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.     

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.     

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 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.     

Selective Synthesis of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanowires Via a Single Precursor: A General Method for Metal Oxide Nanowires

Hematite (α-Fe₂O₃) and magnetite (Fe₃O₄) nanowires with the diameter of about 100 nm and the length of tens of micrometers have been selectively synthesized by a microemulsion-based method in combination of the calcinations under different atmosphere. The effects of the precursors, annealing temperature, and atmosphere on the morphology and the structure of the products have been investigated. Moreover, Co₃O₄ nanowires have been fabricated to confirm the versatility of the method for metal oxide nanowires.     

Synthesis and thermal behavior of Fe<Subscript>3</Subscript>O<Subscript>2</Subscript>(BO<Subscript>4</Subscript>) oxoborate

Iron oxoborate Fe₃O₂(BO₄) has been first produced in solid-phase chemical reactions. Its thermal behavior in the temperature range 20–900°C is studied with the use in-situ high-temperature powder X-ray diffraction. It is shown that Fe₃O₂(BO₄) begins decomposing with the formation of Fe₂O₃ in the temperature range 660–900°C. Thermal expansion is sharply anisotropic at room temperature (α_max/α_min = 7) and becomes more isotropic with an increase in the temperature (α_max/α_min = 1.2). The degree of oxidation of Fe³⁺ has been confirmed by Mössbauer spectroscopy (at a room temperature), and two nonequivalent positions in the structure have been detected, which are occupied by iron atoms with the octahedral environment of the oxygen atoms.     

Preparation of stable magnetic nanofluids containing Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@PPy nanoparticles by a novel one-pot route

Stable magnetic nanofluids containing Fe₃O₄@Polypyrrole (PPy) nanoparticles (NPs) were prepared by using a facile and novel method, in which one-pot route was used. FeCl₃·6H₂O was applied as the iron source, and the oxidizing agent to produce PPy. Trisodium citrate (Na₃cit) was used as the reducing reagent to form Fe₃O₄ NPs. The as-prepared nanofluid can keep long-term stability. The Fe₃O₄@PPy NPs can still keep dispersing well after the nanofluid has been standing for 1 month and no sedimentation is found. The polymerization reaction of the pyrrole monomers took place with Fe³⁺ ions as the initiator, in which these Fe³⁺ ions remained in the solution adsorbed on the surface of the Fe₃O₄ NPs. Thus, the core-shell NPs of Fe₃O₄@PPy were obtained. The particle size of the as-prepared Fe₃O₄@PPy can be easily controlled from 7 to 30 nm by the polymerization reaction of the pyrrole monomers. The steric stabilization and weight of the NPs affect the stability of the nanofluids. The as-prepared Fe₃O₄@PPy NPs exhibit superparamagnetic behavior.     

Gd<Superscript>3+</Superscript> doped Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles with proper magnetic and supercapacitive characteristics: A novel synthesis platform and characterization

A novel electrochemical procedure was developed for the facile preparation of Gd-doped iron oxide nanoparticles (GdIO-NPs). A simple galvanostatic deposition (i=10 mA cm^-2) was done in an additive-free aqueous solution containing FeCl₂·4H₂O, Fe(NO₃)₃·9H₂O and GdCl₃·6H₂O. The XRD, FE-SEM, EDS and TEM characterizations showed that the product is composed of 15% GdIO-NPs with 10 nm in size. VSM analysis proved that the GdIO-NPs are superparamagnetic. The cyclic voltammetry and charge-discharge tests showed that the prepared GdIO-NPs are capable to deliver specific capacity as high as 190.1 F g^-1 at 0.5A g^-1 and capacity retention of 95.1% after 2000 cycling. Based on the results, it was concluded that the developed electrochemical strategy acts as an efficient procedure for the preparation of lanthanide doped MNPs with proper magnetic and supercapacitive characters.     

Research of mica/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> pearlescent pigment by co-precipitation

Experiments on preparation of mica/Fe₃O₄ pearlescent pigment were performed to discuss influences of several crucial parameters on final products. The samples were characterized by XRD, HRSEM, FTIR and color measurement, the content of Fe₃O₄ on the mica surface was also analyzed by XPS. It was found that the smoothness, compactness and colour deepness of the coating were influenced by different pH values and temperatures. The optimum preparation parameters of mica/Fe₃O₄ pearlescent pigment were obtained: the value of pH ≥ 9.2; the concentration of sodium hydroxide was 0.5 mol/l; the concentration ratio of Fe³⁺ to Fe²⁺ was 1.6 : 1; the velocity of magnetic stirring was 138 ≤ v ≤ 151 r/min; reaction temperature was 70–80°C; calcination temperature was 350°C and calcination time was 3 h.     

Soft Template Synthesis of Super Paramagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles a Novel Technique

The present study reports a facile technique for the synthesis of crystalline super paramagnetic nano ferrite (Fe₃O₄) particles using diethyl amine as a soft template. The spectral properties of Fe₃O₄ nanoparticles were characterized by UV–visible and Fourier Transform Infrared (FTIR) spectroscopies while the crystalline structure and particle size was estimated using X-Ray diffraction (XRD) as well as transmission electron microscopy (TEM) techniques. The super paramagnetic behavior of Fe₃O₄ nanoparticles was determined using vibrating sample magnetometer (VSM) at 300 K. The results of the studies revealed that this technique could be adopted to synthesize agglomerate free super paramagnetic Fe₃O₄ nanoparticles which may find potential application in the filed of biosensor and corrosion protective coatings.     

