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In this study, Fe3O4/graphene nanosheets (Fe3O4/GNSs) nanocomposite was synthesized by using the combination of simple hydrothermal treatment and calcination. It was found Fe3O4 nanoparticles with diameter of 15 nm were synthesized and uniformly dispersed on the surface of graphene nanosheets (GNSs). When our cost-effective Fe3O4/GNSs was employed as an anode material in lithium-ion battery, it exhibited a high reversible capacity of 740 mA h/g after 100 cycles at a current density of 100 mA/g. This high performance is attributed to the following reasons: (i) the nanoparticles down to 15 nm act not only as electrochemical active sites but as spacers, (ii) GNSs that carry the nanoparticles enhance electron transport by providing conductive pathways, and (iii) Fe3O4/GNSs creates a three-dimensional architecture that effectively facilitates ion diffusion and lithium-ion storage. This finding would open up an efficient route for synthesis and application of GNSs hybrids as anode materials for lithium-ion batteries of high performance.

A newly designed N-doped porous carbon with magnetic nanoparticles formed in situ (RHC-mag-CN) was fabricated through simple impregnation then polymerization and calcination. The doped nitrogen in RHC-mag-CN was in the form of graphite-type layers with the composition of CN. The resultant nanocomposite maintained a high surface area of 1136 m2 g1 with 18.5 wt% magnetic nanoparticles (Fe3O4 and Fe) inside, which showed a saturation magnetization (Ms) of 22 emu/g. When used as an adsorbent, the RHC-mag-CN demonstrated a very quick adsorption property for the removal of Cr(VI), during which 92% of Cr(VI) could be removed within 10 min for dilute solutions at 2 g L1 adsorbent dose. The high adsorption capacity (16 mg g1) is related to the synergetic effects of physical adsorption from the surface area and chemical adsorption from complexation reactions between Cr(VI) and Fe3O4. Importantly, the basic CNs in RHC-mag-CN increase its negative charge density and simultaneously increase the adsorption of metallic cations, such as Cr3þ formed in the acid solution from the reduction of Cr(VI). The formation of magnetic nanoparticles inside not only supplies complexing sites for the adsorption of Cr(VI), but also shows perfect magnetic separation performance from aqueous solution.

"Nano tungsten oxide (WO3) particles were synthesized on the surface of graphene (GR) sheets by using a simple sonochemical method. The obtained composite, WO3@GR, was characterized by X-ray diffraction, N-2 adsorption/desorption analysis, thermo-gravimetric analysis, Raman spectroscopy and UV-vis diffuse reflectance spectra measurements. It was found that chemical bonds between the nano WO3 particles and the GR sheets were formed. The average particle size of the WO3 was evidenced to be around 12 nm on the GR sheets. When used as photocatalyst for water splitting, the amount of evolved O-2 from water for the WO3@GR composite with 40 wt% GR inside was twice and 1.8 times as much as that for pure WO3 and mixed-WO3/GR, respectively. The excellent photocatalytic property of the WO3@GR composite is due to the synergistic effects of the combined nano WO3 particles and GR sheets. The sensitization of WO3 by GR enhances the visible light absorption property of WO3@GR. The chemical bonding between WO3 and GR minimizes the interface defects, reducing the recombination of the photo-generated electron-hole pairs. Furthermore, the GR sheets in the WO3@GR composite enhance electrons transport by providing low resistance conduction pathways, leading to improved photo-conversion efficiency. The methodology opens up a new way of obtaining photoactive GR-semiconductor composites for photodissociating water under visible light."

Using a kind of plant biomass (coconut shell) as template and carbon precursor, we prepare biomorphic porous carbon materials for electromagnetic interference shielding application. The carbon frameworks of the porous carbon materials are modified by in situ formation of graphitic nanostructures in a catalytic graphitization process, leading to well-tailored electrical conductivity of the resultant materials. The modified porous carbon materials exhibit shielding effectiveness of 40 dB over the X-band frequency, and the shielding by absorption is as high as 91%, indicating an absorptiondominant shielding mechanism. The high absorption contribution is attributed to the coupled effects of the biomorphic porous structures and graphitic nanostructures of the porous graphitic carbon.

