Guangping Li

Mixed low-dimensional nanomaterial: 2D ultranarrow MoS2 inorganic nanoribbons encapsulated in quasi-1D carbon nanotubes.

Quasi-one-dimensional nanotubes and two-dimensional nanoribbons are two fundamental forms of nanostructures, and integrating them into a novel mixed low-dimensional nanomaterial is fascinating and challenging. We have synthesized a stable mixed low-dimensional nanomaterial consisting of MoS(2) inorganic nanoribbons encapsulated in carbon nanotubes (which we call nanoburritos). This route can be extended to the synthesis of nanoburritos composed of other ultranarrow transition-metal chalcogenide nanoribbons and carbon nanotubes. The widths of previously synthesized MoS(2) ribbons are greater than 50 nm, while the encapsulated MoS(2) nanoribbons have uniform widths down to 1-4 nm and layer numbers down to 1-3, depending on the nanotube diameter. The edges of the MoS(2) nanoribbons have been identified as zigzag-shaped using both high-resolution transmission electron microscopy and density functional theory calculations.

Novel One-Dimensional Organometallic Half Metals: Vanadium-Cyclopentadienyl, Vanadium-Cyclopentadienyl-Benzene, and Vanadium-Anthracene Wires

By using the density functional theory, we find that organometallic multidecker sandwich clusters V(2 n+1)Cp(2 n+2), Vn(FeCp2)(n+1) (Cp=cyclopentadienyl), and V(2n)Ant(n+1) (Ant=anthracene) may have linear structures, and their total magnetic moments generally increase with the cluster size. The one-dimensional (VCp)infinity, (VBzVCp)infinity (Bz=benzene), and (V2Ant)infinity wires are predicted to be ferromagnetic half-metals, while the one-dimensional (VCpFeCp)infinity wire is a ferromagnetic semiconductor. The spin transportation calculations show that the finite V2(n+1)Cp2(n+2) and Vn(FeCp2)(n+1) sandwich clusters coupled to gold electrodes are nearly perfect spin-filters.

First-principles study of hydrogen-passivated single-crystalline silicon nanotubes: electronic and optical properties

The electronic structures of hydrogen-passivated single-crystalline silicon nanotubes (Hsc-SiNTs) along the [100], [110], [111], and [112] directions and the absorption spectra of [100]-oriented Hsc-SiNTs are studied by using density functional theory within the generalized gradient approximation. We find that the band gaps of the Hsc-SiNTs generally increase with decreasing wall thickness because of the quantum confinement effects. But when the inner radii of the tubes are extremely small, the quantum confinement effects are weakened significantly by the adsorbed hydrogen atoms. In addition, the band gaps of the Hsc-SiNTs along the [100], [110], and [111] directions are all direct at small sizes, whereas those of the [112]-oriented tubes remain indirect. We also find that the magnitude of the band gap of the Hsc-SiNTs also depends on the tube orientation and morphology. Compared with the absorption spectra of hydrogen-passivated single-crystalline [100]-oriented silicon nanowires with an identical external diameter, a split of the original peak and an overall blue shift are observed in the absorption spectra of [100]-oriented Hsc-SiNTs.

Electronic‐Type‐ and Diameter‐Dependent Reduction of Single‐Walled Carbon Nanotubes Induced by Adsorption of Electron‐Donor Molecules

The adsorption of the organic donor molecules tetrakis(dimethylamino)ethylene (TDAE) and cobaltocene (CoCp(2)) on high-pressure CO decomposition (HiPco) single-walled carbon nanotubes (SWNTs) is investigated using density functional theory (DFT), optical absorption, and Raman spectra methods. The selective reduction of SWNTs according to the electronic type and diameter of SWNTs is revealed. The reduction rate decreases in the order: metallic SWNTs >or= large-diameter semiconducting SWNTs > small-diameter semiconducting SWNTs.