α‐Fe2O3 Cubes with High Visible‐Light‐Activated Photoelectrochemical Activity towards Glucose: Hydrothermal Synthesis Assisted by a Hydrophobic Ionic Liquid

A liquid/liquid interfacial reaction system was designed to fabricate α‐Fe₂O₃ cubes. The reaction system uses a hydrophobic ionic liquid containing iron ions ([(C₈H₁₇)₂(CH₃)₂N]FeCl₄) for manufacturing α‐Fe₂O₃ cubes by a novel and environmentally friendly hydrothermal method under low‐temperature conditions (140 °C). The iron‐containing ionic liquid is hydrophobic and can form a liquid/liquid interface with water, which is vital for fabrication of the α‐Fe₂O₃ cubes. Nanomaterials synthesized from hydrophobic iron‐containing ionic liquids show good crystallinity, well‐developed morphology, and uniform size. The effect of different ionic liquids on the morphology of α‐Fe₂O₃ was investigated in detail. [(C₈H₁₇)₂(CH₃)₂N]FeCl₄ is assumed to perform the triple role of forming a liquid/liquid interface with water and acting as reactant and template at the same time. The effect of the reaction temperature on the formation of the α‐Fe₂O₃ cubes was also studied. Temperatures lower or higher than 140 °C are not conducive to formation of the α‐Fe₂O₃ cubes. Their photoelectrochemical properties were tested by means of the transient photocurrent response of electrodes modified with as‐prepared α‐Fe₂O₃ cubes. The photocurrent response of an α‐Fe₂O₃ cubes/indium tin oxide electrode is high and stable, and it shows great promise as a photoelectrochemical glucose sensor with high sensitivity and fast response, which are beneficial to practical applications of nanosensors.     

Metal Ions Induce Growth and Magnetism Alternation of α‐Fe2O3 Crystals Bound by High‐Index Facets

In this study, quasi‐cubic and hexagonal bipyramid α‐Fe₂O₃ polyhedrons with high‐index facets exposed were controllably synthesized by applying metal ions Zn²⁺ or Cu²⁺ as structure‐directing agents. The growth of the α‐Fe₂O₃ nanostructures with high‐index facets were induced by metal ions without the addition of any other surfactants. The quasi‐cubic form controlled by Zn²⁺ looks like a cube but has an angle of approximately 86° bound by (012), (10‐2), and (1‐12) facets, whereas the hexagonal bipyramid form controlled by Cu²⁺ has a sixfold axis bound by {012} facets. Magnetic measurements confirm that these two kinds of nanocrystals display shape‐ and surface‐dependent magnetic behaviors. The hexagonal bipyramid iron oxide nanocrystals show a lower Morin transition temperature of 240 K and might be spin‐canted ferromagnetically controlled at room temperature, and the ferromagnetism disappears at low temperature. The quasi‐cubic nanocrystals have a splitting between FC curve and ZFC curve from the highest experimental temperature and no Morin transformation occurs; this indicates that they would be defect ferromagnetically controlled at low temperature. The reported metal‐ion‐directing technique could provide a universal method for shape‐ and surface‐controlled synthesis of nanocrystals with high‐index facets exposed.     

A Novel Synthesis and Antioxidant Evaluation of Functionalized [1,3]‐Oxazoles Using Fe3O4‐Magnetic Nanoparticles

In this research, green procedure was employed for biosynthesis of magnetic nanoparticles of iron oxide (Fe₃O₄‐MNPs) by reduction of ferric chloride solution with Orange peel water extract. Also, dihydro‐2H‐cyclopenta[d][1,3]oxazole was generated through multicomponent reaction of 1,3‐oxazole‐2(3H)‐thione, dialkyl acetylenedicarboxylates, α‐haloketones, and Fe₃O₄‐MNPs as catalyst at ambient temperature in good yield. Initially, 1,3‐oxazole‐2(3H)‐thione derivatives as one of the precursors are produced through the reaction of alkyl bromides, isothiocyanate, sodium hydride, and Fe₃O₄‐MNPs as catalyst water at ambient temperature in 83–95% yields. Also, diphenyl‐picrylhydrazine radical trapping and ferric reduction activity potential assays are used for evaluation of antioxidant activity of some synthesized compounds. Among investigated compounds, 4b has good power for radical trapping activity and 4d has good reduction power to butylated hydroxytoluene and 2‐tert‐butylhydroquinone.     

