Synthesis of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Au core–shell nanoparticles

A new two-step synthesis of Fe₃O₄@Au core–shell nanoparticles stabilized in polyethylene glycol is described. The nanoparticles were characterized by transmission electron microscopy, X-ray powder diffraction, UV and Mössbauer spectroscopy. Fe₃O₄@Au nanoparticles featured both optical properties (they featured a plasmon resonance band) and magnetic properties (they responded to an external magnetic field), typical of individual gold and magnetite nanoparticles, respectively.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>·C and ZrO<Subscript>2</Subscript>·Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>·C nanostructures: Synthesis and characterization

A procedure for the synthesis of carbon-encapsulated multilayer magnetite and zirconium oxide–magnetite nanoparticles that form porous nanostructures, for use as biocompatible sorbents, is proposed. The properties, composition, dimensions, particle shapes, surface morphology, and magnetic characteristics of the products are studied.     

Magnetically nano core–shell Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Cu(OH)<Subscript>x</Subscript>: a highly efficient and reusable catalyst for rapid and green reduction of nitro compounds

Magnetically separable nano core–shell Fe₃O₄@Cu(OH)_x with 22 % Cu content was prepared by the addition of sodium hydroxide to a mixture of CuCl₂·2H₂O and nano Fe₃O₄ in water. Characterization of the impregnated copper hydroxide was carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD) atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), value stream mapping (VSM) and Brunauer–Emmett–Teller (BET) analysis. The core–shell nanocatalyst exhibited the excellent catalytic activity toward reduction of various nitro compounds to the corresponding amines with NaBH₄. All reactions were carried out in H₂O (55–60 °C) within 3–15 min to afford amines in high to excellent yields. Reusability of core–shell Cu(OH)_x catalyst was examined 9 times without significant loss of its catalytic activity.     

Synthesis of core–shell structured Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@carboxymethyl cellulose magnetic composite for highly efficient removal of Eu(III)

In this work, a carboxymethyl cellulose (CMC)-modified Fe₃O₄ (denoted as Fe₃O₄@CMC) composite was synthesized via a simple co-precipitation approach. Fourier transform infrared spectroscopy, zeta potential and thermogravimetric analysis results indicated that CMC was successfully coated on the Fe₃O₄ surfaces with a weight percent of ~30 % (w/w). The prepared Fe₃O₄@CMC composite was stable in acidic solution and could be easily collected with the aid of an external magnet. A batch technique was adopted to check the ability of the Fe₃O₄@CMC composite to remove Eu(III) as a function of various environmental parameters such as contact time, solution pH, ionic strength, solid content and temperature. The sorption kinetics process achieved equilibrium within a contact time of 7 h. The sorption isotherms were well simulated by the Langmuir model, and the maximum sorption capacity at 293 K was calculated to be 2.78 × 10^?4 mol/g, being higher than the series of adsorbent materials reported to date. The ionic strength-independent sorption behaviors, desorption experiments by using ammonium acetate and disodium ethylenediamine tetraacetate as well as the spectroscopic characterization suggested that Eu(III) was sequestrated on the hydroxyl and carboxyl sites of Fe₃O₄@CMC via inner-sphere complexation. Overall, the Fe₃O₄@CMC composite could be utilized as a cost-effective adsorbent for the removal of trivalent lanthanide/actinides (e.g., ^152+154Eu, ²⁴¹Am and ²⁴⁴Cm) from radioactive wastewater.     

Effects of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> on the crystallization and structure of CaO–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> glass ceramics

Radiation-induced degradation of the weakly and strongly 4-vinylpyridine basic ion exchange resins by gamma radiolysis was investigated in the presence of air and liquid water. This study is focused on evaluating the radiolytic gases (H₂, CO, CO₂ and CH₄) and liquid products (water-solute TOC and NH₄ ⁺). The weakly basic resin yielded lower amounts of H₂ and CO and higher amounts of CO₂ than those of the strongly basic resin. Moreover, the strong basic resin tended to yield greater amounts of NH₄ ⁺. Resins were characterized by the FTIR spectroscopy technique and the results showed that the resins structures are relatively stable.     

