Constructing magnetic polyaniline/metal hybrid nanostructures using polyaniline/Fe3O4 composite hollow spheres as supports

Polyaniline (PANI)/Fe₃O₄ composite hollow spheres have been successfully synthesized in one step using sulfonated polystyrene (PS) spheres as templates. The magnetic PANI hollow spheres were used as supports for noble metal nanoparticles (NPs) such as Au and Pd. The morphology, composition and magnetic properties of the resulting products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma (ICP) atomic spectra and vibrating sample magnetometer. The catalytic activity of magnetic PANI/Au composite shells on the oxidation of dopamine was investigated by cyclic voltammetry. The obtained results provide our product with a practical application for the detection of dopamine. On the other hand, the catalytic activity of magnetic PANI/Pd composite shells on the reduction of 4-nitroaniline was investigated by spectroscopic methods and compared with Pd/C catalyst which was already widely used in industrial production.     

Polystyrene/Fe3O4 composite latex via miniemulsion polymerization‐nucleation mechanism and morphology

In this research, oil‐based Fe₃O₄ nanoparticles were prepared by means of coprecipitation method followed by a surface modification using lauric acid. Oil‐based Fe₃O₄ could disperse in styrene, and polystyrene/Fe₃O₄ (PS/Fe₃O₄) composite particles were prepared via miniemulsion polymerization in the presence of potassium peroxide (KPS) as an initiator, sodium dodecyl sulphate as a surfactant, hexadecane or sorbitan monolaurate(Span 20) as a costabilizer. The effects of Fe₃O₄ content, homogenization energy, amount of initiator, amount of surfactant and costabilizer on the conversion, size distributions of droplets and latex particles, nucleation mechanism and morphology of composite latex particles were investigated. The results showed that different nucleation mechanisms dominated during the course of reaction when polymerization conditions changed. The most important two key factors to influence the nucleation mechanism were homogenization energy and initiator. High homogenization energy provided critically stabilized size of droplets. Otherwise, secondary nucleation, including micellar and/or homogeneous nucleation, would take place rather than droplet nucleation when a water‐soluble initiator, KPS, was used. It resulted in two populations of latex particles, pure PS particles in smaller size and PS/Fe₃O₄ composite particles in larger size. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1014–1024, 2008     

Synthesis and morphology of an iron oxide/polystyrene/poly(isopropylacrylamide‐co‐methacrylic acid) thermosensitive magnetic composite latex with potassium persulfate as the initiator

In this work, an iron oxide (Fe₃O₄)/polystyrene (PS)/poly(N‐isopropylacryl amide‐co‐methacrylic acid) [P(NIPAAM–MAA)] thermosensitive magnetic composite latex was synthesized by the method of two‐stage emulsion polymerization. The Fe₃O₄ particles were prepared by a traditional coprecipitation method and then surface‐treated with either a PAA oligomer or lauric acid to form a stable ferrofluid. The first stage for the synthesis of the thermosensitive magnetic composite latex was to synthesize PS in the presence of a ferrofluid by emulsion polymerization to form Fe₃O₄/PS composite latex particles. Following the first stage of reaction, the second stage of polymerization was carried out with N‐isopropylacryl amide and methacrylic acid as monomers and with Fe₃O₄/PS latex as seeds. The Fe₃O₄/PS/[P(NIPAAM–MAA)] thermosensitive magnetic particles were thus obtained. The effects of the ferrofluids on the reaction kinetics, morphology, and particle size of the latex were discussed. A reaction mechanism was proposed in accordance with the morphology observation of the latex particles. The thermosensitive property of the thermosensitive magnetic composite latex was also studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3062–3072, 2007     

Synthesis and morphology of Fe3O4/polystyrene/poly(isopropylacrylamide‐co‐methyl acrylate acid) magnetic composite latex – 2,2′‐azobis (2‐methylpropionamidine) dihydrochloride as initiator

