Using a bifunctional polymer for the functionalization of Fe3O4 nanoparticles

A bifunctional maleimido-tetra(ethylene glycol)-poly(glycerol monoacrylate) (MAL-TEG-PGA) polymer was synthesized and used as a linker to couple functional biomolecules to iron oxide nanoparticles. The cell-penetrating peptide Tat was chosen as a model ligand and successfully conjugated to the surface of Fe₃O₄ nanoparticles using MAL-TEG-PGA. The Tat-conjugated Fe₃O₄ nanoparticles can be prepared simply by applying the linker to the iron oxide nanoparticles and then coupling the Tat peptide to the maleimide terminus or by coating the nanoparticles with a pre-coupled linker. Cell-uptake studies demonstrated that the Tat peptide was an efficient functional biomolecule to translocate iron oxide nanoparticles into the cell nucleus. Tat-conjugated nanoparticles thus prepared may be useful for drug or gene delivery.     

Multifuctional Fe3O4@C/YVO4:Dy nanopowers: Preparation,luminescence and magnetic properties

As-synthesized Fe₃O₄ nanoparticles were encapsulated with carbon layers through a simple hydrothermal process. Fe₃O₄/C nanoparticles were coated with YVO₄:Dy³⁺ phosphors to form bifunctional Fe₃O₄@C@YVO₄:Dy³⁺ composites. Their structure, luminescence and magnetic properties were characterized by XRD, SEM, TEM, HRTEM, PL spectra and VSM. The experimental results indicated that the as-prepared bifunctional composites displayed well-defined core–shell structures. The ∼12 nm diameter YVO₄:Dy³⁺ shell exhibited tetragonal structure. Additionally, the composites exhibited a high saturation magnetization (13 emu/g) and excellent luminescence properties, indicating their promising potential as multifunctional biosensors for biomedical applications.     

纳米Fe3O4稳定的Pickering型ASA乳液

利用纳米Fe₃O₄作为稳定剂和乳化剂来制备Pickering型ASA（alkenyl succinic anhydride） 施胶乳液,并研究了固体颗粒浓度、油水比、水分散相pH对乳液类型、稳定性、形态及施胶性能的影响。结果表明,纳米Fe₃O₄能够乳化制备均一稳定的Pickering型ASA乳液。乳液在室温下静置稳定,析出油相体积分数随固体颗粒用量的增加而增大,随油水比的增大而减小。油水比为2：1,水分散相浓度为0.1%（质量分数）时制备的ASA乳液稳定性最佳。固体颗粒部分吸附在油/水界面处,部分分散在分散相中,随分散相中固体颗粒浓度的增加,乳液稳定性变差。乳液静置分层之前,ASA发生部分水解。在放置1 h后用于纸页浆内施胶,随ASA乳液用量的增加,纸页表面接触角逐渐增大,且纸页表面粗糙度下降。在ASA的添加量为1.0%（质量分数）时,纸页表面接触角达到93.5°,纸页表面粗糙度为15.924 μm。     

Sonochemical synthesis of magnetic core–shell Fe3O4@ZrO2 nanoparticles and their application to the highly effective immobilization of myoglobin for direct electrochemistry

In this study, bifunctional Fe₃O₄@ZrO₂ magnetic core–shell nanoparticles (NPs), synthesized by a simple and effective sonochemical approach, were attached to the surface of a magnetic glassy carbon electrode (MGCE) and successfully applied to the immobilization/adsorption of myoglobin (Mb) for constructing a novel biosensor platform. With the advantages of the magnetism and the excellent biocompatibility of the Fe₃O₄@ZrO₂ NPs, Mb could be easily immobilized on the surface of the electrode in the present of external magnetic field and well retained its bioactivity, hence dramatically facilitated direct electron transfer of Mb was demonstrated. The proposed Mb/Fe₃O₄@ZrO₂ biofilm electrode exhibited excellent electrocatalytic behaviors towards the reduction of H₂O₂ with a linear range from 0.64 μM to 148 μM. This presented system avoids the complex synthesis for protecting Fe₃O₄ NPs, supplies a simple, effective and inexpensive way to immobilize protein, and is promising for construction of third-generation biosensors and other bio-magnetic induction devices.     