Visible‐Light‐Driven Water Oxidation with a Polyoxometalate‐Complexed Hematite Core of 275 Iron Atoms

Although metal oxide nanocrystals are often highly active, rapid aggregation (particularly in water) generally precludes detailed solution‐state investigations of their catalytic reactions. This is equally true for visible‐light‐driven water oxidation with hematite α‐Fe₂O₃ nanocrystals, which bridge a conceptual divide between molecular complexes of iron and solid‐state hematite photoanodes. We herein report that the aqueous solubility and remarkable stability of polyoxometalate (POM)‐complexed hematite cores with 275 iron atoms enable investigations of visible‐light‐driven water oxidation at this frontier using the versatile toolbox of solution‐state methods typically reserved for molecular catalysis. The use of these methods revealed a unique mechanism, understood as a general consequence of fundamental differences between reactions of solid‐state metal oxides and freely diffusing “fragments” of the same material.     

Fluorine‐Doped Fe2O3 as High Energy Density Electroactive Material for Hybrid Supercapacitor Applications

Nanostructured α‐Fe₂O₃ with and without fluorine substitution were successfully obtained by a green route, that is, microwave irradiation. The hematite phase materials were evaluated as a high‐performance electrode material in a hybrid supercapacitor configuration along with activated carbon (AC). The presence of fluorine was confirmed through X‐ray photoelectron spectroscopy and transmission electron microscopy. Fluorine‐doped Fe₂O₃ (F‐Fe₂O₃) exhibits an enhanced pseudocapacitive performance compared to that of the bare hematite phase. The F‐Fe₂O₃/AC cell delivered a specific capacitance of 71 F g^?1 at a current density of 2.25 A g^?1 and retained approximately 90 % of its initial capacitance after 15 000 cycles. Furthermore, the F‐Fe₂O₃/AC cell showed a very high energy density of about 28 W h kg^?1 compared to bare hematite phase (～9 W h kg^?1). These data clearly reveal that the electrochemical performance of Fe₂O₃ can be improved by fluorine doping, thereby dramatically improving the energy density of the system.     

Self‐assembled three‐dimensional flower‐like α‐Fe2O3 nanostructures and their application in catalysis

Three‐dimensional flower‐like α‐Fe₂O₃ nanostructures have been successfully synthesized by a simple surfactant‐free environmental friendly solvolthermal process. The as‐prepared products were investigated by X‐ray powder diffraction, transmission electron microscopy, and field emission scanning electron microscopy. By adjusting the synthetic parameters, the shape of the α‐Fe₂O₃ nanostructures can be controlled. The three‐dimensional flower‐like α‐Fe₂O₃ nanostructures were found to be highly active as catalysts for phenol alkylation. The effects of various parameters, such as reaction temperature, reaction time and the amount of catalyst, were studied. The catalyst was stable and could be reused three times in normal atmosphere without suffering appreciable loss in catalytic activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Bulk and surface analysis of Ti1–xFexO2/Fe2O3 composites prepared by solid state reaction for photocatalytic applications

Ti_1–xFe_xO₂ / Fe₂O₃ (x = 0.3, 0.6, and 0.7 wt%) composites were prepared by solid state reaction of the oxides TiO₂ (rutile phase) and Fe₂O₃ at 550 °C. The following techniques were applied for the characterization of the composites: X‐ray powder diffraction, Mössbauer spectroscopy, SEM, energy dispersive X‐ray spectroscopy and adsorption of nitrogen. The anatase/rutile/hematite ratio and the abundance of Fe³⁺ were quantified. The results indicate that Fe³⁺ substituted Ti⁴⁺ in the rutile structure and that the α‐Fe₂O₃ phase was predominantly on the surface of the crystalline Ti_1–xFe_xO₂ powders. A substantial increase of the materials density, with respect to rutile, favoured the application of the composites in photocatalytic experiments. The performance of the solids upon the photodegradation of aqueous solutions of carbofuran was evaluated. The Lewis sites created in the composites correlated directly with the photodegradation rate constant of carbofuran and the decrease of the total organic carbon content in the treated solutions. Copyright © 2011 John Wiley & Sons, Ltd.     