In this work, Fe₃O₄/polystyrene/poly(N‐isopropylacryl amide‐co‐methylacrylate acid) (Fe₃O₄/PS/P(NIPAAM‐co‐MAA)) magnetic composite latex was synthesized by the method of two stage emulsion polymerization. In this reaction system, 2,2′‐azobis(2‐methyl propionamidine) dihydrochloride (AIBA) was used as initiator to initiate the first stage reaction and second stage reaction. The Fe₃O₄ particles were prepared by a traditional coprecipitation method. Fe₃O₄ particles were surface treated by either PAA oligomer or lauric acid to form the stable ferrofluid. The first stage for the synthesis of magnetic composite latex was to synthesize PS in the presence of ferrofluid by soapless emulsion polymerization to form the Fe₃O₄/PS composite latex particles. Following the first stage of reaction, the second stage of polymerization was carried out by the method of soapless emulsion polymerization with NIPAAM and MAA as monomers and Fe₃O₄/PS latex as seeds. The magnetic composite particles, Fe₃O₄/PS/P(NIPAAM‐co‐MAA), were thus obtained. The mechanism of the first stage reaction and second stage reaction were investigated. Moreover, the effects of PAA and lauric acid on the reaction kinetics, morphology, and particle size distribution were studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3912–3921, 2007     

A facile two-step modifying process for preparation of poly(SStNa)-grafted Fe3O4/SiO2 particles

This article reports the synthesis of the poly(sodium 4-styrenesulfonate)-grafted Fe₃O₄/SiO₂ particles via two steps. The first step involved magnetite nanoparticles (Fe₃O₄) homogeneously incorporated into silica spheres using the modified Stöber method. Second, the modified silica-coated Fe₃O₄ nanoparticles were covered with the outer shell of anionic polyelectrolyte by surface-initiated atom transfer radical polymerization. The resulted composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive microscopy (EDS), Fourier transform-infrared (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and vibration sample magnetometer (VSM). The XRD results indicated that the surface modified Fe₃O₄ nanoparticles did not lead to phase change compared with the pure Fe₃O₄. TEM studies revealed nanoparticles remained monodisperse. The detection of sulfur and sodium signals was a convincing evidence that sodium 4-styrenesulfonate was grafted onto the surface of the magnetic silica in XPS analysis. Finally, super-paramagnetic properties of the composite particles, and the ease of modifying the surfaces may make the composites of important use in mild separation, enzyme immobilization, etc.     

Preparation of composite particles with magnetic silica core and fluorescent polymer shell

Dual functions of magnetic and fluorescent properties were created in composite particles that incorporated magnetite (Fe₃O₄) nanoparticles in particle cores of silica and fluorescent pyrene in particle shells of polystyrene. The Fe₃O₄ nanoparticles were prepared with a conventional homogeneous precipitation method and surface modified with a coupling agent of carboxyethylsilanetriol. The silica particles incorporating Fe₃O₄ nanoparticles were synthesized with a modified Stöber method in which the Fe₃O₄ nanoparticles were added to a system of tetraethylorthosilicate (TEOS)/ammonia/water/ethanol. Then, the magnetite/silica composite particles were coated with the pyrene/polystyrene shell in a soap-free emulsion polymerization, which was conducted in the presence of pyrene in a mixed solvent of water/ethanol. The composite particles prepared in the mixed solvent had both magnetic and fluorescent properties. The fluorescent spectrum of the particles with Fe₃O₄ was very similar to that without Fe₃O₄, indicating that the magnetic component within the core particles scarcely interfered with the fluorescent emission from the polymer shell.     

磁性Fe_2O_3/Au/Ag复合纳米粒子的制备及其富集作用研究

利用种子生长法制备了磁性Fe2O3/Au/Ag复合纳米粒子,采用UV-vis和SEM对其光学性质以及表面结构的变化进行了表征.通过调节硝酸银的用量,制备了一系列具有不同Ag壳层厚度和表面结构的双金属外壳纳米粒子.以苯硫酚(TP)为探针分子,研究了不同Ag壳厚度的磁性纳米粒子的表面增强拉曼散射(SERS)活性.结果表明其SERS活性与表面结构的改变有关,在同时出现Ag和Au光学性质的Fe2O3/Au/Ag复合纳米粒子表面可观察到最强的SERS效应,这与表面的针孔效应以及Ag和Au之间的耦合增强作用有关.考察了Fe2O3/Au/Ag复合纳米粒子的磁富集作用,并利用SERS原位监测磁富集溶液中低浓度TP的能力,研究结果表明通过磁富集可提高SERS检测限,并且Fe2O3/Au/Ag的磁富集能力较Fe2O3/Au弱,但前者SERS信号较强.     

