Constructing magnetic Fe3O4‐Au@CeO2 hybrid nanofibers for selective catalytic degradation of organic dyes

Au nanoparticles (Au NPs) play a vital role in heterogeneous catalytic reactions. However, pristine Au NPs usually suffer from poor selectivity and difficult recyclability. In this work, Fe₃O₄‐Au@CeO₂ hybrid nanofibers were prepared via a simple one‐pot redox reaction between HAuCl₄ and Ce (NO₃)₃ in the presence of Fe₃O₄ nanofibers. CeO₂ shell was uniformly coated on the surface of Fe₃O₄ nanofibers to form a unique core‐shell structure, while Au NPs were encapsulated inside the CeO₂ shell. The as‐prepared Fe₃O₄‐Au@CeO₂ hybrid nanofibers have been proved to be positively surface charged due to the formation of CeO₂ shell, enabling them to be good candidates for predominant selective catalytic activity towards the degradation of negatively charged organic dyes. In addition, the Fe₃O₄‐Au@CeO₂ hybrid nanofibers showed magnetic properties, offering them excellent recyclable usability. This work presents a facile and effective solution to prepare magnetic noble metal/metal oxide hybrid nanomaterials with unique chemical structure and surface characteristic for promising applications in heterogeneous catalysis.     

Enhancement of Fe3O4/Au Composite Nanoparticles Catalyst in Oxidative Degradation of Methyl Orange Based on Synergistic Effect

Enhancement of Fe₃O₄ /Au nanoparticles (Fe₃O₄ /Au NPs ) catalyst was observed in the oxidative degradation of methyl orange by employing H₂O₂ as oxidant. To evaluate the catalytic activity of Fe₃O₄ /Au nanoparticles, different degradation conditions were investigated such as the amounts of catalyst, H₂O₂ concentration and pH value. Based on our data, methyl orange was degraded completely in a short time. The enhanced catalytic activity and increased oxidation rate constant may be ascribed to synergistic catalyst‐activated decomposition of H₂O₂ to •OH radical, which was one of the strong oxidizing species. Besides, Fe₃O₄ /Au nanoparticles have exhibited satisfying recycle performance for potential industrial application.     

A Facile Approach to Fabricate Water‐soluble Au‐Fe3O4 Nanoparticle for Liver Cancer Cells Imaging

Au‐Fe₃O₄ nanoparticles were widely used as nanoplatforms for biologic applications through readily further functionalization. Dopamine (DA)‐coated superparamagnetic iron oxide (SPIO) nanoparticles (DA@Fe₃O₄) have been successfully synthesized using a one‐step process by modified coprecipitation method. Then 2–3 nm gold nanoparticles were easily conjugated to DA@Fe₃O₄ nanoparticles by the electrostatic force between gold nanoparticles and amino groups of dopamine to afford water‐soluble Au‐Fe₃O₄ hybrid nanoparticles. A detailed investigation by dynamic light scatting (DLS), transmission electron microscopy (TEM), fourier transform infrared (FT‐IR) and X‐ray diffraction (XRD) were performed in order to characterize the physicochemical properties of the hybrid nanoparticles. The hybrid nanoparticles were easily functionalized with a targeted small peptide A54 (AGKGTPSLETTP) and fluorescence probe fluorescein isothiocyanate (FITC) for liver cancer cell BEL‐7402 imaging. This simple approach to prepare hybrid nanoparticles provides a facile nanoplatform for muti‐functional derivations and may be extended to the immobilization of other metals or bimolecular on SPIO surface.     

General Preparation of Heme Protein Functional Fe3O4@Au‐Nps Magnetic Nanocomposite for Sensitive Detection of Hydrogen Peroxide

Stable magnetic nanocomposite of gold nanoparticles (Au‐NPs) decorating Fe₃O₄ core was successfully synthesized by the linker of Boc‐L‐cysteine. Transmission electron microscope (TEM), energy dispersive X‐ray spectroscopy (EDX) and cyclic voltammograms (CV) were performed to characterize the as‐prepared Fe₃O₄@Au‐Nps. The results indicated that Au‐Nps dispersed homogeneously around Fe₃O₄ with the ratio of Au to Fe₃O₄ nanoparticles as 5–10/1 and the apparent electrochemical area as 0.121 cm². After self‐assembly of hemoglobin (Hb) on Fe₃O₄@Au‐Nps by electrostatic interaction, a hydrogen peroxide biosensor was developed. The Fe₃O₄@Au‐Nps/Hb modified GCE exhibited fast direct electron transfer between heme center and electrode surface with the heterogeneous electron transfer rate constant (Ks ) of 3.35 s⁻¹. Importantly, it showed excellent electrocatalytic activity towards hydrogen peroxide reduction with low detection limit of 0.133 μM (S /D =3) and high sensitivity of 0.163 μA μM⁻¹, respectively. At the concentration evaluated, the interfering species of glucose, dopamine, uric acid and ascorbic acid did not affect the determination of hydrogen peroxide. These results demonstrated that the introduction of Au‐Nps on Fe₃O₄ not only stabilized the immobilized enzyme but also provided large surface area, fast electron transfer and excellent biocompatibility. This facile nanoassembly protocol can be extended to immobilize various enzymes, proteins and biomolecules to develop robust biosensors.     

