Separation techniques covalent/noncovalent interactions

In general, the various synthesis strategies for nanocarbon hybrids can be categorized as ex situ and in situ techniques [3]. The ex situ ( building block ) approach involves the separate synthesis of the two components prior to their hybridization. One can rely on a plethora of scientific work to ensure good control of the component s dimensions (i.e. size, number of layers), morphology (i.e. spherical nanoparticles, nanowires) and functionalization. The components are then hybridized through covalent, noncovalent or electrostatic interactions. In contrast, the in situ approach is a one-step process that involves the synthesis of one of the components in the pres-... 

To further understand the molecular organization in humic systems at the level of covalent and noncovalent interactions, additional developments in the high-resolution analytical tools are needed. To achieve this level of resolution, techniques used to explore the complexity of humic materials must be coupled to separation methods that facilitate substantial reductions in the molecular heterogeneity of studied systems. 

There are two types of surface modifications for CNTs noncovalent interactions (Figure 6.54) and covalent sidewall (Figure 6.55) or defect-sitet (Figure 6.56) functionalization.Both methods, as well as physical techniques such as sonica-tion, are successful in separating individual SWNTs from bundles - a process known as exfoliation. In general, it is most desirable to incorporate isolated SWNTs in a composite rather than bundles, since the latter features poor intertube interactions resulting in a lower overall strength - especially at low CNT concentrations. 

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