Non-aqueous synthesis of water-dispersible Fe3O4-Ca3(PO4)2 core-shell nanoparticles

The Fe(3)O(4)-Ca(3)(PO(4))(2) core-shell nanoparticles were prepared by one-pot non-aqueous nanoemulsion with the assistance of a biocompatible triblock copolymer, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO), integrating the magnetic properties of Fe(3)O(4) and the bioactive functions of Ca(3)(PO(4))(2) into single entities. The Fe(3)O(4) nanoparticles were pre-formed first by thermal reduction of Fe(acac)(3) and then the Ca(3)(PO(4))(2) layer was coated by simultaneous deposition of Ca(2+) and PO(4)(3-). The characterization shows that the combination of the two materials into a core-shell nanostructure retains the magnetic properties and the Ca(3)(PO(4))(2) shell forms an hcp phase (a = 7.490 ?, c = 9.534 ?) on the Fe(3)O(4) surface. The magnetic hysteresis curves of the nanoparticles were further elucidated by the Langevin equation, giving an estimation of the effective magnetic dimension of the nanoparticles and reflecting the enhanced susceptibility response as a result of the surface covering. Fourier transform infrared (FTIR) analysis provides the characteristic vibrations of Ca(3)(PO(4))(2) and the presence of the polymer surfactant on the nanoparticle surface. Moreover, the nanoparticles could be directly transferred to water and the aqueous dispersion-collection process of the nanoparticles was demonstrated for application readiness of such core-shell nanostructures in an aqueous medium. Thus, the construction of Fe(3)O(4) and Ca(3)(PO(4))(2) in the core-shell nanostructure has conspicuously led to enhanced performance and multi-functionalities, offering various possible applications of the nanoparticles.     

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.     

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.     

Facile synthesis of pure BiFeO3 and Bi2Fe4O9 nanostructures with enhanced photocatalytic activity

Journal of Materials Science: Materials in Electronics - In the present work, pure BiFeO3 and pure Bi2Fe4O9 single phases were successfully synthesized by tailoring hydrothermal synthesis route....     

Enhanced photocatalytic activity in Al-substituted Bi2Fe4O9 submicrocrystals

Bi₂(Fe_1−x Al _x )₄O₉ (x = 0, 0.1, 0.3, 0.5, and 0.7) samples were synthesized by a simple hydrothermal method. The samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transformed infrared spectra, N₂-sorption, and UV–Vis diffuse reflectance spectra, and their photocatalytic activities were evaluated by the degradation of methyl orange under visible-light irradiation. The results reveal that the Al substitution can effectively improve photocatalytic performance, which is attributed to the increase of surface area, the improvement of energy band structure, and the distortion of the Fe–O octahedron in Al-substituted samples. In addition, it is found that the photocatalytic activity to decompose methyl orange under visible-light illumination increases monotonically as x increases from zero to 0.5 in Bi₂(Fe_1−x Al _x )₄O₉ and then decreases for x = 0.7, which is believed to be associated with the distribution of Fe³⁺ ions over the octahedral and tetrahedral sites.     

Dumbbell-like bifunctional Au-Fe3O4 nanoparticles

Dumbbell-like Au-Fe(3)O(4) nanoparticles are synthesized using decomposition of Fe(CO)(5) on the surface of the Au nanoparticles followed by oxidation in 1-octadecene solvent. The size of the particles is tuned from 2 to 8 nm for Au and 4 nm to 20 nm for Fe(3)O(4). The particles show the characteristic surface plasmon absorption of Au and the magnetic properties of Fe(3)O(4) that are affected by the interactions between Au and Fe(3)O(4). The dumbbell is formed through epitaxial growth of iron oxide on the Au seeds, and the growth can be affected by the polarity of the solvent, as the use of diphenyl ether results in flower-like Au-Fe(3)O(4) nanoparticles.     

水热合成氧化铁纳米结构及机理分析

利用硝酸铁与油酸钠反应所得的化合物在高温水热条件下分解制备多种氧化铁纳米结构.研究了水热反应温度、反应时间和热处理工艺对于产物结构的影响,并且探讨了产生各种纳米结构的机理.在高温较短反应时间下,可以制得直径为15nm,长度为3μm的纳米线结构,延长反应时间至25h,得到边长为15nm的氧化铁四方颗粒.将含有羟基氧化铁相的氧化铁纳米线在不同温度下进行热处理,得到了直径为15nm,长度为1μm的氧化铁纳米线和直径为1～3μm的氧化铁微米球.     