Preparation and adsorption properties of magnetic Co<Subscript>0.5</Subscript>Ni<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>–chitosan nanoparticles

Magnetic chitosan microspheres were prepared by the emulsification cross-linking technique in the presence of glutaraldehyde as cross-linking agent, liquid paraffin as dispersant, and Span-80 as emulsifier. The optimal cross-linking time and Co_0.5Ni_0.5Fe₂O₄: chitosan ratio were determined. The morphology of particles was studied by different techniques. The adsorption characteristics were studied and the effect exerted by the initial concentration of methyl orange, the time of cross-linking, and the amount of the adsorbent was determined. It is found that the product obtained at the Co_0.5Ni_0.5Fe₂O₄: chitosan ratio 1: 4 and the crosslinking time 5 h has the uniform morphology. At room temperature, the Co_0.5Ni_0.5Fe₂O₄–chitosan magnetic composite has maximal adsorption for methyl orange at the dosage 20 mg.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticle-bonded β-cyclodextrin as an efficient and magnetically retrievable catalyst for the preparation of β-azido alcohols and β-hydroxy thiocyanate

A novel Fe₃O₄ nanoparticle-bonded β-cyclodextrin (β-CD@MNP) has been synthesized and characterized by scanning electron microscopy, vibrating sample magnetometry, and thermogravimetric analysis. It is found that the nanoparticles can be used as an efficient and magnetically retrievable nanocatalyst for the preparation of β-azido alcohols and β-hydroxy thiocyanates under ultrasound irradiation.     

Reduction of Oxide Mixtures of (Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> + CuO) and (Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> + Co<Subscript>3</Subscript>O<Subscript>4</Subscript>) by Low-Temperature Hydrogen Plasma

The paper presents experimental results pertaining to the reduction of oxide mixtures namely (Fe₂O₃ + CuO) and (Fe₂O₃ + Co₃O₄), by low-temperature hydrogen plasma in a microwave hydrogen plasma set-up, at microwave power 750 W and hydrogen flow rate 2.5 × 10^?6 m³ s^?1. The objective was to examine the effect of addition of CuO or Co₃O₄, on the reduction of Fe₂O₃. In the case of the Fe₂O₃ and CuO mixture, oxides were reduced to form Fe and Cu metals. Enhancement of reduction of iron oxide was marginal. However, in the case of the Fe₂O₃ and Co₃O₄ mixture, FeCo alloy was formed within compositions of Fe₇₀Co₃₀, to Fe₃₀Co₇₀. Since the temperature was below 841 K, no FeO formed during reduction and the sequence of Fe₂O₃ reduction was found to be Fe₂O₃ → Fe₃O₄ → Fe. Reduction of Co₃O₄ preceded that of Fe₂O₃. In the beginning, the reduction of oxides led to the formation of Fe–Co alloy that was rich in Co. Later Fe continued to enter into the alloy phase through diffusion and homogenization. The lattice strain of the alloy as a function of its composition was measured. In the oxide mixture in which excessive amount of Co₃O₄ was present, all the Co formed after reduction could not form the alloy and part of it appeared as FCC Co metal. The crystallite size of the alloy was in the range of 22–30 nm. The crystal size of the Fe–Co alloy reduced with an increase in Co concentration.     

Synthesis of TCPP–Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@S/RGO and its application for purification of water

A one-step green-chemistry method was applied to prepare sulfur/reduced graphene oxide (S/RGO). The synthesized S/RGO was modified by 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) and Fe₃O₄ nanoparticles to form TCPP–Fe₃O₄@S/RGO. The prepared composites were investigated by X-ray diffraction (XRD) analysis, Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX) mapping, and transmission electron microscopy (TEM) and scanning electron microscopy (SEM) imaging. Diffuse reflectance spectroscopy (DRS) was used to determine the photocatalytic ability of S/RGO and TCPP–Fe₃O₄@S/RGO. In addition, photocatalytic degradation of a hazardous dye (methylene blue) by the TCPP–Fe₃O₄@S/RGO composite under visible-light irradiation is reported. The results demonstrate synthesis of TCPP–Fe₃O₄@S/RGO by an environmentally friendly method with excellent degradation effect.     