Effect of TiO2 supporting layer on Fe2O3 photoanode for efficient water splitting

For an electrochemical water splitting system, titanate nanotubular particles with a thickness of ∼700 nm produced by a hydrothermal process were repetitively coated on fluorine-doped tin oxide (FTO) glass via layer-by-layer self-assembly method. The obtained titanate/FTO films were dipped in aqueous Fe solution, followed by heat treatment for crystallization at 500 °C for 10 min in air. The UV–vis absorbance of the Fe-oxide/titanate/FTO film showed a red-shifted spectrum compared with the TiO₂/FTO coated film; this red shift was achieved by the formation of thin hematite-Fe₂O₃ and anatase-TiO₂ phases verified using X-ray diffraction and Raman results. The cyclic voltammetry results of the Fe₂O₃/TiO₂/FTO films showed distinct reversible cycle characteristics with large oxidation–reduction peaks with low onset voltage of I–V characteristics under UV–vis light illumination. The prepared Fe₂O₃/TiO₂/FTO film showed much higher photocurrent densities for more efficient water splitting under UV–vis light illumination than did the Fe₂O₃/FTO film. Its maximum photocurrent was almost 3.5 times higher than that obtained with Fe₂O₃/FTO film because of the easy electron collection in the current collector. The large current collection was due to the existence of a TiO₂ base layer beneath the Fe₂O₃ layer.     

Selective synthesis of mixed alcohols from syngas over catalyst Fe2O3/Al2O3 in slurry reactor

The Fe₂O₃/Al₂O₃ catalyst was studied to selectively synthesize mixed alcohols from syngas in a continuously stirred slurry reactor with the oxygenated solvent Polyethylene Glycol-400 (PEG-400). The selectivity of mixed alcohols in the products reached as high as 95 wt.% and the C₂₊ alcohols (mainly ethanol) was more than 40 wt.% in the total alcohol products at the reaction conditions of 250 °C, 3.0 MPa, H₂/CO = 2 and space velocity = 360 ml/g_cat h. The hydrogen temperature programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS) measurements of the catalyst confirmed that the FeO phase was responsible for the high selectivity to mixed alcohols in the process. And the oxygenated solvent PEG-400 was also necessary for the selective synthesis of mixed alcohols in the reaction system.     

Study of intrinsic sulfidation behavior of Fe2O3 for high temperature H2S removal

Iron-based sorbent was preferable for desulfurization from coal-derived gas due to economic consideration and favorable dynamic property. The intrinsic behavior of Fe-based sorbent should be primarily understood in the sulfidation process for improving its performance. A series of tests were carried out with Fe₂O₃, Fe and other compounds containing-Fe (FO) made from the same precursor FeC₂O₄·2H₂O in H₂S-N₂ mixture in this study. The formation of H₂ was observed with Fe and FO as sorbents. While SO₂ was detected with FO and Fe₂O₃ as sorbents, its concentration in outlet was gradually decreased. The crystal phase and surface chemical state of fresh and sulfided Fe₂O₃ with different reaction times were characterized by XRD and XPS measurements. The result suggested that the intrinsic H₂S removal by Fe₂O₃ would produce multi-phase of sulfides. The possible mechanism of sulfidation reaction was discussed.     

