One-step solvothermal synthesis of Fe3O4@C core-shell nanoparticles with tunable sizes

We report the synthesis of Fe3O4@C core-shell nanoparticles (FCNPs) by using a facile one-step solvothermal method. The FCNPs consisted of Fe3O4 particles as the cores and amorphous uniform carbon shells. The content of Fe3O4 is up to 81.6 wt%. These core-shell nanoparticles are aggregated by primary nanocrystals with a size of 10-12 nm. The FCNPs possess a hollow interior, high magnetization, excellent absorption properties and abundant surface hydroxyl groups. A possible growth mechanism of the FCNPs is proposed. The role of glucose in regulating the grain size and morphology of the particles is discussed. The absorption properties of the FCNPs towards Cr(VI) in aqueous solution is investigated. We demonstrate that the FCNPs can effectively remove more than 90 wt% of Cr(VI) from aqueous solution.     

Facile synthesis of capped γ-Fe2O3 and Fe3O4 nanoparticles

Facile methods for the selective preparation of capped iron oxide nanoparticles (γ-Fe₂O₃, Fe₃O₄) are described. The magnetic oxides are obtained via oxidative transformation of an iron hydroxide gel using H₂O₂ or (NH₄)₂S₂O₈ solutions as oxidants. Capping with oleic or other aliphatic acids is established simultaneously in one step by adding a toluene solution of the capping agent and refluxing the resulting biphase system. The method is simple, soft and affords nanoparticles of γ-Fe₂O₃ or Fe₃O₄ of controlled size depending on the reaction conditions. The capped nanoparticles are readily soluble in organic or aqueous media according to the nature of the sheath surrounding the surface of the particles, providing stable and high concentration ferrofluids.     

Soft chemistry synthesis,structure and electrochemical characterization of iron phosphates Fe(H2PO4)3 and Fe(PO3)3

The iron phosphate, Fe(H₂PO₄)₃, was synthesized through a precipitation route by means of acidic media. As the compound is highly hygroscopic, the structure was solved ab initio by powder X-ray diffraction under nitrogen flow at room temperature and 200 °C. This phase is antiferromagnetic below 30 K. It converts into Fe(PO₃)₃ at 550 °C, after dehydration. Electrochemical characterizations, performed on the last compound, show irreversible decomposition into metallic iron.     

Green synthesis of uniform magnetite (Fe3O4) nanoparticles and micron cubes

Single-crystalline Fe3O4 microcubes were obtained through a green hydrothermal procedure using Fe3+, Fe2+ and H2O2 as starting materials. The structures and morphologies of the as-prepared samples were characterized in detail by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) respectively. Magnetite (Fe3O4) cubes averaging 3 microm in diameter were synthesized by H2O2 oxidation of Fe3+ and Fe2+ under neutral conditions. The contrastive experiments were designed to elucidate the effects of Fe3+, Fe2+ and H2O2 on the morphology of the final products. Irregular and ellipsoidal Fe2O3 structures were obtained by H2O2 oxidation of Fe3+ and Fe2+ respectively. Meanwhile, Fe3O4 nanotubes and nanoparticles were obtained when H2O2 was replaced by NH4HCO3 and urea respectively. The results show that H2O2, Fe3+ and Fe2+ in the reactive system play critical roles in obtaining micrometric cube-like Fe3O4. While, other nanometric Fe2O3 and Fe3O4 particles with tube-like and other morphologies could also be developed by controlling the reaction parameters.     

Preparation of Zn-doped β-tricalcium phosphate (β-Ca3(PO4)2) bioceramics

Pure β-tricalcium phosphate (β-TCP) and Zn-doped (600, 2900, 4100, 7000, 9300 and 10,100 ppm) β-TCP samples were prepared by using a wet chemical/coprecipitation synthesis technique, followed by calcination at 1000 °C in air. Precursor powders of the coprecipitation process were Ca-deficient nanoapatites (i.e., Ca/P molar ratio varying from 1.49 to 1.51) with needlelike but agglomerated particles of 30 nm thickness. In vitro culture tests performed by mouse osteoblast-like cells showed that the samples doped with 2900 to 4100 ppm Zn showed the highest cell viability (via Live/Dead counts), and with a further increase in the Zn-content towards 1 wt.% the number of dead cells in the well plates started to increase. Alkaline phosphatase (ALP) activity peaked for the β-TCP sample doped with 4100 pm Zn. The sample surface roughness, measured by non-contact profilometry, was also found to have an effect on the Live/Dead cell counts, and the highest cell viability encountered in this study corresponded to the surface with the least roughness.     

