Synthesis of nanofibrous chitosan/Fe3O4/TiO2@TiO2 microspheres with enhanced biocompatibility and antibacterial property

Multifunctional materials have received considerable attention as they could integrate different functional components in one-single platform. In this study, novel chitosan/Fe₃O₄/TiO₂@TiO₂ nanowire (NW) microspheres having extracellular matrix-like fibrous surface and photothermal antibacterial property were synthesized through in situ hydrothermal growth of TiO₂ NWs on chitosan/Fe₃O₄/TiO₂ microspheres. It is found that the microspheres were spherical in morphology with a diameter of 100–300 µm and exhibited a hierarchical and nanofibrous feature. Their surface was mainly constructed by numerous TiO₂ NWs with a diameter of 20– 30nm. In vitro biological evaluation indicates that the chitosan/Fe₃O₄/TiO₂@TiO₂ NW microspheres significantly enhanced attachment and proliferation of human umbilical vein endothelial cells compared with chitosan/Fe₃O₄/TiO₂ nanocomposite microspheres due to the presence of nanofibrous surface. Moreover, the microspheres showed photothermal antibacterial property to inhibit the growth of bacteria due to the presence of Fe₃O₄ component.     

Synthesis of magnetically separable core–shell structured Ni<Subscript>x</Subscript>Fe<Subscript>1−x</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>@TiO<Subscript>2</Subscript> nanoparticles photocatalysts for the degradation of organic dyes

In this paper, the core–shell structured NiFe₂O₄@TiO₂ nanoparticles and nanochains as photocatalysts were successfully prepared through hydrothermal and hydrolysis method. The as-prepared core–shell structure was composed of a magnetic NiFe₂O₄ core and photocatalytic titanium oxide coating shell. SEM and TEM images characterized the morphology of NiFe₂O₄@TiO₂ nanoparticles. Moreover, the results of XRD patterns proved that the TiO₂ coating shell consisted of anatase. The VSM measurements showed that the saturation magnetization values of NiFe₂O₄ and NiFe₂O₄@TiO₂ nanoparticles was 65 and 53 emu/g, respectively. The photocatalyst of NiFe₂O₄@TiO₂ nanoparticles exhibited the outstanding recyclable performance for RhB. And, the photo_degradation ration of maintained 69 % after the photocatalyst experienced ten photocatalysis experiments, which is better than that of Fe₃O₄@TiO₂ photocatalysts.     

Synthesis of Fe3O4@SiO2@Ption–TiO2 hybrid composites with high efficient UV–visible light photoactivity

Platinum ion doped magnetic TiO₂ (Fe₃O₄@SiO₂@Pt_ion–TiO₂) hybrid microspheres with uniform magnetic cores were synthesized and characterized in this work. The results indicate that the photoactivity of Fe₃O₄@SiO₂@Pt_ion–TiO₂ is much higher than Fe₃O₄@SiO₂@TiO₂ for the decolorization of acid orange 20 under UV–visible light irradiation. The trend for the final degradation ratio with Fe₃O₄@SiO₂@Pt_ion–TiO₂ is quite small, even after seven repetitive experiments. These data indicate that the magnetic microspheres possess the potential to be effective and stable catalysts. The results demonstrate that the Pt ion doped magnetic catalyst meets the needs for both immobilization and high photoactivity.     

Hydrothermal synthesis of 3D hollow porous Fe3O4 microspheres towards catalytic removal of organic pollutants

Three-dimensional hollow porous superparamagnetic Fe₃O₄ microspheres were synthesized via a facile hydrothermal process. A series of characterizations done with X-ray diffraction, Brunauer-Emmett-Teller method, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy indicated that the production of Fe₃O₄ microspheres possessed good monodispersity, uniform size distribution, hollow and porous structural characters, and strong superparamagnetic behavior. The obtained Fe₃O₄ microspheres have a diameter of ca. 300 nm, which is composed of many interconnected nanoparticles with a size of ca. 20 nm. The saturation magnetization is 80.6 emu·g^-1. The as-prepared products had promising applications as novel catalysts to remove organic pollutants (methylene blue) from wastewater in the presence of H₂O₂ and ultrasound irradiation.     

