Photoluminescence–electricity–magnetism trifunction simultaneously assembled into one flexible nanofiber

In order to develop new-typed multifunctional composite nanofibers, Eu(BA)₃phen/PANI/Fe₃O₄/PVP trifunctional composite nanofibers with photoluminescence, electricity and magnetism have been successfully fabricated via electrospinning technology. Polyvinyl pyrrolidone (PVP) is used as a matrix to construct composite nanofibers containing different amounts of Eu(BA)₃phen, polyaniline (PANI) and magnetite Fe₃O₄ nanoparticles (NPs). X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, fluorescence spectroscopy and Hall effect measurement system are used to characterize the morphology and properties of the obtained composite nanofibers. The results indicate that the trifunctional composite nanofibers possess excellent luminescent, electrical conductivity and magnetic properties. Fluorescence emission peaks of Eu³⁺ are observed in the Eu(BA)₃phen/PANI/Fe₃O₄/PVP photoluminescent-electrical-magnetism trifunctional composite nanofibers and assigned to the of ⁵D₀ → ⁷F₀ (580 nm), ⁵D₀ → ⁷F₁ (593 nm) of Eu³⁺, and the ⁵D₀ → ⁷F₂ hypersensitive transition at 615 nm is the predominant emission peak. The electrical conductivity reaches up to the order of 10^?3 S/cm. The luminescent intensity, electrical conductivity and saturation magnetization of the composite nanofibers can be tunable by adding various amounts of Eu(BA)₃phen, PANI and Fe₃O₄ NPs. The multifunctional composite nanofibers are expected to possess many potential applications in areas such as electromagnetic interference shielding, microwave absorption, molecular electronics and biomedicine.     

Synthesis and microwave absorption properties of sandwich-type CNTs/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/RGO composite with Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> as a bridge

A novel sandwich-type CNTs/Fe₃O₄/RGO composite with Fe₃O₄ as a bridge was successfully prepared through a simple solvent-thermal and ultrasonic method. The structure and morphology of the composite have been characterized by Fourier-transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. This new structure can effectively prevent the agglomeration of GO and the combination of CNTs/Fe₃O₄ and RGO shows a strong reflection loss (R_L) (?50 dB) at 8.7 GHz with absorber thickness of 2.5 mm. Moreover, compared with CNTs/Fe₃O₄/GO composite, it is found that the thermal treating process is beneficial to enhance the microwave absorption properties, which may be attributed to high conductivity of RGO. On this basis, the microwave absorbing mechanism is systematically discussed. All the data show that the CNTs/Fe₃O₄/RGO composite exhibits excellent microwave absorption properties with light density and is expected to have potential applications in microwave absorption.     

Synthesis and microwave absorption property of ternary composites: polyaniline/CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/Ba<Subscript>3</Subscript>Co<Subscript>2</Subscript>Fe<Subscript>24</Subscript>O<Subscript>41</Subscript>

Polyaniline (PANI)/CoFe₂O₄/Ba₃Co₂Fe₂₄O₄₁ composite was prepared by an in-situ polymerization method. The phase structure, morphology and magnetic properties of the as-prepared PANI/CoFe₂O₄/Ba₃Co₂Fe₂₄O₄₁ composite were characterized by XRD, FT-IR, SEM, TEM, and VSM, respectively. The microwave absorption properties of the composite were investigated by using a vector network analyzer in the 2–18 GHz frequency range. The results show that the maximum reflection loss value of the PANI/CoFe₂O₄/Ba₃Co₂Fe₂₄O₄₁ composite reaches ?30.5 dB at 10.5 GHz with a thickness of 3 mm and the bandwidth of reflection loss below ?10 dB reaches up to 1.2 GHz. The excellent microwave absorption properties of the as-prepared PANI/CoFe₂O₄/Ba₃Co₂Fe₂₄O₄₁ composite due to the enhanced impedance match between dielectric loss and magnetic loss.     

Multifunctional CNTs nanohybrids decorated with magnetic and fluorescent nanoparticles layer-by-layer

Fe₃O₄/CNTs nanocomposites, which were prepared by polyol-medium in situ high-temperature decomposition of Fe(acac)₃ using PVP as stabilizing agent and modified with SDS, were further decorated with high-quality ZnS nanocrystal via a wet technique in glycol solution. The obtained ZnS/Fe₃O₄/CNTs nanohybrids were characterized by XRD, FT–IR, Raman microscope, TEM, EDS, XPS, VSM and fluorophotometers. Results indicated that magnetic Fe₃O₄ nanoparticles and fluorescent ZnS nanocrystal were uniformly dispersed on the surface of CNTs layer-by-layer with PVP and SDS as stabilizing agent and ion-capture agent, respectively. The novel multi-functional nanohybrids exhibit super-paramagnetic properties with a saturation magnetization about 6·795 emu g^???1 at room temperature and show a strong emission band at 367 nm with a broad shoulder around 342–483 nm due to the interactions and/or background emissions of Fe₃O₄ and CNTs. The superparamagnetic and fluorescent properties of obtained products are promising for potential applications in magnetically guided and fluorescence tracing drug delivery systems.     