Formation of solid solutions of multiferroics in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The sequence of phases appearance during the formation of Bi_1–xNd_xFeO₃ solid solutions in powder oxides mixtures of bismuth, neodymium, and iron has been determined. It has been shown that the closeness of the reaction mixture composition to that of the individual compound (BiFeO₃ or NdFeO₃) is essential for the realization of the series of phase transformations yielding solid solutions of multiferroics Bi_1–xNd_xFeO₃ as the final product, due to the prevalence of various interphase contacts in the starting reaction zone.     

Distribution of niobium and lanthanum between two immiscible melts in the system LaPO<Subscript>4</Subscript>–SiO<Subscript>2</Subscript>–NaF–Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

The system LaPO₄–SiO₂–NaF–Nb₂O₅–Fe₂O₃ is characterized by immiscibility fields in the liquid state region. Addition of iron expands fields of immiscibility of melts and decreases the temperature of their coexistence. A fraction of 87–90% of niobium is extracted into iron silicate melt, and 92–98% of lanthanum is extracted into phosphate salt melt.     

Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanorods–graphene composites as catalysts for rechargeable zinc-air battery

Composite of Co₃O₄ nanorods with reduced graphene oxide (RG-Co₃O₄) for rechargeable zinc-air battery was prepared by a facile method. The Co₃O₄ nanorods with a length of 1–2 μm were homogeneously distributed on the surface of plicated graphene nanosheets. The samples were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The RG-Co₃O₄ composite showed better electrode potential and higher electrical conductivity compared with pure Co₃O₄. The zinc-air battery can be reversibly charged and discharged for hundred cycles with a good cycle performance. The improved battery performance of RG-Co₃O₄ can be attributed to the synergistic coupling effect between the graphene sheets and Co₃O₄.     

ZnO–Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>–Au Hybrid Composites for Thioanisole Oxidation Under Visible Light: Experimental and Theoretical Studies

Organic sulfides are present in many materials such as coal, organic polymers, and xenobiotics and cause severe pollution problems during disposal, and their oxidation is essential from the environmental point of view. ZnO and ZnO–Fe₃O₄–Au NPs were prepared, and characterized by analytical methods (XRD, TEM, HRTEM, XPS and Confocal Microscope Analysis) for employment as photo-catalysts for the oxidation of thioanisole under visible light. A considerable visible light photo-oxidation of sulfur compound was observed in the presence of ZnO–Fe₃O₄–Au NPs, where the content Fe₃O₄ facilitates its isolation and recovery from the reaction medium by an external magnet for reuse in the oxidation. The oxidation of thioanisole was monitored spectroscopically, and was found to follow first order kinetics in the substrate, for which a possible mechanism is proposed. Density functional theory was used to analyze the oxidation pathway in order to predict the rate limiting step in the reaction since the sulfoxidation through sulfide radical cation >S^+· → >S=O is important biotechnologically and environmentally.     

Sol–gel synthesis and characterization of polycrystalline GdFeO<Subscript>3</Subscript> and Gd<Subscript>3</Subscript>Fe<Subscript>5</Subscript>O<Subscript>12</Subscript> thin films

Thin films of the perovskite and garnet structured gadolinium ferrites GdFeO₃ and Gd₃Fe₅O₁₂ have been synthesized by a sol–gel method, based on stoichiometric mixtures of acetyl acetone chelated Gd³⁺ and Fe³⁺ dissolved in 2-methoxy ethanol. After spin coating onto Si wafers, and heating in air at 700 °C for 20 h, neatly grown essentially single phase films were obtained. From X-ray photoelectron spectroscopy an iron deficiency is observed in the uppermost layer of both films, implying that the crystallites preferably end in planes rich in Gd and O but not in Fe. The films were also characterized by X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, and magnetic measurements.     

Synthesis and properties of magnetic superhydrophobic mesoporous Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> composites

Ways to obtain Fe₂O₃–SiO₂ iron-containing silica composites with organized mesoporous structure (MCM-41) and large specific surface area (up to 1476 m² g^–1) were considered. The influence exerted by the method used to synthesize the materials on their structure, texture characteristics, particle size, and magnetic properties were studied. The aggregative stability of samples was examined. It was shown that treatment of the resulting composites with compounds from the chlorosilane group affects their hydrophobic properties.     

