmax = 520 nm). The adsorbent consisting of MnO2 and Fe3O4 was synthesized via precipitation method. The green preparation method was simple and fast; it was performed at room temperature, without consuming organic solvents and thermal treatment. The synthesis strategy is based on using cetrimonium bromide as a surfactant. The surfactant was adsorbed onto negative sites of Fe3O4 then trapped Mn2+ ions and finally by adding NH3, nanoparticles of MnO2 were formed. The nanocomposite was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, alternating gradient force magnetometer and Brunauer–Emmett–Teller. The strong magnetic property of Fe3O4 and porous structure of MnO2 with positive charges enable efficient adsorption of AV-7 via magnetic solid phase extraction. The optimum conditions with respect to circumscribed fractional factorial design were pH (4.0 ± 0.2), sorbent amount (20 mg), adsorption time (20 min), adsorption temperature (308 K), eluent kind [ethanol/NaNO3 (1 mL/50 mg)], desorption time (10 min) and desorption temperature (283 K). The adsorption mechanism of AV-7 onto adsorbent was explained based on FT-IR spectra. The swelling behavior of adsorbent was investigated. Limit of detection (0.86 ng mL−1), relative standard deviation (n = 5) (1.61%), preconcentration factor (50) and linearity of dynamic range (20–400 μg L−1) perform the applicability of adsorbent in AV-7 preconcentration. The adsorbent is reusable for 15 times and durable for 100 days. The swelling behavior was investigated. The effects of interference ions and three dyes on the preconcentration recovery were studied. Temkin model and pseudo-second order were fitted with isotherm adsorption and kinetic adsorption, respectively. According to thermodynamic parameters, the adsorption is endothermic and spontaneous. The adsorbent was successfully applied to quantify AV-7 from a leather sample.

Application of magnetic graphene-based bucky gel as an efficient green sorbent for determination of mercury in fish and water samples

In this article, a highly efficient method based on coupling magnetic solid-phase extraction and dispersive microsolid-phase extraction was proposed to preconcentrate Hg2+. In this technique, extraction of Hg2+ was carried out by magnetic graphene-based bucky gel (MGBG). MGBG was prepared by dispersing magnetic graphene (MG) in a [Hmim][BF4]. Utilization of [Hmim][BF4] led to better dispersion of MG in aqueous solution and decreased the extraction time. In addition, MG was separable by an external magnet so filtration steps were omitted. The sorbent was characterized by X-ray diffraction, scanning electron microscopy, alternating gradient force magnetometer and Fourier transform infrared spectroscopy. The preconcentration conditions were optimized as pH value of 1 ± 0.2, dithizone concentration of 8 × 10−6 mol L−1, [Hmim][BF4] volume of 50 µL, MG amount of 5 mg, n-hexane volume of 200 µL and elution time of 5 min. The quantification of Hg2+ was carried out by UV–visible spectroscopy. Under the optimized conditions, limit of detection (2.11 μg L−1), relative standard deviation (2.59%), preconcentration factor (150) and linearity of dynamic range (7–100 μg L−1) were calculated which showed high reliability of sorbent to preconcentrate Hg2+. The effect of interference ions was investigated. The method was successfully applied to preconcentrate Hg2+ in fish and water samples. To better understand the adsorption of Hg2+ onto MGBG, thermodynamic of adsorption is reported.

Effects of pH and annealing on microstructure and magnetic properties of fabricated Co100-xWx nanowire arrays by AC electrodeposition

Co100-XWX (0 ≤ Χ ≤ 8) nanowire arrays with mean diameters of ~33 nm were synthesized by alternating current electrodeposition of Cobalt and Tungsten into template of anodic aluminum oxide. Effects of W concentration, pH and annealing process on magnetic properties and crystal structure of the fabricated nanowires were studied using Scanning electron microscopy, Energy dispersive X-ray spectroscopy, X-ray diffraction, and alternating gradient force magnetometer. The obtained results demonstrated that the crystal structure of prepared nanowires was hcp and fcc and a mixture of both, and the magnetic parameters such as coercivity and squareness (Sq = Mr/Ms) of nanowire arrays decreased with increasing the tungsten content and pH. For the study the effect of annealing temperature on the nanowire magnetic properties, the fabricated nanowires were annealed at different temperature (300 °C–600 °C). It is observed that the coercivity for all nanowire arrays with the different value of W content and pH increases with annealing temperature and the maximum variation is related to Co97W3 nanowire at pH = 3, which is explained by shape and magnetocrystelline anisotropy that is discussed in detail.

