Chemically reactive species remain alive inside carbon nanotubes: a density functional theory study

Abstract

The behavior of alkyl guest radicals inside carbon nanotube hosts with different diameters is analyzed using density functional theory (DFT) calculations. Here the inner alkyl radicals are assumed to be formed by decomposition of their precursors, which had been incorporated into the tubes. DFT calculations show that inner alkyl radicals prefer to exist separately from the nanotube wall (separate form) rather than forming an inner covalent bond with the wall (bound form). Keeping a radical apart from the inner wall is more likely for a more bulky radical inside a smaller diameter tube. A key to the preference for the separate forms over the bound forms is that the bound forms gain a weak attraction due to the formation of a bond with the inner wall. The weak attraction, ascribed to the inertness of the inner surface, is counteracted by destabilization due to deformations of a tube and radical induced by guest-host coupling. The energy balance argument illuminates that the inertness of the inner wall makes an alkyl radical species remain alive inside a tube and retain its reactivity. These findings can help us to understand experimental results where chemical reactions inside a tube proceed after guests are activated.

Encapsulation and convex‐face thiozonolysis of triatomic sulfur (S3) with carbon nanotubes

“…DFT calculations also indicate that alkyl radicals do not react with the inner walls of carbon nanotubes because of the high-energy cost to produce a "negative" distortion of the tube geometries. [71] In the absence of molecular-dynamics simulations of S 3 molecules within the nanotubes, we speculate a qualitative picture based on the previous static computed structures. Because of the large radii, undoubtedly many S 3 molecules can reside within the (6,6), (7,7), and (8,8) SWNTs, which could oligomerize to other sulfur allotropes or plug the nanotubes.…”

“…An open‐shell stepwise pathway to a biradical intermediate was sought, but no structure optimized to a C–S bonded compound or to a three‐membered ring SWNT‐1‐persulfide structure with a linear sulfur linkage. DFT calculations also indicate that alkyl radicals do not react with the inner walls of carbon nanotubes because of the high‐energy cost to produce a “negative” distortion of the tube geometries …”

Key factors in determining the arrangement of π-conjugated oligomers inside carbon nanotubes

“…2. [33][34][35][36][37][38][39] Following the previous studies, 31,32 we considered methylterminated oligomers consisting of three furan rings (terfuran, 3F). These nanotube clusters are large enough to accurately model the electronic properties of the corresponding infinitely long nanotubes.…”

Confinement Effect on Heterogeneous Electron Transfer in Aqueous Solutions inside Conducting Nanotubes

“…It is well‐known nowadays that carbon nanotubes can serve as containers for small clusters, for example quantum dots, which reveal high catalytic properties. The mechanisms of typical gas‐phase chemical reactions in such specific confinements are in the focus of both experimental [1–5] and theoretical [6,7] studies. Recently nanoconfinement effects on electrochemical redox processes were explored as well and probed by Cyclic Voltammetry (CVA) technique [8–12] .…”