Starched Carbon Nanotubes

Abstract

Since their discovery [1] in 1993, single-walled carbon nanotubes (SWNTs) have found numerous applications [2] in chemistry and physics on account of their anisotropic shapes (diameters of around 1 nm and lengths of micrometers), remarkable strengths and elasticities, and unique physical properties, for example, high thermal and electrical conductivities. By contrast, and despite their clear potential, SWNTs have not yet been fully integrated into biological systems, [3] mainly because of the considerable difficulty in rendering them soluble in aqueous solutions.Initially, the challenge of achieving soluble SWNTs in organic solvents was addressed by their covalent modification-examples include both end-group [4] and side-wall [5] functionalization. Covalent modification, however, has the disadvantage that it impairs their physical properties. For these, and other reasons, we have been attracted by a supramolecular approach [6] to the solubilization problemnamely, the noncovalent functionalization of SWNTs by wrapping polymers around them in the knowledge that desired features can be grafted onto the polymers, prior to their being self-assembled around the SWNTs. Considerable progress [6, 7] has been made in the use of synthetic polymers to render SWNTs soluble in organic solvents. However, while some water-soluble polymers [8] and surfactants [9] can bring aqueous solubilities to SWNTs, they may not be as biocompatible as would be desirable.It was for this reason, amongst others, that we decided to explore the possibility of solubilizing SWNTs in aqueous solutions of starch. [10] We knew from our knowledge of the supramolecular chemistry of fullerenes [11] that cyclodextrins (CDs) of the appropriate dimensions (g-CD commonly and d-CD occasionally), and in the correct stoichiometries, will dissolve fullerenes (C 60 and C 70 , for example) in water. [12] CDs are the macrocyclic analogues [13] of starch. The connection is clear. Here, we report 1) that common starch, provided it is activated toward complexation by wrapping itself helically around small molecules, will transport SWNTs competitively into aqueous solutions, 2) that the process is sufficiently reversible at high temperatures to permit the separation of SWNTs in their supramolecular starch-wrapped form by a series of physical manipulations from amorphous carbon, and 3) that the addition of glucosidases to these starched carbon nanotubes results in the precipitation of the SWNTs from aqueous solution.

Carbon Nanotubes Engineering Assisted by Natural Biopolymers

“…In year 2002, amylose functionalized SWCNTs could be purified for the better affinity of amylose to SWCNTs than carbonaceous impurities. (Star, et al 2002). In our experiment, as shown in figure 5, we also found that gellan gum functionalized SWCNTs could also be separated from carbonaceous impurities by centrifuging their co-suspension .…”

Investigation of Aromatic/Aliphatic Polyimides as Dispersants for Single Wall Carbon Nanotubes

“…There are four prominent methods for achieving dispersion: mechanical methods 8,10 , functionalizing the SWNTs [11][12][13][14][15][16][17][18][19][20] , using surfactants 21 , and non-covalent modification by using small molecules and polymer dispersants [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] . There are advantages and disadvantages associated with each of the listed methods.…”

The Unlikely Surfactant: DNA as a Ligand for Single-Walled Carbon Nanotubes

“…These macromolecules may be either synthetic polymers or biomacromolecules. Nanotube suspensions have been obtained with macromolecules like gum arabic (Bandyopadhyaya et al, 2002), amylomaize (Star et al, 2002;Kim et al, 2003), cyclodextrines (Chen et al, 2001;Dodziuk et al, 2003), peptides (Dieckmann et al, 2003;Wang et al, 2003), polymers (O'Connell et al, 2001), or fluorene-based polymers Nish et al, 2007) as "surfactants". Among the biomacromolecules used to solubilize carbon nanotubes, DNA sticks out as the one producing particularly high yields of solubilized tubes (Figure 2).…”