Electronic, Optical, and Mechanical Properties of Diamond Nanowires Encapsulated in Carbon Nanotubes: A First-Principles View

Abstract

In recent years, carbon-based complex nanostructures have been explored due to many of their unique properties and related applications. Here we employ theoretical simulation based on density functional theory to investigate electronic, optical, and mechanical properties of a new type of the carbon-based complex nanostructure, i.e., experimentally fabricated one-dimensional complex material of hydrogenated diamond nanowires encapsulated in carbon nanotubes (CNW@CNT). The complex structure CNW@CNT is found to possess metallicity for the outer CNT and wide band gap nature for the inner CNW simultaneously. Under uniaxial strain a specific insulator-to-metal transition occurs for the inner CNW in the complex structure, with threshold value much smaller than that for the individual insulator. This effect is interpreted as that the strain induces relative shifting of bands of CNW and CNT and even charge transfer between them, making the valence band of CNW become not fully occupied. The inner CNW in the complex structure has optical absorption only in the ultraviolet waveband. The further examinations on the conductive bands reveal existences of nearly free-electron states which entirely dominate the conductive bands of the inner CNW and suggest that the electron–hole separation will happen in the CNW@CNT upon the ultraviolet illumination. The simulation results also reveal higher Young’s modulus of the CNW@CNT and the individual CNW even larger than those of CNT and graphene. We propose a simple parallel spring model to establish the relationship between the Young’s modulus of the complex structure and the one of its component which should be helpful to future predictions for other complex structures. The potential applications of this new type of carbon-based complex structure as a multifunctional integrated nanomaterial in future nanoelectronics, nano-optoelectronics, and nanoelectromechanics are discussed.

Structural, optoelectronic and charge transport properties of the complexes of indigo encapsulated in carbon nanotubes

“…49 In another study, Wang et al reported a distortion in the structure of CNTs with the encapsulation of carbon nanowires. 14 Unlike in indigo@ (6,6)CNT, in all other complexes indigo was found to be slightly tilted with respect to the tube-axis, keeping the geometric centres of indigo and the CNT coincident with each other. Compared to indigo@(7,7)CNT, in indigo@(8,8)CNT, a larger inclination for indigo with respect to the tube-axis was observed so as to bring the distance between the phenyl groups of indigo and the (8,8)CNT into the range of p-p stacking.…”

“…The endohedral complexes of carbon nanotubes with organic molecules are mainly stabilized by the p-p and X-HÁ Á Áp (X = C, N, and O) interactions. The importance of p-p interactions in the complexes such as oligothiophene@CNT, 10,11 pioglitazone@ CNT, 12 acetone@CNT 13 and diamond nanowire@CNT 14 was elucidated using theoretical and experimental methods. The above studies report that the attractive interactions between the p-conjugated CNT and the encapsulated moiety impart stability to these complexes.…”

“…31 Very recently, Wang et al examined the electronic and optical properties of the inclusion complexes of CNTs with diamond nanowires (CNW). 14 Their study showed that the absorption spectrum of the complexes covers a wide spectral range from the ultraviolet to the near-infrared, suggesting that they are useful in the area of nano-optoelectronics.…”