A new strategy to assemble enhanced magnetic–photoluminescent bifunction into a flexible nanofiber

A new type of magnetic–photoluminescent bifunctional [Fe₃O₄@Y₂O₃:Eu³⁺]/polyvinyl pyrrolidone (PVP) flexible composite nanofibers were successfully prepared via electrospinning through dispersing Fe₃O₄@Y₂O₃:Eu³⁺ core–shell structured nanoparticles (NPs) into the PVP matrix. The structure, morphology, and properties of the flexible composite nanofibers were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), and fluorescence spectroscopy. The diameter of [Fe₃O₄@Y₂O₃:Eu³⁺]/PVP nanofibers is ca. 128.57 ± 36.72 nm. Fluorescence emission peaks of Eu³⁺ in both Fe₃O₄@Y₂O₃:Eu³⁺ NPs and [Fe₃O₄@Y₂O₃:Eu³⁺]/PVP nanofibers are observed and assigned to the energy levels transitions of ⁵D₀ → ⁷F₀ (580 nm), ⁵D₀ → ⁷F₁ (533, 586, 592, 599 nm), ⁵D₀ → ⁷F₂ (612 nm), and ⁵D₀ → ⁷F₃ (629 nm) of Eu³⁺ ions. Compared with Fe₃O₄/Y₂O₃:Eu³⁺/PVP nanofibers, [Fe₃O₄@Y₂O₃:Eu³⁺]/PVP nanofibers possess much stronger luminescence. The as-prepared [Fe₃O₄@Y₂O₃:Eu³⁺]/PVP flexible composite nanofibers simultaneously exhibit excellent magnetism and photoluminescent performance. The intensities of magnetism and luminescence of the composite nanofibers can be simultaneously tuned by adjusting the amount of Fe₃O₄@Y₂O₃:Eu³⁺ NPs introduced into the nanofibers. The high performance [Fe₃O₄@Y₂O₃:Eu³⁺]/PVP flexible composite nanofibers have potential applications in bioimaging, cell separation, and future nanomechanics.     

Electrospun Fe3O4/PVP//Tb(BA)3phen/PVP magnetic–photoluminescent bifunctional bistrand aligned composite nanofibers bundles

Fe₃O₄/PVP//Tb(BA)₃phen/PVP magnetic–photoluminescent bifunctional bistrand aligned composite nanofibers bundles based on Fe₃O₄ nanoparticles (NPs) and terbium complex Tb(BA)₃phen (BA = benzoic acid) were fabricated by employing a parallel axial electrospinning setup and were characterized by X-ray diffraction, field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscopy, fluorescence spectroscopy, and vibrating sample magnetometer. It is found that Fe₃O₄ NPs were only dispersed into one strand of the bistrand aligned composite nanofibers bundles, but no nanoparticles in the other strand. And the average diameter of the individual strand fiber was 200 ± 25 nm. The bistrand aligned composite nanofibers bundles exhibit strong green emissions under the excitation of 275 nm ultraviolet light, and the ⁵ D ₄ → ⁷ F ₅ hypersensitive transition at 545 nm was the predominant emission peak of Tb³⁺ ions. The newly obtained bifunctional nanofibers bundles exhibit excellent magnetism and high fluorescence intensity and are expected to apply in biology cell separation, magnetic resonance imaging, drug deliver, and fluorescence immunoassays/imaging.     

