Modification of Mg<Subscript>3</Subscript>Si<Subscript>2</Subscript>O<Subscript>5</Subscript>(OH)<Subscript>4</Subscript> nanotubes by magnetite nanoparticles

The magnetite nanoparticles and nanocomposite “Nanotube of hydrosilicate Mg—magnetite nanoparticles—Mg-ChR-NT/Fe₃O₄-NP” were obtained by coprecipitation. The composition of the synthesized samples has been established by X-ray diffraction. Using transmission electron microscopy, the presence of magnetite nanoparticles has been detected both inside the NTs and at the external surface of the NT walls. The specific surface of the NTs, nanoparticles, and composite is determined.     

Physical–chemical properties of xylan/PAAc magnetic semi‐interpenetrating network hydrogel

A novel magnetic semi‐IPN hydrogel based on xylan and poly(acrylic acid) was prepared, and the prepared hydrogels had excellent thermal stability, magnetic‐, and pH‐ sensitive properties. The physical‐chemical properties of the prepared hydrogels depended on the contents of xylan and Fe₃O₄ nanoparticles. The thermal stability of the hydrogels enhanced as the contents of xylan and Fe₃O₄ nanoparticles increased; however, the equilibrium swelling ratio decreased with increasing the contents of Fe₃O₄ nanoparticles and xylan. The interconnected pore channels were formed in the hydrogels and the amount of the channels increased with an increase in xylan content. The prepared hydrogels had a super‐paramagnetic property, and the magnetization increased with an increase in the content of Fe₃O₄ nanoparticles. The superior characteristics of the xylan/PAAc magnetic semi‐IPN hydrogel would expand its applications in drug delivery and magnetic separation aspects. POLYM. COMPOS., 36:2317–2325, 2015. © 2014 Society of Plastics Engineers     

Fabrication of PMMA/PANI/Fe3O4 as a Novel Conducting Hybrid Coating

In this paper, an excellent new hybrid coating including poly(methyl methacrylate) (PMMA), polyaniline (PANI), and magnetite nanoparticles (Fe₃O₄) was obtained. Fe₃O₄ nanoparticles were synthesized using coprecipitation method, and then magnetite nanoparticles have been dispersed into the PANI to increase compatibility with PMMA. Also, PANI/Fe₃O₄ nanocomposites were synthesized through in situ emulsion polymerization, and then PMMA/PANI/Fe₃O₄ hybrid coating was successfully synthesized using batch emulsion polymerization method. Structure, morphology and thermal stability of the samples were characterized using Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal gravimetric analysis (TGA). The synthesized samples were well distributed with an average diameter smaller than 20?nm. Microscopy and X-ray photoelectron spectroscopy results illustrated a great dispersion of magnetite nanoparticles in hybrid matrix. Moreover, the TGA results demonstrated that the PMMA/PANI/Fe₃O₄ hybrid coating nanoparticle is an excellent hybrid coating with high thermal resistance.     

Synthesis of spinel Ni<Subscript>0.75</Subscript>Zn<Subscript>0.25</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> and the properties of a coating obtained by gas-flame spraying

Ferrite Ni_0.75Zn_0.25Fe₂O₄ was prepared by the solid-state synthesis and thermal decomposition of the complex oxalate Ni_0.75Zn_0.25Fe₂(C₂O₄)₃ · 6H₂O. The oxalate precursor and the products obtained at different stages of the thermal decomposition were identified by differential thermal analysis and X-ray and X-ray photoelectron spectroscopy. The properties of a ferromagnetic coating deposited on a substrate by gasflame coating were studied. The magnetic properties of the Ni-Zn ferrite product and the ferromagnetic coating were also investigated.     

Characterization of stabilized porous magnetite core–shell nanogel composites based on crosslinked acrylamide/sodium acrylate copolymers