Simultaneous synthesis of polyaniline nanorods and magnetite nanoparticles via self-assembly method

In this work, polyaniline (PANI) nanorods and magnetite (Fe₃O₄) nanoparticles have been synthesised by using ammonium persulphate as oxidant via in-situ chemical oxidative polymerisation of aniline in presence of excess of organic sulphonic acid. The resulting PANI/Fe₃O₄ nanocomposites materials were characterised using X-ray diffraction, UV-visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, vibrating sampling magnetometer and thermogravimetric analysis. Spectroscopic results indicated the successful formation of PANI/Fe₃O₄ nanocomposites. As obtained, PANI/Fe₃O₄ nanocomposites have Fe₃O₄ particle size in the range of 3.2–7?nm. Morphologies of PANI/Fe₃O₄ nanocomposites were found to be dependent on the molar ratio of aniline to organic acid. Under certain polymerisation conditions, PANI rods like structures were obtained. PANI/Fe₃O₄ nanocomposites have superparamagnetism and higher thermal stability.     

Enhanced electromagnetic wave absorption properties of polyaniline-coated Fe3O4/reduced graphene oxide nanocomposites

Fe₃O₄-reduced graphene oxide-polyaniline (Fe₃O₄–RGO–PANI) ternary electromagnetic wave absorbing materials were prepared by in situ polymerization of aniline monomer on the surface of Fe₃O₄–RGO nanocomposites. The morphology, structure and other physical properties of the nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, vibration sample magnetism, etc. The electromagnetic wave absorbing properties of composite materials were measured by using a vector network analyzer. The PANI–Fe₃O₄–RGO nanocomposites demonstrated that the maximum reflection loss was ?36.5 dB at 7.4 GHz with a thickness of 4.5 mm and the absorption bandwidth with the reflection loss below ?10 dB was up to 12.0 GHz with a thickness in the range of 2.5–5.0 mm, suggesting that the microwave absorption properties and the absorption bandwidth were greatly enhanced by coating with polyaniline (PANI). The strong absorption characteristics of PANI–Fe₃O₄–RGO ternary composites indicated their potential application as the electromagnetic wave absorbing material.     

Fabrication and microwave absorption performances of hollow-structure Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/PANI microspheres

The hollow polyaniline (PANI) microspheres were prepared by controlling the mass ratio of the aniline to polystyrene (PS) via a template method, and Fe₃O₄/PANI composite microspheres have been fabricated by blending the hollow PANI microspheres with Fe₃O₄ magnetic particles. The effects of the mass ratio of aniline/PS on the microwave absorption performances of Fe₃O₄/PANI microspheres were investigated. It was found that the value of minimum reflection loss (RL_min) of the microspheres were respectively ?14.06, ?22.34 and ?24.3 dB, corresponding to the mass ratio of aniline/PS of 1:1.5, 1:3, and 1:6. In addition, when the mass ratio of aniline/PS was 1:6, with the thickness of 1.5 and 2.0 mm, the bandwidth below ?10dB were respectively 2.48 GHz (15.52–18 GHz) and 4.64 GHz (11.04–15.68 GHz), indicating that the Fe₃O₄/PANI microspheres could be a potential electromagnetic wave absorbing material in X (8–12 GHz) and Ku (12–18 GHz) bands.     

Lightweight glass/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-polyaniline composite hollow spheres with conductive and magnetic properties

Lightweight composite hollow spheres with conductive and magnetic properties were prepared by using Hollow Glass Spheres (HGS) as substrate. The morphology, composition, conductive, and magnetic properties of the resultant products were characterized by SEM, EDX, XRD, FTIR spectra, conductivity measurement, and vibrating-sample magnetometry. Polyaniline (PANI) were in situ polymerized on HGS with increasing ratios of PANI to HGS, resulting in the enhanced conductivity of HGS/PANI composites from 1.3 × 10⁻² S/cm to 4.4 × 10⁻² S/cm. Lightweight glass/Fe₃O₄-PANI composite hollow spheres (HGS/Fe₃O₄-PANI) with conductivity of 5.4 × 10⁻³ S/cm and magnetization of 9.25 emu/g were prepared by deposition of Fe₃O₄ nanoparticles onto HGS via electrostatic adsorption first, and then polymerization of aniline onto HGS/Fe₃O₄. The glass/PANI-Fe₃O₄ composite hollow spheres (HGS/PANI-Fe₃O₄) composed of Fe₃O₄ as the outmost layer and PANI as the inner layer were prepared for comparison. The conductivity and magnetization of HGS/PANI-Fe₃O₄ were 1.1 × 10⁻⁴ S/cm and 2.61 emu/g, respectively.     