Fabrication of magnetic-luminescent bifunctional composite nanofibers via facile electrospinning

Fe₃O₄/Eu(BA)₃phen/polyvinyl pyrrolidone (PVP) magnetic-luminescent bifunctional composite nanofibers have been successfully fabricated based on ferroferric oxide (Fe₃O₄) nanoparticles (NPs) and europium complexes Eu(BA)₃phen (BA = benzoic acid, phen = phenanthroline) via electrospinning technology. The as-prepared samples were characterized by X-ray diffractometry, field-emission scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, fluorescence spectroscopy and vibrating sample magnetometry. The as-prepared Fe₃O₄/Eu(BA)₃phen/PVP composite nanofibers possess good fibrous morphology, and Fe₃O₄ NPs are evenly dispersed into nanofibers. Under the excitation of 274-nm ultraviolet light, Fe₃O₄/Eu(BA)₃phen/PVP composite nanofibers exhibit red emissions of predominant peaks at 592 and 616 nm, which are respectively attributed to the ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ energy levels transitions of Eu³⁺ ions. The optimum mass percentage of Eu(BA)₃phen to PVP is 15 %. The fluorescence intensity of composite nanofibers is decreased when more Fe₃O₄ NPs were added. The saturation magnetization is increased with the increase of Fe₃O₄ NPs, indicating that the magnetism of the composite nanofibers can be tuned by adjusting Fe₃O₄ NPs content. The magnetic-luminescent bifunctional composite nanofibers are expected to apply in the fields of cell separation and biological labeling imaging, etc.     

General strategy for embedding high quality Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> quantum dots and ZnS:Mn<Superscript>2+</Superscript> quantum dots in a silica matrix

In this paper, ZnS:Mn²⁺ quantum dots (QDs) Fe₃O₄ quantum dots (QDs)/SiO₂ nanocomposites were successfully synthesized by reverse microemulsion method. The average diameter of ZnS:Mn²⁺ QDs, Fe₃O₄ QDs and ZnS:Mn²⁺ QDs Fe₃O₄ QDs/SiO₂ nanocomposites was about 5.8, 9 and 29 nm, respectively. As the mass ratio of ZnS:Mn²⁺ to Fe₃O₄ QDs increased from 2.5:4 to 7.5:4, the intensity of the yellow–orange emission coming from Mn²⁺ ions was increased. The superparamagnetic property of ZnS:Mn²⁺ QDs Fe₃O₄ QDs/SiO₂ nanocomposites was observed at room temperature, and the saturation magnetization was decreased as the amount of ZnS:Mn²⁺ QDs increased.     

Synthesis and characterization of one-dimensional magnetic photocatalytic CNTs/Fe3O4–ZnO nanohybrids

One dimensional bifunctional magnetic-photocatalytic CNTs/Fe₃O₄–ZnO nanohybrids were synthesized by one-pot polyol sequential process. The as synthesized products were characterized by X-ray diffraction, Fourier transform infrared spectrometer, transmission electronic microscope, energy dispersive spectrometer, physical properties measurement system and UV–Vis absorption spectroscopy. The results exhibit the ZnO forms heterogenerously on the surface of CNTs/Fe₃O₄ and the nanohybrids display superparamagnetic behavior at room temperature. Photocatalytic studies verify the as-prepared sample have high photocatalytic activity toward the photodegradation of methyl orange in solution. In addition, the photocatalyst can be recycled using magnetic field and maintain high photocatalytic activity.     

Synthesis of PVP-coated ultra-small Fe3O4 nanoparticles as a MRI contrast agent

Ultra-small Fe₃O₄ nanoparticles were prepared by using the coprecipitation method, in which the polyvinylpyrrolidone (PVP) serves as a stabilizer. The nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), infra spectrum (IR), X-ray photoelectron spectroscopy (XPS) and in vivo magnetic resonance imaging (MRI) test. The results showed that the particles’ size was determined by the dripping rate and that PVP molecules played the role of preventing the aggregation and restricting the size of Fe₃O₄ nanoparticles. The Fe₃O₄ nanoparticles with diameter from 6.5 to 1.9 nm obviously exhibited negative contrast enhancement and concentrated at the target area guided by a permanent magnet.     