Synthesis of beta-cyclodextrin-modified water-dispersible Ag-TiO2 core-shell nanoparticles and their photocatalytic activity

The beta-cyclodextrin-modified Ag-TiO2 core-shell nanoparticles were prepared by sodium borohydrate reduction of AgNO3 and the subsequent hydrolysis of the tetraisopropyl orthotitanate in an aqueous medium. Inversely in the preparation of beta-cyclodextrin-modified TiO2-Ag core-shell nanoparticles, first hydrolysis and then following reduction were carried out. The synthesized spherical core-shell nanoparticles were highly water-dispersible and had an average diameter in the range of 9 to 12 nm. A significant shifting of surface plasmon band was observed for the synthesized Ag-TiO2 and TiO2-Ag core-shell nanoparticles. On a model reaction, namely, the photodegradation of phenol by the UV light irradiation, the photocatalytic property of TiO2 nanoparticles was enhanced, when the Ag nanoparticle was embedded in the core of TiO2 nanoparticles but TiO2 nanoparticles coated by Ag shell decreased the photocatalytic property of TiO2 nanoparticles. The mechanism is ascribed to the surface plasmon characteristics of Ag in the core of the TiO2 nanoparticles under the acceleration by host-guest inclusion characteristics.     

电纺纳米纤维自组装制备强磁性Fe_3O_4@SiO_2核壳结构纳米粒

通过电纺纤维自组装制备了具有强磁性敏感性的Fe3O4@SiO2复合纳米颗粒.电纺纤维的形貌通过扫描电镜(SEM)进行表征。纳米颗粒的尺寸分布,形貌和磁性分别通过FESEM、TEM和VSM进行确定。结果显示,该复合纳米颗粒具有近似球形的结构,并且具有多个磁性内核被包覆其中。纳米颗粒的尺寸大约为40 nm。Fe3O4@SiO2复合颗粒典型的比饱和磁化强度高达43.842 A·m2/kg,并且其在室温下具有超顺磁性。由于该磁性纳米颗粒具有强磁性敏感性,它们势必可以应用于更加广泛的领域。     

Synthesis and characterization of Fe/Nd2O3 core-shell nanoparticles by hydrogen plasma-metal reaction

Fe/Nd2O3 core-shell nanoparticles (CSNs) with a mean diameter of 35 nm were produced successfully by using hydrogen plasma-metal reaction (HPMR) method. This core-shell structure was confirmed by high resolution transmission electron microscopy (HRTEM), energy dispersion X-ray spectroscopy (EDS), X-ray photoelectron spectral (XPS), and induction-coupled plasma (ICP) spectroscopy. The magnetic properties were measured by vibrating sample magnetometer (VSM). It was found that the mole ratio of Nd to Fe on the nanoparticle surface is 1.2:1, about 7 times of that of the whole nanoparticle. The saturation magnetization Ms and remanence Mr of Fe/Nd2O3 nanoparticles decrease prominently from Fe nanoparticles, whereas the coercivity Hc drops only less than 5% of Fe nanoparticle. These CSNs have potential applications in magnetic and catalytic fields.     

Aerosol-assisted synthesis of thiol-functionalized mesoporous silica spheres with Fe3O4 nanoparticles

Thiol-functionalized mesoporous silica spheres having Fe3O4 nanoparticles are fabricated in one-pot by aerosol-assisted synthesis. A TEM image shows that Fe3O4 nanoparticles are successfully embedded within the mesoporous silica spheres. SEM images and SAXS profiles reveals that the encapsulating Fe3O4 nanoparticles do not affect the ordering of a mesoporous structure. The spherical morphologies are also well retained. The presence of cage-type mesopores with uniform size is confirmed by N2 adsorption-desorption isotherms and TEM observations. The spray-dried thiol-functionalized particles with Fe3O4 nanoparticles effectively adsorb mercury (II) ions due to their strong interaction to thiol groups embedded in the framework. The particles with the amount of Fe3O4 nanoparticles (3.5 wt%) show a saturated magnetization (over 1.0 emu/g). This magnetic property is useful for practical collection with magnet.     

