Van der Waals Gap Engineering of Multiwalled Carbon Nanotubes in Ionic Liquids at Room Temperature

Among various two-dimensional (2D) materials, graphene possesses similar interlayer spacing as that of multiwalled carbon nanotubes (0.32-0.35 nm). However, this interlayer spacing could be modulated by several strategies such as the intercalation of cations and anions, the nature of the solvent, and surface functionalization. The resultant graphene nanoribbons are useful for many applications such as nanoelectronics, electrocatalysis, biosensing, solar energy conversion, and energy storage. We report an ionic liquid-assisted transformation of multiwalled carbon nanotubes of an average diameter (similar to 21 nm) to graphene nanoribbons (similar to 40 nm) and graphene quantum dots having an emission wavelength of 445 nm in 1-butyl-3-methylimidazolium tetrafluoroborate as the electrolyte. This electrochemical approach not only reveals the introduction of multiple heteroatoms at room temperature but also modulates the van der Waals gap between the layers of multiwalled carbon nanotubes, which could have significant implications for the mechanical and electrical properties of the nanoribbons. The tunability of this spacing depends on the nature of the ionic liquid, the size of the incoming ions, the applied potential, and the time. This study highlights the importance of van der Waals gap engineering in designing advanced 2D materials and their composites for various applications and is in agreement with density functional theory calculations.

Automated summary

In this study, a transformation of multiwalled carbon nanotubes to graphene nanoribbons and graphene quantum dots was achieved through an ionic liquid-assisted electrochemical approach. The tunability of interlayer spacing and the introduction of heteroatoms in carbon nanotubes could significantly impact the mechanical and electrical properties of the resulting nanoribbons. This research highlights the importance of van der Waals gap engineering in designing advanced 2D materials and their composites for various applications.