The Effect of Cation Distribution on Initial Permeability and Dynamic Magnetic Properties of Ni0.5(Zn1−xMgx/2Cux/2)0.5Fe2O4 Ferrites

Ferrites with the formula Ni0.5(Zn1−xMgx/2Cux/2)0.5Fe2O4, where x ranges from 0.0 to 0.8 with a step of 0.4, were prepared via the auto combustion method. The structure and chemical composition of the ferrites were analyzed using x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy, respectively. The presence of peaks in the XRD patterns was confirmed by the formation of a cubic spinel structure, because the main peaks of the patterns were related to the single-phase cubic spinel structure with PDF-number of 008-0234. The XRD patterns showed a slight shifting in peaks position due to unstable spacing values with increasing Mg2+, Zn2+ and Cu2+ contents in all ferrites. The mean crystallite size and lattice constant were determined from the Scherer’s formula and XRD data. They were found to have been increased by the increase of x concentration. Field emission scanning electron microscopy images were used to analyze the ferrites’ structures. In addition, room temperature magnetization and coercivity of ferrites were determined from the hysteresis loops in a magnetic field of 9 kOe by alternative gradient force magnetometer. It was found that the magnetization and coercivity of ferrites with increasing x contents were increased, which is discussed according to the site’s occupation of the substituted cations on the sub-lattices. Among all synthesized ferrites, Ni0.5(Zn1−xMgx/2Cux/2)0.5Fe2O4 with x = 0.8 showed the highest magnetization and coercively, whereas Ni0.5(Zn1−xMgx/2Cux/2)0.5Fe2O4 with x = 0.0 displayed the lowest corresponding values. The initial permeability of ferrites as a function of frequency were measured over a frequency range of 10 kHz to 10 MHz. In all curves, the initial permeability remained almost constant during increasing frequency until ∼ 1 MH,z and then it fell rapidly. This constant trend of the initial permeability shows the high operating frequency of the ferrites.

Strontium hexa-ferrites and polyaniline nanocomposite: Studies of magnetization, coercivity, morphology and microwave absorption

In this work, the investigation of wave absorption, phase formation, crystal structure and magnetic properties of SrFe12O19 hexa-ferrites nanoparticles that synthesized by co-precipitation using a microwave heating system and polyaniline-SrFe12O19 was carried out by using a combination of vector network analyser (VNA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. Alternating gradient force magnetometer proofs the magnetic property of the hexa-ferrite nanostructures. We studied Sr Hexa-ferrite nanoparticles and nanocomposite by changing in many parameters like power of microwave system and calcination temperature.In this work, the investigation of wave absorption, phase formation, crystal structure and magnetic properties of SrFe12O19 hexa-ferrites nanoparticles that synthesized by co-precipitation using a microwave heating system and polyaniline-SrFe12O19 was carried out by using a combination of vector network analyser (VNA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. Alternating gradient force magnetometer proofs the magnetic property of the hexa-ferrite nanostructures. We studied Sr Hexa-ferrite nanoparticles and nanocomposite by changing in many parameters like power of microwave system and calcination temperature.

