Surface Of Fe3O4 Nanoparticles Research Articles

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 18.430emu/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.

Superparamagnetic iron oxide nanoparticles coated with a folate-conjugated polymer

Folate-functionalized magnetic fluids were prepared by direct chemisorption of a folate-tetra(ethylene glycol)-poly(glycerol monoacrylate) (FA-TEG-PGA) conjugate on Fe3O4nanoparticles. In the magnetic fluids, the PGA block of FA-TEG-PGA was chemisorbed onto the Fe3O4nanoparticle surface through its 1,2-diol groups, while the TEG chain conjugated with FA extended into the water matrix. Characterization by transmission electron microscopy, X-ray diffraction and a vibrating sample magnetometer indicated that the pure Fe3O4 superparamagnetic nanoparticles were formed and the coating process did not significantly affect the size and structure of Fe3O4nanoparticles. Fourier transform infrared spectroscopy, UV-vis spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy confirmed the successful coating of FA-TEG-PGA on the Fe3O4nanoparticles, suggested a coating mechanism for the FA-TEG-PGA, and revealed the maximum weight ratio of FA-TEG-PGA to Fe3O4. The dispersion of FA-TEG-PGA-coated Fe3O4nanoparticles possessed excellent stability over a wide range of pH and salt concentrations. Such folate-functionalized magnetic fluids are expected to be targeting contrast agents for magnetic resonance imaging (MRI) applications. This approach represents a new strategy to synthesize functionalized magnetic nanoparticles that form stable dispersions in water and facilitates potential biomedical applications of these magnetic nanoparticles.

PH-Sensitive Magnetic Ion Exchanger for Protein Separation

A pH-sensitive magnetic ion exchanger was synthesized by binding carboxymethylated chitosan (CMCH) covalently on the surface of Fe3O4 nanoparticles. The diameter for magnetic particles observed at 25 °C was 15 nm. The ion exchanger was superparamagnetic with a saturation magnetization of 64.21 emu/g and an isoelectric point (pI) of 5.75. In a model system, the laccase adsorption capacity reached equilibrium within 15 min (pH 5). The adsorption process followed the Langmuir adsorption isotherm, and the maximum equilibrium adsorption capacity was calculated to be 198.81 mg/g. The laccase can be completely desorbed at pH 8. About 97% laccase can be effectively desorbed from the surface of particles within 15 min. Moreover, the specific activity of the laccase remained constant during the adsorption and desorption process. Finally, the pH-sensitive magnetic ion exchanger was used for separation of laccase directly from culture supernatant, and nearly pure laccase was isolated by a single step with an activity...

Surface organic modification of Fe3O4 magnetic nanoparticles

The surface organic modification of Fe3O4 nanoparticles with silane coupling reagent KH570 was studied. The modified and unmodified nanoparticles were characterized by FT-IR, XPS and TEM. The spectra of FT-IR and XPS revealed that KH570 was coated onto the surface of Fe3O4 nanoparticles to get Fe-OSi bond and an organic coating layer also was formed. Fe3O4 nanoparticles were spheres partly with mean size of 18.8 nm studied by TEM, which was consistent with the result 17.9 nm calculated by Scherrer’s equation. KH570 was adsorbed on surface and formed chemistry bond to be steric hindrance repulsion which prevented nanoparticles from reuniting. Then glycol-based Fe3O4 magnetic liquids dispersed stably was gained.

Preparation of magnetic γ‐Al2O3 supported palladium catalyst for hydrogenation of nitrobenzene

AbstractSpherical alumina support with magnetic core of 134 nm in diameter was prepared by the controlled hydrolysis of aluminums iso‐propoxide. The magnetite Fe3O4 nanoparticles were first synthesized by coprecipitation. Later silica film was coated onto the surface of Fe3O4 nano particles with the sodium silicate acidification method. Alumina was supported on Fe3O4/SiO2 film by the controlled hydrolysis of aluminum alkoxide in a dilute solution consisting of cyclohexane and 2‐propanol. Finally, magnetic alumina supported palladium catalysts were prepared by microemulsion method. The surface morphology and crystal structure of the magnetic alumina and catalysts were characterized by XRD, TEM, BET, and VSM, respectively. The results showed that these kinds of composite particle exhibit superparamagnetic behavior with zero coercivity and remanence. The catalysts show high activity for nitrobenzene directly hydrogenating to aniline under mild conditions. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Preparation of poly (ethylene oxide)‐graft‐poly (acrylic acid) copolymer stabilized iron oxide nanoparticles via an in situ templated process

