Selective gas transport through few-layered graphene and graphene oxide membranes.

Graphene is a distinct two-dimensional material that offers a wide range of opportunities for membrane applications because of ultimate thinness, flexibility, chemical stability, and mechanical strength. We demonstrate that few- and several-layered graphene and graphene oxide (GO) sheets can be engineered to exhibit the desired gas separation characteristics. Selective gas diffusion can be achieved by controlling gas flow channels and pores via different stacking methods.

Synthesis of multilayer graphene balls by carbon segregation from nickel nanoparticles.

Three-dimensional (3D) structured graphene is a material of great interest due to its diverse applications in electronics, catalytic electrodes, and sensors. However, the preparation of 3D structured graphene is still challenging. Here, we report the fabrication of multilayer graphene balls (GBs) by template-directed carbon segregation using nickel nanoparticles (Ni-NPs) as template materials.

Conformational-induced doping effect of sodium dodecyl benzene sulfonate on single walled carbon nanotubes.

The doping behavior of single-walled carbon nanotubes (SWCNTs) was investigated with an emphasis on the control of the conformation of sodium dodecylbenzene sulfonate (NaDDBS) with sulfonate groups acting as an electro-withdrawing group. The conformation of adsorbed NaDDBS on SWCNTs was controlled as a function of the amount of NaDDBS. The doping behavior of SWCNTs was significantly affected by the dosing amount of NaDDBS due to the conformational change of NaDDBS adsorbed on the SWCNT surface, which affected the spatial distance between the SWCNT surface and the sulfonate groups in NaDDBS.

Interface effect of magnetic properties in Ni nanoparticles with a hcp core and fcc shell structure.

We have fabricated hexagonal close-packed (hcp) Ni nanoparticles covered by a face-centered cubic (fcc) Ni surface layer by polyol method. The magnetic properties have been investigated as a function of temperature and applied magnetic field. The magnetic behavior reveals that the system should be divided magnetically into three distinct phases with different origins.

Thermal conversion of electronic and electrical properties of AuCl3-doped single-walled carbon nanotubes.

By using carbon-free inorganic atomic layer involving heat treatment from 150 to 300 °C, environmentally stable and permanent modulation of the electronic and electrical properties of single-walled carbon nanotubes (SWCNTs) from p-type to ambi-polar and possibly to n-type has been demonstrated. At low heat treatment temperature, a strong p-doping effect from Au(3+) ions to CNTs due to a large difference in reduction potential between them is dominant. However at higher temperature, the gold species are thermally reduced, and thermally induced CNT-Cl finally occurs by the decomposition reaction of AuCl(3).

Control of electronic structure of graphene by various dopants and their effects on a nanogenerator.

It is essential to control the electronic structure of graphene in order to apply graphene films for use in electrodes. We have introduced chemical dopants that modulate the electronic properties of few-layer graphene films synthesized by chemical vapor deposition. The work function, sheet carrier density, mobility, and sheet resistance of these films were systematically modulated by the reduction potential values of dopants.

Fermi level engineering of single-walled carbon nanotubes by AuCl3 doping.

We investigated the modulation of optical properties of single-walled carbon nanotubes (SWCNTs) by AuCl 3 doping. The van Hove singularity transitions (E 11 (S), E 22 (S), E 11 (M)) in absorption spectroscopy disappeared gradually with an increasing doping concentration and a new peak appeared at a high doping concentration. The work function was downshifted up to 0.

Spatial control of quantum sized nanocrystal arrays onto silicon wafers.

Monolayer arrays of monodispersed nanocrystals (<10 nm) onto three dimensional (3D) substrates have considerable potential for various engineering applications such as highly integrated memory devices, solar cells, biosensors and photo and electro luminescent displays because of their highly integrated features with nanocrystal homogeneity. However, most reports on nanocrystal arrays have focused on two dimensional (2D) flat substrates, and the production of wafer-scale monolayer arrays is still challenging. Here we address the feasibility of arraying nanocrystal monolayers in wafer-scale onto 3D substrates.

Hierarchical organization of Au nanoparticles in a poly(vinyl carbazole) matrix for hybrid electronic devices.

We report a novel one-step method for the preparation of hierarchically patterned Au nanoparticles in a conducting polymer matrix by controlling the interface properties between Au nanoparticles and the conducting polymer matrix. The terminal group of capping molecules for the Au nanoparticles was modified to change the interface properties, not to change the size of the Au nanoparticles which affects their intrinsic properties. By modulating the interface properties, it is possible to construct Au nanoparticle-conducting polymer composites with two different structures: one presents a triple layer in which the conducting polymer layer is sandwiched between Au nanoparticle layers at the top and bottom; the other exhibits a form like a raisin cake in which Au nanoparticles are homogeneously organized in the conducting polymer matrix.

Selective oxidation on metallic carbon nanotubes by halogen oxoanions.

Chlorine oxoanions with the chlorine atom at different oxidation states were introduced in an attempt to systematically tailor the electronic structures of single-walled carbon nanotubes (SWCNTs). The degree of selective oxidation was controlled systematically by the different oxidation state of the chlorine oxoanion. Selective suppression of the metallic SWCNTs with a minimal effect on the semiconducting SWCNTs was observed at a high oxidation state.

Tailoring electronic structures of carbon nanotubes by solvent with electron-donating and -withdrawing groups.

Various electron-donating and -withdrawing groups in aromatic and aliphatic backbones of solvent have been introduced to tailor the electronic structures of single-walled carbon nanotubes (SWCNTs). In the case of solvent with a withdrawing group, electrons were extracted mainly from metallic SWCNTs, whereas small charge transfer was also observed in semiconducting SWCNTs. On the other hand, in the case of solvent with a donating group, electrons were donated to both metallic and semiconducting SWCNTs.

A new design strategy for dispersion stabilization of Ni particles based on the surface acid and base properties of Ni particles.

A dispersion technology for Ni particles suspended in a non-aqueous medium based on the quantitative evaluation of surface acid-base properties of Ni particles is described. A quantitative analysis of surface acid-base properties of Ni particles was performed using non-aqueous titration. Dimethylamino ethanol and acetic acid were used as probe molecules to detect surface acid-base amounts of Ni particles.