Electromagnetic and microwave absorbing properties of magnetite nanoparticles decorated carbon nanotubes/polyaniline multiphase heterostructures

Magnetite nanoparticles decorated CNTs/PANI multiphase heterostructures were prepared by polymerization of aniline monomer and an additional process of the coprecipitation of Fe²⁺ and Fe³⁺. Scanning electron microscopy and transmission electron microscopy observation indicated that the monodispersed magnetite nanoparticles were uniformly decorated on the surface of CNTs/PANI. The formation of magnetite nanoparticles on CNTs/PANI was mainly through a preferentially position-selective precipitation process. More interestingly, a portion of Fe₃O₄ nanoparticles was found to form core–shell structures with PANI. The effects of different additional amounts of NH₂Fe(SO₄)₂·6H₂O reactant on the magnetic properties and microwave absorbing performances of CNTs/PANI/Fe₃O₄ heterostructures were investigated. The CNTs/PANI/Fe₃O₄ multiphase heterostructures were proved to be superparamagnetic. The microwave absorption measurement showed that the CNTs/PANI/Fe₃O₄ samples under 1.5 g of NH₂Fe(SO₄)₂·6H₂O condition exhibited much more effective absorption performance. These results suggested the novel CNTs/PANI/Fe₃O₄ multiphase heterostructures with PANI as the second phase may be potential candidate for microwave absorption systems.     

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.     

Coaxial electrospinning preparation and properties of magnetic–photoluminescent bifunctional CoFe2O4@Y2O3:Eu3+ coaxial nanofibers

CoFe₂O₄@Y₂O₃:Eu³⁺ magnetic–fluorescent bifunctional coaxial nanofibers have been successfully obtained via calcination of the [CoFe₂O₄/PVP]@[(Y(NO₃)₃ + Eu(NO₃)₃)/PVP] composite coaxial nanofibers which were fabricated by coaxial electrospinning technique. The diameter of CoFe₂O₄@Y₂O₃:5 %Eu³⁺ magnetic–fluorescent bifunctional coaxial nanofibers was 133 ± 17 nm. Strong fluorescence emission peaks of Eu³⁺ in the CoFe₂O₄@Y₂O₃:Eu³⁺ coaxial nanofibers were observed and assigned to ⁵D₀ → ⁷F₁ (588 nm), ⁵D₀ → ⁷F₁ (593 nm), ⁵D₀ → ⁷F₁ (599 nm), ⁵D₀ → ⁷F₂ (612 nm) and ⁵D₀ → ⁷F₂ (630 nm) energy levels transitions of Eu³⁺ ions, and the predominant emission peak was located at 612 nm. Compared with CoFe₂O₄/Y₂O₃:Eu³⁺ composite nanofibers, CoFe₂O₄@Y₂O₃:Eu³⁺ magnetic–fluorescent bifunctional coaxial nanofibers simultaneously provided higher magnetism and fluorescent intensity. The color, photoluminescent intensity and magnetism of the coaxial nanofibers can be tuned via adjusting the diversity and content of fluorescent compounds and the content of magnetic compounds. Formation mechanism of CoFe₂O₄@Y₂O₃:Eu³⁺ coaxial nanofibers was also presented. The bifunctional magnetic–photoluminescent CoFe₂O₄@Y₂O₃:Eu³⁺ coaxial nanofibers have potential applications in many fields due to their excellent magnetism and fluorescence.     

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.     

High refractive index films of ZnS/PVP nanocomposite by in situ thermolysis

A simple and rapid process for deposition of high refractive index films of ZnS/PVP nanocomposite (NC) is described. Precursor films are dip-coated on glass/quartz substrates from methanolic solution of polyvinylpyrrolidone (PVP) containing Zn⁺²–thiourea (TU) complex. ZnS/PVP nanocomposite films are produced by heating the solid precursor at 200°C for 10 min in air. Heat treatment converts the Zn⁺²–TU complex to ZnS by thermolysis in situ PVP. The transmission spectra of the films (typically 700 nm thickness) in the wavelength range of 200–1000 nm showed an absorption edge near 300 nm due to ZnS nanoparticles and high transmission of 97% beyond 400 nm. ZnS nanoparticles are uniformly dispersed in PVP matrix having sizes of about 3–4 nm. For ZnS loading of 45% by weight, the refractive index of ZnS/PVP is 1.65 which is in between that of PVP (1.48) and ZnS (2.36). Fourier Transform Infrared (FTIR) spectroscopy of the composite showed that there is a strong interaction between ZnS nanocrystals and PVP. The root mean square (RMS) roughness of the films is about 3 nm as determined by atomic force microscope (AFM).     

