Intramolecular Hydrogen Bonds in Tip-Functionalized Single-Walled Carbon Nanotubes as pH-Sensitive Gates

Area of Science:

• Nanomaterials Science
• Computational Chemistry
• Physical Chemistry

Background:

• Carbon nanotubes (CNTs) possess unique structures and properties, making them valuable for diverse applications.
• Their cage-like structure is ideal for encapsulating molecules, isolating them from surrounding environments.
• Functionalization of CNTs can create responsive nanomaterials for specific tasks.

Purpose of the Study:

• To computationally investigate the covalent tip-functionalization of single-walled carbon nanotubes (SWCNTs) with carboxymethyl groups.
• To characterize the development of pH-sensitive molecular gates using density functional theory (DFT).
• To assess the potential of these functionalized SWCNTs in drug delivery and separation technologies.

Main Methods:

• Density functional theory (DFT) calculations were employed to model and analyze the functionalized SWCNTs.
• Topological analysis was used to evaluate hydrogen bonding interactions within the molecular models.
• pKa calculations were performed to determine the acidity of the functional groups.

Main Results:

• The study successfully characterized carboxymethyl-functionalized SWCNTs as pH-sensitive molecular gates.
• Conformational changes were observed in response to pH fluctuations due to variations in protonation and noncovalent interactions.
• Analysis confirmed the presence and significance of hydrogen bonds in the functionalized systems.

Conclusions:

• Functionalized SWCNTs exhibit pH-responsive behavior, acting as molecular gates.
• The characterized hydrogen bonding and pKa values suggest suitability for advanced applications.
• These findings support the potential use of functionalized SWCNTs in drug delivery systems, catalysis, and separation processes within nanocomposites.