Nucleophilic-alkylation-reoxidation: a functionalization sequence for single-wall carbon nanotubes

Area of Science:

• Materials Science
• Nanotechnology
• Organic Chemistry

Background:

• Single-wall carbon nanotubes (SWNTs) possess unique electronic properties but often suffer from aggregation, hindering their applications.
• Chemical functionalization is crucial for tailoring SWNT properties and improving their processability.

Purpose of the Study:

• To develop a novel reaction sequence for the chemical functionalization of SWNT sidewalls.
• To investigate the debundling effect during the functionalization process.
• To characterize the functionalized SWNTs and determine the degree of functionalization.

Main Methods:

• Nucleophilic addition of tert-butyllithium (t-BuLi) to SWNT sidewalls.
• Subsequent reoxidation of the intermediate species.
• Characterization using photoelectron spectroscopy, Raman spectroscopy, and scanning tunneling microscopy (STM).

Main Results:

• A repeatable reaction sequence yielding functionalized SWNTs (t-Bu(n)SWNT) was established.
• Homogeneous dispersion of SWNTs was achieved due to electrostatic repulsion of negatively charged intermediates, leading to debundling.
• High degrees of functionalization, with carbon-to-addend ratios up to 31, were reached.
• Spectroscopic and microscopic analyses confirmed covalent attachment of tert-butyl groups and revealed preferred functionalization of metallic SWNTs.

Conclusions:

• The developed method provides effective functionalization and debundling of SWNTs.
• The functionalization process significantly alters the electronic properties of SWNTs, reducing pi-derived density of states.
• This approach offers a pathway for producing processable SWNTs with tunable properties for diverse applications.