α‐Fe2O3 Polyhedral Nanoparticles Enclosed by Different Crystal Facets: Tunable Synthesis,Formation Mechanism Analysis,and Facets‐dependent n‐Butanol Sensing Properties

Three kinds of polyhedral α‐Fe₂O₃ nanoparticles enclosed by different facets including oblique parallel hexahedrons (op‐hexahedral NPs), cracked oblique parallel hexahedrons (cop‐hexahedral NPs), and octadecahedral nanoparticles (octadecahedral NPs), were successfully prepared by simply changing only one reaction parameter in the hydrothermal process. The structural and morphological of the products were systematically studied using various characterizations including X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), revealing that the three kinds of α‐Fe₂O₃ nanoparticles were enclosed by {104}, {110}/{104}, and {102}/{012}/{104} crystal planes, respectively. The exposed facets and shape of the nanocrystals were found to be affected by the adding amount of ethylene glycol in the solvent. The gas‐sensing properties and mechanism of the α‐Fe₂O₃ samples were studied and analyzed, which indicated that the sensitivity of the three samples followed the order of octadecahedral NPs > cop‐hexahedral NPs > op‐hexahedral NPs due to the combined effects of specific surface area and oxygen defects in the nanocrystals.     

Controlled Synthesis of Fe3O4/ZIF‐8 Nanoparticles for Magnetically Separable Nanocatalysts

Fe₃O₄/ZIF‐8 nanoparticles were synthesized through a room‐temperature reaction between 2‐methylimidazolate and zinc nitrate in the presence of Fe₃O₄ nanocrystals. The particle size, surface charge, and magnetic loading can be conveniently controlled by the dosage of Zn(NO₃)₂ and Fe₃O₄ nanocrystals. The as‐prepared particles show both good thermal stability (stable to 550 °C) and large surface area (1174 m²g^?1). The nanoparticles also have a superparamagnetic response, so that they can strongly respond to an external field during magnetic separation and disperse back into the solution after withdrawal of the magnetic field. For the Knoevenagel reaction, which is catalyzed by alkaline active sites on external surface of catalyst, small Fe₃O₄/ZIF‐8 nanoparticles show a higher catalytic activity. At the same time, the nanocatalysts can be continuously used in multiple catalytic reactions through magnetic separation, activation, and redispersion with little loss of activity.     

Controllable Synthesis of Mesoporous Iron Oxide Nanoparticle Assemblies for Chemoselective Catalytic Reduction of Nitroarenes

Iron(III) oxide is a low‐cost material with applications ranging from electronics to magnetism, and catalysis. Recent efforts have targeted new nanostructured forms of Fe₂O₃ with high surface area‐to‐volume ratio and large pore volume. Herein, the synthesis of 3D mesoporous networks consisting of 4–5 nm γ‐Fe₂O₃ nanoparticles by a polymer‐assisted aggregating self‐assembly method is reported. Iron oxide assemblies obtained from the hybrid networks after heat treatment have an open‐pore structure with high surface area (up to 167 m² g^?1) and uniform pores (ca. 6.3 nm). The constituent iron oxide nanocrystals can undergo controllable phase transition from γ‐Fe₂O₃ to α‐Fe₂O₃ and to Fe₃O₄ under different annealing conditions while maintaining the 3D structure and open porosity. These new ensemble structures exhibit high catalytic activity and stability for the selective reduction of aryl and alkyl nitro compounds to the corresponding aryl amines and oximes, even in large‐scale synthesis.     