A simple route to form magnetic chitosan nanoparticles from coaxial-electrospun composite nanofibers

Composite non-woven mats of poly(vinyl pyrrolidone) (PVP), chitosan, and Fe₃O₄ were successfully fabricated using coaxial-electrospinning technique with PVP/chitosan as the shell and PVP/Fe₃O₄ as the core. Because of the templating and confinement properties of the nanofibers, magnetic chitosan nanoparticles (MCNPs) could be spontaneously formed through molecular self-assembly when the composite fibers were dissolved on treatment with acetum solution. By changing the weight ratio of Fe₃O₄:chitosan, the size of the MCNPs could be varied. The morphology, chemical composition, and magnetic characteristics of composite particles were characterized by means of scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometer. Experimental results indicated that the composite particles were super-paramagnetic with sizes in the range of 15–40 nm. This facile and new synthesis route comprises a convenient strategy to generate composite particles and should be broadly applicable to a wide range of systems, serving as a platform for the facile development of novel composite materials.     

Fabrication and mechanical properties of β-sialon–Fe x Si y –CNTs composites

Silicon nitride composites were fabricated by adding Fe₃Al and carbon nanotubes and hot-pressing at a low sintering temperature of 1600 °C. The resulted composites were characterized by X-ray diffraction, Fourier-transform infrared spectrum, and field emission scanning electron microscopy. It was found that the Fe₃Al could react with Si₃N₄ to form the series of compound of Fe _x Si _y , and CNTs could keep chemical stability in the system. Mechanical properties of the composites were also investigated. For Fe₃Al as the additive, the relative density could reach to 93.6 % with the maximum hardness of 15.7 GPa. When the Fe₃Al and CNTs were added into matrix simultaneously, the relative density reached to 92.6 %, and the maximum fracture toughness was 6.7 MPa m^1/2. Finally, the toughening mechanism of Fe₃Al and CNTs in sialon composites, containing crack deflection and bridging, and nanotubes pullout and bridging, were also discussed.     

Patterning Graphene Surfaces with Iron‐Oxide‐Embedded Mesoporous Polypyrrole and Derived N‐Doped Carbon of Tunable Pore Size

This study develops a novel strategy, based on block copolymer self‐assembly in solution, for preparing two‐dimensional (2D) graphene‐based mesoporous nanohybrids with well‐defined large pores of tunable sizes, by employing polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) spherical micelles as the pore‐creating template. The resultant 2D nanohybrids possess a sandwich‐like structure with Fe₂O₃ nanoparticle‐embedded mesoporous polypyrrole (PPy) monolayers grown on both sides of reduced graphene oxide (rGO) nanosheets (denoted as mPPy‐Fe₂O₃@rGO). Serving as supercapacitor electrode materials, the 2D ternary nanohybrids exhibit controllable capacitive performance depending on the pore size, with high capacitance (up to 1006 F/g at 1 A/g), good rate performance (750 F/g at 20 A/g) and excellent cycling stability. Furthermore, the pyrolysis of mPPy‐Fe₂O₃@rGO at 800 °C yields 2D sandwich‐like mesoporous nitrogen‐doped carbon/Fe₃O₄/rGO (mNC‐Fe₃O₄@rGO). The mNC‐Fe₃O₄@rGO nanohybrids with a mean pore size of 12 nm show excellent electrocatalytic activity as an oxygen reduction reaction (ORR) catalyst with a four‐electron transfer nature, a high half‐wave‐potential of +0.84 V and a limiting current density of 5.7 mA/cm², which are well comparable with those of the best commercial Pt/C catalyst. This study takes advantage of block copolymer self‐assembly for the synthesis of 2D multifunctional mesoporous nanohybrids, and helps to understand the control of their structures and electrochemical performance.     