Thermosensitive and control release behavior of poly(N-isopropylacrylamide-co-acrylic acid)/nano-Fe3O4 magnetic composite latex particle that is synthesized by a novel method

In this study, a novel method was used to synthesize the poly(N-isopropylacrylamide-co-acrylic acid)/Fe₃O₄ (poly(NIPAAm-AA)/Fe₃O₄) magnetic composite latex. The crosslinked poly(NIPAAm-AA) polymer latex particles were first synthesized by the method of soapless emulsion polymerization, then Fe²⁺ and Fe³⁺ ions were introduced to bond with the -COOH groups of AA segments in poly(NIPAAm-AA) polymer latex particles. Further by a reaction with NH₄OH, Fe₃O₄ nanoparticles were generated in situ. The concentrations of acrylic acid (AA), crosslinking agent (N,N′-methylene bisacrylamide (MBA)), and Fe₃O₄ nanoparticles were important factors to influence the morphology and lower critical solution temperature (LCST) of poly(NIPAAm-AA)/Fe₃O₄ magnetic composite latex particles. The poly(NIPAAm-AA)/Fe₃O₄ latex particles were used as a thermosensitive drug carrier to load caffeine. The control release of caffeine was studies. Morphology-based schematic models were proposed to explain the control release behavior of the composite particles with different compositions. Moreover, the protein (albumin, acetylated from bovine serum (BSA)) was bound on the surface of poly(NIPAAm-AA)/Fe₃O₄ composite latex particles. The effects of AA, crosslinking agent and Fe₃O₄ contents on the amount of BSA binding were investigated at different temperatures and pH values. The composition-morphology-BSA conjugation relationship was established.     

Surface-enhanced Raman scattering from magneto-metal nanoparticle assemblies

Binary nanoparticles composed of a superparamagnetic Fe₃O₄ core and an Au nanoshell (Fe₃O₄@Au) were prepared via a simple co-precipitation method followed by seed-mediated growth process. The nanoparticles exhibited functions of both fast magnetic response and local surface plasmon resonance. The Fe₃O₄@Au nanoparticles were used as probes for surface-enhanced Raman scattering (SERS) using p-thiocresol (p-TC) as reporter molecule. With the ability of analyte capture and concentration magnetically, the Fe₃O₄@Au nanoparticles showed significant SERS properties with excellent reproducibility. Under non-optimized conditions, detection limit as low as 4.55 pM of analyte can be reached using Fe₃O₄@Au nanoparticle assemblies, which excel remarkably the cases with traditional Au nanoprobes.     

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

Summary: 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.     

Alginate-Coated Fe3O4 Hollow Microspheres for Drug Delivery

Novel hollow Fe₃O₄ nanoparticles for drug delivery were synthesized via a one-step templatefree approach. These nanoparticles were obtained by modifing the Fe₃O₄ nanoparticles with 3-aminopropyltrimethoxy silane, and then grafting alginate onto the surface of amine magnetic. The hollow structure of Fe₃O₄ spheres was characterized by TEM, XRD, and XPS. The M-H hysteresis loop indicated that the magnetic spheres exhibit superparamagnetic characteristics at room temperature. Daunorubicin acting as a model drug was loaded into the carrier, and the maximum percent of envelop and load were 28.4% and 14.2% respectively. The drug controlled releasing behaviors of the carriers were compared in different pH media.     

Peapod‐Type Nanocomposites through the In Situ Growth of Gold Nanoparticles within Preformed Hexaniobate Nanoscrolls

A facile in situ method to grow Au nanoparticles (NPs) in hexaniobate nanoscrolls is applied to the formation of plasmonic Au@hexaniobate and bifunctional plasmonic‐magnetic Au‐Fe₃O₄@hexaniobate nanopeapods (NPPs). Utilizing a solvothermal treatment, rigid multiwalled hexaniobate nanoscrolls and partially filled Fe₃O₄@hexaniobate NPPs were first fabricated. These nanostructures were then used as templates for the controlled in situ growth of Au NPs. The resulting peapod structures exhibited high filling fractions and long‐range uniformity. Optical measurements showed a progressive red shift in plasmonic behavior between Au NPs, Au NPPs, and Au‐Fe₃O₄ NPPs; magnetic studies found that the addition of gold in the Fe₃O₄@hexaniobate NPPs reduced interparticle coupling effects. The development of this approach allows for the routine bulk preparation of noble‐metal‐containing bifunctional nanopeapod materials.     