A novel platform of hemoglobin on core–shell structurally Fe3O4@Au nanoparticles and its direct electrochemistry

A novel platform, which hemoglobin (Hb) was immobilized on core–shell structurally Fe₃O₄/Au nanoparticles (simplified as Fe₃O₄@Au NPs) modified glassy carbon electrode (GCE), has been developed for fabricating the third biosensors. Fe₃O₄@Au NPs, characterized using transmission electron microscope (TEM), scanning electron microscope (SEM) and energy dispersive spectra (EDS), were coated onto GCE mediated by chitosan so as to provide larger surface area for anchoring Hb. The thermodynamics, dynamics and catalysis properties of Hb immobilized on Fe₃O₄@Au NPs were discussed by UV–visible spectrum (UV–vis), electrochemical impedance spectroscopy (EIS), electrochemical quartz crystal microbalance technique (EQCM) and cyclic voltammetry (CV). The electrochemical parameters of Hb on Fe₃O₄@Au NPs modified GCE were further carefully calculated with the results of the effective working area as 3.61 cm², the surface coverage concentration (Γ) as 1.07 × 10⁻¹² mol cm⁻², the electron-transfer rate constant (K_s) as 1.03 s⁻¹, the number of electron transferred (n) as 1.20 and the standard entropy of the immobilized Hb (ΔS⁰′) as calculated to be −104.1 J mol⁻¹ K⁻¹. The electrocatalytic behaviors of the immobilized Hb on Fe₃O₄@Au NPs were applied for the determination of hydrogen peroxide (H₂O₂), oxygen (O₂) and trichloroacetic acid (TCA). The possible functions of Fe₃O₄ core and Au shell as a novel platform for achieving Hb direct electrochemistry were discussed, respectively.     

Porous TiO2-coated Magnetic Core-Shell Nanocomposites: Preparation and Enhanced Photocatalytic Activity

The core-shell structured TiO₂/SiO₂@Fe₃O₄ photocatalysts were prepared using Fe₃O₄ as magnetic core, tetraethoxysilane (TEOS) as silica source and tetrabutyl titanate (TBOT) as titanium sources. The as-obtained structure was composed of a SiO₂@Fe₃O₄ core and a porous TiO₂ shell. The diameter of SiO₂@Fe₃O₄ core was about 205 nm with thickness of porous TiO₂ of about 5-6 nm. The 9%TiO₂/6% SiO₂@Fe₃O₄ microspheres possess the highest BET surface area and the BJH pore volume, which are 373.5 m²穏^-1 and 0.28 cm³穏^-1, respectively. The 9%TiO₂/6%SiO₂@Fe₃O₄ photocatalyst exhibited an excellent performance for the degradation of methyl orange and methylene blue dyes. Two different dyes were completely decolorized in 60 min under UV irradiation. The photocatalytic activity and the amount of catalyst were almost not decrease after recycling for 6 times by using external magnetic field.     

Trilayer Composite Poly(styrene/butyl acrylate/acrylic acid) Terpolymer Microspheres with Fe2O3 Middle Layer: Synthesis and Characterization

Fe₂O₃ particles with diameter of 3–5 nm were encapsulated in polymer spheres (styrene/butyl acrylate/acrylic acid terpolymer latex) by emulsion polymerization. Control of the pH value of the medium and modification of the latex prior to the second polymerization were of importance in determining the microstructure and morphology of the composite particles. The interaction between Fe₂O₃ and seed latex was confirmed by IR spectral changes of the surface groups of the latex particles. Mossbauer spectra gave evidence for the changes of electric density and electric field symmetry around Fe₂O₃, and surface photovoltage spectra indicated that the Fe₂O₃ particles were encapsulated in polymer. It was shown by all the results that the composite microspheres of size 80 nm had a core–shell structure with trilayers of seed latex core, Fe₂O₃ nanoparticles middle layer and polymer shell. © 1997 SCI.     