Streptomycin-modified Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>–Au@Ag core–satellite magnetic nanoparticles as an effective antibacterial agent

The fabrication of ideal Ag-modified magnetic nanoparticles (MNPs) as a recyclable antibacterial agent that possesses good dispersibility, strong magnetic responsiveness, and high bactericidal activity is still a challenge. In this study, we described a simple polyethyleneimine (PEI)-assisted connection method for fabricating high-performance Au@Ag-loaded MNPs (Fe₃O₄–Au@Ag). The Fe₃O₄ cores are first modified with uniform PEI shell (2 nm) through self-assembly under sonication. And then, the negatively charged Au@Ag NPs with a uniform size of 5 nm are adsorbed on the surface of the Fe₃O₄ cores through electrostatic interaction. The Au@Ag-loaded MNPs were obtained within 30 min, and they were highly uniform in size and shape with good dispersibility and strong magnetic responsivity. With the aid of the magnetic core, the residual nanoparticles can be recycled from solution through an external magnetic field. These dense Au@Ag NPs acted as antibacterial satellites in highly active areas for Ag ion releasing and bacteria contacting. The Fe₃O₄–Au@AgMNPs exhibited good antibacterial activity against both Gram-negative and Gram-positive bacteria. Moreover, the antibacterial activity of Fe₃O₄–Au@AgMNPs was significantly improved by streptomycin antibiotic modification. Enhancement of the bactericidal efficiency of Fe₃O₄–Au@Ag-streptomycin revealed the presence of a synergistic effect between the MNPs and the introduced antibiotic.     

Efficient in situ growth of platinum nanoclusters on the surface of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> for the detection of latent fingermarks

Hydrophobic Fe₃O₄ nanoparticles were modified with polyethyleneimine (PEI) to obtain hydrophilic Fe₃O₄ nanoparticles. By reducing the content of H₂PtCl₆ solution by using l-ascorbic acid (AA) as a reductive agent, fluorescent platinum nanoclusters (Pt NCs) were incubated into the PEI-modified Fe₃O₄ nanoparticles. The prepared Fe₃O₄@Pt NCs microspheres possessed a uniform size, improved monodispersity, high magnetization (40.8 emu/g) and high fluorescence quantum yield (9.0%). Moreover, compared to the reported methods, this method demonstrated that the incubation of Pt NCs on the surface of PEI-Fe₃O₄ was more convenient and needed less reaction time (about 10 min). The experimental results showed that latent fingermarks developing with Fe₃O₄@Pt NCs powder exhibit excellent ridge details. The Fe₃O₄@Pt NCs with superparamagnetism and excellent fluorescence showed great potential in forensic science.     

Preparation and characterization of structure-tailored magnetic fluorescent Fe3O4/P(GMA–EGDMA–NVCz) core–shell microspheres

Fe₃O₄ nanoparticles were prepared by solvothermal reaction, and structure-tailored Fe₃O₄/poly(glycidyl methacrylate-ethyleneglycol dimethacrylate-N-vinylcarbazole) (Fe₃O₄/P(GMA–EGDMA–NVCz)) core–shell microspheres were achieved by distillation–precipitation polymerization of GMA, EGDMA, and NVCz in the presence of Fe₃O₄ nanoparticles. The properties of Fe₃O₄/P(GMA–EGDMA–NVCz) microspheres were characterized by transmission electron microscopy(TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), and fluorescence spectroscopy. The results showed that the size of Fe₃O₄/P(GMA–EGDMA–NVCz) core–shell microspheres could be controlled to 930–470 nm by adjusting the amount of shell monomers, corresponding magnetic content of 45–82 wt%, and saturation magnetization of 32–63 emu/g. Moreover, the intensity of the fluorescence increased considerably with the decrease of shell thickness and the increase of NVCz concentration in the monomer mixture.     

