Hybrid Au nanoparticles on Fe3O4@polymer as efficient catalyst for reduction of 4-nitrophenol

In this paper, we attempted to synthesize a hybrid nanostructure by the incorporation of Au nanoparticles (NPs) with polymer-coated Fe₃O₄ microspheres. Also, Au NPs on 3-aminopropyl triethylsilane (APTS)-modified Fe₃O₄@SiO₂ and Fe₃O₄@polymer microspheres were synthesized to assess the catalytic activity of Au NPs on Fe₃O₄@polymer microspheres for the reduction of 4-nitrophenol. It was found that Au NPs on Fe₃O₄@polymer catalysts showed higher catalytic activity and recyclability than other APTS-modified catalysts.     

Preparation and characterization of conductive and magnetic PPy/Fe3O4/Ag nanocomposites

In this article, conductive and magnetic nanocomposites composed of polypyrrole (PPy), magnetite (Fe₃O₄) nanoparticles (NPs), silver (Ag) NPs, have been successfully synthesized with a two step process. First, the PPy/Fe₃O₄ was prepared by the ultrasonic in situ polymerization. Next, the PPy/Fe₃O₄/Ag was synthesized through the electrostatic adsorption. The products were characterized by fourier‐transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM), Thermogravimetric (TG), conductivity and magnetization analysis, and the results showed that the Ag NPs with the good conductivity coated uniformly on the surface of PPy/Fe₃O₄ and improved the conductivity of PPy/Fe₃O₄/Ag composites. In addition, as compared with PPy/Fe₃O₄, PPy/Fe₃O₄/Ag composites also have the excellent electro‐magnetic property and enhanced thermostability. POLYM. COMPOS., 35:450–455, 2014. © 2013 Society of Plastics Engineers     

Highly selective purification of ferulic acid from wheat bran using deep eutectic solvents modified magnetic nanoparticles

Fe₃O₄ nanoparticles (Fe₃O₄NPs) were prepared by chemical coprecipitation. Deep eutectic solvents (DESs) (ChCl/glycol, 1/2, n/n) were used to modify Fe₃O₄NPs. The obtained Fe₃O₄NPs and DESs–Fe₃O₄NPs were applied for purification of ferulic acid from wheat bran by magnetic solid-phase extraction (MSPE). The satisfactory extraction recoveries for ferulic acid (88.7%) were obtained by changing different washing and eluted solvents. The recovery of the proposed method at three spiked level analysis was 77.9–97.5%, with the relative standard deviation less than 4.5%. DESs–Fe₃O₄NPs showed good performance for ferulic acid and the proposed approach might offer a novel method for purifying complex samples.     

Iron Oxide and Titanium Dioxide Nanoparticle Effects on Plant Performance and Root Associated Microbes

In this study, we investigated the effect of positively and negatively charged Fe₃O₄ and TiO₂ nanoparticles (NPs) on the growth of soybean plants (Glycine max.) and their root associated soil microbes. Soybean plants were grown in a greenhouse for six weeks after application of different amounts of NPs, and plant growth and nutrient content were examined. Roots were analyzed for colonization by arbuscular mycorrhizal (AM) fungi and nodule-forming nitrogen fixing bacteria using DNA-based techniques. We found that plant growth was significantly lower with the application of TiO₂ as compared to Fe₃O₄ NPs. The leaf carbon was also marginally significant lower in plants treated with TiO₂ NPs; however, leaf phosphorus was reduced in plants treated with Fe₃O₄. We found no effects of NP type, concentration, or charge on the community structure of either rhizobia or AM fungi colonizing plant roots. However, the charge of the Fe₃O₄ NPs affected both colonization of the root system by rhizobia as well as leaf phosphorus content. Our results indicate that the type of NP can affect plant growth and nutrient content in an agriculturally important crop species, and that the charge of these particles influences the colonization of the root system by nitrogen-fixing bacteria.     