Preparing particulate magnetites with pigment properties from suspensions of basic iron(III) sulphates with the structure of jarosite

The transformation of a suspension of hydronium jarosite, H₃O⁺Fe₃(SO₄)₂(OH)₆, into Fe₃O₄ (magnetite) of pigment quality is described. The process consists in the neutralization of the hydronium jarosite suspension in FeSO₄ aqueous solutions with NH₃ and subsequent thermal treatment of this mixture at controlled pH and temperature.     

Light weight RGO/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocomposite for efficient electromagnetic absorption coating in X-band

Reduced graphene oxide (RGO)/magnetite (Fe₃O₄) nanocomposite has been synthesized by an in-situ facile hydrothermal method. The XRD pattern reveals the development of nanocomposite in which both phases are coexistent. Raman Spectroscopy shows the main characteristics peaks of D and G bands at 1349 cm^?1 and 1595 cm^?1 for graphitic structures. The intensity ratio (I_D/I_G) is also calculated, which indicate the degree of defects in the material. This ratio (I_D/I_G), increases from 0.84 for GO to 0.91 for RGO/Fe₃O₄ nanocomposite and promotes the defects which are beneficial for electromagnetic (EM) absorption. The SEM image depicts that, Fe₃O₄ spherical nanoparticles are dispersed over the surface of graphene sheets and provide a thermal conducting path for heat dissipation between different layers of graphene. The EM absorption properties have been analyzed at 2–18 GHz of RGO and RGO/Fe₃O₄. The addition of proper content of Fe₃O₄ magnetic nanoparticles in RGO sheets improved the Reflection Loss (RL) from ??13.5 dB to ??20 dB at a frequency of 9.5 GHz. Moreover, due to magnetic loss and interfacial polarization, the effective bandwidth increases from 2.5 GHz to 3.8 GHz at a coating thickness of 1.5 mm. Hence this light weight nanocomposite is an excellent material for strong EM absorption in X-band.     

Kinetic sorption study of Cerium (IV) on magnetite nanoparticles

Magnetite nanoparticles (Fe₃O₄) and humic acid-coated magnetite nanoparticles (Fe₃O₄/HA) were prepared by co-precipitation method for cerium ions removal from aqueous solution. The success of preparation in nanoscale was confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The TEM image shows that the size of Fe₃O₄ is around 15 nm and the presence of humic acid reduces the magnetite aggregation and stabilizes the magnetite suspension. Adsorption studies with respect to various process variables such as contact time, pH, and temperature were investigated by batch technique. The sorption kinetics and isotherms of Fe₃O₄ and Fe₃O₄/HA for Ce (IV) ions show that the sorption kinetics follow the pseudo-second-order and Langmuir isotherm models for both sorbents. The maximum capacities (Q_max) of Ce (IV) onto Fe₃O₄ and Fe₃O₄/HA were found to be 160 and 280 mg/g, respectively. The thermodynamic parameters (ΔG^o, ΔH^o and ΔS^o) were calculated, and the results revealed that the sorption process of Ce (IV) ions on both Fe₃O₄ and Fe₃O₄/HA are spontaneous, endothermic for Fe₃O₄ and exothermic for Fe₃O₄/HA.     

Elaborately Designed Hierarchical Heterostructures Consisting of Carbon‐Coated TiO2(B) Nanosheets Decorated with Fe3O4 Nanoparticles for Remarkable Synergy in High‐Rate Lithium Storage

The capacity and conductivity deficiencies of TiO₂(B) are addressed simultaneously through a smart morphological and compositional design. Elaborately designed hierarchical heterostructures are reported, consisting of carbon‐coated TiO₂(B) nanosheets decorated with Fe₃O₄ nanoparticles, based on a facile self‐assembly strategy. The novel hierarchical heterostructures exhibit a remarkable synergy by bridging the intriguing functionalities of TiO₂(B) nanosheets (high safety and durability), Fe₃O₄ nanoparticles (high theoretical capacity), and carbon coatings (high conductivity), which results in significantly improved cycle and rate performances. A startlingly high reversible capacity of 763 mA h g⁻¹ is delivered at 500 mA g⁻¹ after 200 charging−discharging cycles. Even when the current density is as high as 10 000 mA g⁻¹, the reversible capacity is still up to 498 mA h g⁻¹. This smart morphological and compositional design opens up new opportunities for developing novel, multifunctional hierarchical heterostructures as promising anode materials for next‐generation, high‐power lithium‐ion batteries.     