Stabilized and dispersed superparamagnetic porous nanogels based on sodium acrylate (AA‐Na) and acrylamide (AM) in a surfactant‐free aqueous system were synthesized via solution polymerization at room temperature. The formation of magnetite nanoparticles was confirmed and their properties characterized using Fourier transform infrared spectroscopy. Extensive characterization of the magnetic polymer particles using transmission electron microscopy (TEM), dynamic light scattering and zeta potential measurements revealed that Fe₃O₄ nanoparticles were incorporated into the shells of poly(AM/AA‐Na). The average particle size was 5–8 nm as determined from TEM. AM/AA‐Na nanoparticles with a diameter of about 11 nm were effectively assembled onto the negatively charged surface of the as‐synthesized Fe₃O₄ nanoparticles via electrostatic interaction. Crosslinked magnetite nanocomposites were prepared by in situ development of surface‐modified magnetite nanoparticles in an AM/AA‐Na hydrogel. Scanning electron microscopy was used to study the surface morphology of the prepared composites. The morphology, phase composition and crystallinity of the prepared nanocomposites were characterized. Atomic force microscopy and argon adsorption–desorption measurements of Fe₃O₄.AM/AA indicated that the architecture of the polymer network can be a hollow porous sphere or a solid phase, depending on the AA‐Na content. © 2013 Society of Chemical Industry     

Effect of surface modification of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles on the preparation of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/polystyrene composite particles via miniemulsion polymerization

Fe₃O₄ nanoparticles were modified by n-octadecyltrimethoxysilane (C18TMS) and 3-trimethoxysilylpropylmethacrylate (MPS). The modified Fe₃O₄ nanoparticles were used to prepare Fe₃O₄/polystyrene composite particles by miniemulsion polymerization. The effect of surface modification of Fe₃O₄ on the preparation of Fe₃O₄/polystyrene composite particles was investigated by transmission electron microscopy, Fourier transform infrared spectrophotometer (FT-IR), contact angle, and vibrating sample magnetometer (VSM). It was found that C18TMS modified Fe₃O₄ nanoparticles with high hydrophobic property lead to the negative effect on the preparation of the Fe₃O₄/polystyrene composite particles. The obtained composite particles exhibited asymmetric phase-separated structure and wide size distribution. Furthermore, un-encapsulated Fe₃O₄ were found in composite particles solution. MPS modified Fe₃O₄ nanoparticles showed poor hydrophobic properties and resulted in the obtained Fe₃O₄/polystyrene composite particles with regular morphology and narrow size distribution because the ended C=C of MPS on the surface of Fe₃O₄ nanoparticles could copolymerize with styrene which weakened the phase separation distinctly.     

A Comparison Study on the Magneto-Responsive Properties and Swelling Behaviors of a Polyacrylamide-Based Hydrogel Incorporating with Magnetic Particles

This work investigates the mechanical properties, microstructures, and water-swelling behavior of a novel hydrogel filled with magnetic particles. The nanoparticles of magnetite (Fe₃O₄) and the micro-particles of carbonyl iron (CI) were selected and filled into a polyacrylamide (PAAM) hydrogel matrix to create two types of magnetic hydrogels. The isotropy and anisotropy of magnetic hydrogels are also presented in this study. The isotropic samples were cured without applying a magnetic field (MF), and the anisotropic samples were cured by applying an MF in the direction perpendicular to the thickness of the samples. The effects of the size, content, and inner structures of magnetic particles on the magneto-responsive and swelling properties of magnetic hydrogels were investigated. It was found that the magnetorheological (MR) effect of anisotropic samples was apparently higher than that of isotropic samples, and the hydrogels with CI exhibited a noticeable MR effect than those with Fe₃O₄. The storage modulus can be enhanced by increasing the filler content and size, forming an anisotropic structure, and applying an external MF. In addition, the magnetic hydrogels also have a swelling ability that can be tuned by varying the content and size of the particle fillers.     

3D gel printing of magnetic hydrogel scaffolds assisted by in-situ gelation in a water level-controlled crosslinker bath

Polyvinylalcohol/chitosan (PVA/CS) is an excellent dual-network hydrogel material, but some significant challenges remain in fabricating composites with specific structures. In this study, 3D gel printing (3DGP) combined with a water-level controlled crosslinker bath was proposed for the rapid in-situ prototyping of PVA/CS/Fe₃O₄ magnetic hydrogel scaffolds. Specifically, the PVA/CS/Fe₃O₄ hydrogels were extruded into the crosslinker water to achieve rapid in-situ gelation, improving the printability of hydrogel scaffolds. The effect of the PVA/CS ratio on the rheological and mechanical properties of dual-network magnetic hydrogels was evaluated. The printing parameters were systematically optimized to facilitate the coordination between the crosslinking water bath and printer. The different crosslinking water baths were investigated to improve the printability of PVA/CS/Fe₃O₄ hydrogels. The results showed that the printability of the sodium hydroxide (NaOH) crosslinker was significantly better than that of sodium tripolyphosphate (TPP). The magnetic hydrogels (PVA: CS= 1: 1) crosslinked by NaOH had better compressive strength, swelling rate, and saturation magnetization of 1.17 MPa, 92.43%, and 22.19 emu/g, respectively. The MC3T3-E1 cell culture results showed that the PVA/CS/Fe₃O₄ scaffolds promoted cell adhesion and proliferation, and the scaffolds crosslinked by NaOH had superior cytocompatibility. 3DGP combined with a water-level controlled crosslinker bath offers a promising approach to preparing magnetic hydrogel materials.     