Controlled preparation of Fe3O4/P (St-MA) magnetic composite microspheres by DPE method

In this work, controlled radical polymerization based on 1, 1-diphenylethylene (DPE method) was used to prepare magnetic composite microspheres. By this method, Fe₃O₄/P (St-MA) magnetic composite microspheres were prepared via copolymerization of styrene (St) and maleic anhydride (MA) using DPE as radical control agent in the presence of Fe₃O₄ nanoparticles. The structure and properties of the magnetic composite microspheres obtained were characterized by IR, ¹H-NMR, SEC-MALLS, TEM, TGA, VSM, DLS and other instruments. It was found that the DPE method allows the controlled preparation of magnetic composite microspheres, and Fe₃O₄/ P(St-MA) microspheres possess perfect sphere-shaped morphology, homogeneous particle size, carboxylic surface, superparamagnetism with a saturation magnetization of 14.704 emu/g, and magnetic content with a value of 25%.     

Preparation and characterization of magnetic composite microspheres using a free radical polymerization system consisting of DPE

In this paper, a free radical polymerization system consisting of DPE was used to prepare magnetic composite microspheres. Fe₃O₄/P(AA-MMA-St) core-shell magnetic composite microspheres have been synthesized by copolymerization of acrylic acid, methyl methacrylate and styrene using DPE as radical control agent in the presence of Fe₃O₄ nanoparticles. The structure and properties of the magnetic composite microspheres were analyzed by FTIR, ¹H NMR, SEC-MALLS, TEM, TGA, VSM and other instruments, and the formation mechanism of composite microspheres was supposed by those results. It was found that the Fe₃O₄/P(AA-MMA-St) microspheres were nano-size with relatively homogeneous particle size distribution, perfect sphere-shaped morphologies, superparamagnetism with a saturation magnetization of 18.430 emu/g, and high magnetic content with a value of 40%. ¹H NMR and TEM analysis indicated that at the first stage of polymerization, a DPE-containing copolymer of acrylic acid, methyl methacrylate formed and was then absorbed on the surface of Fe₃O₄ nanoparticles. Contact angle analysis indicated that the DPE-containing copolymer improved hydrophobicity of Fe₃O₄ nanoparticles through chemical absorption. In the second step polymerization, certain amount of monomers of styrene and residue methacrylate were initiated by the DPE-containing copolymer on the Fe₃O₄ nanoparticles' surface and resulted in the formation of Fe₃O₄/P(AA-MMA-St) composite microspheres.     

Copper nanowire/PA6 composites prepared by in situ polymerization and its properties

Most magnetic composite materials have a serious sedimentation problem because of their large density. When the nanomaterials are combined with magnetic materials, the density would become larger. In this article, polystyrene (PS) beads were used as core to synthesize raspberry-like PS-Fe₃O₄@TiO₂ particles (PFTPs) by a facile method, which could float on the water. The loaded Fe₃O₄@TiO₂ particles were characterized by X-ray diffraction (XRD), which could confirm the anatase phase TiO₂ coated on Fe₃O₄ nano-particles. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) confirmed the presence of acrylic acid in reaction media could effectively tune the morphology of resulting composite particles between “core-shell” and “raspberry-like”. The data of Vibrating sample magnetometer (VSM) indicated the change in saturation magnetization before and after TiO₂ coated, the introduction of PS could further influence the saturation magnetization of Fe₃O₄. Lastly, we proved the sedimentation stability of PFTPs via capturing the photographs of them in water and oil.     

