Lihong Qi

Graphene–Fe3O4 nanohybrids: Synthesis and excellent electromagnetic absorption properties

Graphene (G)–Fe3O4 nanohybrids were fabricated by first depositing β-FeOOH crystals with diameter of 3–5 nm on the surface of the graphene sheets. After annealing under Ar flow, β-FeOOH nanocrystals were reduced to Fe3O4 nanoparticles by the graphene sheets, and thus G–Fe3O4 nanohybrids were obtained. The Fe3O4 nanoparticles with a diameter of about 25 nm were uniformly dispersed over the surface of the graphene sheets. Moreover, compared with other magnetic materials and the graphene, the nanohybrids exhibited significantly increased electromagnetic absorption properties owing to high surface areas, interfacial polarizations, and good separation of magnetic nanoparticles. The maximum reflection loss was up to −40.36 dB for G–Fe3O4 nanohybrids with a thickness of 5.0 mm. The nanohybrids are very promising for lightweight and strong electromagnetic attenuation materials.

Three‐Dimensional Hierarchical Architectures Constructed by Graphene/MoS2 Nanoflake Arrays and Their Rapid Charging/Discharging Properties as Lithium‐Ion Battery Anodes

Charged up: Three-dimensional architectures constructed from graphene/MoS2 nanoflake arrays have been successfully fabricated by a one-step hydrothermal method. MoS2 nanoflakes with thicknesses less than 13 nm grow vertically on both sides of graphene sheets (see figure), which allows the architectures to be more stable during charging and discharging. Even at a high current density of 8000 mA g(-1), their discharge capacity is still up to 516 mA h g(-1).

Fe2O3/TiO2 tube-like nanostructures: synthesis, structural transformation and the enhanced sensing properties.

The paper describes for the first time the successful synthesis of Fe(2)O(3)/TiO(2) tube-like nanostructures, in which TiO(2) shell is of quasi-single crystalline characteristic and its thickness can be controlled through adjusting the added amount of aqueous Ti(SO(4))(2) solution. The characterization of samples obtained at different stages using transmission electron microscope indicates that the outer TiO(2) shell is changed gradually from amorphous and polycrystalline phase into quasi-single crystal under thermal actions through the Ostwald ripening process, accompanying the corrosion of the central parts of Fe(2)O(3) nanorods, and the formation of small particles separating each other, leading to the special core/shell nanorods. Furthermore, Fe(2)O(3)/TiO(2) tube-like nanostructures can be transformed into Fe(2)TiO(5) nanostructures after they are thermally treated at higher temperatures. Those nanostructures exhibit enhanced ethanol sensing properties with respect to the monocomponent. Our results imply that not only hollow nanostructures, but also a novel type of nanostructures can be fabricated by the present method for nanodevices.

Hierarchical nanosheet-based NiMoO4 nanotubes: synthesis and high supercapacitor performance

Hierarchical nanosheet-based NiMoO4 nanotubes were synthesized by a hydrothermal treatment and a subsequent in situ diffusion reaction method. The nanotubes with a high surface area of 128.5 m2 g−1 were composed of highly ordered ultrathin nanosheets with a thickness of less than 10 nm. When used as electrodes in electrochemical capacitors, the hierarchical nanotubes exhibited excellent electrochemical performances. The specific capacitance of the hierarchical nanotubes was up to 864 F g−1 at a current density of 1 A g−1. The results indicate that the hierarchical nanosheet-based NiMoO4 nanotubes are very promising for applications in energy storage and other electrochemical devices. Furthermore, the strategy presented here is facile, and may be expended as a typical method to synthesize other kinds of metal molybdate nanotubes.

Porous iron molybdate nanorods: in situ diffusion synthesis and low-temperature H2S gas sensing.

In the paper, we developed an in situ diffusion growth method to fabricate porous Fe2(MoO4)3 nanorods. The average diameter and the length of the porous nanorods were 200 nm and 1.2-4 μm, respectively. Moreover, many micropores existed along axial direction of the Fe2(MoO4)3 nanorods. In terms of nitrogen adsorption-desorption isotherms, calculated pore size was in the range of 4-115 nm, agreeing well with the transmission electron microscope observations. Because of the uniquely porous characteristics and catalytic ability at low temperatures, the porous Fe2(MoO4)3 nanorods exhibited very good H2S sensing properties, including high sensitivity at a low working temperature (80 °C), relatively fast response and recovery times, good selectivity, and long-term stability. Thus, the porous Fe2(MoO4)3 nanorods are very promising for the fabrication of high-performance H2S gas sensors. Furthermore, the strategy presented here could be expended as a general method to synthesize other hollow/porous-type transition metal molybdate nanostructures by rational designation in nanoscale.

