Porous magnetite (Fe 3 O 4 ) nanospheres composed of primary nanocrystals have been successfully synthesized by solvothermal method with FeCl 3 3 6H 2 O serving as the single iron resource, polyvinylpyrrolidone (PVP) as the capping agent, and sodium acetate as the precipitation agent. To understand the formation mechanism of the porous Fe 3 O 4 nanospheres, the reaction conditions such as the concentration of the precursor, capping agent, precipitation agent, the reaction temperature, and reaction time were investigated. The characterization of the asprepared product was identified with transmission electronic microscopy (TEM), field emission scanning electronic microscopy (FE-SEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), N 2 adsorptionÀdesorption technique, and Fourier transform infrared spectroscopy (FTIR). The results indicate that the porous Fe 3 O 4 nanospheres display excellent magnetic properties at room temperature, which allows them to be easily separated from the reaction system with the help of external magnet when they serve as catalysts. Catalytic activity studies show that the as-prepared porous Fe 3 O 4 nanospheres are highly effective catalysts for the degradation of xylenol orange (XO) in aqueous solution with H 2 O 2 as oxidant. The degradation reaction is first-order, its rate constant at room temperature being 0.056 min À1 . Furthermore, the catalytic activity of Fe 3 O 4 nanospheres decreases very slightly after seven cycles of the catalysis experiment. Therefore, porous Fe 3 O 4 nanospheres can serve as effective recyclable catalysts for the degradation of XO.

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A simple hydrothermal process for fabrication of hematite (α-Fe2O3) nanostructures with narrow size distribution was developed by using PVP as surfactant and NaAc as precipitation agent. The influence of experimental parameters including the concentration of the precursor, precipitation agent, stabilizing agent, and reaction time was systematically investigated to study the possible formation mechanism of α-Fe2O3. Finally, the electrochemical properties of the obtained hematite particles were studied using cyclic voltammetry and galvanostatic charge–discharge measurement by a three-electrode system. The results reveal that their specific capacitances are related to their sizes. By virtue of large surface area, the as-prepared hematite nanoparticles can present the highest capacitance (340.5 F·g–1) and an excellent long cycle life within the operated voltage window (−0.1 to 0.44 V), demonstrating that the as-prepared hematite nanoparticles can serve as one of the most excellent electrode materials for supercapacitors.

In this work, we reported a facile approach to prepare a uniform copper ferrite nanoparticle-attached graphene nanosheet (CuFe2O4-GN). A one-step solvothermal method featuring the reduction of graphene oxide and formation of CuFe2O4 nanoparticles was efficient, scalable, green, and controllable. The composite nanosheet was fully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), which demonstrated that CuFe2O4 nanoparticles with a diameter of approximately 100 nm were densely and compactly deposited on GN. To investigate the formation mechanism of CuFe2O4-GN, we discussed in detail the effects of a series of experimental parameters, including the concentrations of the precursor, precipitation agent, stabilizer agent, and graphene oxide on the size and morphology of the resulting products. Furthermore, the electrochemical properties of the CuFe2O4-GN composite were studied by cyclic voltammetry and galvanostatic charge-discharge measurements. The composite showed high electrochemical capacitance (576.6 F·g(-1) at 1 A·g(-1)), good rate performance, and cycling stability. These results demonstrated that the composite, as a kind of electrode materials, had a high specific capacitance and good retention. The versatile CuFe2O4-GN holds great promise for application in a wide range of electrochemical fields because of the remarkable synergistic effects between CuFe2O4 nanoparticles and graphene.

This review focuses on the synthesis and application of nanostructured composites containing magnetic nanostructures and carbon-based materials. Great progress in fabrication of magnetic carbon nanocomposites has been made by developing methods including filling process, template-based synthesis, chemical vapor deposition, hydrothermal/solvothermal method, pyrolysis procedure, sol-gel process, detonation induced reaction, self-assembly method, etc. The applications of magnetic carbon nanocomposites expanded to a wide range of fields such as environmental treatment, microwave absorption, magnetic recording media, electrochemical sensor, catalysis, separation/recognization of biomolecules and drug delivery are discussed. Finally, some future trends and perspectives in this research area are outlined.