Facile synthesis of folate-conjugated magnetic/fluorescent bifunctional microspheres

In this paper, we investigated the functional imaging properties of magnetic microspheres composed of magnetic core and CdTe quantum dots in the silica shell functionalized with folic acid (FA). The preparation procedure included the preparation of chitosan-coated Fe₃O₄ nanoparticles (CS-coated Fe₃O₄ NPs) prepared by a one-pot solvothermal method, the reaction between carboxylic and amino groups under activation of NHS and EDC in order to obtain the CdTe-CS-coated Fe₃O₄ NPs, and finally the growth of SiO₂ shell vent the photoluminescence (PL) quenching via a Stöber method (Fe₃O₄-CdTe@SiO₂). Moreover, in order to have a specific targeting capacity, the magnetic and fluorescent bifunctional microspheres were synthesized by bonding of SiO₂ shell with FA molecules via amide reaction (Fe₃O₄-CdTe@SiO₂-FA). The morphology, size, chemical components, and magnetic property of as-prepared composite nanoparticles were characterized by ultraviolet-visible spectroscopy, fluorescent spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning transmission electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM), respectively. The results show that the magnetic and fluorescent bifunctional microspheres have strong luminescent which will be employed for immuno-labeling and fluorescent imaging of HeLa cells.     

Fe3O4@mesoporouspolyaniline: A Highly Efficient and Magnetically Separable Catalyst for Cross‐Coupling of Aryl Chlorides and Phenols

A high surface, magnetic Fe₃O₄@mesoporouspolyaniline core‐shell nanocomposite was synthesized from magnetic iron oxide (Fe₃O₄) nanoparticles and mesoporouspolyaniline (mPANI). The novel porous magnetic Fe₃O₄ was obtained by solvothermal method under sealed pressure reactor at high temperature to achieve high surface area. The mesoporouspolyaniline shell was synthesized by in situ surface polymerization onto porous magnetic Fe₃O₄ in the presence of polyvinylpyrrolidone (PVP) and sodium dodecylbenzenesulfonate (SDBS), as a linker and structure‐directing agent, through ‘blackberry nanostructures’ assembly. The material composition, stoichiometric ratio and reaction conditions play vital roles in the synthesis of these nanostructures as confirmed by variety of characterization techniques. The role of the mesoporouspolyaniline shell is to stabilize the porous magnetic Fe₃O₄ nanoparticles, and provide direct access to the core Fe₃O₄ nanoparticles. The catalytic activity of magnetic Fe₃O₄@mesoporousPANI nanocomposite was evaluated in the cross‐coupling of aryl chlorides and phenols.     

Synthesis of Fe3O4 nanowire@CeO2/Ag nanocomposites with enhanced photocatalytic activity under sunlight exposure

Ternary magnetic Fe₃O₄ nanowire@CeO₂/Ag nanocomposites have been firstly synthesized by means of hydrothermal and co–precipitation techniques, and their ability to adsorb, photocatalytic degradation organic pollutants, methylene blue present in water, and separate, has been demonstrated. The results show that CeO₂ and Ag nanoparticles are uniformly deposited on the surface of Fe₃O₄ nanowires. The photocatalytic experiments demonstrate that the Fe₃O₄@CeO₂/Ag nanocomposites exhibit remarkably enhanced photocatalytic properties and stability compared to CeO₂, CeO₂/Ag, Fe₃O₄@CeO₂, Fe₃O₄ under natural sunlight exposure. Moreover, excellent photocatalytic degradation efficiency for phenol and MO are also observed. The enhanced photocatalytic performance may be attributed to the synergetic effect of Fe₃O₄ nanowire, CeO₂ and Ag nanoparticles, which lead to the enhanced light harvesting, the promoted charge separation and enhanced adsorption capacity. In addition, the Fe₃O₄@CeO₂/Ag photocatalyst can be easily collected and separated by an external magnet. These results suggest that the nanocomposites could be exploited as potential candidates for solar photocatalysis.     