"A high-performance anode material was prepared from a hierarchically structured activated carbon which contains in situ graphene and nano-graphite. The activated carbon was immersed in a solution of SnCl(2)center dot 2H(2)O and subjected to ultrasound. As a result, nanoparticles of SnO(2) were uniformly deposited on the surface of the activated carbon. The composite material was then coated with a thin layer of carbon by soaking it in a sucrose solution, followed by carbonization of the adsorbed sucrose at 500 degrees C. The resulting composite showed an outstanding high-rate cycling performance that can deliver an initial discharge capacity of 1417 mAh g(-1) and maintain a discharge capacity of more than 400 mAh g(-1) after 100 cycles at a high current density of 1000 mA g(-1). This outstanding electrochemical performance is likely to be related to a unique combination of the excellent electrical conductivity of the activated carbon with graphite layers formed inside, its hierarchical pore structure which enhances lithium-ion transportation, and the carbon coating which alleviates the effects of volume changes, shortens the distance for Li(+) diffusion, facilitates the transmission of electrons, and keeps the structure stable."

Using ultrasonication we succeed in a controlled incorporation of TiO2 nanoparticles on the graphene layers homogeneously in a few hours. The average size of the TiO2 nanoparticles was controlled at around 4–5 nm on the sheets without using any surfactant, which is attributed to the pyrolysis and condensation of the dissolved TiCl4 into TiO2 by ultrasonic waves. The photocatalytic activity of the resultant graphene–TiO2 composites containing 25 wt.% TiO2 is better than that of commercial pure TiO2. This is partly due to the extremely small size of the TiO2 nanoparticles and partly due to the graphene–TiO2 composite structure consisting of homogeneous dispersion of crystalline TiO2 nanoparticles on the graphene sheets. As the graphene in the composites has a very good contact with the TiO2 nanoparticles it enhances the photo-electron conversion of TiO2 by reducing the recombination of photo-generated electron–hole pairs.

Cu-doped photonic crystal (PC) WO3 replicas from Morpho butterfly wings have been prepared by using a combined sol–gel templating and calcination method. The exact replications in the Cu-doped PC WO3 replicas at the micro- and nanoscales were confirmed by scanning electronic microscopy (SEM) and transmission electron microscopy (TEM). A combination of X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Raman and X-ray photoelectron spectra (XPS) measurements revealed that copper does not form clusters, but is randomly distributed inside the WO3 matrix lattice. The optical properties of the Cu-doped PC WO3 replica as well as the Morpho butterfly wing template were investigated by using reflectance spectroscopy, and it was found that the reflected light chromaticity of the Cu-doped PC WO3 replica was inherited from the PC Morpho butterfly wings. Cu-doped WO3 replicas without photonic crystal structures (Cu-W replica) were also fabricated in the same way as the Cu-doped PC WO3 replica but using Euploea mulciber butterfly wings as the template. Chemical sensors fabricated from the Cu-doped PC WO3 as well as the non-PC Cu-doped WO3 replicas were tested for a range of gases: (CH3)3N (TMA), NH3, C2H5OH, HCHO, CH3OH, acetone, H2, CO and NO2 and they showed a high selectivity for TMA. The sensitivity of the Cu-doped PC WO3 replica sensors can reach up to 2.0 for a trimethylamine concentration as low as 0.5 ppm at 290 °C. The high sensitivity of the Cu-doped WO3 replica sensors to TMA is attributed to the catalytic effect of Cu on the reaction between the testing gas and the oxide surface. Furthermore, the Cu-doped PC WO3 replica sensor is twice as sensitive as the Cu-doped non-PC WO3 replica to trimethylamine. This may be explained by the photonic crystal structure of the Cu-doped PC WO3.