Chitosan- and dehydroascorbic acid-coated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles: preparation,characterization and their potential as draw solute in forward osmosis process

Forward osmosis (FO) is a natural osmosis process that has attracted a significant attention due to its many advantages. However, the development of FO process depends on the development of proper draw solutions. In this work, chitosan (CS)-coated Fe₃O₄ nanoparticles and dehydroascorbic acid (DHAA)-coated Fe₃O₄ nanoparticles were successfully synthesized by co-precipitation method and their performance as draw solutes was investigated for application in FO systems. CS and DHAA could improve the surface hydrophilicity of the Fe₃O₄ nanoparticles. The synthesized nanoparticles were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometry (VSM) which the results presented a small size, crystalline morphology and high magnetization value for their structure as well as a good dispersion in water. Cellulose triacetate/cellulose acetate (CTA/CA)-based membranes were also prepared by immersion precipitation and used as FO membranes. The synthesized FO membranes were characterized by FESEM. The performance evaluation of synthesized nanoparticles revealed that the water flux of Fe₃O₄ nanoparticles capped with DHAA was higher than that of the chitosan-coated Fe₃O₄ nanoparticles. At the end of the process, the Fe₃O₄ nanoparticles were easily separated from the diluted draw solution by applying the magnetic field.     

Removal of heavy metal ions from aqueous solutions by radiation‐induced chitosan/(acrylamidoglycolic acid‐co‐acrylic acid) magnetic nanopolymer

An effective method was developed to isolate toxic heavy metal ions from the aqueous solution by the magnetic nanopolymers. The magnetic sorbent was prepared with radiation‐induced crosslinking polymerization of chitosan (CS), 2‐acrylamido‐glycolic acid (AMGA), and acrylic acid (AAc), which stabilized by magnetite (Fe₃O₄) as nanoparticles. The formation of magnetic nanoparticles (MNPs) into the hydrogel networks was confirmed by Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, and Scanning electron microscopy, which revealed the formation of MNPs throughout the hydrogel networks. The swelling behavior of the hydrogels and magnetic ones was evaluated at different pH values. The adsorption activity for heavy metals such as Cu²⁺ and Co²⁺ by nonmagnetic and magnetic hydrogels, Fe₃O₄/CS/(AMGA‐co‐AAc), in terms of adsorption amount was studied. It was revealed that hydrogel networks with magnetic properties can effectively be used in the removal of heavy metal ions pollutants and provide advantageous over conventional ones. POLYM. ENG. SCI., 55:1441–1449, 2015. © 2015 Society of Plastics Engineers     

One-Pot Green Synthesis and Bioapplication of<Emphasis Type="SmallCaps">l</Emphasis>-Arginine-Capped Superparamagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles

Water-soluble l-arginine-capped Fe₃O₄ nanoparticles were synthesized using a one-pot and green method. Nontoxic, renewable and inexpensive reagents including FeCl₃, l-arginine, glycerol and water were chosen as raw materials. Fe₃O₄ nanoparticles show different dispersive states in acidic and alkaline solutions for the two distinct forms of surface binding l-arginine. Powder X-ray diffraction and X-ray photoelectron spectroscopy were used to identify the structure of Fe₃O₄ nanocrystals. The products behave like superparamagnetism at room temperature with saturation magnetization of 49.9 emu g⁻¹ and negligible remanence or coercivity. In the presence of 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride, the anti-chloramphenicol monoclonal antibodies were connected to the l-arginine-capped magnetite nanoparticles. The as-prepared conjugates could be used in immunomagnetic assay.     