Preparation of composite magnetic microspheres by reactive blending

A novel method for preparation of polymer-based magnetic microspheres was proposed by utilizing melt reactive blending,which was based on selective location of Fe_3O_4 nanoparticles in PA6 domains of polystyrene(PS)/polyamide 6 (PA6) immiscible blends.The morphology of PA6/Fe_3O_4 composite magnetic microspheres was studied by scanning electronic microscopy(SEM).The composite magnetic microspheres were spherical with a diameter range of 0.5-8μm;the diameter was sharply decreased with a very narrow distri...     

Facile Hydrogen‐Bond‐Assisted Polymerization and Immobilization Method to Synthesize Hierarchical Fe3O4@Poly(4‐vinylpyridine‐co‐divinylbenzene)@Au Nanostructures and Their Catalytic Applications

Hierarchical Fe₃O₄@poly(4‐vinylpyridine‐co‐divinylbenzene)@Au (Fe₃O₄@P(4‐VP–DVB)@Au) nanostructures were fabricated successfully by means of a facile two‐step synthesis process. In this study, well‐defined core–shell Fe₃O₄@P(4‐VP–DVB) microspheres were first prepared with a simple polymerization method, in which 4‐VP was easily polymerized on the surface of Fe₃O₄ nanoparticles by means of strong hydrogen‐bond interactions between ? COOH groups on poly(acrylic acid)‐modified Fe₃O₄ nanoparticles and a 4‐VP monomer. HAuCl₄ was adsorbed on the chains of a P(4‐VP) shell and then reduced to Au nanoparticles by NaBH₄, which were embedded into the P(4‐VP) shell of the composite microspheres to finally form the Fe₃O₄@P(4‐VP–DVB)@Au nanostructures. The obtained Fe₃O₄@P(4‐VP–DVB)@Au catalysts with different Au loadings were applied in the reduction of 4‐nitrophenol (4‐NP) and exhibited excellent catalytic activity (up to 3025 h^?1 of turnover frequency), facile magnetic separation (up to 31.9 emu g^?1 of specific saturation magnetization), and good durability (over 98 % of conversion of 4‐NP after ten runs of recyclable catalysis and almost negligible leaching of Au).     

Iron oxide modified with pyridyl‐triazole ligand for stabilization of gold nanoparticles: An efficient heterogeneous catalyst for A3 coupling reaction in water

Fe₃O₄ nanoparticles were modified with pyridyl‐triazole ligand and the new magnetic solid was applied for the stabilization of very small and uniform gold nanoparticles. The resulting magnetic material, Fe₃O₄@PT@Au, was characterized using various methods. These gold nanoparticles on a magnetic support were applied as an efficient heterogeneous catalyst for the three‐component reaction of amines, aldehydes and alkynes (A³ coupling) in neat water with 0.01 mol% Au loading. Using magnetic separation, this catalyst could be recycled for seven consecutive runs with very small decrease in activity. Characterization of the reused catalyst did not show appreciable structural modification.     

Monodispers and Multifunctional Magnetic Composite Core Shell Microspheres for Demulsification Applications

Iron oxide@Poly(Glycidylmethacrylate‐methyl methacrylate‐divinyl benzene) magnetic composite core shell microspheres Fe₃O₄@P(GMA‐MMA‐DVB) with epoxy group on the surface was designed and synthesized by solvothermal process followed by distillation polymerization. The surface epoxy group was modified with amino group of ethylene diamine (EDA) to prepare Fe₃O₄@P(GMA‐MMA‐DVB)/NH₂ microspheres, and then effects of modification on the structure, interfacial behavior and hence demulsification of the amino modified epoxy coating were examined. The prepared magnetic microspheres were characterized using a laser particle size analyzer, transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and thermogravimetric analysis. Fourier transform infrared spectrometer analysis indicates the presence of epoxy group, amino group and Fe₃O₄ in the final Fe₃O₄@P(GMA‐MMA‐DVB) and Fe₃O₄@P(GMA‐MMA‐DVB)/NH₂ magnetic core shell microspheres. Our experimental results show that Fe₃O₄@P(GMA‐MMA‐DVB)/NH₂ magnetic core shell microspheres exhibit good interfacial and demulsification properties and able to remove emulsified water from stable emulsion. The resulting microspheres showed excellent magnetic properties and further these can be recycled and reused by magnetic separation.     

Selected-Control Synthesis of Monodisperse Fe3O4@C Core–Shell Spheres,Chains, and Rings as High-Performance Anode Materials for Lithium-Ion Batteries

A method is reported for the first time for the selected-control, large-scale synthesis of monodispersed Fe₃O₄@C core–shell spheres, chains, and rings with tunable magnetic properties based on structural evolution from eccentric Fe₂O₃@poly(acrylic acid) core–shell nanoparticles. The Fe₃O₄@C core–shell spheres, chains, and rings were investigated as anode materials for lithium-ion batteries. Furthermore, a possible formation mechanism of Fe₃O₄@C core–shell chains and rings has also been proposed.     