AbstractSuperparamagnetic iron oxide nanoparticles were prepared in the presence of poly (ethylene oxide)‐graft‐poly (acrylic acid) copolymers via an in situ templated coprecipitation process. The resulted composite nanoparticles consisted of clusters of iron oxide monocrystals embedded inside the polymer chains, and were highly dispersible in aqueous solution. In these graft copolymers, the PAA segments were chemisorbed onto the Fe3O4 nanoparticle surface through their carboxylic acid groups by forming carboxylate groups with the Fe atoms, while PEO segments as the stabilizers extended into the water matrix. Thus the composite nanoparticles exhibited narrow size distribution by the dynamic light scattering measurement. X‐ray diffraction and magnetometer data confirmed the crystalline structure and superparamagnetic property of the particles. This procedure provided a good choice for preparing stable iron oxide magnetic nanoparticles with PEO modified surfaces. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Preparation of Well-Dispersed Superparamagnetic Iron Oxide Nanoparticles in Aqueous Solution with Biocompatible N-Succinyl-O-carboxymethylchitosan

N-succinyl-O-carboxymethylchitosan (NSOCMCS), an amphiphilic polyelectrolyte with the property of biocompatibility and functional carboxyl groups, was used as a stabilizer to prepare a well-dispersed suspension of superparamagnetic Fe3O4 nanoparticles, which were composed of a magnetite Fe3O4 core and a NSOCMCS shell. The carboxyl groups of NSOCMCS can coordinate with Fe3O4, which makes NSOCMCS chemically adsorb onto the surface of Fe3O4 nanoparticles. The stabilizing mechanisms were proven to be both the steric hindrance and electrostatic repulsion arisen from the NSOCMCS. Transmission electron microscopy showed that the resulting Fe3O4 particles were in spherical morphology with the diameter ranging from 12 to 18 nm. Magnetic property measurements indicated that NSOCMCS/Fe3O4 nanoparticles preserved superparamagnetic behavior. In vitro biocompatibility studies showed that the NSOCMCS/Fe3O4 nanoparticles had good cytocompatibility.

Preparation and properties of magnetic Fe3O4–chitosan nanoparticles

Abstract Magnetic Fe3O4–chitosan nanoparticles were prepared by the covalent binding of chitosan (CTS) onto the surface of magnetic Fe3O4 nanoparticles which were prepared by hydrothermal method using H2O2 as an oxidizer. Transmission electron microscopy (TEM) showed that Fe3O4 particles and Fe3O4–chitosan nanocomposites were regular sphere with a mean diameter of 23 nm and 25 nm, respectively. X-ray diffraction patterns (XRD) indicated that the magnetic Fe3O4 nanoparticles were pure Fe3O4 with a spinel structure and the coating of chitosan did not result in a phase change. The coating of CTS onto the Fe3O4 nanoparticles was also demonstrated by the measurement of thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectra. Magnetic measurement revealed that the saturated magnetization of the Fe3O4–chitosan nanoparticles reached 21.5 emu g−1 and the nanoparticles showed the characteristics of superparamagnetism.

Magnetic Core/Shell Fe3O4/Au and Fe3O4/Au/Ag Nanoparticles with Tunable Plasmonic Properties

Core/shell structured Fe3O4/Au and Fe3O4/Au/Ag nanoparticles are synthesized by depositing Au and Ag on the Fe3O4 nanoparticle surface in aqueous solution at room temperature. The control on shell thickness allows the tuning of plasmonic properties of the core/shell structure to be either red-shifted (to 560 nm) or blue-shifted (to 501 nm). Such magneto-optical nanoparticles should have great potentials for nanoparticle-based diagnostic and therapeutic applications.