Fe3O4纳米颗粒的溶剂热法制备及电磁特性研究

采用溶剂热方法分别在聚乙二醇、三乙二醇溶液中热分解乙酰丙酮铁,得到分散性能良好、尺寸均匀、形貌一致的Fe3O4纳米颗粒,颗粒尺寸为7～8nm。通过X射线衍射及透射电镜研究发现,两种溶液中制备样品均为面心立方结构,且在三乙二醇溶液中制备颗粒分散性更好。分别对两种样品进行磁测量,发现室温时均表现出超顺磁性,398kA/m时的磁化强度分别为50、40A·m2/kg。微波吸收测试显示,颗粒的分散性有利于改善样品的反射损耗。     

Fabricating mono-dispersed Fe3O4-SiO2 core-shell particles with help of triboelectrification

For years, it has been widely held that triboelectrification is not the sought-after technique to develop innovative materials with enhanced functionalities. In this study, we tried to break such a traditional concept and find its ever-expanding roles in material science. In our strategy, triboelectrification brought adequate charge to particles, so as to achieve their mono-dispersity in solutions. Following this strategy, the synthesis of mono-dispersed Fe₃O₄-SiO₂ core-shell particles involved two-stage triboelectrification treatment. In the first-stage treatment, positive triboelectric charges on Fe₃O₄ cores ensured their uniform SiO₂ coating and well-defined core-shell structure. In the second-stage treatment, positive triboelectric charges on Fe₃O₄-SiO₂ core-shell particles guaranteed their mono-dispersity for further biological use. The Zeta potential of these triboelectrically-treated Fe₃O₄-SiO₂ core-shell particles still maintained at ca. +55 mV after standing for two months, and their conglomeration was negligible owing to their limited increase in hydrodynamic size. Besides, their excellent linearity between relaxivities and iron concentration, and their virtually unchanged r₂/r₁ ratio within two months manifested that triboelectrification can be a promising technique in fabricating advanced materials.     

Ni doped Fe3O4 magnetic nanoparticles

In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure.     

Synthesis and electromagnetic, microwave absorbing properties of core-shell Fe3O4-poly(3, 4-ethylenedioxythiophene) microspheres

Highly regulated core-shell Fe(3)O(4)-poly(3, 4-ethylenedioxythiophene) (PEDOT) microspheres were successfully synthesized by a two-step method in the presence of polyvinyl alcohol (PVA) and p-toluenesulfonic acid (p-TSA). And their morphology, microstructure, electromagnetic and microwave absorbing properties were subsequently characterized. By simply adjusting the molar ratio of 3, 4-ethylenedioxythiophene (EDOT) to Fe(3)O(4) (represented by (EDOT)/(Fe(3)O(4))), the thickness of the polymer shell can be tuned from tens to hundreds of nanometers. Moreover, it was found that the composite exhibited excellent microwave absorbing property with a minimum reflection loss (RL) of about -30 dB at 9.5 GHz with a (EDOT)/(Fe(3)O(4)) ratio of 20.     

Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

The assembly of superparamagnetic Fe₃O₄ nanoparticles on submicroscopic SiO₂ spheres have been prepared by an in situ reaction using different molar ratios of Fe³⁺/Fe²⁺ (50–200%). It has been observed that morphology of the assembly and properties of these hybrid materials composed of SiO₂ as core and Fe₃O₄ nanoparticles as shell depend on the molar ratio of Fe³⁺/Fe²⁺.     

多孔HAp-(β-Ca3(PO4)2)-Si3N4生物复合材料的力学性能与微观结构

利用有机泡沫浸渍结合无压烧结的方法成功制备了大孔径、高孔隙率,不同氮化硅含量的HAp-(β-Ca3(PO4)2)-Si3N4生物复合材料.测定了复合材料的抗压强度、显微硬度和孔隙率等性能.发现复合材料具有一定的抗压强度,其孔隙率较高,均超过45%.随着复合材料中氮化硅含量的增加,复合材料的孔隙率呈现出上升的趋势,但其显微硬度和抗压强度则先升高后降低.利用SEM观察了复合材料的断口形貌,发现复合材料中孔径从几十微米到500μm左右,孔隙相互贯通,可满足工程支架材料的要求.