Thermal analysis study of LiFeO<Subscript>2</Subscript> formation from Li<Subscript>2</Subscript>CO<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> mechanically activated reagents

Series of n-octadecane/expanded graphite composite phase-change materials (PCMs) with different mass ratio were prepared using n-octadecane as PCMs, expanded graphite as multi-porous supporting matrix through vacuum impregnation method. Microstructure, crystallization properties, energy storage behavior, thermal cycling property and intelligent temperature-control performance of the composite PCMs were investigated. Results show that the composite PCMs have a good energy storage property. The melting enthalpy and crystallization enthalpy can reach 164.85 and 176.51 J g^?1, respectively. Furthermore, the good thermal conductivity of expanded graphite reduces the super-cooling degree of n-octadecane and endows the composite PCMs with fast thermal response rate and excellent thermal cycling stability. As a result, the phase-change temperatures and phase-change enthalpy almost have no change after 50 thermal-cooling cycles. The test of intelligent temperature-control performance shows that the electronic radiator filled with the composite PCMs possesses a high intelligent temperature-control performance, and its temperature can sustain in the range of 22–27.5 °C for about 6120 s. These results indicate that the prepared composite PCMs possess good comprehensive property and can be widely used in energy storage and thermal management systems.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> magnetic nanoparticles for bulk scale synthesis of 4′-chloro-2,2′:6′,2″-terpyridine

Terpyridines are unique class of functional compounds that is extensively spotlighted in diverse fields like synthesis of supramolecular chemistry, nanomaterials, medicinal chemistry intermediates, drugs and active pharmaceutical ingredients and so on. The key challenges for the production of terpyridine lie in the bulk scale synthesis of intermediates. The expansively used synthon for terpyridine synthesis is 4′-chloro-2,2′:6′,2″-terpyridine and their bulk scale synthesis under the ambient conditions using a Fe₃O₄@SiO₂ magnetic nanomaterial catalyst is investigated in the present work. In the protocol stabilized, ethyl-2-pinacolate and acetone were reacted in the presence of NaH to obtain 1,5-bis(2-pyridinyl) pentane-1,3,5-trione. The enolate of acetone is difficult to generate even with NaH and we used Fe₃O₄@SiO₂ to increase the rate of H₂ gas evolution. The triketone is cyclized with CH₃COONH₄ to obtain 2,6-bis(2-pyridinyl)-4-pyridine. This reaction proceeds quantitatively and the off-white solid was easy to isolate from the reaction medium. The subsequent aromatization was observed with PCl₅/POCl₃ and acidic silica gel promoted the product yield to reach ~78%. The crux of the present protocol is that it does not involve any column purification and significant yield of 4′-chloro-2,2′:6′,2″-terpyridine can be conveniently attained. The Fe₃O₄@SiO₂ aids in the stabilization of carbonyl on the solid support and abstraction of hydrogen from methyl group of acetone. The 40 nm sized Fe₃O₄@SiO₂ favored the maximum yield attributed to the density of active sites to promote the reactions. Due to high value nature of 4′-chloro-2,2′:6′,2″-terpyridine, the nominal 30% yield improvement achieved at the bulk scale gauges significant at the industrial scale.     

Preparation and characterization of rapid magnetic recyclable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript>@TiO<Subscript>2</Subscript>–Sn photocatalyst

Effective procedure to synthesize Fe₃O₄@SiO₂@TiO₂–Sn magnetically separable photocatalyst by a combination of co-precipitation, sol–gel and photodeposition methods was introduced. Products were characterized by XRD, SEM, VSM, EDS, DRS, TEM, ICP-OES and IR techniques. The dimensions of catalyst particle size were evaluated by scanning electron microscopy, and results approved nanoscale size for product. In addition, studying the magnetic nature by VSM analysis showed superparamagnetic properties for all samples. XRD pattern indicates that TiO₂ coated on Fe₃O₄@SiO₂ core well crystallized at 400 °C in anatase phase. Synthesized photocatalyst shows good photocatalytic performance in decolorization of rhodamine B aqueous solution. The composite nanoparticles showed high recycling efficiency and stability over five separation cycles.