The pristine boron nitride nanotubes have a large direct band gap around 5 eV. This band gap can be engineered by doping. We investigate electronic structure of the doped hexagonal boron nitride (5,5) nanotubes using the linearized augmented cylindrical wave method. In particular, this work focuses on systematical study of the band gap and the density of states around the Fermi-level when the nanotubes are doped by intrinsic impurities of two substitutional boron atoms in a super cell and a comparative analysis of the relative stability of three structures studied here. This corresponds to 3.3% of impurity concentration. We calculate 29 configurations of the nanotubes with different positions of the intrinsic impurities in the nanotube. The band gap and density of states around the Fermi level show strong dependence on the relative positions of the impurity atoms. The two defect sub bands called () appear in the band gap of the pristine nanotube. The doped nanotubes possess p-type semiconductor properties with the band gap of 1.3-1.9 eV.

ABSTRACT:Carbon nanotubes are possible building blocks in the development of new generation of electronic devices. The carbon nanotubes allow one fabrication of devices using nanometric scales. They can be used in projects of a wide range of electronic and optoelectronic components such as diodes, transistors and interconnection elements, among others. This paper presents the state-of-the-art of this area, emphasizing the influence of quantum effects on the characteristics of such components.

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This review intends to show how nanotechnology is currently being applied in concrete. Both organic and inorganic species can be used as nanoagents, producing materials with improved properties, promoting economic and environmental gains by extending the materials' lifetime. Thus, this paper covers nanotechnology applications to improve mechanical, thermal, and corrosive properties of concrete and shows bibliometric results, proving the increase of interest in these fields. Results have shown that organic agents are more commonly used than inorganic ones, and that nanotechnology is applied mainly to improve mechanical and thermal properties.