Preparation and properties of poly(acrylic acid-co-styrene)/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocomposites

Poly(acrylic acid-co-styrene)/Fe₃O₄ nanocomposites were prepared using poly(acrylic acid-co-styrene) (P(AA-co-St)) and nano-Fe₃O₄ particles. The resultant materials were characterized by transmission electron microscope (TEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), advanced rheology expand system and superconducting quantum interference device (SQUID) magnetometer. The diameter of the magnetic particles was around 3–14 nm. The experimental results reveal that the acrylic acid segment of P(AA-co-St) can react with nano-Fe₃O₄. With increasing reaction time the storage modulus, loss modulus, complex viscosity and shear stress of the P(AA-co-St)/Fe₃O₄ ethanol suspension were increased, and the suspension changed from liquid-like behavior to gel-like behavior for the reaction between P(AA-co-St) and Fe₃O₄, as found during the rheology measurements. The thermal stability of P(AA-co-St) decreased with the addition of nano-Fe₃O₄, and the nanocomposites exhibited superparamagnetic properties above the blocking temperature.     

Synthesis and properties of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles by sol-vothermal method using iron(III) acetylacetonate

Well dispersed Fe₃O₄ nanoparticles were synthesized at 180°C by sol-vothermal method, using iron (III) acetylacetonate as iron source and poly-vinilpyrrolidone (PVP) as special surfactant. The factors affecting reaction system, such as reaction temperature and time, the amount of iron source and surfactant are discussed. The synthesized Fe₃O₄ particles show excellent saturation magnetization and super-paramagnetic properties, demonstrating their potential applicability in magnetic nanodevices and bio-medicine.     

A study on synthesis and properties of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles by solvothermal method

Magnetic nanoparticles (Fe₃O₄) were synthesized by the solvothermal method using FeCl₃ · 6H₂O and ethylene glycol as a reactant. Powder X-ray diffraction, FT-IR, TEM, SEM, and VSM were used to characterize the magnetic particles. The reacting factors, such as reacting time, the concentration of iron source and surfactant, especially the effect of NaAc · 3H₂O, were studied. The results indicated that NaAc · 3H₂O plays the role not only as a dispersant but also a structure-directing agent. The synthesized Fe₃O₄ particles showed excellent magnetic property, which made them have potential for application in magnetic nanodevices and biomedicine.     

Effect of HCl Concentration on the Dispersity of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles

In this paper, monodisperse 6 nm-sized Fe₃O₄ nanoparticles with spinel crystalline structure were synthesized via a co-precipitation method. The effect of HCl concentrations on Fe₃O₄ samples was investigated by TEM, VSM and UV–vis. HCl-modified Fe₃O₄ nanoparticles solution was a stable, clear, transparent cationic colloid. The results showed that HCl had a great influence on the dispersity of Fe₃O₄ nanoparticles and almost no influence on the materials magnetism.     

Preparation and characterization of spindle-like Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> mesoporous nanoparticles

Magnetic spindle-like Fe₃O₄ mesoporous nanoparticles with a length of 200 nm and diameter of 60 nm were successfully synthesized by reducing the spindle-like α-Fe₂O₃ NPs which were prepared by forced hydrolysis method. The obtained samples were characterized by transmission electron microscopy, powder X-ray diffraction, attenuated total reflection fourier transform infrared spectroscopy, field emission scanning electron microscopy, vibrating sample magnetometer, and nitrogen adsorption-desorption analysis techniques. The results show that α-Fe₂O₃ phase transformed into Fe₃O₄ phase after annealing in hydrogen atmosphere at 350°C. The as-prepared spindle-like Fe₃O₄ mesoporous NPs possess high Brunauer-Emmett-Teller (BET) surface area up to ca. 7.9 m² g^-1. In addition, the Fe₃O₄ NPs present higher saturation magnetization (85.2 emu g^-1) and excellent magnetic response behaviors, which have great potential applications in magnetic separation technology.     

Efficient visible light magnetic modified iron oxide photocatalysts

Magnetite iron oxide (Fe₃O₄) nanoparticles were synthesized via simple co-precipitation method using ferrous and ferric ions salts. Fe₃O₄ nanoparticles were modified by silica and titania. Pure and modified nanoparticles were employed for dye degradation under visible light. X-ray diffraction analysis indicated inverse spinel structure of Fe₃O₄ nanoparticles. The particle size of magnetite nanoparticles is decreased due to coating of silica and titania. Scanning and transmission electron microscopy indicated the spherical morphology for all samples. The synthesized Fe₃O₄ nanoparticles were ferromagnetic in nature with highest saturation magnetization value of 1.1034 emu as compared to silica and titania coated samples. Fourier transform infra-red spectra confirmed the incorporation of magnetite nanoparticles with silica and titania. Titania modified magnetite sample showed the highest photocatalytic activity as compared to silica modified magnetite nanoparticles and bare iron oxide under visible light irradiations.     