Factors influencing magnetic polymer microspheres prepared by dispersion polymerization

Magnetic iron oxide (Fe₃O₄) was prepared by a coprecipitation method. Core–shell composite magnetic polymer microspheres with carboxyl groups were synthesized by the dispersion polymerization of styrene and acrylic acid in the presence of magnetic oxide, and dibenzoyl peroxide was used as an initiator. The synthesized magnetic polymer microspheres were characterized with X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and so forth. The results indicated that the product was single‐phase Fe₃O₄, and its average size was about 10 nm. The configuration of the microspheres, which contained carboxyl groups, was spherical, and the average size was about 2 μm. The results of vibrating sample magnetometry tests showed that the magnetic powders produced by different surfactants had different saturation magnetizations. When poly(ethylene glycol) with a weight‐average molecular weight of 4000 was used as a surfactant, the saturation magnetization of the samples reached 69.2 emu/g. The factors that affected the shape, magnetism, size, and distribution of the microspheres were also studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and characterization of magnetic poly(styrene–glycidyl methacrylate) microspheres for highly efficient protein adsorption by two‐stage dispersion polymerization

Micrometer‐sized superparamagnetic poly(styrene–glycidyl methacrylate)/Fe₃O₄ spheres were synthesized by two‐stage dispersion polymerization with modified hydrophobic Fe₃O₄ nanoparticles, styrene (St), and glycidyl methacrylate (GMA). The morphology and properties of the magnetic Fe₃O₄–P (St‐GMA) microspheres were examined by scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, thermogravimetric analysis, and attenuated total reflectance. The average size of the obtained magnetic microspheres was 1.50 μm in diameter with a narrow size distribution, and the saturation magnetization of the magnetic microspheres was 8.23 emu/g. The magnetic Fe₃O₄–P (St‐GMA) microspheres with immobilized iminodiacetic acid–Cu²⁺ groups were used to investigate the adsorption capacity and selectivity of the model proteins, bovine hemoglobin (BHb) and bovine serum albumin (BSA). We found that the adsorption capacity of BHb was as high as 190.66 mg/g of microspheres, which was 3.20 times greater than that of BSA, which was only 59.64 mg/g of microspheres as determined by high‐performance liquid chromatography. With a rather low nonspecific adsorption, these microspheres have great potential for protein separation and purification applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43005.     

Preparation and characterization of chitosan-poly(acrylic acid) polymer magnetic microspheres

A modified method to prepare chitosan-poly(acrylic acid)(CS-PAA) polymer magnetic microspheres was reported in this paper. First, via self-assembly of positively charged CS and negatively charged Fe₃O₄ nanoparticles, magnetic CS cores with a large amount of Fe₃O₄ nanoparticles were successfully prepared. Subsequently, the AA monomers were polymerized on the magetic CS cores based on the reaction system of water-soluble polymer-monomer pairs. These polymer magnetic microspheres had a high Fe₃O₄ loading content, and showed unique pH-dependent behaviors on the size and zeta potential. From the magnetometer measurements data, the CS-PAA polymer magnetic microspheres also had superparamagnetic property as well as fast magnetic response. A continuous release of the entrapped ammonium glycyrrhizinate in such polymer magnetic microspheres occurred, which confirmed the potential applications of these microspheres for the targeted delivery of drugs.     

Preparation of novel Ni/Co co-doping Fe3O4/TiO2 core–shell nanocomposites and their use in effective photocatalytic degradation of Amlodipine drug.

Ni/Co co-doping Fe₃O₄/TiO₂ magnetic core–shell nanocomposites (wt% varied amount of dopants) have been prepared by sol-gel method at low temperature. X-ray diffraction, Fourier transform infrared, energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma optical emission spectroscopy and vibrating sample magnetometry studies have been made to investigate the crystalline structure, morphology and magnetic properties of these composites. The prepared Ni/Co co-doping Fe₃O₄/TiO₂ nanocomposites exhibit high degree of crystallinity and suitable magnetic properties at room temperature. Their use has been made in effective photocatalytic degradation of Amlodipine a pharmaceutical contaminant under UV light irradiation at 365 nm. The results have shown that wt% amount of dopants, calcination time, calcination temperature and pH of the Amlodipine aqueous solution are important factors in degradation efficiency of Amlodipine. The optimal weight ratios of Ni and Co to Ti were 0.015%. The nanocomposites can be recovered from the aqueous system easily by using a magnet. Their photocatalytic degradation activity for Amlodipine drug remained 94.43% after five times of repetitive use.     