Conductivity,structure, and thermal properties of chitosan‐based polymer electrolytes with nanofillers

This paper focus on the effect of nanosize (<50 nm BET) inorganic alumina (Al₂O₃) filler on the structural, conductivity, and thermal properties of chitosan‐based polymer electrolytes. Films of chitosan and its complexes were prepared using solution‐casting technique. Different amounts of Al₂O₃ viz., 3, 4.5, 6, 7.5, 9, 12, and 15 wt% were added to the highest room temperature conducting sample in the chitosan–salt system, i.e. sample containing 60 wt% chitosan–40 wt% NH₄SCN. The conductivity value of the sample is 1.29 × 10^?4 S cm^?1. On addition of 6 wt% Al₂O₃ filler the ionic conductivity increased to 5.86 × 10^?4 S cm^?1. The amide and amino peaks in the spectrum of chitosan at 1636 and 1551 cm^?1, respectively, shift to lower wavenumbers on addition of salt. The glass transition temperature T_g for the highest conducting composite is 190°C. The increase in T_g with increase in more than 6 wt% filler content is attributed to the increase in degree of crystallinity as proven from X‐ray diffraction studies. Copyright © 2009 John Wiley & Sons, Ltd.     

Ferric Sulphate Hydrate–Catalyzed,Microwave‐Assisted Synthesis of 2,3‐Unsaturated O‐Glycosides via the Ferrier Reaction

Fe₂(SO₄)₃ · xH₂O catalyzes the Ferrier reaction of per‐O‐acetylated/benzylated glycals with alcohols to give 2,3‐unsaturated α‐glycosides in a few minutes under microwave irradiation.     

An investigation into synergistic effects of rare earth oxides on intumescent flame retardancy of polypropylene/poly (octylene‐co‐ethylene) blends

Synergistic effects of two kinds of rare earth oxides (REOs), neodymium oxide (Nd₂O₃) or lanthanum oxide (La₂O₃) on the intumescent flame retardancy of thermoplastic polyolefin (TPO) made by polypropylene/poly (octylene‐co‐ethylene) blends were investigated systemically by various methods. The limiting oxygen index (LOI) of flame retardant TPO (FRTPO) filled by 30 wt% intumescent flame retardants (IFR) composed of ammonium polyphosphate (APP) and pentaerythritol (PER) has been increased from 30 to 32.5 and 33.5 when 0.5 wt% of IFR was substituted by La₂O₃ and Nd₂O₃, respectively. Cone calorimetry tests also reveal the existence of synergistic effects. Thermalgravimetric analyses (TGA) demonstrate that the presence of REOs promotes the esterification and carbonization process in low‐temperature range while enhances the thermal stability of IFR and FRTPO in high‐temperature range. X‐ray diffraction (XRD) reveals that the interaction of Nd₂O₃ with IFR results in the formation of neodymium phosphate (NdP₅O₁₄) with high‐thermal stability. Thermal scanning rheological tests show that the presence of REOs increases complex viscosity of FRTPO in the temperature range of 190～300°C so as to suppress melt dripping but decreases the complex viscosity and increases the loss factors tan δ in temperature range of 300～400°C to make the carbonaceous strucuture more flexible and viscous to resist stress, expand better and keep intact. Copyright © 2009 John Wiley & Sons, Ltd.     

Green one‐pot preparation of α‐Fe2O3@carboxyl‐functionalized yeast composite with high adsorption and catalysis properties for removal of methylene blue

Herein, the α‐Fe₂O₃@carboxyl‐functionalized yeast composite (α‐F@CFYC) was synthesized by direct oxidation of yeast with K₂FeO₄ and used as a novel adsorbent/heterogeneous Fenton catalyst for removal of methylene blue (MB). The obtained α‐F@CFYC was fully characterized by scanning electron microscopy, EDX, X‐ray diffraction analysis, Fourier‐transform infrared, thermogravimetry, and X‐ray photoelectron spectroscopy, respectively, and the corresponding results showed that α‐Fe₂O₃ nanoparticles were successfully obtained and deposited on yeast surface, as well as more functional groups were introduced/exposed on yeast surface. Furthermore, various influence parameters (eg, contact time, initial pH, and MB concentration) on the adsorption/catalysis ability of α‐F@CFYC for MB have been investigated in detail under ambient conditions. As a result, owing to the synergetic effect of the loaded α‐Fe₂O₃ and the introduced/exposed functional groups on yeast surface, the as‐obtained α‐F@CFYC exhibited high adsorption capacities and good catalysis degradation properties for MB.     