Modification of Fe2O3-contained lignocellulose nanocomposite with silane group to remove nitrate and bacterial contaminations from wastewater

Natural composite containing iron oxide in lignocellulose (L/IO) was obtained from an extract of apricot tree wood by heating it in a wood coal furnace. This method provided a facile, “green” pathway for the fabrication of magnetic carbon substrate without using chemical reactions. Ion exchange technology was used to remove the nitrate using (L/IO) modified with 3-chloropropyltrimethoxysilane and 1,4-diazabicyclo[2.2.2]octane (Dabco) (ML/IO). The physicochemical properties were characterized by field emission scanning electron micrographs (FESEM), energy-dispersive X-ray analysis (EDX), alternating gradient force magnetometer (AGFM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectra for both (L/IO) and (ML/IO) as adsorbents. Preliminary experiments indicated less favorability of (L/IO) in removing nitrate from water compared to (ML/IO). Batch adsorption experiments were performed and the effects of pH, contact time, adsorbent dosage, initial nitrate concentration (Ci), temperature and competing anions were assayed on nitrate adsorption by (ML/IO). The obtained data were modeled using four kinetic models including the pseudo-first order (PFO), pseudo-second order (PSO), Weber–Morris and Elovich. The best fit of experimental adsorption data was exhibited by means of the pseudo-second-order model (R2 0.99). Also, the equilibrium data were fitted to the Langmuir, Freundlich, Temkin, Redlich–Peterson isotherm equations and the favorable fit exhibited with two Langmuir and Redlich–Peterson isotherms (R2 0.98). Finally, the desorption and regeneration studies showed a promising reusability of the (ML/IO). Antimicrobial activities of both (L/IO) and (ML/IO) were investigated by disc diffusion method against two Gram-positive bacteria, namely S. aureus and B. cereus, and four Gram-negative bacteria, namely E. coli, K. pneumoniae, P. aeruginosa and S. typhi, and two fungi, namely Aspergillus niger and Saccharomyces cerevisiae, in vitro. The antimicrobial effects were more prominent in all cases for (ML/IO) compared to (L/IO). The investigations confirmed that (ML/IO) was more active against Gram-negative (IZD 8–19 mm) than Gram-positive (IZD 6–8 mm) bacteria. The highest antibacterial activity of (ML/IO) was exhibited against E. coli with IZD value of 19 mm.

Synthesis of FeLaO3 and FeNdO3 Magnetic Nanocomposites as Photocatalyst for Organic Dye Removal

The resent work reports synthesis of mixed metal oxides of FeLaO3 and FeNdO3 nanocomposites via Co-precipitation method, as effective photocatalyst. The synthesized metal oxides were characterized by Fourier transfer infrared (FT–IR) spectroscopy; X-ray diffraction pattern, and transmission electron microscopy. Alternating gradient force magnetometer illustrates magnetic behavior of mixed metal oxides of FeLaO3 and FeNdO3 nanocomposites. The photocatalytic property of FeLaO3 and FeNdO3 nanocomposites were evaluated using the photodegradation of methyl violet, and malachite green oxalate under ultraviolet light irradiation at various parameters such as temperature, pH of solution, the concentration of dyes, does of catalysts, and time of illumination of UV light. The results show that these nanocomposites have applicable magnetic and photocatalytic performance.

Photocatalytic degradation of rhodamine B, and phenol red dyes using NiMn2O4 nanoparticles prepared by a new approach

NiMn2O4 nanoparticles have been successfully prepared through sol-gel method. The effects of different factors such as the type of solvent, and amino acid temperature were investigated on the size and morphologies of products. The smallest particle size of NiMn2O4 nanoparticles was found to be 25 nm in diameter. The magnetic properties of the samples were also measured by an alternating gradient force magnetometer (AGFM). The optical property of the desired products was investigated by UV–vis diffuse reflectance spectroscopy , and the band gap of product was computed nearly 3 eV. The estimated band gap confirms that this product may be used as a photocatalyst, so the photocatalytic test was conducted by photooxidation of dyes under ultraviolet irradiation and in the presence of NiMn2O4 nanoparricles. The results demonstrated that rhodamine B degradation was about 98 % under ultraviolet light for 80 min. Therefore, the synthesized product can be employed as an effective photocatalyst.