Superparamagnetic POT/Fe3O4 nanoparticle composites with supported Au nanoparticles as recyclable high-performance nanocatalysts

A novel method has been developed to successfully synthesize Fe₃O₄ nanoparticles with tunable size and morphology supported on shells of poly(o-Toluidine)(POT) hollow microspheres. The as-prepared POT/Fe₃O₄ nanoparticle composites can be used as novel and magnetic-responsive catalyst supports to produce highly efficient and recyclable noble metal catalysts. The size of Fe₃O₄ nanoparticles supported on shells of POT hollow microspheres can be tuned from 4 to 12 nm by changing the concentration of Fe ions. The roles of the doping acid of POT and Zeta potentials of Fe₃O₄ nanoparticles and POT in the formation of the POT/Fe₃O₄ nanoparticle composites were discussed. Furthermore, gold nanoparticles that were supported on the as-synthesized POT/Fe₃O₄ nanoparticle composites have been achieved by utilizing the reactivity of POT towards Au ions. The size of gold nanoparticles can be tuned by altering the concentration of HAuCl₄. Finally, the catalytic activity of the obtained POT/Fe₃O₄/Au composites for 4-nitrophenol (4NP) reduction is investigated. The results demonstrate that such magnetic-responsive polymer-supported gold nanoparticles can be easily recovered and reused five times still remains high catalytic performance, which indicate their potential applications in the field of catalysis.     

Fe3O4磁性纳米粒子的超声包金及其表征

超声条件下, 在乙醇分散的3-氨丙基三乙氧基硅烷(APTES)功能化的磁性Fe₃O₄纳米粒子和四氯合金酸的混合溶液中滴加柠檬酸钠, 成功地制备了磁性Fe₃O₄/Au复合纳米粒子. 采用X射线粉末衍射仪(XRD)、紫外吸收可见光谱(UV-Vis)、带有电子能谱仪(EDS)的扫描电子显微镜(SEM)、透射电子显微镜(TEM)、光电子能谱(XPS)、超导量子干涉仪(SQUID)等方法, 对复合粒子的形态、结构、组成以及磁学性质进行了表征. 结果表明: 在此条件下制得的复合粒子粒径在30 nm左右, 室温下磁化强度可达63 emu/g.     

Synthesis of magnetic,reactive, and thermoresponsive Fe3O4 nanoparticles via surface‐initiated RAFT copolymerization of N‐isopropylacrylamide and acrolein

A reversible addition‐fragmentation chain transfer (RAFT) agent was directly anchored onto Fe₃O₄ nanoparticles in a simple procedure using a ligand exchange reaction of S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate with oleic acid initially present on the surface of pristine Fe₃O₄ nanoparticles. The RAFT agent‐functionalized Fe₃O₄ nanoparticles were then used for the surface‐initiated RAFT copolymerization of N‐isopropylacrylamide and acrolein to fabricate structurally well‐defined hybrid nanoparticles with reactive and thermoresponsive poly(N‐isopropylacrylamide‐co‐acrolein) shell and magnetic Fe₃O₄ core. Evidence of a well‐controlled surface‐initiated RAFT copolymerization was gained from a linear increase of number‐average molecular weight with overall monomer conversions and relatively narrow molecular weight distributions of the copolymers grown from the nanoparticles. The resulting novel magnetic, reactive, and thermoresponsive core‐shell nanoparticles exhibited temperature‐trigged magnetic separation behavior and high ability to immobilize model protein BSA. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 542–550, 2010     

Fabrication and characterization of double‐shelled CeO2‐La2O3/Au/Fe3O4 hollow architecture as a recyclable and highly thermal stability nanocatalyst

