Interaction between alkyl radicals and single wall carbon nanotubes

Area of Science:

• Computational Chemistry
• Materials Science
• Nanotechnology

Background:

• Single-wall carbon nanotubes (SWCNTs) are versatile nanomaterials with potential applications in various fields.
• Understanding the interaction of organic molecules, such as alkyl radicals, with SWCNTs is crucial for tailoring their properties.
• Previous studies have explored SWCNT functionalization, but the role of specific interactions requires further investigation.

Purpose of the Study:

• To investigate the addition of primary, secondary, and tertiary alkyl radicals to SWCNTs using computational methods.
• To determine the influence of Van der Waals and nonbonded interactions on the energetics of alkyl radical addition.
• To compare the accuracy of different density functional theory (DFT) functionals in describing these interactions.

Main Methods:

• Dispersion-corrected density functional theory (DFT) calculations were employed.
• Four DFT functionals were tested: PBE, B97-D, M06-L, and M06-2X.
• Calculations focused on the addition of methyl, ethyl, isopropyl, and tert-butyl radicals to (5,5) and (11,0) SWCNTs.

Main Results:

• Van der Waals interactions are essential for accurate prediction of addition energies.
• Enthalpy changes for radical addition vary significantly depending on the DFT functional used.
• Nonbonded interactions become more important for larger alkyl radicals, with tert-butyl radical favoring physisorption over chemisorption on (11,0) SWCNT.

Conclusions:

• Alkyl radicals are expected to be stable on SWCNTs due to large desorption barriers, despite small binding energies.
• The trend in bond dissociation energies aligns with radical stabilization energies but may differ from experimental functionalization degrees.
• Discrepancies with experiments could arise from stronger nonbonded interactions in certain HiPco nanotubes compared to covalent bonds.