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We elucidate the atomic and electronic structure of graphene oxide (GO) using annular dark field imaging of single and multilayer sheets and electron energy loss spectroscopy for measuring the fine structure of C and O K-edges in a scanning transmission electron microscope. Partial density of states and electronic plasma excitations are also measured for(More)
We examined the structure, morphology, and orientation of catalyst nanoparticles used for seeding and growing multiwall carbon nanotubes (MWCNTs) by plasma enhanced chemical vapor deposition in CH4/H2 gas mixtures. Iron catalyst nanocrystals are converted to Fe3C in CH4/H2 plasmas and the MWCNTs grow from Fe3C nanocrystals. Initially faceted and equiaxed(More)
The mineralogical constitution of the Earth's mantle dictates the geophysical and geochemical properties of this region. Previous models of a perovskite-dominant lower mantle have been built on the assumption that the entire lower mantle down to the top of the D″ layer contains ferromagnesian silicate [(Mg,Fe)SiO3] with nominally 10 mole percent Fe. On the(More)
Internal crystalline structure of cementite catalyst particles located inside the base of mul-tiwall carbon nanotubes was studied using nanoprobe convergent-beam electron diffrac-tion. The catalyst particles are single crystalline but exhibit combinations of small-angle ($1°–3°) rotations, twists, and bends along their axial length between adjacent(More)
Nanometer-scale semiconductors that contain a few intentionally added impurity atoms can provide new opportunities for controlling electronic properties. However, since the physics of these materials depends strongly on the exact arrangement of the impurities, or dopants, inside the structure, and many impurities of interest cannot be observed with(More)
The structures of carbon nanotubes grown from catalytic nanoparticles via plasma-enhanced chemical vapor deposition in CH 4 / H 2 mixtures show a strong dependence on the H 2-to-CH 4 ratio in the feed gas. A suite of characterization techniques, including optical emission, infrared, and Raman spectroscopies combined with convergent-beam and selected-area(More)
We report a new, simple, hydrazine-free, high-yield method for producing single-layer graphene sheets. Graphene sheets were formed from graphite oxide by reduction with simple deionized water at 95 °C under atmospheric pressure. Over 65% of the sheets are single graphene layers; the average sheet diameter is 300 nm. We speculate that dehydration of graphene(More)
Localized surface plasmon resonances (LSPRs) enable tailoring of the optical response of nanomaterials through their free carrier concentration, morphology, and dielectric environment. Recent efforts to expand the spectral range of usable LSPR frequencies into the infrared successfully demonstrated LSPRs in doped semiconductor nanocrystals. Despite(More)
to enticing optical and electronic properties. [ 1 ] TMD materials exhibit a large variety of electronic behaviors such as metallic, semiconductivity and super-conductivity. [ 2–4 ] MoS 2 , a semiconducting TMD material, possesses an indirect band gap of ≈1.3 eV in its bulk form and a direct band gap of ≈1.8 eV as a monolayer, allowing its realization in(More)