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Using density functional theory (DFT) computations, we investigated pyridinelike structures in a series of single-walled CNx nanotubes and found that tube chirality and diameter play important roles in the formation of pyridinelike structures. Not pyridinelike structures but more NC defects (N atoms substituting for C atoms) should be responsible for the experimentally observed donor states of CNx nanotubes. The adsorption energies of Li at the pyridinelike defect are so large and the energy barrier for lithium penetrating the defect is so low that CNx nanotubes with pyridinelike structures have enhanced capability for lithium storage. [ABSTRACT FROM AUTHOR]

The synthesis of Cs-encapsulated single-walled carbon nanotubes (Cs@SWNTs) and double-walled carbon nanotubes (Cs@DWNTs) is realized by a plasma ion-irradiation method. Transmission electron microscopy observations confirm that chainlike and amorphous Cs fill SWNTs and DWNTs, respectively. The electronic transport properties of Cs@SWNTs and Cs@DWNTs are experimentally investigated at both room and low temperatures by fabricating them as the channels of field-effect transistor devices. Our results reveal that both Cs@SWNTs and Cs@DWNTs exhibit n-type semiconducting behavior at room temperature. The electronic properties of the Cs-encapsulated nanotubes can be controlled by adjusting the Cs filling levels during the plasma ion irritation process. At low temperatures, Coulomb blockade transport characteristics are observed for both encapsulated nanotubes, and the size of quantum dots formed in Cs@DWNTs is much smaller than that formed in Cs@SWNTs. More importantly, the n-type characteristics of Cs@SWNTs and Cs@DWNTs are found to remain stable, even in air, owing to Cs encapsulation. [ABSTRACT FROM AUTHOR]

Five kinds of nanowires and a nanochain that is embedded in a carbon nanotube have been optimized by density function theory, and the electronic transport properties through these nanowires and nanochain are studied. Our results indicate that the transmission spectra exhibit size-dependent oscillations. We observe and study the nonlinear contribution to the I-V characteristic (current-voltage) curves that is due to the quantum size effect. The I-V curve of the single chain is different from that when the chain is embedded in a carbon nanotube. The results provide valuable information on the correlation between the transport properties of nanowires and their microstructures. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are carried out to examine the heterogeneous solidification of aluminum solution seeded by foreign boron-nitride nanotubes (BNNTs). The final structure indicates noticeably that Al atoms are concentrated to form incredible hierarchical nanostructures composed of coaxial and equidistant cylindrical shells with the BNNTs as the heterogeneous core. The structures of so-formed Al cylinders show strict structural matching and strong structural relevance with BNNTs. Heterogeneous solidification occurred on BNNTs follows a spiral nucleating mechanism. Heredity effect of these hollow cylinders can be clearly observed during the heterogeneous nucleation. The uniform internal potential field around BNNTs is found to be responsible for the formation of the coaxial cylindrical Al shells. [ABSTRACT FROM AUTHOR]

The transport properties of field-effect transistors based on C60 fullerene peapods have been investigated and our findings indicate that the transport characteristics of single-walled carbon nanotubes (SWNTs) are highly sensitive to the encapsulated fullerenes due to the charge-transfer effect. Under light illumination, the photoinduced electron transfer characteristics are found in C60 peapods, which is different from those observed for empty SWNTs. The response characteristic of peapod devices to light is reflected in a shift of threshold voltage toward negative values, indicating an electron-doping process. After removing light the photoresponse is fully recoverable, indicating complete restoration of transferred electrons. [ABSTRACT FROM AUTHOR]

The authors report electrical transport properties of p-n junction based on semiconducting single-walled carbon nanotubes (SWCNTs). The formation of p-n junction is realized in SWCNTs, which are encapsulated with Fe nanoparticles at low filling fractions. The devices exhibit an excellent rectifying behavior, and no current down to 10-14 A level flows when the device is biased in reverse. During measurements performed in the temperature range from 10 to 300 K, the devices maintain high reproducibility. More importantly, even after exposure to air, the rectifying characteristic keeps stable, which strongly suggests that ideal p-n junction diodes can be fabricated by SWCNTs. [ABSTRACT FROM AUTHOR]

Electronic transport properties of Cs-encapsulated double-walled carbon nanotubes (DWNTs) synthesized via a plasma irradiation method are investigated by fabricating them as field-effect transistor devices. The authors’ results indicate that Cs-encapsulated DWNTs exhibit a high performance n-type characteristic in contrast to ambipolar behavior of pristine DWNTs. Coulomb blockade oscillations are observed on the Cs-encapsulated DWNTs at low temperatures. In addition, it is found that the semiconducting characteristics of the as-synthesized Cs-encapsulated DWNTs can possibly be controllable by adjusting applied negative dc bias voltages during the plasma synthesis process. [ABSTRACT FROM AUTHOR]

Electrical properties of single-walled carbon nanotubes (SWCNTs) filled with Fe are studied by fabricating them as the channels of field-effect transistor devices. The synthesis of Fe-filled SWCNTs is realized by using ferrocene as the starting material. Our results reveal that ferrocene-filled SWCNTs show the interesting ambipolar behavior. In contrast, Fe-filled SWCNTs can exhibit high performance unipolar n-type semiconducting characteristics, suggesting the possibility of creating ferromagnetic semiconducting SWCNTs. Moreover, Coulomb blockade oscillations are significantly observed on Fe-filled SWCNTs, which indicates that they exhibit excellent single-electron transistor characteristics at low temperatures. [ABSTRACT FROM AUTHOR]