Tuning the First Hyperpolarizabilities of Boron Nitride Nanotubes

Abstract

Various carbon-substituted boron nitride (8,0) and (4,4) nanotubes are designed for application as nonlinear optical materials. The structure and first (static and frequencydependent) hyperpolarizabilities of these boron nitride nanotubes are predicted. The substitution of carbon in the boron nitride nanotube clip significantly enhances the first hyperpolarizabilities by up to several orders of magnitude. The doping pattern of the carbon circle and π electron conjugation are crucial in determining the large first hyperpolarizabilities of these nanotubes. KEYWORDS: carbon-substituted boron nitride nanotubes, first hyperpolarizability, frequency dispersion, charge transfer based electronic excitation N onlinear optical (NLO) materials have attracted increasing attention due to their potential important applications, e.g., laser tuning, frequency conversion, all-optical switches, signal processing, optical communication, information security, optical data storage processing, and biological imaging. 1,2 Minerals, 3 inorganic oxides, 4 semiconductors, 5 atomic clusters, 6 organometallic compounds, 7 and metal complexes 8−11 have been explored for these applications. Nanotubes could be potential NLO materials due to their unique structures and properties.Carbon nanotubes (CNTs) could be semiconducting or metallic depending on their chirality 12 with possible exceptions of CNTs (4,0) and (5,0). 13 On the other hand, boron nitride nanotubes (BNNTs) are electric insulators (or wide-gap semiconductors) with band gaps of about 5.5 eV 14 in spite of chirality and their tube diameter. 15 BNNT was predicted theoretically 16 before the experimental synthesis of single-and multiple-wall tubes. 17 The combination of BNNTs and CNTs (BCNNTs) could have some new properties due to the large property differences between BNNTs and CNTs, 18,19 and such combinations were the targets in the synthesis of nanotubes with desired properties. 20−25 The hybridized nanotubes with zigzag conformations may be semiconducting 23 with good thermal stability. The band gaps of hybridized armchair nanotubes [C 0.5 (BN) 0.5 ] do not change with the radius of the tubes. 24 The electronic structures of certain BCNNTs with proper hybridization, e.g., BC 2 N, depend on the radii or chiralities of the tubes, 25 providing new opportunities for the design of electronic devices.First-principles calculations predict large second-order nonlinear optical properties for BNNTs 26 and possible applications of BN-doped carbon nanotubes in NLO devices. 27 The NLO properties of zigzag BNNTs were predicted to converge to those of a hexagonal-BN sheet. 28 The bonding pattern of C with BN and the composition dictate the electronic structure of BCNNTs, 23−25 and the charge distributions have large effects on the NLO properties 29 of these tubes as well. The polarities, polarizabilities, and the second hyperpolarizabilities of armchair BCNNTs are significantly enhanced 30 with respect to those of BNNTs. However, hybridization of C with BN has little effect on the first hyper...

Tuning the edge states in X-type carbon based molecules for applications in nonlinear optics

“…This is similar to the second order NLO properties of zigzag and armchair nanotube. 53 It is desirable to find another means of stabilizing the zigzag edge states while enhancing the NLO properties of the X-type GNRs.…”

The interaction between Boron-carbon-nitride heteronanotubes and lithium atoms: Role of composition proportion

“…Boron-carbon-nitride nanotubes [18][19][20][21] (BCN) are expected to be novel candidates of nano materials due to the diversity of structure, which might break through the limitation of CNTs and BNNTs. Generally, these heteronanotubes are considered as the substitution of CNT segments by BN segments with a suitable formation proportion [22][23][24][25][26][27][28]. Recently, our study indicates that the N-connecting pattern of the BN-segment linking to the C-segment is an efficient way to decrease the transition energy which might be a suitable strategy to enhance the NLO response of heterojunction nanotubes [29][30][31].…”

Electronic and vibrational hyperpolarizabilities of alkali‐ and alkaline‐earth‐doped boron nitride nanotubes

“…Even the methods of intermediate accuracy, as second‐order many‐body perturbation theory, to study these molecules are very expensive. On the other hand, DFT, with appropriate choice of the exchange‐correlation functional, is frequently an option that allows obtaining reliable results with much lower computational cost . In this work, we made use of the M06‐2X functional because it has been successfully employed to study a number of similar systems, especially some of the nanotubes investigated here .…”