Core–Shell α‐Fe2O3@α‐MoO3 Nanorods as Lithium‐Ion Battery Anodes with Extremely High Capacity and Cyclability

α‐Fe₂O₃ nanoparticles are uniformly coated on the surface of α‐MoO₃ nanorods through a two‐step hydrothermal synthesis method. As the anode of a lithium‐ion battery, α‐Fe₂O₃@α‐MoO₃ core–shell nanorods exhibit extremely high lithium‐storage performance. At a rate of 0.1 C (10 h per half cycle), the reversible capacity of α‐Fe₂O₃@α‐MoO₃ core–shell nanorods is 1481 mA h g^?1 and a value of 1281 mA h g^?1 is retained after 50 cycles, which is much higher than that retained by bare α‐MoO₃ and α‐Fe₂O₃ and higher than traditional theoretical results. Such a good performance can be attributed to the synergistic effect between α‐Fe₂O₃ and α‐MoO₃, the small size effect, one‐dimensional nanostructures, short paths for lithium diffusion, and interface spaces. Our results reveal that core–shell nanocomposites have potential applications as high‐performance lithium‐ion batteries.     

Hydrothermal Synthesis and Properties of Controlled α‐Fe2O3 Nanostructures in HEPES Solution

A facile, template‐free, and environmentally friendly hydrothermal strategy was explored for the controllable synthesis of α‐Fe₂O₃ nanostructures in HEPES solution (HEPES=2‐[4‐(2‐hydroxyethyl)‐1‐piperazinyl]ethanesulfonic acid). The effects of experimental parameters including HEPES/FeCl₃ molar ratio, pH value, reaction temperature, and reaction time on the formation of α‐Fe₂O₃ nanostructures have been investigated systematically. Based on the observations of the products, the function of HEPES in the reaction is discussed. The different α‐Fe₂O₃ nanostructures possess different optical, magnetic properties, and photocatalytic activities, depending on the shape and size of the sample. In addition, a novel and facile approach was developed for the synthesis of Au/α‐Fe₂O₃ and Ag/α‐Fe₂O₃ nanocomposites in HEPES buffer solution; this verified the dual function of HEPES both as reductant and stabilizer. This work provides a new strategy for the controllable synthesis of transition metal oxide nanostructures and metal‐supported nanocomposites, and gives a strong evidence of the relationship between the property and morphology/size of nanomaterials.     

Detection of Dexamethasone Sodium Phosphate in Blood Plasma: Application of Hematite in Electrochemical Sensors

We studied sensor application of a graphene oxide and hematite (α‐Fe₂O₃/GO) composite electrode well‐characterized by the SEM and XRD. Through differential pulse voltammetry (DPV), oxidation of dexamethasone sodium phosphate (DSP) was studied at the surface of a glassy carbon electrode (GCE) modified with graphene oxide nanosheets (GO) and the α‐Fe₂O₃/GO composite. The values of the transfer coefficient (α) and the diffusion coefficient (D) of DSP were 0.5961 and 4.71×10^?5 cm² s^?1 respectively. In the linear range of 0.1–50 μM, the detection limit (DL) was 0.076 μM. In the second step, a GCE was modified with α‐Fe₂O₃/GO composite and the DSP measurement step was repeated to analyzed and compare the effects of hematite nanoparticles present on graphene oxide surfaces. According to the results, α and D were 0.52 and 2.406×10^?4 cm² s^?1 respectively and the DL was 0.046 μM in the linear range of 0.1–10.0 μM. The sensor is simple, inexpensive and uses blood serum.     

