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a b s t r a c tIron nanoparticles were produced using extracts of green tea leaves (GT-Fe NPs). The materials were characterized using TEM, SEM/EDX, XPS, XRD, and FTIR techniques and were shown to contain mainly iron oxide and iron oxohydroxide. The obtained nanoparticles were then utilized as a Fenton-like catalyst for decolorization of aqueous solutions containing methylene blue (MB) and methyl orange (MO) dyes. The related experiments investigated the removal kinetics and the effect of concentration for both MB and MO. The concentrations of dyes in aqueous solution were monitored using ultraviolet-visible (UV-vis) spectroscopy. The results indicated fast removal of the dyes with the kinetic data of MB following a second order removal rate, while those of MO were closer to a first order removal rate. The loading experiments indicated almost complete removal of both dyes from water over a wide range of concentration, 10-200 mg L −1 . Compared with iron nanoparticles produced by borohydride reduction, GT-Fe nanoparticles demonstrated more effective capability as a Fenton-like catalyst, both in terms of kinetics and percentage removal.

Atomically thick graphene layers produced from graphite reveal unique electro-thermal, and mechanical properties, [1][2][3][4][5][6][7] and are considered to have a wide range of applications in nanoelectronics, catalysis and biosensing. [1,3,[8][9][10] Graphene monolayers exhibiting exceptional electron/hole carrier mobility have been prepared by mechanical exfoliation of highly ordered pyrolytic graphite, [1,3] by epitaxial growth using chemical vapour deposition of hydrocarbons onto silicon carbide, [11] or via thermal fusion of polycyclic aromatic hydrocarbons.[12] These methods are constrained by low yields and processing limitations, and more practical approaches based on the chemical [6,12,13] or thermal [15,16] reduction of exfoliated sheets of oxidised graphite (graphene oxide, GO) have been developed. High yields of GO monolayers, 0.78 nm in thickness, can be readily prepared by treatment of graphite under strongly acidic and oxidising conditions. [17][18][19] The GO single sheets can be readily dispersed in water and mounted onto substrates using spin-, dip-and spray-coating techniques, and reduced in situ to produce isolated graphene monolayers or transparent 2D films [20][21][22][23][24] with conductivities ranging from as low as 2 S cm À1 , [20] or 23 S cm À1, [15] to a value of 550 S cm À1 for a 10 nm-thick film, [20] comparable with polycrystalline graphite (1250 S cm À1).[25] Alternatively, aqueous dispersions of GO oxide can be chemically reduced directly to produce aggregated sols of graphene sheets that can be assembled into graphene thin films with a typical conductivity of 72 S cm À1. [26] Moreover, by undertaking the reduction step in the presence of poly(sodium 4-styrenesulfonate), [13] or pyrene butyrate, [14] or exploiting electrostatic repulsions between adjacent sheets in an alkaline medium, [26] stable aqueous dispersions of coated graphene monolayers have been produced. Similar approaches have been used to prepare stable graphene dispersions in polar organic solvents by chemical reduction of GO sheets functionalized with hydrophobic residues such as alkylamines, [27] phenyl isocyanate [6] or anhydrous hydrazine. [28] Alternatively, Coleman and coworkers [29] have recently prepared graphene dispersions by ultrasonicating graphite powders in various solvents, for example, N-methylpyrrolidinone, followed by subsequent fractionation using low-speed centrifugation to produce sols comprising single and multilayered graphene sheets. Interestingly, thin films produced from the above dispersions showed conductivity values of $65 S cm À1, comparable to that of chemically reduced graphene oxide paper.Recent studies have demonstrated that hydrophobic carbon nanotubes (CNTs) can be successfully functionalized using single-stranded (ss) DNA to produce novel nanocomposites with potential applications in nanoelectronics and bionanotechnology. [30,31] Adsorption of the biomolecules onto the surface of the CNTs is facilitated by non-covalent p-p stacking interactions involving both purine and pyrimidi...

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