Facile synthesis of Au nanoparticles supported on polyphosphazene functionalized carbon nanotubes for catalytic reduction of 4-nitrophenol

Carbon nanotubes (CNTs) functionalized with cyclotriphosphazene-containing polyphosphazenes (PZS) were found to cause the facile immobilization of Au nanoparticles on the surface. The PZS functional layers not only improved the dispersion of CNTs in aqueous solution but also used as a platform for subsequent immobilization of Au nanoparticles. The functionalized CNTs and the Au@PZS@CNTs nanohybrids were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectrometer, X-ray diffraction, thermogravimetric analysis, Atomic absorption spectrum, and X-ray photoelectron spectroscopy. The results showed that the PZS layers with thickness of about 25 nm were formed uniformly on CNT surfaces by polycondensation between hexachlorocyclotriphosphazene and 4,4′-sulfonyldiphenol, and that high density of homogeneously dispersed spherical Au nanoparticles with average size of 6 nm was immobilized on their outer surface. Meanwhile, the catalytic activity and reusability of the Au@PZS@CNTs nanohybrids were investigated by employing the reduction of 4-nitrophenol into 4-aminophenol by NaBH₄ as a model reaction.     

Development of poly(vinyl acetate-methylacrylic acid)/chitosan/Fe3O4 nanoparticles for the diagnosis of non-alcoholic steatohepatitis with magnetic resonance imaging

Non-alcoholic steatohepatitis is a burgeoning health problem. To diagnose NASH with magnetic resonance imaging (MRI), an effective contrast agent, a stable suspension of superparamagnetic Fe₃O₄ nanoparticles, were newly developed. The negatively charged Fe₃O₄ nanoparticles were coated with positive chitosan (CS) firstly, and then assembled with poly(vinyl acetate-methylacrylic acid) (P(VAc-MAA)). Transmission electron microscope and dynamic light scattering confirmed that the obtained P(VAc-MAA)/CS/Fe₃O₄ nanoparticles had a spherical or ellipsoidal morphology with an average diameter in the range of 14–20 nm. The superparamagnetic property and spinel structure of the Fe₃O₄ nanoparticles were well preserved due to the protection of the P(VAc-MAA)/CS layers on the surface of the Fe₃O₄ nanoparticles. The in vivo rat experiments confirmed that the P(VAc-MAA)/CS/Fe₃O₄ nanoparticles were an effective contrast agent for MRI to diagnose NASH.     

Study of CoFe2O4 Particles Synthesized with Various Concentrations of PVP Polymer

CoFe₂O₄ particles were synthesized using metallic nitrates and polyvinylpyrolidone (PVP) using sol–gel method followed by calcination for 2 h at 960 °C. PVP performed as a surfactant and the effect of various concentrations of PVP on the resultant CoFe₂O₄ powder was studied. The resultant samples were characterized by XRD, TG/DSC, HR-SEM and VSM. X-ray diffraction results indicated the crystalline phase of CoFe₂O₄ particles and impurity phase of hematite was observed for higher PVP concentrations. SEM images demonstrated the influence of PVP concentration on the size of the particles. By VSM measurements, the variations in magnetic properties with respect to PVP concentration are studied. All the magnetic characteristics H _c , M _s and M _r increased for 6 wt% and 15 wt% of PVP concentration. The CoFe₂O₄ particles synthesized with the optimum concentration of PVP may be very attractive for potential applications because of their outstanding magnetic properties (M _s =81.1 Am²/kg, H _c =831 Gauss).