Noncovalent Functionalization with Aromatic Molecules

Some aromatic molecules, such as pyrene, porphyrin, and their derivatives, have strong affinity with the basal plan of graphene sheets via n-n interactions. Noncovalent functionalization has been used in the functionalization of CNTs, and as the rise of graphene, it has been used for functionalization of graphene. 

---

It often becomes necessary to prepare dispersions of graphene in organic or aqueous media [73-74]. For this purpose, different approaches have been successfully employed for few-layer graphene. The two main approaches for obtaining this type of graphene are covalent functionalization or by means of noncovalent interactions. There has been some recent effort to carry out covalent and noncovalent functionalization of graphene with aromatic molecules, which help to exfoliate and stabilize the individual graphene sheets and to modify their electronic properties [75 84]. 

Encapsulation of different entities inside the CNT channel stands alone as an alternative noncovalent functionalization approach. Many studies on the filling of carbon nanotubes with ions or molecules focus on how the presence of these fillers affects the physical properties of the tubes. From a different point of view, confinement of materials inside the cylindrical structure could be regarded as a way to protect such materials from the external environment, with the tubes acting as a nanoreactor or a nanotransporter. It is fascinating to envision specific reactions between molecules occurring inside the aromatic cylindrical framework, tailored by CNT characteristic parameters such as diameter, affinity towards specific molecules, etc. 

In ESI-MS, a wealth of noncovalent ion/molecule adduct ions can be also generated. For instance, the formation of ion/solvent (So) adducts, [M + So]+, were observed during ESI-MS of 3-hydroxyaniline as well as other aromatic molecules. The relative abundances of ions [M + H]+, [M + So + H]+ and [M + 2 So + H]+ were studied as a function of the temperature and pH, with the solvents being mixtures of methanol/water and acetonitrile/water sometimes containing ammonium acetate as additive118. 

CNTs can be further functionalized through noncovalent or covalent interactions for better dispersibility and stability in polymer matrix. The noncovalent functionalization of CNTs normally involves van der Waals, n-n, CH-n, or electrostatic interactions between polymer molecules and CNT surfaces. The advantage of noncovalent functionalization is that it does not destroy the conjugated system of the CNT sidewall, and therefore it does not affect their final properties (Spitalsky et al., 2010). It should be noted that, the graphitic sidewalls of CNTs provide the possibility for tt-stacking interactions with conjugated and aromatic... 

As is shown in Section 3.3.2, biomolecules such as proteins and DNA bind to CNTs by nonspecific interactions. Dai and coworkers sought to develop a chemical method for the noncovalent functionalization of SWNTs with biomolecules.To this end, 1-pyrenebutanoic acid, succinimidyl ester was employed this molecule adsorbs irreversibly to the wall of pristine SWNTs in organic solvents such as A,A-dimethylformamide (DMF) or methanol. The pyrenyl group of 1-pyrenebutanoic acid, succinimidyl ester, which is aromatic, is known to strongly bind to the... 

---