Adsorption and desorption of Pb2+ on magnetic Mn2O3 as highly efficient adsorbent: Isotherm, kinetic and thermodynamic studies

This article focuses on adsorption and desorption of Pb2+ on a novel adsorbent consisting of Mn2O3 and Fe3O4. The adsorbent was prepared through combining Sol-Gel and precipitation methods to in-situ magnetization. Decreasing preparation time, synthesizing at room temperature, not using organic solvents are advantages of the presented approach. The characterizations were done by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, alternating gradient force magnetometer and Brunauer-Emmett-Teller. High surface area and strong magnetic property propose the nanocomposite as a magnetic solid phase extraction adsorbent. Under the optimum preconcentration conditions, (a) limit of detection of 0.36 μg L−1, (b) relative standard deviation (n = 5) of 0.94%, (c) preconcentration factor of 33.33 and (d) linearity of dynamic range of 10–200 μg L−1 show the applicability of the adsorbent. The adsorbent was found to be durable for 3 months and efficiently applicable during this time but it is not reusable. To understand the adsorption mechanism, isotherm adsorption, kinetic adsorption and thermodynamic adsorption were established. The sorbent was employed to preconcentrate Pb2+ from water and vegetables samples.

Effect of Cation Distribution on the Structural and Magnetic Properties of Mg Substituted Nanosized Manganese Ferrites

In the present investigation, A series of Mg-Mn ferrite nanopowders with composition MgxMn[Formula: see text]Fe2O4 (with [Formula: see text], 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by the co-precipitation method. Thereafter, the obtained powders were pressed separately to form pellets, and sintered at 1250∘C for 3[Formula: see text]h at air atmosphere. Finally, the samples were characterized by X-ray Diffraction (XRD) technique, Scanning Transmission Electron Microscopy (STEM), Alternating Gradient Force Magnetometer (AGFM) and Curie temperature measuring instrument. The lattice constant and distribution of cation in the tetrahedral and octahedral sites have been deduced through XRD data analysis. The XRD pattern confirmed the existence of single phase of cubic spinel crystal structure with the lattice parameter ranging from 8.49 Å (for MnFe2O4) to 8.35 Å (for MgFe2O4). This behavior was attributed to the ionic radii. STEM micrographs exhibit that the particles are spherically shaped and agglomerated with particle size ranging 50–90[Formula: see text]nm quite consistent with particle size obtained from XRD data. The average crystallite size was 70[Formula: see text]nm. Magnetization decreases with increasing Mg concentration except for [Formula: see text], where it shows increasing trend. Curie temperature measurements exhibit increasing trend with increase in magnesium content. The variation of the saturation magnetization and Curie temperature with increasing concentration of the Mg[Formula: see text] ions can be explained on the basis of cation distribution, strengthening A–B interaction and Neel’s two sub-lattice.

Magnetic nanotubes obtained from atomic layer deposition coated electrospun nanofibers

High-aspect ratio Al2O3/Ni/Al2O3 core–shell hollow nanotubes were prepared by combining electrospinning, atomic layer deposition, and a subsequent chemical reduction process. Electrospun poly(vinyl alcohol) (PVOH) nanofibers were obtained by electrospinning. Then, these fibers were coated with atomic layer deposition to obtain PVOH/Al2O3/NiO/Al2O3 core–shell nanowires. Since the NiO must be deposited at 200 °C, the PVOH nanofibers must first be coated with Al2O3 at 80 °C, which act as a protective layer of the fibers so that they can withstand higher temperatures. Once PVOH/Al2O3/NiO/Al2O3 core–shell nanowires are obtained, they are subjected to a chemical reduction process that generates Al2O3/Ni/Al2O3 core–shell hollow nanotubes. Their morphologies were studied by scanning and transmission electron microscopies, the thickness was determined by ellipsometry, and all magnetic measurements were performed in an alternating-gradient force magnetometer. Finally, assuming that the nanostructures exhibit a curling reversal process, the authors have analytically calculated the coercivity of the nanotubes.