Thermal and mechanical properties of epoxy resin reinforced with modified iron oxide nanoparticles

Epoxy polymers, having good mechanical properties and thermal stability, are often used for engineering applications. Their properties can be further enhanced by the addition of iron oxide (Fe₃O₄) nanoparticles (NPs) as fillers to the resin. In this study, pristine Fe₃O₄ NPs were functionalized with polydopamine (PDA), (3-glycidoxypropyl)trimethoxysilane (GPTMS), and (3-aminopropyl)trimethoxysilane (APTES). X-ray diffraction and scanning electron microscopy (SEM) were used to study any changes in the crystal structure and size of the NPs while Fourier-Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) were used to ensure the presence of functional groups on the surface. The mechanical properties of the Fe₃O₄-based nanocomposites generally improved except when reinforced with Fe₃O₄/PDA. The maximum improvement in tensile strength (∼34%) and fracture toughness (∼13%) were observed for pristine Fe₃O₄-based nanocomposites. Dynamic mechanical analysis (DMA) showed that the use of any of the treated NPs improved the material's initial storage modulus and had a substantial impact on its dissipation potential. Also, it was observed that the glass transition temperature measurements by DMA and differential scanning calorimetry were below that of pure epoxy. SEM of the cracked surfaces shows that the incorporation of any NPs leads to an enhancement in its thermal and mechanical properties.     

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.     

Well-Dispersed Fe3O4/SiO2 Nanoparticles Synthesized by a Mechanical Stirring and Ultrasonication Assisted St?ber Method

Core–shell structured Fe₃O₄/SiO₂ nanoparticles (NPs) sized 40–50 nm with a narrow size distribution have been synthesized by a mechanical stirring and ultrasonication assisted St?ber method at the room temperature. It is shown that the combination of the ultrasonication and mechanical stirring during the preparation process benefits the formation of the well-dispersed NPs. The Fe₃O₄/SiO₂ core–shell microstructure is identified with X-ray diffraction and transmission electron microscopy measurements and such NPs exhibit superparamagnetism.     

Ultrafine palladium nanoparticle-bonded to polyetheylenimine grafted reduced graphene oxide nanosheets: Highly active and recyclable catalyst for degradation of dyes and pigments

Much attention has been increasingly focused on the applications of noble metal nanoparticles (NPs) for the catalytic degradation of various dyes and pigments in industrial wastewater. We have demonstrated that Pd NPs/Fe₃O₄-PEI-RGO nanohybrids exhibit high catalytic activity and excellent durability in reductive degradation of MO, R6G, RB. Specific surface area was successfully prepared by simultaneous reduction of Pd(OAc)₂ chelating to PEI grafted graphene oxide nanosheets modified with Fe₃O₄. The as-prepared Pd NPs/Fe₃O₄-PEI-RGO nanohybrids were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, high-resolution TEM and energy dispersive X-ray spectroscopy, and UV-lambda 800 spectrophotometer, respectively. The catalytic activity of Pd NPs/Fe₃O₄-PEI-RGO nanohybrids to the degradation of MO, R6G, RB with NaBH4 was tracked by UV-visible spectroscopy. It was clearly demonstrated that Pd NPs/Fe₃O₄-PEI-RGO nanohybrids exhibited high catalytic activity toward the degradation of dyes and pigments, which could be relevant to the high surface areas of Pd NPs and synergistic effect on transfer of electrons between reduced graphene oxide (RGO), PEI and Pd NPs. Notably, Pd NPs/Fe₃O₄-PEI-RGO nanohybrids were easily separated and recycled thirteen times without obvious decrease in system. Convincingly, Pd NPs/Fe₃O₄-PEI-RGO nanohybrids would be a promising catalyst for treating industrial wastewater.     