Synthesis of a soluble polyaniline–ferrite composite: magnetic and electric properties

We report the preparation of a processible magnetite/polyaniline (Fe₃O₄/PANI) nanocomposite, containing dodecylbencensulfonic acid (DBSA) as a surfactant and dopant, with both magnetic and conducting properties. Different amounts of Fe₃O₄ nanoparticles were successfully disposed with FeCl₃ solution to prevent their aggregation in the solution by the application of common ion effect. The magnetic properties of the resulting composites were investigated by a quantum design magnetometer (PMPS). The (Fe₃O₄/PANI) nanocomposite showed at 300 K no loop of hysteresis indicating the superparamagnetic nature. The saturation magnetization varies from 0.167 to 28.45 emu/g with increasing Fe₃O₄ content. Zero field cooling (ZFC) and Field cooling (FC) profiles showed that the polyaniline matrix allows each ferrite nanoparticles to behave independently and interparticle interactions are not important for iron oxide content lower than 36 wt.%. The electrical conductivity of composites was found to be higher than that of the pure PANI in spite of the insertion of the insulating material Fe₃O₄ particles. It is noticeable that conductivity increases with low Fe₃O₄ particles content and then decreases. Structural characterization by X-ray diffraction (XRD), UV spectroscopy and thermogravimetric analysis (TGA) have been performed.     

Immobilization of albumin on magnetite nanoparticles

The magnetite (Fe₃O₄) nanoparticles were prepared by the co-precipitation of ferrous and ferric salts with NH₄OH, and then modified with 3-aminopropyltriethoxysilane (APTES) by silanization reaction and subsequent reaction with glutaraldehyde (GA) to obtain functional groups on their surface. The influence of different terminated groups on protein binding was studied with bare and modified magnetite nanoparticles. Amine terminated magnetite nanoparticles were shown the highest binding ability for immobilization process compared to Fe₃O₄ NPs and GA bonded NPs. This binding ability was shown by using sodium dodecyl polyacrylamide gel electrophoresis technique (SDS-PAGE). Albumin attached magnetite nanoparticles were also examined by Scanning Electron Microscopy (SEM).     

A single nanobelt to achieve simultaneous photoluminescence–electricity–magnetism trifunction

In order to develop new-typed multifunctional composite nanobelts, polymethyl methacrylate (PMMA) is used as the matrix to construct composite nanobelts containing different amounts of Eu(BA)₃phen(BA = benzoic acid, phen = phenanthroline), polyaniline (PANI) and Fe₃O₄ nanoparticles (NPs), and Eu(BA)₃phen/PANI/Fe₃O₄/PMMA trifunctional composite nanobelts with simultaneous photoluminescence, electricity and magnetism have been successfully fabricated via electrospinning technology. The morphology and properties of the obtained composite nanobelts were characterized by X-ray diffractometry, scanning electron microscopy, vibrating sample magnetometry, fluorescence spectroscopy and Hall effect measurement system. The results indicate that the trifunctional composite nanobelts simultaneously possess excellent photoluminescence, electrical conduction and magnetic properties. Fluorescence emission peaks of Eu³⁺ ions in the composite nanobelts are observed and assigned to the energy levels transitions of ⁵D₀ → ⁷F₀ (580 nm), ⁵D₀ → ⁷F₁ (593 nm) and ⁵D₀ → ⁷F₂ (615 nm) of Eu³⁺ ions, and the ⁵D₀ → ⁷F₂ hypersensitive transition at 615 nm is the predominant emission peak. The electrical conductivity reaches up to the order of 10^?3 S/cm. Furthermore, the luminescent intensity, electrical conductivity and saturation magnetization of the composite nanobelts can be tunable by adjusting amounts of Eu(BA)₃phen, PANI and Fe₃O₄ NPs. The formation mechanism of the composite nanobelts is also proposed. The obtained photoluminescence–electricity–magnetism trifunctional composite nanobelts have potential applications in many areas such as electromagnetic interference shielding, microwave absorption, molecular electronics, biomedicine and future nanomechanics. More importantly, the design concept and construct technique are of universal significance to fabricate other trifunctional naonobelts.     

