Defect Functionalization - Transformation of Carboxylic Functions

The oxidative introduction of carboxylic functions to nanotubes provides a large number of CNT-functional exploitations and permits covalent functionalization by the formation of amide and ester linkages and other carboxyl derivatives [24]. Bifunctional molecules (diamines, diols, etc.) are often utilized as linkers. More illustrative examples are nanotubes decorated with amino-functionalized dendrimers, nucleic acids, enzymes, etc., and the formation of bioconjugates of CNTs [96]. 

Newkome-type dendrons were attached to the carbon scaffold of SWCNTs and MWCNTs by defect group functionalization [108], First- and second-generation amine dendrons such as those depicted in Fig. 1.5 were condensed with the carboxyl groups of purified and opened SWCNTs and MWCNTs according to the car-bodiimide technique [108], These CNTderivatives can be expected to combine the characteristics of carbon nanotubes with those of dendrimers, potential building blocks for supramolecular, self-assembling and interphase systems. 

A gas-phase derivatization procedure was employed for direct amidization of oxidized SWCNTs with simple aliphatic amines. In some cases a minor amount 

HiPCO-SWCNTs were oxidized in a UV-03 gas-solid interface reaction and subsequently assembled on a rigid oligo(phenylenethynylene) self-assembled monolayer (SAM). In a chemical assembly , based on condensation between the carboxylic acid functionalities of the 03-oxidized SWNTs and the amine functionalities of the SAMs, SWCNT-amides were formed in ordered arrays [116]. 

The reduction of the amido functions of amide-solubilized MWCNTs by LiAlH4 afforded the corresponding hydroxy-substituted CNTs, confirmed by FT-IR and XPS studies [133]. No morphology change of the nanotubes after reduction could be observed by Raman spectroscopy [133]. 

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