Copper(II) Schiff Base Complex Immobilized on Superparamagnetic Fe3O4@SiO2 as a Magnetically Separable Nanocatalyst for Oxidation of Alkenes and Alcohols

A new heterogeneous catalyst containing a copper(II) Schiff base complex covalently immobilized on the surface of silica‐coated Fe₃O₄ nanoparticles (Fe₃O₄@SiO₂‐Schiff base‐Cu(II)) was synthesized. Characterization of this catalyst was performed using various techniques. The catalytic potential of the catalyst was investigated for the oxidation of various alkenes (styrene, α‐methylstyrene, cyclooctene, cyclohexene and norbornene) and alcohols (benzyl alcohol, 3‐methoxybenzyl alcohol, 3‐chlorobenzyl alcohol, benzhydrol and n ‐butanol) using tert ‐butyl hydroperoxide as oxidant. The catalytic investigations revealed that Fe₃O₄@SiO₂‐Schiff base‐Cu(II) was especially efficient for the oxidation of norbornene and benzyl alcohol. The results showed that norbornene epoxide and benzoic acid were obtained with 100 and 87% selectivity, respectively. Moreover, simple magnetic recovery from the reaction mixture and reuse for several times with no significant loss in catalytic activity were other advantages of this catalyst     

Surviving High‐Temperature Calcination: ZrO2‐Induced Hematite Nanotubes for Photoelectrochemical Water Oxidation

Nanotubular Fe₂O₃ is a promising photoanode material, and producing morphologies that withstand high‐temperature calcination (HTC) is urgently needed to enhance the photoelectrochemical (PEC) performance. This work describes the design and fabrication of Fe₂O₃ nanotube arrays that survive HTC for the first time. By introducing a ZrO₂ shell on hydrothermal FeOOH nanorods by atomic layer deposition, subsequent high‐temperature solid‐state reaction converts FeOOH‐ZrO₂ nanorods to ZrO₂‐induced Fe₂O₃ nanotubes (Zr‐Fe₂O₃ NTs). The structural evolution of the hematite nanotubes is systematically explored. As a result of the nanostructuring and shortened charge collection distance, the nanotube photoanode shows a greatly improved PEC water oxidation activity, exhibiting a photocurrent density of 1.5 mA cm⁻² at 1.23 V (vs. reversible hydrogen electrode, RHE), which is the highest among hematite nanotube photoanodes without co‐catalysts. Furthermore, a Co‐Pi decorated Zr‐Fe₂O₃ NT photoanode reveals an enhanced onset potential of 0.65 V (vs. RHE) and a photocurrent of 1.87 mA cm⁻² (at 1.23 V vs. RHE).     

Ceramic Filter Balls Loaded with α-Fe2O3 and Their Application to NH3-N Wastewater Treatment

Hydrolysis reaction of Fe(NO₃)₃ at a high temperature in the presence of urea as the homogeneous precipitant was studied. With the prepared ceramic filter balls loaded with α-Fe₂O₃ after high temperature calcination, the loading of α-Fe₂O₃ on the porous ceramic filter balls from Fe(NO₃)₃ solutions of different concentrations and mechanical stability of the loaded α-Fe₂O₃ were studied. The product was characterized using XRD and SEM. Adsorption experiments were conducted to evaluate the performance of the product in adsorbing NH₃-N. It turned out that the specific surface area of the ceramic filter balls loaded with α-Fe₂O₃ had increased to 36.5387 m²/g from original 4.6127 m²/g. When the concentration of Fe(NO₃)₃ was 0.40 mol/L, the loading of α-Fe₂O₃ on the ceramic filter balls accounted for 8.4% of the total mass of the adsorbent and α-Fe₂O₃ was adsorbed on the filter balls very well. The adsorption isotherm of NH₃-N on the ceramic filter ball adsorbent loaded with α-Fe₂O₃ was of Langmuir type. The saturated adsorption capacity was 3.33 mg/L, and the adsorption constant K was 0.1873. NH₃-N was adsorbed by α-Fe₂O₃ more easily, which was a kind of specific adsorption.