Synthesis of a magnetic WO3 nanocomposite for use in highly selective preconcentration of Pb(II) prior to its quantification by FAAS.

A novel sorbent consisting of WO3 and Fe3O4 is described for preconcentration of Pb(II). It was prepared without consumption of organic solvents. The nano composite was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, alternating gradient force magnetometer and Brunauer-Emmett-Teller. Having high surface area and being formed oxygen sheets propose the nanocomposite as a sorbent. Adsorption and desorption conditions were optimized and Pb(II) is quantified by flame atomic absorption spectroscopy. The sorbent can highly selectively preconcentrate Pb(II) at pH values between 3 and 7. The preconcentration time is short and sorbent is re-usable. Under the optimized conditions, the method has the following figures of merit: (a) limit of detection of 0.60ngmL-1, (b) relative standard deviation (n= 5) of 0.87%, (c) preconcentration factor of 33.33 and (d) linearity of dynamic range (10-200ng.mL-1). Isotherm adsorption, kinetic adsorption and thermodynamic adsorption were stablished. The material was applied to the preconcentration of Pb(II) from herbal medicines. Graphical abstract Schematic presentation of a nanocomposite (Fe3O4 - WO3) that was prepared from sodium tungstate (Na2WO4), oxalic acid, HCl and magnetic Fe3O4 nanoparticles for the magnetic solid phase extraction of lead at trace levels.

Ferromagnetic resonance in coupled magnetic nanostructured arrays

The modulated field sweep ferromagnetic resonance (FMR) spectroscopy was used to study the magnetization dynamics in large arrays of interacting cubic nanomagnets. A 60nm thick permalloy (Ni80Fe20) thin films were patterned using a lift-off process into several large arrays of 60 x 60 nm2 nanostructures where the spacing between the magnetic nanocubes was varied to control the strength of dipolar coupling. Electron beam lithography was used for device patterning using lift-off. The permalloy films were deposited using magnetron sputtering. DC magnetic properties were evaluated using alternating gradient force magnetometer (AGFM). In the FMR measurements, the orientation of DC bias magnetic field was varied from the in-plane to out-of-plane with respect to the 2D plane of the arrays. The FMR peak splitting and multiple FMR modes were observed in the evolution of the FMR spectra as the function of the bias field orientation, and were strongly influenced by the nanomagnet geometry and the spacing between the nanomagnets. Two resonance modes, shape and lattice, were particularly well pronounced in the observed FMR spectra. These modes are characterized by effective demagnetizing factors representing different symmetries of the system of interacting nanomagnets. Micromagnetic modeling suggest that micromagnetic texture within the nanomagnets modulated by the stray fields from the neighbors correlates with the FMR spectra.

Synthesis of iron oxide nanoparticles modified mesoporous carbon and investigation of its application for removing dibenzothiophene from fuel model

In this study, magnetic ordered mesoporous carbon (γ-Fe2O3/CMK-3) containing iron oxide nanoparticles embedded in the carbon walls by wet impregnation method was prepared and used as a high effective magnetic adsorbent to adsorb polyaromatic sulfur compound (dibenzothiophene). The structure and morphology of adsorbent were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption (BET), thermal gravimetric (TGA) and alternating gradient force magnetometer techniques (AGFM). These techniques illustrate that the maghemite nanoparticles have an average size of 10 ± 3 nm and are well distributed on the ordered mesoporous carbon host. After embedding maghemite nanoparticles, the uniformity of mesoporous framework of CMK-3 still remaining stable, which has an ordered two-dimensional hexagonal (p6mm) structure, high specific surface area, maxima pore size of 5.5 nm and large pore volume (up to 1.01 cm3 g−1). The γ-Fe2O3/CMK-3 nanocomposite shows superparamagnetic behavior with a saturation magnetization of 0.5 emu g−1, which makes it favorable compound for magnetic separation procedure. The resulting magnetic mesoporous nanocomposite was investigated for adsorption of dibenzothiophene (DBT) as a model sulfur compound in n-hexane as fuel model. Various factors influencing the adsorption of DBT, including adsorption temperature, contact time and initial DBT concentration were studied. The kinetic data was well described by pseudo-second-order kinetic model and the equilibrium adsorption data was fitted to the Langmuir thermodynamic model. In addition, the adsorbent could be regenerated by washing with toluene and over 85% adsorption capacity could be maintained after three regeneration cycles. The results confirmed that γ-Fe2O3/CMK-3 has the potential superiority in removal of DBT from fuel model with a maximum adsorption capacity of 67 mg DBT per gram of adsorbent and an easy magnetically separable process.