Preparation and antibacterial activity ofFe3O4@Ag nanoparticles

Bifunctional Fe3O4@Ag nanoparticles with both superparamagnetic and antibacterialproperties were prepared by reducing silver nitrate on the surface ofFe3O4 nanoparticles using the water-in-oil microemulsion method. Formation of well-dispersed nanoparticles withsizes of 60 ± 20 nm was confirmed by transmission electron microscopy and dynamic light scattering.X-ray diffraction patterns and UV–visible spectroscopy indicated that bothFe3O4 and silver are present in the same particle. The superparamagnetism ofFe3O4@Ag nanoparticles was confirmed with a vibrating sample magnetometer. Theirantibacterial activity was evaluated by means of minimum inhibitory concentrationvalue, flow cytometry, and antibacterial rate assays. The results showed thatFe3O4@Ag nanoparticles presented good antibacterial performance againstEscherichia coli (gram-negative bacteria), Staphylococcus epidermidis(gram-positive bacteria) and Bacillus subtilis (spore bacteria). Furthermore,Fe3O4@Ag nanoparticles can be easily removed from water by using amagnetic field to avoid contamination of surroundings. ReclaimedFe3O4@Ag nanoparticles can still have antibacterial capability and can be reused.

Pd on Amine-Terminated Ferrite Nanoparticles: A Complete Magnetically Recoverable Facile Catalyst for Hydrogenation Reactions

[structure: see text]. The present communication reports a facile route for Pd(0) immobilization on the surface of amine-terminated Fe3O4 and NiFe2O4 nanoparticles for a series of hydrogenation reactions. The catalysts are completely recoverable with the simple application of an external magnetic field, and the efficiency of the catalyst remains unaltered even after 10 repeated cycles for each of the reactions.

In situ chemical formation of iron phthalocyanine (FePc) monolayer on the surface of magnetite nanoparticles

The surface of magnetic nanoparticles (Fe3O4) has been modified chemically with iron phthalocyanine monolayer. The under-coordinated Fe sites on the surface of SCFD-derived Fe3O4 nanoparticles (NPs) and phthalic nitrile acted as template ions and components, respectively, for the formation of FePc. The presence of chemical linkages between in situ formed FePc monolayer and the surface of Fe3O4 NPs has been characterized by TEM, FTIR, UV-Vis, MS and TG-DSC etc. As compared to the neat Fe3O4 nanoparticles, the FePc monolayer-protected Fe3O4 nanoparticles (FePc@Fe3O4 NPs) that resulted could be dissolved in common organic solvents and showed much higher antioxidativity to oxygen.

Surface Functionalization of Fe3O4 Magnetic Nanoparticles via RAFT‐Mediated Graft Polymerization

AbstractSummary: Surface functionalization of Fe3O4 magnetic nanoparticles (MNP) via living radical graft polymerization with styrene and acrylic acid (AAc) in the reversible addition‐fragmentation chain transfer (RAFT)‐mediated process was reported. Peroxides and hydroperoxides generated on the surface of Fe3O4 nanoparticles via ozone pretreatment facilitated the thermally initiated graft polymerization in the RAFT‐mediated process. A comparison of the MNP before and after the RAFT‐mediated process was carried out using transmission electron microscopy (TEM) analysis, Fourier transform infrared (FTIR), and X‐ray photoelectron spectroscopy (XPS). Gel permeation chromatography (GPC) was used to determine the molecular weight of the free homopolymer in the reaction mixture. Well‐defined polymer chains were grown from the MNP surfaces to yield particles with a Fe3O4 core and a polymer outer layer. The resulting core–shell Fe3O4‐g‐polystyrene and Fe3O4‐g‐poly(acrylic acid) (PAAc) nanoparticles formed stable dispersions in the organic solvents for polystyrene (PS) and PAAc, respectively.Schematic illustration of thermally induced graft polymerization of styrene and AAc with the ozone‐treated Fe3O4 MNP.imageSchematic illustration of thermally induced graft polymerization of styrene and AAc with the ozone‐treated Fe3O4 MNP.