Enhanced antibacterial activity and mechanism studies of Ag/Bi2O3 nanocomposites

In this work, sphere-like Ag/Bi₂O₃ nanocomposites with the average size of ca. 170?nm were successfully synthesized by simple deposition-precipitation method. The antibacterial activities of as-prepared Ag/Bi₂O₃ nanocomposites were evaluated by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and colony counting methods. It was found that Ag/Bi₂O₃ nanocomposites displayed greatly improved antibacterial ability against common pathogenic Gram-positive and Gram-negative bacteria in comparison with single-component Bi₂O₃ nanospheres. More importantly, Ag/Bi₂O₃ nanocomposites exhibited remarkably outstanding antibacterial activities against clinical drug-resistant bacteria. The antibacterial activity of Ag/Bi₂O₃ nanocomposite increased with the increase of Ag content and 15?wt% Ag/Bi₂O₃ nanocomposites showed the highest antibacterial activity. Furthermore, a plausible antibacterial mechanism of Ag/Bi₂O₃ nanocomposite was proposed. It was believed that the enhanced generation of H₂O₂ could lead to the membrane leakage of cytosol and the inactivation of respiratory chain dehydrogenaes, which was possibly responsible for the enhanced antibacterial activities of nanocomposites.     

Deposition and Magnetic Properties of Fe3O4/Fe/Fe3O4Tri-layer Films

1. IntroductionIron oxides include several crystalline forms:hematite (or-FeZO3), magnetite (Fe3O4), maghemite(7-Felon) and wustite (FeO). They have interesting structural and magnetic properties, and are practically important in magnetic and electronic applications. The strongly ferrimagnetic 7--FeZO3 phaseearned much attention due to their applications asrecording media. The attainment of 7-FeZO3 involves complicated processing[1]. In our previousstudies, high coercivity 7-FeZO3, Fe3…     

Fe2O3-Modified Porous BiVO4 Nanoplates with Enhanced Photocatalytic Activity

Nano-Micro Letters - As BiVO4 is one of the most popular visible-light-responding photocatalysts, it has been widely used for visible-light-driven water splitting and environmental purification....     

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.     

Bonding MnO2/Fe3O4 shell-core nanostructures to catalyze H2O2 degrading organic dyes

Shell-core nanostructures with both high catalytic activation and recyclability have been becoming hot property in nano-catalysis. By respectively using co-precipitation method, sol-gel method, and homogeneous precipitation method we manufactured shell-core nano-particles of Fe3O4 core and MnO2 shell. The Bonding mechanism of the composite is discussed in detail, and the efficiency and nature of the particles to degrade methyl orange by catalyzing H2O2 is also demonstrated. We show that by using homogeneous precipitation method one can obtain morphologically uniform nano-particles of about 5-6 nm MnO2 shell and 13-14 nm Fe3O4 core. The characteristic peak of Fe3O4 in the Infrared spectra of the composite particles was blue shifted, and a novel peak appears at 775.68 cm(-1) referring to occurrence of new bond. X-ray Photoelectron Spectroscopy analysis showed that the bonding energy of Fe2p and Ols was increased due to the combination of the MnO2 shell and the Fe3O4 core, suggesting a new bond of Fe-O-Mn occurred in the composite. The MnO2 shell has abundant hydroxyl radicals and exhibits high chemical activity in catalyzing H2O2 and degrading methyl orange with a degree of greater than 95%. On the other hand, the shell-core nanostructures are super-paramagnetic, and the saturated magnetization reaches 33.5 eum/g, which is sufficient for the catalyst to be recycled.     

Modifying Fe3O4-functionalized nanoparticles with N-halamine and their magnetic/antibacterial properties

Magnetic/antibacterial bifunctional nanoparticles were fabricated through the immobilization of antibacterial N-halamine on silica-coated Fe(3)O(4)-decorated poly(styrene-co-acrylate acid) (PSA) nanoparticles. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDX), Fourier transform infrared (FTIR), and thermogravimetric analysis (TGA). The N-halamine was developed from the precursor 5,5-dimethylhydantoin (DMH) by chlorination treatment, and experimental results showed that the loading amount of DMH on the silica-coated Fe(3)O(4)-decorated poly(styrene-co-acrylate acid) nanoparticles was adjustable. The as-synthesized nanoparticles exhibited superparamagnetic behavior and had a saturation magnetization of 18.93 emu g(-1). Antibacterial tests showed that the resultant nanoparticles displayed enhanced antibacterial activity against both Gram-positive and Gram-negative bacteria compared with their bulk counterparts.     

Glycothermal synthesis of fluorinated Fe3O4 microspheres with distinct peroxidase-like activity

The intrinsic peroxidase-like activity of magnetite (Fe₃O₄) has to be improved to activate H₂O₂ under mild conditions for practical applications. Herein fluorinated Fe₃O₄ microspheres (F-Fe₃O₄-r, r: 0.1–3), where r indicates the F/Fe molar ratio in the reaction mixture, were prepared by glycothermal synthesis and characterized by various complementary techniques. Fluoride ions were enriched on the surface of F-Fe₃O₄-1, and may substitute lattice oxygen or ion-exchange with surface hydroxyl groups. Kinetic study showed that the apparent activation energy for catalytic decomposition of H₂O₂ over F-Fe₃O₄-1 was significantly lower than those over unmodified Fe₃O₄ or other heterogeneous peroxidase-like catalysts (20.3 vs. 32.8–142?kJ?mol^?1), which improved the low-temperature activity of the former (decomposition rate of H₂O₂ at 25?°C: 0.0150?h^?1). Potential applications of F-Fe₃O₄-1 in wastewater treatment were demonstrated by catalytic degradation of orange G with H₂O₂ at pH 6.8 and 25?°C.     