Synthesis of carbon nanotube, graphene, CoFe2O4, and NiFe2O4 polypyrrole nanocomposites and study their microwave absorption

In this experimental work, different conductive polymer nanocomposites were synthesized using polypyrrole as conductive polymer and CoFe2O4, NiFe2O4, CNT and graphene as fillers. X-ray diffraction pattern was used to study the crystallinity of the products and it was found CoFe2O4, NiFe2O4, CNT, and graphene were successfully embedded in the polymer matrix. To further approve the synthesis of the nanocomposites, energy dispersive X-ray spectroscopy was served. Surface groups of the synthesized nanocomposites were studied by Fourier transform infrared and Raman spectroscopy. The morphology of the products was examined by scanning electron microscopy and transmission electron microscopy. It was found the fillers were successfully embedded in the polymer matrix and they were in nanometer scales. To investigate the magnetic properties and conductivity of the polymer nanocomposites, alternating gradient force magnetometer and four-point probe were used, respectively. Finally, the microwave absorption properties of the polymer nanocomposites were studied and it was found the fillers have different effects on the polymer microwave absorption value.

Tailoring the structural and magnetic properties of masked CoPt thin films using ion implantation

The effects of ion implantations through a mask on the structural and magnetic properties of Co80Pt20 films were investigated. The mask was patterned using the self-assembly of diblock copolymers. For implantation, high (40 keV for 14N+ and 100 keV for 40Ar+) and low (7.5 keV for 14N+ and 4.5 keV for 40Ar+) energy 14N+ and 40Ar+ ions were used to modify the structural and magnetic properties of these films. X-ray diffraction and TRIM simulations were performed for understanding the structural changes due to ion implantations. These results revealed the intermixing of Co atoms in lower layers and lattice expansion in Co80Pt20 magnetic and Ru layers. A lateral straggling of Co caused an increase in the exchange coupling in the masked region. Depletion of Co atoms in Co80Pt20 layer caused a decrease in the anisotropy constant, which were further confirmed by the alternating gradient force magnetometer and magnetic force microscopy results. The magnetic force microscopy images showed an increase in domain width and domain wall width confirming the above-mentioned effects.

Solvent-free preparation of copper ferrite microspheres composed of nanorods using a new coordination compound as precursor

This work presents a simple solvent-free route based on solid-state thermal decomposition approach to synthesize magnetic copper ferrite (CuFe2O4) microspheres and copper ferrite/metal oxide composites. For this purpose, [Cu(en)3]3[Fe(ox)3]2 complex (where en = ethylenediamine and ox = oxalate) was introduced as a new single-source precursor. Ferromagnetic property of the nanostructures was determined by alternating gradient force magnetometer. The effect of different ligands and temperatures on the morphology of the products was investigated. Solid-state thermal decomposition of the precursor at different temperatures in the range of 400–800 °C led to the fabrication of magnetic copper ferrites with various particle sizes. X-ray powder diffraction patterns and images of scanning electron microscopy showed formation of CuFe2O4/Fe2O3 microspheres with very smooth surfaces and CuFe2O4/CuO microspheres coated with nanorods by thermal decomposition of the precursor at 400 and 700 °C, respectively. The results confirmed that copper ferrite and CuFe2O4/CuO nanocomposites were suitable materials with appropriate performance in catalyst and photo-catalytic applications.