Polypyrrole‐Fe3O4 Magnetic Nanocomposite Prepared by Ultrasonic Irradiation

AbstractSummary: Ultrasonic irradiation was employed to prepare polypyrrole (PPY)/Fe3O4 magnetic nanocomposite by chemical oxidative polymerization of pyrrole in the presence of Fe3O4 nanoparticles. This approach can solve the problem in the dispersion and stabilization of inorganic nanoparticles in polymer. The structure and properties of PPY/Fe3O4 nanocomposite were characterized by TEM, XPS, FT‐IR, TG, and XRD. PPY deposits on the surface of Fe3O4 nanoparticles while Fe3O4 nanoparticles are dispersed at the nanoscale by ultrasonic irradiation, which leads to the formation of polypyrrole‐encapsulated Fe3O4 composite particles. The doping level of PPY in PPY/Fe3O4 nanocomposite is higher than that of neat PPY. The composites possess good electrical and magnetic properties. With the increase in the Fe3O4 content, the magnetization increases and the conductivity first increases and then decreases. When the Fe3O4 content is 40 wt.‐%, the conductivity reaches a maximum value of 11.26 S · cm−1, about nine times higher than that of neat PPY, and the saturation magnetization is 23 emu · g−1. Also, the introduction of Fe3O4 nanoparticles enhances the thermal stability of PPY/Fe3O4 composite.Conductivity of PPY/Fe3O4 composite at different Fe3O4 content.magnified imageConductivity of PPY/Fe3O4 composite at different Fe3O4 content.

Binding and Sulfonation of Poly(acrylic acid) on Iron Oxide Nanoparticles: a Novel, Magnetic, Strong Acid Cation Nano‐Adsorbent

AbstractSummary: A novel, magnetic, strong acid cation nano‐adsorbent has been developed by the covalent binding of poly(acrylic acid) on the surface of Fe3O4 nanoparticles followed by sulfonation using sulfanilic acid via carbodiimide activation. The nano‐absorbent can be easily recovered or manipulated with an external magnetic field and shows a good capacity for the rapid and efficient adsorption of multivalent metal cations from aqueous solutions.An illustration for the binding and sulfonation of PAA on Fe3O4 nanoparticles to produce a magnetic, strong acid cation nano‐adsorbent.magnified imageAn illustration for the binding and sulfonation of PAA on Fe3O4 nanoparticles to produce a magnetic, strong acid cation nano‐adsorbent.

Photoswitchable Magnetic Layer-by-Layer Films Consisting of Azobenzene Derivatives and Iron Oxide Nanoparticles

Abstract The photoswitchable magnetic thin films have been designed by alternate depositions of bipolar amphiphilic azobenzene and Fe3O4 nanoparticles by using the layer-by-layer adsorption technique. In these films, reversible photoisomerizations of the azobenzene chromophore affected the electrostatic interaction between the azobenzene chromophore and the surface of Fe3O4 nanoparticles. As a result, we have succeeded in controlling the magnetization of these films by photoillumination at room temperature.

Bifunctional Fe3O4/CdS Nanocomposites Synthesized by Surface-initiated Atom Transfer Radical Polymerization

Abstract This paper described the fabrication of a new Fe3O4/CdS nanocomposite. PCd(MA)2 was firstly polymerized by surface-initiated atom transfer radical polymerization (ATRP) on the surface of Fe3O4 nanoparticles, and then the formation of CdS nanoparticles took place in situ when S2− ions were released by thioacetamide upon heating. The nanocomposites were characterized by XPS, TEM, and UV–vis. The PL and magnetic properties were also studied.

Fe3O4 Nanoparticles coated with homopolymers of glycerol mono(meth)acrylate and their block copolymers

Highly stable aqueous magnetic fluids were prepared by coating Fe3O4 nanoparticles with poly(glycerol monoacrylate), poly(glycerol monomethacrylate), or diblock copolymers, poly(acrylic acid)-b-poly(glycerol monoacrylate), poly[(N,N-dimethylamino)ethyl methacrylate]-b-poly(glycerol monomethacrylate) or poly(ethylene glycol) monomethyl ether-b-poly(glycerol monoacrylate). These homopolymers and block copolymers were synthesized by atom transfer radical polymerization. These dispersions were stable in 10% NaCl, 10% CaCl2, or in wide pH ranges. In these magnetic fluids, poly(glycerol monoacrylate) or poly(glycerol monomethacrylate) were chemisorbed onto the Fe3O4 nanoparticle surface through their 1,2-diol groups by forming five-membered chelate rings with the Fe atoms, while the other blocks in the cases of the block copolymers as the stabilizers extended into the water matrix. Thus the nanoparticles prepared with these three block copolymers mentioned above respectively contain negatively charged, positively charged or uncharged and biocompatible surfaces under physiological conditions. This procedure provided a good choice for preparing stable magnetic fluids with tailored surfaces and/or tailored functional groups on the surfaces of the magnetic nanoparticles.