Sidewall functionalization

Nakashima, N., Tomonari, Y., and Murakami, H. (2002) Water-soluble single-walled carbon nanotubes via noncovalent sidewall-functionalization with a pyrene-carrying ammonium ion. Chem. Lett. 31, 638-639. 

Chen RJ, Zhang Y G, Wang DW, Dai HJ(2001b)N oncovalent sidewall functionalization of single-walled carbon nanotubes for protein immobilization. J. Am. Chem. Soc. 123 3838-3839. 

COOH)2, swnt- phenyl-S03Na, underivi-tized SWNT stabilized in 1% Pluronic F108 (3 pg/ml-30 mg/ml) (HDF) cytotoxic as the degree of sidewall functionalization increases The sidewall functionalized SWNT samples are substantially less cytotoxic than surfactant stabilized SWNTs (2006)... 

Barrera et al. (3) sidewall functionalized carbon nanotubes with organosilanes for polymer composites, (III), with glass fibers for use in advanced cylindrical nanotube (CNT)-polymer composites. 

Because of the low reactivity of the surface of CNTs, fluorination was taken into consideration as one of the first sidewall functionalization reactions [27]. Fluorine as the most electronegative element in its elemental form is a powerful oxidizer. Mickelson et al. reported in 1998 extensive controlled and nondestructive sidewall fluorination of SWCNTs (Fig. 1.3) [28]. The functionalized F-SWCNTs dissolved well in alcohol and gave long-living metastable solutions [29]. 

The fluorotubes are very soluble and open new routes to solution-phase chemistry. F-SWCNTs can serve as a starting material for a wide variety of chemical sidewall functionalizations (see Section 1.3.1.4). By treatment with hydrazine or LiBH4-LiAlH4, the majority of the covalently bound fluorine could be removed (Scheme 1.1) [29, 41], restoring most of the conductivity and spectroscopic properties of the pristine material. 

Scheme 1.16 Sidewall functionalization by addition of nucleophilic dipyridyl imidazolidene to the electrophilic SWCNT jt-system.

Scheme 1.19 Sidewall functionalization of SWCNTs by [2+1]-cycloaddition of alkoxycarbonyl nitrenes obtained from azides.

Sidewall functionalization of SWCNTs was achieved via the addition of reactive alkyloxycarbonyl nitrenes obtained from alkoxycarbonyl azides. The driving force for this reaction is the thermally-induced N2 extrusion. The nitrenes generated attack nanotube sidewalls in a [2+l]-cycloaddition forming an aziridine ring at the tubes sidewalls (Scheme 1.19). 

Fig. 1.8 Sidewall functionalization of SWCNTs via addition of (R)-oxycarbonyl nitrenes.

Reductive alkylation of carbon nanotubes using lithium and alkyl halides yields sidewall-functionalized nanotubes soluble in common organic solvents. Billups group prepared dodecylated SWCNTs from raw HiPCO tubes using lithium and dodecyl iodide in liquid ammonia and demonstrated the occurrence of exten-... 

Noncovalent functional strategies to modify the outer surface of CNTs in order to preserve the sp2 network of carbon nanotubes are attractive and represent an effective alternative for sidewall functionalization. Some molecules, including small gas molecules [195], anthracene derivatives [196-198] and polymer molecules [118, 199], have been found liable to absorb to or wrap around CNTs. Nanotubes can be transferred to the aqueous phase through noncovalent functionalization of surface-active molecules such as SDS or benzylalkonium chloride for purification [200-202]. With the surfactant Triton X-100 [203], the surfaces of the CNTs were changed from hydrophobic to hydrophilic, thus allowing the hydrophilic surface of the conjugate to interact with the hydrophilic surface of biliverdin reductase to create a water-soluble complex of the immobilized enzyme [203]. 

Fig. 1. 13 Water-soluble SWCNTs via noncovalent sidewall functionalization with a pyrene-carrying ammonium ion.

A very popular recent research topic has been the functionalization of curved graphenes, in fullerenes and especially in CNTs [47-50], Not only surface functional groups but also organic compounds and biomaterials have been used [49,51] in the latter case, a more appropriate term is grafting, and the SCI identified 26 papers explicitly devoted to this procedure for nanotubes, all of them published in the last 3 years. The following two issues—one more fundamental and the other more utilitarian— merit our attention here (i) Are only the graphene terminations (edges) functionalized, or is sidewall functionalization feasible as well (ii) Which procedures are of special interest for electrochemical applications ... 

The effect of (presumably covalent) sidewall functionalization on the conductivity of SWCNTs was also reported recently in a theoretical study [61]. The authors found it important (and possible ) to distinguish between monovalent and divalent sidewall additions, the latter with or without sidewall opening. They concluded that the conductance of the monovalently functionalized tube decreases rapidly with the increasing addend concentration, and the nanotube loses its metallic-ity around 25% of modification, whereas for the divalent case, the CNTs remain substantially conductive. ... 

C. A. Dyke and J. M. Tour, Overcoming the insolubility of carbon nanotubes through high degrees of sidewall functionalization, Chem. Eur. J. 10(4), 813-817 (2004). 

These efforts indicated that the sidewall functionalization effectively enhances the tensile strength and tensile modulus by improving dispersion and interfacial bonding in SWNTs reinforced polymer composite. 

Sidewall-functionalized carbon nanotubes were prepared by Wong [4] using ozone with an oxygen carrier then postreacted with sodium hydride or DMS to decompose primary ozonides to form aldehydes and ketones. 

Figure 6.55. Schematic of the various methods to perform sidewall functionalization of SWNTs. Reproduced with permission from Baneijee, S. Hemraj-Benny, T. Wong, S. S. Adv. Mater. 2005, 17, 17. Copyright 2005 Wiley-VCH.

Figure 1.6 Several possible functionalization mechanisms for SWCNTs." (A) defect-group functionalization, (B) covalent sidewall functionalization, (C) noncovalent exohedral functionalization with surfactants, (D) noncova-lent exohedral functionalization with polymers, (E) endohedral functionalization with fullerene (C6o)-...

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