Recyclable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Tween20@Ag Nanocatalyst for Catalytic Degradation of Azo Dyes

Silver nanoparticles supported on superparamagnetic iron oxide (SPION)-Tween20 nanocomposite were prepared by a combined polyol and chemical reduction routes. The morphology, composition and structure of Fe₃O₄@Tween20@Ag nanocatalyst were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy, energy dispersive X-ray spectroscopy, thermal gravimetric analyzer, and X-ray powder diffraction. In addition the magnetic properties were evaluated with vibrating sample magnetometry. It was found that Fe₃O₄@Tween20@Ag nanocatalyst could catalyze the degradation of various organic azo dyes and could easily be recovered from the reaction medium with external magnet. Also, the magnetic catalyst can be succesfully recycled and reused for at least five successive degradation cycles of methyl orange, methylene blue and Rhodamine B, confirming a high recycling efficiency. The cost effective and recyclable Fe₃O₄@Tween20@Ag nanocatalyst provide an novel nanomaterials architecture for environmental remediation applications.     

Additive-free photosynthesis of acrylamide hydrogels initiated with CdS and TiO<Subscript>2</Subscript> as light visible nano-photocatalysts

Hydrogels are three-dimensional polymer networks which can be synthesized by different techniques, such as free-radical addition reaction which is the most well-known technique in functional vinyl monomer polymerization. Photopolymerization, as an attractive technique, has been used in radical polymerization of monomers and has revitalized interest in the idea that it congregates a wide range of economic and ecological expectations. Due to the spatial–temporal control and a mild curing process of polymerization, photoinitiator semiconductor nano-particles offer great advantages, such as effective and quantitative reaction. Cadmium sulfide nanowire, titanium dioxide (TiO₂) nanotube, and TiO₂ nanowire were used as visible photocatalysts for photopolymerization of acrylamide hydrogel without using any additive under the sunlight and purple LED irradiations. The effects of different synthetic parameters, including initiator type and concentration and type of light sources, were investigated to achieve hydrogels with maximum swelling capacity. The results showed that the swelling of hydrogel reached 80 g water/g hydrogel when the TiO₂ nanowire was used as the photoinitiator. The synthesized semiconductors and hydrogels were characterized by X-ray diffractometry, adsorption isotherm, infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy. According to the results, the new initiators led to semiconductor-based hydrogels, achieved with high swelling property through a high-speed high-efficient photopolymerization reaction in a safe manner.     

Synthesis and Characterization of Magnetite/Polyvinyl Alcohol Core–Shell Composite Nanoparticles

Magnetite (Fe₃O₄)/polyvinyl alcohol (PVA) core–shell composite nanoparticles were successfully synthesized using a coprecipitation of ferrous and ferric chloride followed by coating with PVA. The resulting nanoparticles were characterized using X‐ray diffraction, Fourier Transform Infrared Spectroscopy, Transmission Electron Microscopy, X‐ray photo electron spectroscopy, Zeta potential measurements, UV–Vis spectroscopy, Thermogravimetric Analysis, and Vibrating Sample Magnetometry (VSM). The average particle size was 13 nm. The presence of characteristic functional groups of PVA around the core of magnetite nanoparticles was confirmed by FTIR spectroscopy while the amount of PVA (%) bound to it was estimated by TGA analysis. Zeta potential measurements made by dispersing dilute sonicated samples in a Phosphate Buffer Saline (PBS pH 7.4) confirmed that the particles were negatively charged. The stability and retention of the coating material PVA in PBS (pH7.4) over a period of time were substantiated by UV–Vis spectroscopy. Room‐temperature magnetic measurements were made with a VSM which demonstrated the superparamagnetic nature of the particles with higher saturation magnetization of 56.41 emu/g. Furthermore, in vitro cytocompatibility testing of Fe₃O₄/PVA core–shell composite nanoparticles was carried out on human cervix cancer cells. This confirmed a 97% cell viability with no significant cytotoxicity and thereby substantiated their biocompatibility.