A novel magnetic binary‐metal‐oxide‐coated nanocataly composing of a hollow Fe₃O₄ core and CeO₂‐La₂O₃ shells with Au nanoparticles encapsulated has been created in this work. The structural features of catalysts were characterized by several techniques, including SEM, TEM, UV‐vis, FTIR, XRD, XPS and TGA analyses. After the coating of CeO₂‐La₂O₃ layer, CeO₂‐La₂O₃/Au/C/Fe₃O₄ microspheres showed a superior thermal stability and catalytic reactivity compared with a pure CeO₂ or La₂O₃ layer. Accompanied by the burning of carbon layer, the specific surface could be increased by the formation of double‐shelled structure. Besides, the desired samples could be separated by magnet, implying the superior recycle performance. Using the reduction of 4‐nitrophenol by NaBH₄ as a model reaction, the microspheres exhibited highly reusability, superior catalytic activity, thermal stability, which are attributed to the unique double‐shelled structure of the support, uniform distribution of Au nanoparticles, the highly thermal stability of CeO₂‐La₂O₃ layer and mixed oxide synergistic effect. As a consequence, the unique nanocatalyst will open a promising way in the fabrication of the double‐shelled hollow binary‐metal‐oxide materials for future research and has great potential in other applications.     

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.     

Fe3O4/PEI/Au@CdSe/CdS多功能复合材料的制备与表征

以共沉淀法制备出Fe₃O₄纳米粒子,通过聚乙烯亚胺(PEI)修饰Fe₃O₄纳米粒子,再原位复合上Au纳米粒子,制得Fe₃O₄/PEI/Au纳米颗粒微球。再将Fe₃O₄/PEI/Au纳米颗粒与巯基乙酸修饰的量子点CdSe/CdS连接,成功制备了Fe₃O₄/PEI/Au@CdSe/CdS多功能复合微球。经过傅里叶变换红外光谱仪(FTIR)、荧光分光光度计、荧光显微镜、X射线衍射(XRD)、透射电子显微镜(TEM)及振动样品磁强计(VSM)的表征。结果表明:多功能复合微球的粒径在40 nm左右,具有超顺磁性,剩磁,矫顽力近似等于零,饱和磁化强度为28.83 A·m²·kg^-1,同时兼有优越的荧光性能和金纳米粒子的特性。     

Fe3O4/PEI/Au@CdSe/CdS多功能复合材料的制备与表征

以共沉淀法制备出Fe₃O₄纳米粒子,通过聚乙烯亚胺(PEI)修饰Fe₃O₄纳米粒子,再原位复合上Au纳米粒子,制得Fe₃O₄/PEI/Au纳米颗粒微球。再将Fe₃O₄/PEI/Au纳米颗粒与巯基乙酸修饰的量子点CdSe/CdS连接,成功制备了Fe₃O₄/PEI/Au@CdSe/CdS多功能复合微球。经过傅里叶变换红外光谱仪(FTIR)、荧光分光光度计、荧光显微镜、X射线衍射(XRD)、透射电子显微镜(TEM)及振动样品磁强计(VSM)的表征。结果表明:多功能复合微球的粒径在40nm左右,具有超顺磁性,剩磁,矫顽力近似等于零,饱和磁化强度为28.83A·m₂·kg^-1,同时兼有优越的荧光性能和金纳米粒子的特性。     

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.     

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).     

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.     

A General Route to Construct Diverse Multifunctional Fe3O4/Metal Hybrid Nanostructures

Multifunctional nanostructures : By using 3‐aminopropyltrimethoxysilane as a linker, Au nanoparticles (NPs), Au shells, flowerlike Au/Pt hybrid NPs, and Ag or Au/Ag core/shell NPs could be supported on the surface of superparamagnetic Fe₃O₄ spheres to construct hybrid nanostructures that display near‐IR absorption, high catalytic activity towards an electron‐transfer reaction, or excellent surface‐enhanced Raman scattering activity. The picture shows SEM images of Fe₃O₄ spheres coated with Au shells (top) and with Au/Pt hybrid NPs (bottom).

     

Double‐Layered Plasmonic–Magnetic Vesicles by Self‐Assembly of Janus Amphiphilic Gold–Iron(II,III) Oxide Nanoparticles

Janus nanoparticles (JNPs) offer unique features, including the precisely controlled distribution of compositions, surface charges, dipole moments, modular and combined functionalities, which enable excellent applications that are unavailable to their symmetrical counterparts. Assemblies of NPs exhibit coupled optical, electronic and magnetic properties that are different from single NPs. Herein, we report a new class of double‐layered plasmonic–magnetic vesicle assembled from Janus amphiphilic Au‐Fe₃O₄ NPs grafted with polymer brushes of different hydrophilicity on Au and Fe₃O₄ surfaces separately. Like liposomes, the vesicle shell is composed of two layers of Au‐Fe₃O₄ NPs in opposite direction, and the orientation of Au or Fe₃O₄ in the shell can be well controlled by exploiting the amphiphilic property of the two types of polymers.     

