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Chlorine oxoanions with different oxidation states are introduced in order to correlate the degree of oxidation with the electronic structures of the carbon nanotubes (CNTs). The density functional theory calculations have shown that physisorption is involved at a high oxidation state and selective doping on the metallic nanotubes is seen, whereas chemisorptions have played a key role in modifying the electronic structures of the CNTs at a low oxidation state.

Thermal nitridation is adopted to modify [Li.sub.4][Ti.sub.5][O.sub.12] to make it electronically more conductive. Electrochemically induced [Li.sub.4+[delta]][Ti.sub.5][O.sub.15] with a TiN surface layer has increased the electrochemical properties at high current densities.

The modulation of optical properties of single-walled carbon nanotubes (SWCNTs) by Au[Cl.sub.3] doping is examined. The large work function shift has forced the Fermi level of the SWCNTs to be located deep in the valence band, thus invoking a new asymmetric transition in the absorption spectroscopy from a deeper level to newly generated empty states.

The electronic structures of single-walled carbon nanotubes (SWCNTs) were tailored by using various electron-donating and -withdrawing groups in solvents with various aromatic and aliphatic backbones. The results from the experiments suggest that the electronic structures of SWCNTs could be modified by a solvent treatment.

Abstract: We investigated the modulation of optical properties of single-walled carbon nanotubes (SWCNTs) by AuCI3 doping. The van Hove singularity transitions (E11S, E22S, E11M) 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 0.42 eV by a strong charge transfer from the SWCNTs to AuCl3 by a high level of p-doping. We propose that this large work function shift forces the Fermi level of the SWCNTs to be located deep in the valence band, i.e., highly degenerate, creating empty van Hove singularity states, and hence the work function shift invokes a new asymmetric transition in the absorption spectroscopy from a deeper level to newly generated empty states. [ABSTRACT FROM AUTHOR]

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 0.42 eV by a strong charge transfer from the SWCNTs to AuCl 3 by a high level of p-doping. We propose that this large work function shift forces the Fermi level of the SWCNTs to be located deep in the valence band, i.e., highly degenerate, creating empty van Hove singularity states, and hence the work function shift invokes a new asymmetric transition in the absorption spectroscopy from a deeper level to newly generated empty states.

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. The adsorption behavior and charge transfer at a low oxidation state were in contrast to that observed at a high oxidation state. Density functional calculations demonstrated the chemisorption of chloro oxoanions at the low oxidation state and their physisorption at high oxidation states. These results concurred with the experimental observations from X-ray photoelectron spectroscopy. The sheet resistance of the SWCNT film decreased significantly at high oxidation states, which was explained in terms of a p-doping phenomenon that is controlled by the oxidation state.

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. This effect was less prominent in solvent with an aliphatic backbone than that with an aromatic backbone. The strong correlation between the sheet resistance and electronic structures of nanotubes is further discussed in conjunction with a modulation of Schottky barrier height.