One-pot polyelectrolyte assisted hydrothermal synthesis of NiFe 2 O 4 -reduced graphene oxide nanocomposites with improv
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Reduced graphene oxide–nickel ferrite (RGO–NiFe2O4) has been successfully synthesized by the hydrothermal method in the presence of poly(diallyldimethylammonium chloride) (PDDA). PDDA is used both as a reducing agent and as a stabilizer. The prepared RGO–NiFe2O4 nanocomposites have been thoroughly characterized by spectroscopic (Fourier-transform infrared spectroscopy, Raman spectroscopy, and x-ray diffraction) and thermogravimetric analysis. Microscopy techniques (scanning electron microscopy, atomic force microscopy, and transmission electron microscopy) were used to probe the morphological structures as well as to investigate the exfoliation of RGO sheets. It is interesting to find that RGO–NiFe 2 O4 nanocomposites exhibited much better electrochemical capability than NiFe 2 O4. In addition, the as-prepared RGO–NiFe2O4 nanocomposites can effectively remove methyl orange from water under ultraviolet light irradiation, which can be used as novel photocatalysts for environmental protection.
I. INTRODUCTION
Graphene, a two-dimensional monolayer of sp2-hybridized carbon atoms, has attracted enormous interest in recent years due to its unusual mechanical strength, ultralarge specific surface area, and extraordinary electrical properties.1–3 Several procedures, including mechanical exfoliation, liquid exfoliation, chemical vapor deposition, and the chemical method, have been developed for the preparation of graphene.4–6 Among them, chemical method is a very good method when graphite oxide (GO) is used as the raw material because of its simplicity and mass productivity.7 Generally, GO can form stable dispersion in water because of its high rate of oxygen-containing groups. However, if the oxygen functionalities are removed by reduction to yield reduced graphene oxide (RGO), it would immediately lose its water dispersibility, then aggregate, and eventually precipitate due to the prominent interlayer conjugate interaction of RGO. Thus, it is essential to modify the GO and RGO surface to enhance its dispersion in different kinds of solvents.8 From both fundamental science and technological applications, it is beneficial to devise synthetic methodologies to add specific functionalities to graphene, thus providing them with new and tunable electrochemical and photocatalytic properties. Recent results demonstrate that doping is a good method to harvest the full potential a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.250 J. Mater. Res., Vol. 29, No. 18, Sep 28, 2014
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applications of graphene sheets.9 Nickel ferrite (NiFe2O4) nanocrystalline material is one of the most important ferrites because of their promising applications in power and signal transformation, storage devices, microwave devices, gas sensors, ferrofluids, and catalysts. Considerable attention has been paid on NiFe2O4 with different morphologies and properties.10 Polyelectrolytes can improve stability with a stronger repulsive force through either steric or ele
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