Non-covalent and reversible functionalization of carbon nanotubes

Abstract

SummaryCarbon nanotubes (CNTs) have been proposed and actively explored as multipurpose innovative nanoscaffolds for applications in fields such as material science, drug delivery and diagnostic applications. Their versatile physicochemical features are nonetheless limited by their scarce solubilization in both aqueous and organic solvents. In order to overcome this drawback CNTs can be easily non-covalently functionalized with different dispersants. In the present review we focus on the peculiar hydrophobic character of pristine CNTs that prevent them to easily disperse in organic solvents. We report some interesting examples of CNTs dispersants with the aim to highlight the essential features a molecule should possess in order to act as a good carbon nanotube dispersant both in water and in organic solvents. The review pinpoints also a few examples of dispersant design. The last section is devoted to the exploitation of the major quality of non-covalent functionalization that is its reversibility and the possibility to obtain stimuli-responsive precipitation or dispersion of CNTs.

Effect of functionalization and charging on resonance energy and radial breathing modes of metallic carbon nanotubes

“…In this final section, we perform full calculations of hydrogenated and fluorinated (6,6) bonding, and changes in effective mass). For such calculations, it is no longer possible to work with a single unit cell since the repeat vector along the nanotube axis is too short.…”

“…When the Raman excitation laser energy matches the spacing between such peaks (typically the M 11 transition for metallic tubes and S 22 or S 33 for semiconducting tubes), the Raman scattering process becomes resonant, and signal intensity typically increases by a factor of 10 6 . Typically only nanotubes in resonance with the laser are observed.…”

“…It is often desirable to tune the nanotube properties, which is typically achieved through chemical functionalization [4][5][6]. However, it remains difficult to accurately determine the nature and degree of chemical functionalization.…”

Layer-by-Layer technique employed to construct multitask interfaces in polymer composites

“…The good dispersion of carbon nanotubes in PSS can be explained by the presence of aromatic rings which have a strong affinity for graphitic surfaces via π-stacking. Typical effective dispersants are polymers consisting of repetitive units of an alkyl chain and aromatic rings, exploiting both the π-stacking on the surface of CNTs and the Van Der Waals attractions between the hydrophobic part of the surface of nanotubes and the alkyl parts [20] .…”

Transactivator of transcription (TAT) peptide–chitosan functionalized multiwalled carbon nanotubes as a potential drug delivery vehicle for cancer therapy

“…15 CNTs can also noncovalently interact with various molecules through weak interactions such as surface adsorption, π-π stacking, electrostatic interactions, hydrogen bonding or van der Waals force. [16][17][18] Since covalent functionalization would definitely alter the electronic structure of CNTs, and hence might potentially affect their physical properties, noncovalent functionalization is more attractive as it offers the facility of associating functional groups with the CNT surface without changing the system of the grapheme lattice, and thus not modifying their electrical or physical properties. A variety of biomolecules, polymers, and surfactants have been utilized for noncovalent functionalization of CNTs.…”