Corrosion mechanisms of Al2O3/MgAl2O4 by V2O5, NiO, Fe2O3 and vanadium slag

The effects of V₂O₅, NiO, Fe₂O₃ and vanadium slag on the corrosion of Al₂O₃ and MgAl₂O₄ have been investigated. The specimens of Al₂O₃ and MgAl₂O₄ with the respective oxides above mentioned were heated at 10 °C/min from room temperature up to three different temperatures: 1400, 1450 and 1500 °C. The corrosion mechanisms of each system were followed by XRD and SEM analyses. The results obtained showed that Al₂O₃ was less affected by the studied oxides than MgAl₂O₄. Alumina was only attacked by NiO forming NiAl₂O₄ spinel, while the MgAl₂O₄ spinel was attacked by V₂O₅ forming MgV₂O₆. It was also observed that Fe₂O₃ and Mg, Ni, V and Fe present in the vanadium slag diffused into Al₂O₃. On the other hand, the Fe₂O₃ and Ca, S, Si, Na, Mg, V and Fe diffused into the MgAl₂O₄ structure. Finally, the results obtained were compared with those predicted by the FactSage software.     

Synthesis of Fe2O3 nanoparticles for nitrogen dioxide gas sensing applications

Iron (III) oxide, Fe₂O₃, nanoparticles of approximately 40 nm diameter were synthesized by sol–gel method and their nitrogen dioxide adsorption and desorption kinetics were investigated by custom fabricated gas sensor unit. The morphology and crystal structure of Fe₂O₃ nanoparticles were studied by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) respectively. The roughness of film surface was investigated by atomic force microscopy (AFM). Relative sensitivity of Fe₂O₃ nanoparticles for NO₂ sensor was determined by electrical resistance measurements. Our reproducible experimental results show that Fe₂O₃ nanoparticles have a great potential for nitrogen dioxide sensing applications operating at a temperature of 200 °C.     

Accommodation of impurities in α-Al2O3, α-Cr2O3 and α-Fe2O3

Atomic scale computer simulation was used to predict the mechanisms and energies associated with the accommodation of aliovalent and isovalent dopants in three host oxides with the corundum structure. Here we consider a much more extensive range of dopant ions than has previously been the case. This enables a rigorous comparison of calculated mechanism energetics. From this we predict that divalent ions are charge compensated by oxygen vacancies and tetravalent ions by cation vacancies over the full range of dopant radii. When defect associations are included in the model these conclusions remain valid. At equilibrium, defects resulting from extrinsic dopant solution dominate intrinsic processes, except for the largest dopant cations. Solution reaction energies increase markedly with increasing dopant radius. The behaviour of cluster binding energies is more complex.     

Synthesis and magnetic properties of nanoporous Co3O4 nanoflowers

Nanoporous Co₃O₄ hierarchical nanoflowers have been prepared through sequential process of a hydrothermal reaction and heat treatment. These nanoflowers consisting of a great deal of Co₃O₄ nanofibers have bimodal pore structures and Brunauer–Emmett–Teller surface area of 34.61 m²/g. The temperature dependence curves of magnetization in zero-field-cooled and field-cooled exhibit main antiferromagnet and weak ferromagnet of Co₃O₄ nanoflowers at blocking temperature of 34 K, respectively. In addition, analysis of their optic properties obviously indicates red shift of absorption peaks, exhibiting quantum-confined effect and traits of semiconductor.     

Structure and electrochemical performance of nanostructured Fe3O4/carbon nanotube composites as anodes for lithium ion batteries

Polyvinyl alcohol (PVA) was used as a hydrogen bond functionalizing agent to modify multi-walled carbon nanotubes (CNTs). Nanoparticles of Fe₃O₄ were then formed along the sidewalls of the as-modified CNTs by the chemical coprecipitation of Fe²⁺ and Fe³⁺ in the presence of CNTs in an alkaline solution. The structure and electrochemical performance of the Fe₃O₄/CNTs nanocomposite electrodes have been investigated in detail. Electrochemical tests indicated that at the 145th cycle, the CNTs-66.7 wt.%Fe₃O₄ nanocomposite electrode can deliver a high discharge capacity of 656 mAh g⁻¹ and stable cyclic retention. The improvement of reversible capacity and cyclic performance of the Fe₃O₄/CNTs nanocomposite could be attributed to the nanosized Fe₃O₄ particles and the network of CNTs.     