Branched polyaniline/molybdenum oxide organic/inorganic heteronanostructures: synthesis and electromagnetic absorption properties

In this work, we developed an efficient and facile method to fabricate branched polyaniline (PANI)/α-MoO3 organic/inorganic heteronanostructures. Scanning electron and transmission electron microscope measurements showed that PANI nanorods with an average diameter and length of about 55 and 110 nm respectively were grown perpendicularly on the surfaces of α-MoO3 nanorods and the density of the PANI nanorods could be readily controlled by simply changing the addition amount of aniline in the reaction system. The minimal reflection loss for the electromagnetic wave absorbent material was up to −33.7 dB at 16.88 GHz for the branched heteronanostructures/paraffin composites with a thickness of 2.0 mm, and all of the minimal reflection losses were less than those of the pure PANI nanorods in the frequency range of 2–18 GHz. More importantly, the content of the branched nanostructures in the paraffin matrix was only 10 wt%. Thus, the method presented here is a very efficient strategy to fabricate lightweight materials for strong electromagnetic wave absorbents.

Growth of γ-Fe2O3 nanosheet arrays on graphene for electromagnetic absorption applications

We developed a seed-assisted method to grow ultra-thin γ-Fe2O3 nanosheets with a paramagnetic behaviour on the surfaces of graphene sheets. Scanning electron microscopy and the transmission electron microscopy measurements showed that the length, height and thickness of the nanosheets were about 140, 120 and 5 nm, respectively. The measured electromagnetic parameters indicated that the three-dimensional (3D) graphene/γ-Fe2O3 nanosheet arrays exhibited a significantly enhanced electromagnetic wave absorption property compared to that of the graphene sheets and some magnetic nanomaterials. The minimal reflection loss was less than −15.2 dB for 3D graphene/γ-Fe2O3 nanosheet arrays with thicknesses of 2 mm, and it was up to −64.1 dB when the thickness was 4.92 mm. Good electromagnetic wave absorption properties of the 3D graphene/γ-Fe2O3 nanosheet arrays indicate that they are very promising for applications in the electromagnetic wave absorbing field.

Synthesis and enhanced nonlinear optical properties of graphene/CdS organic glass

Graphene/CdS (G/CdS) nanocomposite was first fabricated by a hydrothermal method. G/CdS nanocomposite was then dispersed in polymethyl methacrylate (PMMA) for preparation of organic glass by a casting method. The G/CdS/PMMA organic glass exhibits enhanced nonlinear optical (NLO) properties compared to G/PMMA and CdS/PMMA organic glass. Moreover, NLO properties of the G/CdS/PMMA organic glass can be controlled by adjusting the addition amount of G/CdS nanocomposite in PMMA. Our results demonstrate that the G/CdS/PMMA organic glass is very promising for optical devices, such as optical limiters and optical switch.

Enhanced photocatalytic activities of net-like hematite nanoparticle/graphene oxide composite

A facile strategy was developed to fabricate net-like hematite nanoparticle/graphene oxide (GO) composite (NHG), in which the degree of oxidization of GO could be controlled by simply changing annealing time. NHG with GO of appropriate oxidization degree and content exhibited much higher photocatalytic activities than α-Fe2O3 nanorods and commercial α-Fe2O3.

Enhanced reverse saturable absorption in graphene/Ag2S organic glasses

G/Ag2S composites were synthesized for the first time by a hydrothermal method. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analysis demonstrated that Ag2S nanoparticles with a diameter of about 130 nm uniformly covered the graphene surfaces. G/Ag2S composites were dispersed in methyl methacrylate (MMA), polymerized at 75 °C for 30-35 min, and finally dried at 45 °C for 10 h, to afford G/Ag2S/PMMA organic glasses. The nonlinear absorption (NLA) properties of the G/Ag2S/PMMA organic glasses with different amounts of G/Ag2S were investigated by an open-aperture Z-scan technique. The experimental results showed that the G/Ag2S/PMMA organic glass with an appropriate amount of G/Ag2S exhibited enhanced reverse saturable absorption (RSA) properties compared to G/PMMA and Ag2S/PMMA organic glasses, which was attributed to the notable synergistic effects between graphene and Ag2S. Both one-photon absorption (OPA) in Ag2S and two-photon absorption (TPA) in graphene played important roles in RSA processes of the G/Ag2S/PMMA organic glasses. The effective NLA coefficient βeff of the G/Ag2S/PMMA organic glasses was in the order of 10(3) cm GW(-1). Thus this kind of organic glasses have great promise in optical limiter and optical shutter applications.