Fabrication of core-shell Fe3O4/polypyrrole and hollow polypyrrole microspheres

A facile synthesis of highly-regulated core-shell Fe₃O₄/polypyrrole (PPy) microspheres is achieved using a surfactant directed chemical oxidation polymerization in aqueous solution. The thickness of the PPy layer can be tuned by the quantity of the pyrrole monomer. The formation of core-shell Fe₃O₄/PPy microspheres lies on the static interactions between the SO₃⁻ group in sodium dodecyl sulphate molecules and Fe₃O₄ microspheres. Other surfactants such as cetyltrimethylammonium bromide and polyoxyethylene (10) isooctylcyclohexyl ether (Triton X-100) directed polymerization cannot produce such highly-regulated core-shell Fe₃O₄/PPy microspheres. XPS spectra proved the core-shell structure of the composite microspheres. XRD, FTIR, and UV–vis spectra are used to characterize the chemical structure of the composite microspheres. The electrical and magnetic properties are also investigated. Moreover, the obtained core-shell Fe₃O₄/PPy microspheres can be converted to highly-regulated hollow PPy microspheres by dissolving the Fe₃O₄ core with acid solution. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Fe3O4 coupled BiOCl: A highly efficient magnetic photocatalyst

The magnetic photocatalyst, Fe₃O₄/BiOCl nanocomposite, was prepared and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), physical property measurement system (PPMS). It was found that Fe₃O₄/BiOCl was an effective photocatalyst to degrade the organic dyes. Compared with the conventional core–shell magnetic photocatalysts, such as Fe₃O₄/TiO₂ system which dramatically lost their intrinsically photocatalytic activity due to the introduction of the magnetic core, the as-synthesized Fe₃O₄/BiOCl reserved as high photocatalytic activity as that of BiOCl. The high catalytic activity possibly involved in a coupled structure and the special interfaces, that is, the probability of combination of the carriers could be reduced in this system. Moreover, the superparamagnetic Fe₃O₄/BiOCl can be not only easily recycled but also fluidized by applying an external magnetic field.     

Porous Fe3O4/C microspheres for efficient broadband electromagnetic wave absorption

Porous Fe₃O₄/C microspheres, which were Fe₃O₄ nanocrystals (～8?nm) embedded in an open nanostructured carbon network, were successfully synthesized via a facile hydrothermal process. The porous Fe₃O₄/C microspheres possessed many distinct attributes that facilitate efficient broadband electromagnetic wave absorption (EMWA). EMWs were attenuated through multiple reflections and absorption in the 3D interconnected porous structure of the microspheres; these processes collectively improved the interaction between the EMWs and the absorber. Additionally, the carbon network and embedded Fe₃O₄ nanoparticles caused significant dielectric losses and magnetic losses, respectively, which also enhanced EMWA. The EMWA characteristics of the microspheres could be precisely tuned via changing the carbon content to achieve optimized impedance matching. Porous Fe₃O₄/C microspheres with a 71.5?wt% carbon content displayed particularly impressive EMWA properties: a maximum reflection loss (RL) value of ??31.75 across broad band frequencies in the range of 7.76–12.88?GHz (RL < ?10?dB) at an absorber thickness of 3.0?mm. These excellent EMWA properties may be attributed to both dielectric loss (carbon) and magnetic loss (Fe₃O₄). Additionally, the 3D interconnected porous structure of the Fe₃O₄/C microspheres is especially favorable for impedance matching.