Reduction and oxidation properties of Fe2O3/ZrO2 oxygen carrier for hydrogen production

Fe₂O₃ is a promising oxygen carrier for hydrogen production in the chemical-looping process. A set of kinetic studies on reduction with CH₄, CO and H₂ respectively, oxidation with water and oxygen containing Ar for chemical-looping hydrogen production was conducted. Fe₂O₃ (20 wt.%)/ZrO₂ was prepared by a co-precipitation method. The main variables in the TGA (thermogravimetric analyzer) experiment were temperatures and gas concentrations. The reaction kinetics parameters were estimated based on the experimental data. In the reduction by CH₄, CO and H₂, the reaction rate changed near FeO. Changes in the reaction rate due to phase transformation were observed at low temperature and low gas concentration during the reduction by CH₄, but the phenomenon was not remarkable for the reduction by CO and H₂. The reduction rate achieved using CO and H₂ was relatively faster than achieved using CH₄. The Hancock and Sharp method of comparing the kinetics of isothermal solid-state reactions was applied. A phase boundary controlled model (contacting sphere) was applied to the reduction of Fe₂O₃ to FeO by CH₄, and a different phase boundary controlled model (contacting infinite slab) was fit well to the reduction of FeO to Fe by CH₄. The reduction of Fe₂O₃ to Fe by CO and H₂ can be described by the former phase boundary controlled model (contacting sphere). This phase boundary controlled model (contacting sphere) also fit well for the oxidation of Fe to Fe₃O₄ by water and FeO to Fe₂O₃ by oxygen containing Ar. These kinetics data could be used to design chemical-looping hydrogen production systems.     

Enhanced cycling performance of Fe3O4-graphene nanocomposite as an anode material for lithium-ion batteries

Fe₃O₄-graphene nanocomposite was prepared by a gas/liquid interface reaction. The structure and morphology of the Fe₃O₄-graphene nanocomposite were characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. The electrochemical performances were evaluated in coin-type cells. Electrochemical tests show that the Fe₃O₄-22.7 wt.% graphene nanocomposite exhibits much higher capacity retention with a large reversible specific capacity of 1048 mAh g⁻¹ (99% of the initial reversible specific capacity) at the 90th cycle in comparison with that of the bare Fe₃O₄ nanoparticles (only 226 mAh g⁻¹ at the 34th cycle). The enhanced cycling performance can be attributed to the facts that the graphene sheets distributed between the Fe₃O₄ nanoparticles can prevent the aggregation of the Fe₃O₄ nanoparticles, and the Fe₃O₄-graphene nanocomposite can provide buffering spaces against the volume changes of Fe₃O₄ nanoparticles during electrochemical cycling.     

Synthesis of magnetic Pb/Fe3O4/SiO2 and its catalytic activity for propylene carbonate synthesis via urea and 1,2-propylene glycol

To facilitate the recovery of Pb/SiO₂ catalyst, magnetic Pb/Fe₃O₄/SiO₂ samples were prepared separately by emulsification, sol-gel and incipient impregnation methods. The catalyst samples were characterized by means of X-ray diffraction and N₂ adsorption-desorption, and their catalytic activity was investigated in the reaction for synthesizing propylene carbonate from urea and 1,2-propylene glycol. When the gelatin was applied in the preparation of Fe₃O₄ at 60°C and the pH value was controlled at 4 in the preparation of Fe₃O₄/SiO₂, the Pb/Fe₃O₄/SiO₂ sample shows good catalytic activity and magnetism. Under the reaction conditions of a reaction temperature of 180°C, reaction time of 2 h, catalyst percentage of 1.7 wt-% and a molar ratio of urea to PG of 1:4, the yield of propylene carbonate attained was 87.7%.     