A novel method for the synthesis of Fe3O4 nanoparticles/CdS nanowires heterostructure nanocomposite and uses in photodegradation of methylene blue

We report here a simple, efficient, practical, and novel method for the preparation of Fe₃O₄ nanoparticles (NPs)/CdS nanowires. The CdS nanowire/Fe₃O₄ NP reported here was characterized by transmission electron microscopy (TEM), X-ray Diffraction (XRD), vibrating sample magnetometer (VSM), and energy-dispersive X-ray. Cadmium diethyl dithiophosphate has been used as a 3 in 1 precursor (cadmium, sulfur, and ligand source) for the synthesis of high-quality one-dimensional Fe₃O₄ NPs/CdS nanowires using a simple hydrothermal method in the presence of Fe₃O₄ NPs in water. Photocatalytic activity studies show that the nanocomposite has good photocatalytic activity toward the photodegradation of methylene blue in an aqueous solution.     

Bimagnetic hard/soft and soft/hard ferrite nanocomposites: Structural,magnetic and hyperthermia properties

Recent studies show that the chemical composition and shape of magnetic nanoparticles (NPs) play an important role in their properties. In particular, the bimagnetic NPs display useful and in many cases, more interesting properties than single-phase NPs. In this work, we prepared Fe₃O₄ and CoFe₂O₄ cube-like NPs and bimagnetic hard/soft (CoFe₂O₄/Fe₃O₄) and soft/hard (Fe₃O₄/CoFe₂O₄) nanocomposites (core/coating) using a facile and eco-friendly co-precipitation method that allows the synthesis of the cube-like NPs at temperatures near room temperature. The phase purity and the crystallinity of the NPs with a spinel structure were confirmed by the X-ray diffraction and infrared spectra techniques. Transmission electron microscopy (TEM) images revealed that the NPs have a cubic-like shape with an average dimension of 20 nm. Energy dispersive X-ray analysis, Mössbauer spectroscopy and SQUID magnetic measurements indicated the co-existence of Fe₃O₄ and CoFe₂O₄ phases in nanocomposites. In addition, the hysteresis loops exhibited a single-phase behavior in the nanocomposites that indicates there is a good exchange-coupling interaction between the hard and soft magnetic phases. The CoFe₂O₄/Fe₃O₄ nanocomposites presented a larger saturation magnetization than the CoFe₂O₄ NPs that is effective for their use in magnetic hyperthermia. Finally, we studied the hyperthermia properties of samples in an alternating magnetic field with a frequency of 276 kHz and field amplitude of 13.9 kA/m. Our results showed that magnetic hyperthermia efficiency simultaneously depends on the composition of samples along with magnetic anisotropy and saturation magnetization.     

Sonochemical synthesis of magnetic core–shell Fe3O4@ZrO2 nanoparticles and their application to the highly effective immobilization of myoglobin for direct electrochemistry

In this study, bifunctional Fe₃O₄@ZrO₂ magnetic core–shell nanoparticles (NPs), synthesized by a simple and effective sonochemical approach, were attached to the surface of a magnetic glassy carbon electrode (MGCE) and successfully applied to the immobilization/adsorption of myoglobin (Mb) for constructing a novel biosensor platform. With the advantages of the magnetism and the excellent biocompatibility of the Fe₃O₄@ZrO₂ NPs, Mb could be easily immobilized on the surface of the electrode in the present of external magnetic field and well retained its bioactivity, hence dramatically facilitated direct electron transfer of Mb was demonstrated. The proposed Mb/Fe₃O₄@ZrO₂ biofilm electrode exhibited excellent electrocatalytic behaviors towards the reduction of H₂O₂ with a linear range from 0.64 μM to 148 μM. This presented system avoids the complex synthesis for protecting Fe₃O₄ NPs, supplies a simple, effective and inexpensive way to immobilize protein, and is promising for construction of third-generation biosensors and other bio-magnetic induction devices.     