Preparation of sulfate- and carboxyl-functionalized magnetite/polystyrene spheres for further deposition of gold nanoparticles

A synthetic method developed for preparation of sulfate- and carboxyl-functionalized magnetite/polystyrene (Fe₃O₄/PS) spheres that can be further decorated with gold (Au) nanoparticles is reported. By using emulsifier-free emulsion polymerization based on potassium persulfate (KPS)/methyl acrylic acid (MAA)/water system in the presence of Fe₃O₄/PS spheres used as the seeds, PMAA-coated magnetic Fe₃O₄-PS spheres were readily obtained. The sulfate group is inherent in KPS for initiating the polymerization of PMAA, and eventually it acts as the reducing agent for the deposition of Au nanoparticles. The carboxyl group, on the other hand, could seemingly contribute to immobilize Au nanoparticles precipitated. The morphologies, magnetic properties, and characteristics of oleate-stabilized Fe₃O₄ nanoparticles, Fe₃O₄/PS spheres, PMAA-coated Fe₃O₄/PS spheres, and Au-decorated resultant spheres were respectively studied using transmission electron microscopy, X-ray diffraction, Fourier transform infrared, and superconducting quantum interference device magnetometer.     

h‐BN Nanosheets as 2D Substrates to Load 0D Fe3O4 Nanoparticles: A Hybrid Anode Material for Lithium‐Ion Batteries

h‐BN, as an isoelectronic analogue of graphene, has improved thermal mechanical properties. Moreover, the liquid‐phase production of h‐BN is greener since harmful oxidants/reductants are unnecessary. Here we report a novel hybrid architecture by employing h‐BN nanosheets as 2D substrates to load 0D Fe₃O₄ nanoparticles, followed by phenol/formol carbonization to form a carbon coating. The resulting carbon‐encapsulated h‐BN@Fe₃O₄ hybrid architecture exhibits synergistic interactions: 1) The h‐BN nanosheets act as flexible 2D substrates to accommodate the volume change of the Fe₃O₄ nanoparticles; 2) The Fe₃O₄ nanoparticles serve as active materials to contribute to a high specific capacity; and 3) The carbon coating not only protects the hybrid architecture from deformation but also keeps the whole electrode highly conductive. The synergistic interactions translate into significantly enhanced electrochemical performances, laying a basis for the development of superior hybrid anode materials.     

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.     

Synthesis and characterization of chitosan–polyvinylpyrrolidone–bovine serum albumin-coated magnetic iron oxide nanoparticles as potential carrier for delivery of tamoxifen

The proposed study examined the preparation of chitosan (CS)–polyvinylpyrrolidone (PVP)–bovine serum albumin (BSA)-coated magnetic iron oxide (Fe₃O₄) nanoparticles (Fe₃O₄–CS–PVP–BSA) to use as potential drug delivery carriers for delivery of tamoxifen drug (TAM) . The anticancer drug selected in this study was tamoxifen which can be used for the human breast cancer treatment. These prepared nanoparticles were characterized by FTIR, XRD, SEM, AFM, TEM, CD and VSM techniques. The swelling studies have been measured at different (10, 20, 30, 40, 50%) drug loading. The mean particle size of the tamoxifen-loaded nanoparticles system (Fe₃O₄–CS–TAM, Fe₃O₄–CS–TAM–PVP and Fe₃O₄–CS–TAM–PVP–BSA) as measured by Malvern Zetasizer ranged between 350 ± 2.3 and 601 ± 1.7 nm. As well as these drug-loaded nanoparticles were positively charged. The zeta potential was in the range of 28.9 ± 3.5 and 50.8 ± 3.9 mV. The encapsulation efficiency was between 63.60 ± 2.11 and 96.45 ± 2.12%. Furthermore, in vitro release and drug loading efficiency from the nanoparticles were investigated. The cytotoxicity of prepared nanoparticles was verified by MTT assay. In vitro release studies were executed in 4.0 and 7.4 pH media to simulate the intestinal and gastric conditions and different temperature (37 and 42 °C). Hence, the prepared tamoxifen-loaded nanoparticles system (Fe₃O₄–CS–TAM, Fe₃O₄–CS–TAM–PVP and Fe₃O₄–CS–TAM–PVP–BSA) could be a promising candidate in cancer therapy.