Terahertz processes in carbon nanotubes

Copyright 2010 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.We investigated several proposals utilizing the unique electronic properties of carbon nanotubes (CNTs) for a broad range of applications to THz optoelectronics, including THz generation by Cerenkov-type emitters based on carbon nanotubes and by hot electrons in quasimetallic nanotubes, frequency multiplication in chiral-nanotube-based superlattices controlled by a transverse electric field, and THz radiation detection and emission by armchair nanotubes in a strong magnetic field. Dispersion equations of the electron beam instability and the threshold conditions of the stimulated emission have been derived and analyzed, demonstrating realizability of the nanotube-based nanoFEL at realistic parameters of nanotubes and electronic beams

Chirality effects in carbon nanotubes

We consider chirality related effects in optical, photogalvanic and electron-transport properties of carbon nanotubes. We show that these properties of chiral nanotubes are determined by terms in the electron effective Hamiltonian describing the coupling between the electron wavevector along the tube principal axis and the orbital momentum around the tube circumference. We develop a theory of photogalvanic effects and a theory of d.c. electric current, which is linear in the magnetic field and quadratic in the bias voltage. Moreover, we present analytic estimations for the natural circular dichroism and magneto-spatial effect in the light absorption.Comment: 23 pages, 3 figure

Water purification from chlorobenzenes using heteroatom functionalized carbon nanofibers produced on self organizing Ni Pd catalyst

The development of effective methods for the processing of hazardous wastes containing chlorinated hydrocarbons still remains a big challenge. Herein, the approach allowing the transformation of chlorohydrocarbons into functionalized carbon nanomaterials was demonstrated for 1,2 dichloroethane DCE used as a model compound. Carbon nanofibers CNF doped with nitrogen and oxygen heteroatoms were fabricated by a joint decomposition of DCE and co reagent CH3CN, NH4OH, C2H5OH, and H2O . The Ni Pd 5 alloy was used as a catalyst precursor for the CNF synthesis. Pristine Ni Pd alloy was found to undergo disintegration under the reaction conditions and to induce an active growth of the functionalized carbon nanofibers. The obtained CNF were shown to have a similar segmental structure of carbon filaments and to possess high specific surface area up to 470 m2 g and porosity up to 0.9 cm3 g . According to X ray photoelectron spectroscopy data, the nitrogen content within CNF samples prepared using N comprising precursors was about 1.0 1.7 at . The total oxygen content reaches 3.6 at . The obtained materials were demonstrated to be attractive for the dichlorobenzene adsorption from its aqueous solution

Terahertz applications of carbon nanotubes

Copyright © 2007 Elsevier. NOTICE: this is the pre-print version of a work that was accepted for publication in Superlattices and Microstructures. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Superlattices and Microstructures Volume 43, Issues 5–6, pp. 399–407 (2008). DOI: 10.1016/j.spmi.2007.07.026We formulate and justify several proposals utilizing unique electronic properties of carbon nanotubes for a broad range of applications to THz optoelectronics, including THz generation by hot electrons in quasi-metallic nanotubes, frequency multiplication in chiral-nanotube-based superlattices controlled by a transverse electric field, and THz radiation detection and emission by armchair nanotubes in a strong magnetic field