Magnetoresistive polyaniline-magnetite nanocomposites with negative dielectrical properties

Magnetic polyaniline (PANI) polymer nanocomposites (PNCs) reinforced with magnetite (Fe₃O₄) nanoparticles (NPs) have been successfully synthesized using a facile surface initiated polymerization (SIP) method. The chemical structures of the PANI/Fe₃O₄ PNCs are characterized by Fourier transform infrared (FT-IR) spectroscopy. The thermal stability of the PANI/Fe₃O₄ PNCs is performed by thermogravimetric analysis (TGA). Both transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are used to characterize the morphologies of the PANI, Fe₃O₄ nanoparticles (NPs) and the PNCs. X-ray diffraction (XRD) shows a significant effect of the Fe₃O₄ NPs on the crystallization structure of the formed PANI. The dielectrical properties of these PNCs are strongly related to the Fe₃O₄ nanoparticle loadings and unique negative permittivity is observed in all the samples. Temperature dependent resistivity analysis from 50 to 290 K reveals a quasi 3-dimension variable range hopping (VRH) electron conduction mechanism for the nanocomposite samples. The PNCs do not show hysteresis loop with zero coercivity, indicating the superparamagnetic behavior at room temperature. The PNCs with 30 wt% Fe₃O₄ NP loading exhibit a larger positive magnetoresistance (MR = 95%) than 53% of the pure PANI.     

Studies on Properties of Rice Straw/Polymer Nanocomposites Based on Polycaprolactone and Fe3O4 Nanoparticles and Evaluation of Antibacterial Activity

Modified rice straw/Fe₃O₄/polycaprolactone nanocomposites (ORS/Fe₃O₄/PCL-NCs) have been prepared for the first time using a solution casting method. The RS/Fe₃O₄-NCs were modified with octadecylamine (ODA) as an organic modifier. The prepared NCs were characterized by using X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). The XRD results showed that as the intensity of the peaks decreased with the increase of ORS/Fe₃O₄-NCs content in comparison with PCL peaks, the Fe₃O₄-NPs peaks increased from 1.0 to 60.0 wt. %. The TEM and SEM results showed a good dispersion of ORS/Fe₃O₄-NCs in the PCL matrix and the spherical shape of the NPs. The TGA analysis indicated thermal stability of ORS/Fe₃O₄-NCs increased after incorporation with PCL but the thermal stability of ORS/Fe₃O₄/PCL-NCs decreased with the increase of ORS/Fe₃O₄-NCs content. Tensile strength was improved with the addition of 5.0 wt. % of ORS/Fe₃O₄-NCs. The antibacterial activities of the ORS/Fe₃O₄/PCL-NC films were examined against Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) by diffusion method using nutrient agar. The results indicated that ORS/Fe₃O₄/PCL-NC films possessed a strong antibacterial activity with the increase in the percentage of ORS/Fe₃O₄-NCs in the PCL.     

Synthesis and properties of magnetite nanoparticles with peroxide-containing polymer shell and nanocomposites based on them

Magnetite nanoparticles (Fe₃O₄ NPs) with peroxide-containing polymer shell have been synthesized using the method of coprecipitation from the mixture solutions of Fe (II) and Fe (III) salts in the presence of peroxide-containing copolymer (PCC). Polymer shell presence has been proved by elemental and complex thermal analysis. Synthesized Fe₃O₄ NPs possess superparamagnetic properties. Their specific saturation magnetization decreases gradually from 65 to 54 A·m²·kg⁻¹ with increasing PCC concentration owing to the surface spin pinning effect caused by a polymer shell. The average sizes of Fe₃O₄ NPs estimated from the data of XRD analysis and magnetic measurements are in the range of 9–12 nm. The NP sizes determined by the DLS method lie in the range of 150–270 nm; this result is significantly larger than the sizes estimated by the two aforementioned methods evidencing a tendency for Fe₃O₄ NPs toward self-association. Cross-linked composite films based on polyvinyl alcohol have been obtained via radical curing initiated by the PCC shell of nanoparticles. The resulting composite films are magnetically sensitive films with rather high physico-mechanical properties (tensile strength reaches 48–67 MPa and relative elongation – 4%–21% depending on cross-linking degree), a priori non-toxic and biocompatible, which makes them promising materials for various applications.     