Gold‐loading magnetic core–shell organic/inorganic nanocomposites: facile preparation and multiple properties

Magnetic composite nanospheres (MCS) were first prepared via mini‐emulsion polymerization. Subsequently, the hybrid core–shell nanospheres were used as carriers to support gold nanoparticles. The as‐prepared gold‐loading magnetic composite nanospheres (Au‐MCS) had a hydrophobic core embed with γ‐Fe₃O₄ and a hydrophilic shell loaded by gold nanoparticles. Both the content of γ‐Fe₃O₄ and the size of gold nanoparticles could be controlled in our experiments, which resulted in fabricating various materials. On one hand, the Au‐MCS could be used as a T₂ contrast agent with a relaxivity coefficient of 362 mg^?1 ml S^?1 for magnetic resonance imaging. On the other hand, the Au‐MCS exhibited tunable optical‐absorption property over a wavelength range from 530 nm to 800 nm, which attributed to a secondary growth of gold nanoparticles. In addition, dynamic light scattering results of particle sizing and Zeta potential measurements revealed that Au‐MCS had a good stability in an aqueous solution, which would be helpful for further applications. Finally, it showed that the Au‐MCS were efficient catalysts for reductions of hydrophobic nitrobenzene and hydrophilic 4‐nitrophenol that could be reused by a magnetic separation process. Copyright © 2014 John Wiley & Sons, Ltd.     

Magnetic nanoparticle supported catalytic Cu(II)–poly(amindoamine) complexes for aerobic oxidative polymerization to form poly(2,6-dimethyl-1,4-phenylene oxide) in water

Poly(amindoamine) (PAMAM) was grafted onto magnetic Fe₃O₄ nanoparticles to produce PAMAM grafted Fe₃O₄ (shortened as Mag-PAMAM). Mag-PAMAM coordinated with Cu(II) to form the supported Cu(II)–PAMAM complex (shortened as Cu(II)/Mag-PAMAM). The stoichiometric ratio between amine groups in Mag-PAMAM and Cu(II) was found to be 4. The Cu(II)/Mag-PAMAM complexes were employed to catalyze the oxidative polymerization of 2,6-dimethylphenol (DMP) in water. The Cu(II)/Mag-PAMAM complexes demonstrated the excellent selectivity of C–O/C–C coupling and reactivity to form poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). After polymerization, the Cu(II)/Mag-PAMAM complexes were recovered by an external magnetic field and used repeatedly in the next run with additional Mag-PAMAM and copper ions. After three runs of oxidative polymerization of DMP, the recovery ratio of the catalyst was about 95% and the yield of PPO maintained a relatively high value.     

Bovine serum albumin stabilized iron oxide and gold bimetallic heterodimers: Synthesis,characterization and Stereological study

In this time researchers make a great efforts to develop new hybrid nanoparticles for medical and pharmaceutical applications. Fe₃O₄‐Au hybrid heterodimers have been prepared with superior properties for various claims. Unfortunately, Fe₃O₄‐Au heterodimers are not stable in the physiological medium. In this study, we employed the albumin macromolecules as a stabilizer of Fe₃O₄‐Au hybrid nanoparticles (noted as Fe₃O₄‐Au‐BSA hybrid nanoparticles). After characterization of synthesized nanoparticles by FTIR, UV–Vis, TEM, DLS, DSC, VSM and XRD techniques, the in vitro and in vivo biocompatibility of these nanoparticles were also evaluated. We encountered with an amazing result which confirmed nanoparticles could be stabilized by linking the BSA on the surface of Fe₃O₄‐Au heterodimers. Also, intravenous injection of Fe₃O₄‐Au‐BSA hybrid nanoparticles up to 400 mg/kg to Balb C mice show that these nanoparticles were non‐toxic. The biocompatibility and stereological study had been performed for more than 30 days after nanoparticles administration, using hystomorphometric analysis. Remarkably, to the best of our knowledge, it was the first time the biocompatibility and biodegradability of Fe₃O₄‐Au were studied and evaluated by stereological technique. Further promotion and biomedical usage of this type of hybrid nanoparticles are underway in our laboratory.