Enhanced photocatalytic activity of Fe3O4-WO3-APTES for azo dye removal from aqueous solutions in the presence of visible irradiation

Development of highly active photocatalysts for treatment of dye-laden wastewaters is vital. The photocatalytic removal of azo dye Reactive Black 5 was investigated by Fe₃O₄-WO₃-3-aminopropyltriethoxysilane (APTES) nanoparticles in the presence of visible light. The Fe₃O₄-WO₃-APTES nanoparticles were synthesized via a facile coprecipitation method. The photocatalyst was characterized by XRD, FT-IR, SEM, EDX, VSM, UV–Vis, and pH_PZC techniques. The effects of some operational parameters such as solution pH, nanophotocatalyst dosage, initial RB5 concentration, H₂O₂ concentration, different purging gases, and type of organic compounds on the removal efficiency were studied by the Fe₃O₄-WO₃-APTES nanoparticles as a photocatalyst. Maximum phtocatalytic activity was obtained at pH 3. The photocatalytic removal of RB5 increased with increasing H₂O₂ concentration up to 5?mM. The removal efficiency declined in the presence of different purging gases and all types of organic compounds. First-order rate constant (k_obs) decreased from 0.027 to 0.0022?min^?1 and electrical energy per order (E_Eo) increased from 21.33 to 261.82 (kWh/m³) with increasing RB5 concentration from 10 to 100?mg/L, respectively. The efficiency of LED/Fe₃O₄-WO₃-APTES process for RB5 removal was approximately 89.9%, which was more effective than the LED/Fe₃O₄-WO₃ process (60.72%). Also, photocatalytic activity decreased after five successive cycles.     

Fe3O4 octahedral colloidal crystals

We present a facile and controllable method for the large-scale fabrication of highly-ordered octahedral Fe₃O₄ colloidal “single crystals” without the assistance of a substrate. Oleic acid is used to reduce the solubility of the nano-building blocks in colloidal solution and to induce a “crystallization” process. Our colloidal crystals are of multimicron size and show typical crystallographic characteristics. They have a very robust structure and can serve as a novel ordered magnetic mesoporous material with a relatively narrow pore size distribution. The sample possesses an extremely high Verwey transition temperature (T _V) of 100 K and a high saturation magnetization (M _S) of 86 emu/g at 5 K based on its good crystallinity, as well as the interparticle dipolar interaction behavior arising from its unique structure. Electrochemical measurements have demonstrated the excellent capacity of the mesoporous colloidal crystals when used in lithium-ion batteries.      

Enhanced electromagnetic wave absorption properties of polyaniline-coated Fe3O4/reduced graphene oxide nanocomposites

Fe₃O₄-reduced graphene oxide-polyaniline (Fe₃O₄–RGO–PANI) ternary electromagnetic wave absorbing materials were prepared by in situ polymerization of aniline monomer on the surface of Fe₃O₄–RGO nanocomposites. The morphology, structure and other physical properties of the nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, vibration sample magnetism, etc. The electromagnetic wave absorbing properties of composite materials were measured by using a vector network analyzer. The PANI–Fe₃O₄–RGO nanocomposites demonstrated that the maximum reflection loss was ?36.5 dB at 7.4 GHz with a thickness of 4.5 mm and the absorption bandwidth with the reflection loss below ?10 dB was up to 12.0 GHz with a thickness in the range of 2.5–5.0 mm, suggesting that the microwave absorption properties and the absorption bandwidth were greatly enhanced by coating with polyaniline (PANI). The strong absorption characteristics of PANI–Fe₃O₄–RGO ternary composites indicated their potential application as the electromagnetic wave absorbing material.     

TiO2/Fe2O3核-壳粒子的制备及光学性能

钛酸四丁酯(TBOT)水解产生的TiO2沉积在单分散准球形α-Fe2O3颗粒的表面,形成均匀、连续的核-壳结构.TiO2壳层的厚度约为30 nm.在500℃热处理后,TiO2壳层从非晶态转变为锐钛矿结构.在光激发下,TiO2/Fe2O3核-壳粒子的电子从TiO2价带跃迁到能量较低的α-Fe2O3导带,在可见光区产生新的强吸收峰.光谱计算结果表明TiO2价带与α-Fe2O3导带的能量差为1.6 eV.