Heterogeneous Fenton degradation of Orange II by immobilization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles onto Al-Fe pillared bentonite

A novel catalyst, Fe₃O₄ nanoparticle decorated Al-Fe pillared bentonite (Fe₃O₄/Al-Fe-P-B), was prepared by in situ precipitation oxidization method. The catalyst was characterized by SEM, XRD and Raman spectroscopy. The Fe₃O₄ nanoparticles mainly exist on the surface or enter into the pore of bentonite, with better dispersing and less coaggregation. The catalytic activity of Fe₃O₄/Al-Fe-P-B was investigated in the degradation of Orange II (OII) by heterogeneous Fenton-like process. The effects of initial concentration of hydrogen peroxide, catalyst loading, temperature and initial pH on the degradation of OII were investigated. The Fe₃O₄/Al-Fe-P-B showed higher degradation efficiency of OII than bare Fe₃O₄ or Al-Fe-P-B in the degradation experiment. The enhanced catalytic activity of Fe₃O₄/Al-Fe-P-B in heterogeneous Fenton system was due to the synergistic effect between Al-Fe-P-B and Fe₃O₄. The novel catalyst can achieve solid-liquid separation easily by sample magnetic separation and has a good reusability and stability.     

Examining the use of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles to enhance the NH<Subscript>3</Subscript> sensitivity of polypyrrole films

Summary Polypyrrole (PPy) composite films with different contents of Fe₃O₄ were prepared by in-situ polymerization of pyrrole in aqueous solutions. The dependence of dc current changes on the response of the samples exposure to NH₃ vapor has been investigated. The results shows the composite films are more stable than the pristine ones after being exposed to NH₃ vapor. Meanwhile, the response time was reduced with increasing the Fe₃O₄ content in the films. The results might be originated from the structural changes in the PPy films caused by the addition of Fe₃O₄.     

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.     

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 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.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles coated by new functionalized tetraaza-2,3 dialdehyde micro-crystalline cellulose: synthesis,characterization, and catalytic application for degradation of Acid Yellow 17

In this study, we developed an original approach for preparing cellulose-coated magnetite nanoparticles (NPs). Two novel Schiff bases (PDA-g-DAC) and [Bz-(PDA-g-DAC)] were synthesized via condensation reactions of periodate oxidized micro-crystalline cellulose (DAC) with o-phenylene diamine (PDA) to obtain its azomethine derivative with 85% yield. Subsequently, the functionalization of (PDA-g-DAC) with benzil (Bz) yields the tetraaza macrocycle [Bz-(PDA-g-DAC)]. The physicochemical characterization of the condensation products was performed using ¹³CNMR, FTIR, ATG, DSC, and X-ray diffraction techniques. Magnetic nanomaterial-based Schiff base cellulose was successfully prepared using in situ chemical co-precipitation of coordinated ferric and ferrous ions in cellulose Schiff base matrix under optimized conditions, and then, its magnetic properties were characterized. The results demonstrated that the Fe₃O₄ NPs coated with [Bz-(PDA-g-DAC)] were homogeneously coated in the matrix under ultrasonic irradiation with the saturation magnetization of 69.50 emu g^?1. In addition, XRD line broadening analysis showed that the average particle size of the NPs was 37.3 nm. Furthermore, FTIR spectra demonstrated that [Bz-(PDA-g-DAC)] concavity was anchored to magnetite Fe₃O₄ NPs through azomethine groups. Vibrating sample magnetometry (VSM) of [Bz-(PDA-g-DAC)@Fe₃O₄] magnetic nanocomposite samples showed the typical behavior of ferromagnetism. This study provided a green and facile method to inhibit magnetic nanoparticle aggregation. Activity results revealed that the prepared [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst shows the maximum activity for degradation of Acid Yellow 17 (AY17) compared to other prepared catalysts. After degradation reaction, the [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst was recovered from the reaction mixture via an external magnet and used for further five consecutive cycles with excellent catalytic activity, successively, which was comparable to the fresh catalyst. The catalyst degradation efficiency and its easy separation exhibited that [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst is a promising material for the removal of AY17 from aqueous solutions in green chemistry perspectives.     

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.     

Controlling exchange bias in Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/FeO composite particles prepared by pulsed laser irradiation

Spherical iron oxide nanocomposite particles composed of magnetite and wustite have been successfully synthesized using a novel method of pulsed laser irradiation in ethyl acetate. Both the size and the composition of nanocomposite particles are controlled by laser irradiation condition. Through tuning the laser fluence, the Fe₃O₄/FeO phase ratio can be precisely controlled, and the magnetic properties of final products can also be regulated. This work presents a successful example of the fabrication of ferro (ferri) (FM)/antiferromagnetic (AFM) systems with high chemical stability. The results show this novel simple method as widely extendable to various FM/AFM nanocomposite systems.