New alignment procedure of magnetite–CNT hybrid nanofillers on epoxy bulk resin with permanent magnets

The main properties of epoxy composites reinforced with aligned carbon nanotubes (CNTs) have been studied. The alignment was carried out in a specific designed device applying a weak magnetic field (0.3 T) with permanent magnets. CNTs were modified with magnetite nanoparticles (Fe₃O₄) functionalized, in a one-stage-process which does not require use of strong acids or aggressive treatments which could affect the structural integrity of CNTs. The study by transmission electron microscopy confirmed that the Fe₃O₄ nanoparticles were closely bonded over CNT surfaces. The thermo-mechanical and tensile properties of composites measured were higher than neat epoxy resin and were similar for both composites: reinforced with neat CNTs and magnetite–CNT hybrid nanofillers. The electrical behaviour indicates a high anisotropy for aligned composites, showing an increase of one order of magnitude for the electrical conductivity in the direction of aligned nanotubes.     

Low-temperature spin spray deposited ferrite/piezoelectric thin film magnetoelectric heterostructures with strong magnetoelectric coupling

We report low-temperature spin spray deposited Fe₃O₄/ZnO thin film microwave magnetic/piezoelectric magnetoelectric heterostructures. A voltage induced effective ferromagnetic resonance field of 14 Oe was realized in Fe₃O₄/ZnO magnetoelectric (ME) heterostructures. Compared with most thin film magnetoelectric heterostructures prepared by high temperature (>600 °C) deposition methods, for example, pulsed laser deposition, molecular beam epitaxy, or sputtering, Fe₃O₄/ZnO ME heterostructures have much lower deposition temperature (<100 °C) at a much lower cost and less energy dissipation, which can be readily integrated in different integrated circuits.     

Fast microwave synthesis of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/Ag magnetic nanoparticles using Fe<Superscript>2+</Superscript> as precursor

A simple and quick microwave method to prepare high performance magnetite nanoparticles (Fe₃O₄ NPs) directly from Fe has been developed. The as-prepared Fe₃O₄ NPs product was fully characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The results show that the as-prepared Fe₃O₄ NPs are quite monodisperse with an average core size of 80 × 5 nm. The microwave synthesis technique can be easily modified to prepare Fe₃O₄/Ag NPs and these NPs possess good magnetic properties. The formation mechanisms of the NPs are also discussed. Our proposed synthesis procedure is quick and simple, and shows potential for large-scale production and applications for catalysis and biomedical/biological uses.     

Removal and reuse of Ag nanoparticles by magnetic polyaniline/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanofibers

For the treatment of wastewater containing Ag nanoparticles (NPs), PANI/Fe₃O₄ nanofibers were firstly prepared by a novel self-assemble. And then, the efficiency for the removal of Ag NPs from wastewater was investigated. The magnetic performance of PANI/Fe₃O₄ nanofibers could be optimized by adjusting the pH of the self-assemblied system. Under pH of 3, the as-prepared nanofibers exhibited the highest magnetism and also displayed good efficiency (>?12 mg g^?1) for the removal of Ag NPs. Importantly, the resulted product (PANI/Fe₃O₄/Ag composite) could act as a catalysis for cleaning durable pollutant, 4-nitrophenol. After 10 cycles, only slight decrease in rate constant was found, indicating excellent reusability. Those approaches provide a new way to merge the recovery of Ag NPs as pollutants and reuse of recovered Ag NPs as recyclable material for environmental remediation.     

Solvothermal synthesis of hollow glass microspheres/Fe3O4 composites as a lightweight microwave absorber

Hollow glass microspheres/Fe₃O₄ (HGMs/Fe₃O₄) composites with low density were successfully synthesized by solvothermal method at 160 °C. The morphology, composition, and microstructure of the samples were characterized by scanning electron microscopy and X-ray diffraction, respectively. The results show that the HGMs/Fe₃O₄ composites exhibit compact and continuous Fe₃O₄ particles coating on the surface of HGMs. The complex permeability and permittivity of HGMs/Fe₃O₄ composites obtained at 160 °C for different reaction times were measured in the frequency range of 1–18 GHz by vector network analysis. The microwave absorption properties were well-elucidated by the traditional coaxial line method. The as-prepared HGMs/Fe₃O₄ composites show excellent microwave absorption properties. When the thicknesses of these HGMs/Fe₃O₄ composites are more than 1.5 mm, they all exhibit strong absorption peaks (lower than ?10 dB). A possible mechanism of the improved microwave absorption properties was discussed.