Environmental Engineering Reference
In-Depth Information
(a)
(b)
figure 14.3
CNTs: (a) Impure, (b) Pure. Reproduced with permission from Ref. [6]. © springer.
+
Non-covalent interaction
+
Covalent interaction
= Ligands
= Covalent bond
= Functional groups
figure 14.4
sketch of covalent and noncovalent functionalization on a CNT.
14.2.2
fullerenes
FUls have attracted considerable attention in different fields of science since their discovery in 1985. Physical, chemical,
and biological properties of FUls indicate that they have promising applications. It is inferred that size, hydrophobicity, three-
dimensionality, and electronic configurations make them an appealing subject in chemistry. FUls are often accompanied with
large amounts of soots; therefore, purification is necessary before their real applications are realized. Purification of FUls nor-
mally involves extraction from soots and then separation by liquid chromatography. Additionally, other purification techniques,
like elution on molecular sieves or activated charcoal, gel permeation, and supercritical fluids purification, have also been used [4].
FUls are practically insoluble in water and generally tend to form aggregates in aqueous media. To disperse them in water,
prolonged stirring for days is needed. The addition of additives, for example, surfactants, cyclodextrins (Cds), or sugar poly-
mers, aids their efficient dispersion in water. FUls can also be dispersed in water by first dissolving them in an organic solvent
and then adding the solution to water and evaporating off the organic solvent.
Incorporation of FUls into polymeric materials to improve their processability has become a common practice in applica-
tions such as optoelectronics, photovoltaics, fuel cell membranes, and the life sciences. The unique properties of FUls, such as
their spherical shape, conjugated three-dimensional π-electronic system, and the ability to exhibit donor-acceptor or π-π inter-
actions, make them attractive candidates for analytical applications. As a result, these have been used as chromatographic
 
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