Facile Synthesis of FeCo/Fe3O4 Nanocomposite with High Wave-Absorbing Properties

The FeCo/Fe₃O₄ nanocomposite was synthesized using the hydrothermal approach, in which the FeCo alloy and Fe₃O₄ are formed by one step. The structure of the FeCo/Fe₃O₄ nanocomposite was characterized by means of Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray energy-dispersive spectrometer spectroscopy (EDX). They show that the mass ratio of FeCo/Fe₃O₄ strongly depends on the reaction temperature. Such various architectures follow a stepwise growth mechanism of the composites prepared in various reaction temperatures were also discussed. It indicates that this strategy is facile, effective and controllable for the synthesis of FeCo/Fe₃O₄ by the one-step method. Furthermore, the magnetic and wave-absorbing properties of the nanocomposites with various structures were investigated in detail. The results show that the FeCo/Fe₃O₄ with higher mass ratio has higher magnetic properties. Moreover, the FeCo/Fe₃O₄ nanocomposite shows high wave-absorbing properties (e.g., −37.9 dB), which are expected to apply in microwave absorbing materials.     

Density,viscosity and surface tension of high-silicate CaO–SiO2 and CaO–SiO2–Fe2O3 slags derived by aerodynamic levitation. The behavior of Fe3+ in high-silicate melts

Thermophysical data for liquid slag are required for the optimization and control of metallurgical processes. The density, surface tension and viscosity were measured by employing aerodynamic levitation under contactless conditions. The high-silicate slag (44 and 63 mass-% of SiO₂) of the CaO–SiO₂ and CaO–SiO₂–Fe₂O₃ systems (with 5 and 10 mass-% Fe₂O₃) was investigated under (80% Ar + 20% O₂) gas atmosphere. The temperature ranges were between 800 °C and 2000 °C for the density and 1500 °C–2000 °C for surface tension and viscosity measurements. The influence of the CaO/SiO₂ ratio on the investigated properties and the behavior of Fe³⁺ ions in high-silicate melts were examined. The density of the CaO–SiO₂ melt was lower than that of the CaO–SiO₂–Fe₂O₃ systems. The surface tension of all compositions tested decreased with temperature and showed compositional dependence. The viscosity measured was higher in the Fe₂O₃-containing slag. The Raman spectroscopy analyses confirmed the increase in the degree of polymerization with the addition of Fe₂O₃ for the silicate-rich slag. The formation of a complex anion of a ferric ion and contribution to the silicate network were assumed. The trends observed were related to the structural properties and different interionic bonding. Urbain's viscosity model and FactSage? 7.3 were applied for the assessment of the experimental data.     

Graphene/acid assisted facile synthesis of structure-tuned Fe3O4 and graphene composites as anode materials for lithium ion batteries

Structure-tuned Fe₃O₄ and graphene composites were prepared using a facile graphene/acid assisted facile one-pot hydrothermal method. The structural characteristics of Fe₃O₄ can be tuned by adjusting the initial molar ratio between iron acetylacetonate and citric acid. The citric acid serves dual function as a reducing agent during the production of Fe₃O₄ nanoparticles (NPs), and as a bridging agent which under optimized conditions can result in mesoporous Fe₃O₄ nanospheres (NSs) self-assembled by numerous Fe₃O₄ NPs. The fabricated mesoporous Fe₃O₄ NSs and graphene composites were evaluated as potential anode materials for lithium ion batteries. These composites exhibit better electrochemical performance with high reversible capacity, good rate capability and cyclic stability derived from their unique mesoporous structural features.     

Chemical Synthesis of Monodisperse Magnetic Nanoparticles for Sensitive Cancer Detection

This short tutorial review highlights the advance in high temperature solution phase chemical synthesis of monodisperse magnetic nanoparticles (MNPs), especially iron oxide NPs, as contrast enhancement agents for cancer detection by magnetic resonance imaging (MRI). It introduces briefly the unique nanomagnetism of MNPs required for MRI. It then summarizes some typical methods used to prepare monodisperse Fe₃O₄ and ferrite MFe₂O₄ MNPs from high temperature organic phase reaction with controlled magnetic properties. It further outlines the chemistry used to make these MNPs biocompatible and target-specific. Finally it presents two examples to demonstrate the MNP control achieved from chemical synthesis for sensitive detection of cancer.     

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.     

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.