Low-temperature synthesis of Bi2Fe4O9 nanoparticles via a hydrothermal method

Bi₂Fe₄O₉ (BFO) nanoparticles were successfully synthesized by a hydrothermal method at a temperature as low as 100 °C. The as-prepared powders, characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM) and physical property measurement system (PPMS), exhibited a pure BFO phase about 100 nm size with uniform sheet-like shape and exhibited an AF order at room temperature. It was found that high alkali concentration and alkali ion Na⁺ played a key role in the formation of BFO nanoparticles at a low temperature of 100 °C.     

Nanocomposite Fe2O3-Se as a new lithium storage material

The electrochemical properties of nanocomposite Fe₂O₃-Se thin film prepared by pulsed laser deposition (PLD) method have been investigated by cyclic voltammetry and charge/discharge measurements. A large reversible capacity of nanocomposite Fe₂O₃-Se thin film was found to be around 650 mAh g⁻¹. A new couple of reduction and oxidation peaks at 1.4 and 1.8 V were observed from cyclic voltammogram for the first time. Our data demonstrated that nanocomposite Fe₂O₃-Se exhibit larger capacity and better cycle performance than pure Fe₂O₃. The electrochemical reaction mechanisms of Fe₂O₃-Se with lithium were examined by X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED). The reversible conversions reaction of nanosized metal Fe with Li₂Se and Li₂O formed after initial discharge process into FeSe and Fe₂O₃ respectively were revealed.     

Laser machining of Al2O3-ZrO2 (3%Y2O3) eutectic composite

In this work we present the study of the interaction between NIR pulsed laser and Al₂O₃-ZrO₂ (3%Y₂O₃) eutectic composite. The effect produced by modifying the reference position as well as the working conditions and laser beam features has been studied when the samples are processed by means of pulse bursts.The samples were obtained by the laser floating zone technique using a CO₂ laser system. The laser machining was carried out with a Q-switched Nd:YAG laser at its fundamental wavelength of 1064 nm with pulse-widths in the nanosecond range.Geometric dimensions, i.e. ablated depth, machined width and removed volume as well as ablation yield of the resulting holes have been studied. We have described and discussed the morphology, composition and microstructure of the processed samples.     

磁性Fe3O4纳米粒子用作靶向药物载体的制备及分析

Fe3O4 magnetic nanoparticles were prepared by the aqueous co-precipitation of FeCl3-6H2O and FeCl2-4H2O with addition of ammonium hydroxide. The conditions for the preparation of Fe3O4 magnetic nanoparticles were optimized, and Fe3O4 magnetic nanoparticles obtained were characterized systematically by means of transmission electron microscope （TEM）, dynamic laser scattering analyzer （DLS） and X-ray diffraction （XRD）. The results revealed that the magnetic nanoparticles were cubic shaped and dispersive, with narrow size distribution and average diameter of 11.4 nm. It was found that the homogeneous variation of pH value in the solution via the control on the dropping rate of aqueous ammonia played a critical role in size distribution. The magnetic response of the product in the magnetic field was also analyzed and evaluated carefully. A 32.6 mT magnetic field which is produced by four ferromagnets was found to be sufficient to excite the dipole moments of 0.05 g Fe3O4 powder 2 cm far away from the ferromagnets. In conclusion, the Fe3O4 magnetic nanoparticles with excellent properties were competent for the magnetic carders of targeted-drug in future application.     

Hydrothermal preparation of octadecahedron Fe3O4 thin film for use in an electrochemical supercapacitor

A Fe₃O₄ film with regularly edge-affected cubic (octadecahedron) morphology was successfully prepared on stainless steel foil by a simple and benign hydrothermal process. The potential for the use of the film in a supercapacitor was tested by investigating the electrochemical behavior of the Fe₃O₄ film using cyclic voltammetry (CV) and galvanostatic charge/discharge tests. The Fe₃O₄ film showed a CV indicative of a typical pseudocapactive behavior in 1 mol L⁻¹ Na₂SO₃ solution. Furthermore, this film exhibited a specific capacitance of 118.2 F g⁻¹ at the current of 6 mA between −1 and 0.1 V with a capacity retention of 88.75% after 500 cycles.