Vibrational and electronic properties of single-walled and double-walled boron nitride nanotubes

Abstract

We calculated IR, nonresonance Raman spectra and vertical electronic transitions of the zigzag single-walled and double-walled boron nitride nanotubes ((0,n)-SWBNNTs and (0,n)@(0,2n)-DWBNNTs). In the low frequency range below 600 cm(-1), the calculated Raman spectra of the nanotubes showed that RBMs (radial breathing modes) are strongly diameter-dependent, and in addition the RBMs of the DWBNNTs are blue-shifted reference to their corresponding one in the Raman spectra of the isolated (0,n)-SWBNNTs. In the high frequency range above similar to 1200 cm(-1), two proximate Raman features with symmetries of the A(1g) (similar to 1355 +/- 10 cm(-1)) and E-2g (similar to 1330 +/- 25 cm(-1)) first increase in frequency then approach a constant value of similar to 1365 and similar to 1356 cm(-1), respectively, with increasing tubes' diameter, which is in excellent agreement with experimental observations. The calculated IR spectra exhibited IR features in the range of 1200-1550 cm(-1) and in mid-frequency region are consistent with experiments. The calculated dipole allowed singlet-singlet and triplet-triplet electronic transitions suggesting a charge transfer process between the outer- and inner-shells of the DWBNNTs as well as, upon irradiation, the possibility of a system that can undergo internal conversion (IC) and intersystem crossing (ISC) processes, besides the photochemical and other photophysical processes. (C) 2013 Elsevier B.V. All rights reserved.