Download Kinetics of the Selective Reaction of Diazonium Salts with Single

Kinetics of the Selective Reaction of Diazonium Salts with Single-Walled
Carbon Nanotubes in Aqueous Surfactant Solutions
Adam J. Blanch, A manda V. Ellis, Claire E. Lenehan, Jamie S. Quinton
School of Chemical and Physical Sciences, Flinders University
GPO Box 2100, Adelaide SA 5001
Current methods of synthesis for carbon nanotubes (CNTs) usually produce
heterogeneous mixtures of different nanotube diameters, thus a mixture of electronic
properties. Consequently, many techniques have been developed in attempts to
separate nanotubes according to their electronic type, w ith varying degrees of
success. One such technique involves the selective chemical reaction of CNTs with
electron w ithdraw ing diazonium salts, w here metallic nanotubes are preferentially
functionalised due to their higher electron density at the Fermi level.1 Since this
reaction requires the nanotubes to be individualised, it is usually carried out in a
surfactant stabilised dispersion. Despite the potential offered by such selective
reactions as a pathw ay tow ards separation by electronic type, little research has
been performed into the reaction kinetics 2,3, likely due to the limited success reported
in separating CNTs via this method.4 Here w e present kinetic data for electric arc
produced CNTs reacting w ith three different compounds; 4-bromo, 4-nitro and 4carboxy benzenediazonium tetrafluoroborate salts in aqueous solution. The CNTs
w ere dispersed by a variety of commonly utilised surfactants, both ionic and nonionic. The selectivity of these reactions was monitored through the reduction of the
absorbance of semiconducting S22 and metallic M11 transitions in the UV-vis-NIR
spectra of the solutions as the reaction proceeds.3 It w as observed that this
selectivity depends heavily on the type of diazonium salt and its concentration,
temperature of the reaction, type of surfactant and also on surfactant concentration in
some instances. It is clear that for certain combinations of surfactant and diazonium
salt the selectivity is markedly improved, particularly in dispersions of the non- ionic
surfactants Pluronic F-127 and Brij S- 100.
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Doyle, C. D.; Rocha, J.-D. R.; Weisman, R. B.; Tour, J. M. J. Am. Chem. Soc. 2008, 130, 67956800.
Schmidt, G.; Gallon, S.; Esnouf, S.; Bourgoin, J.-P.; Pascale Chenevier Chem. Eur. J. 2009, 15,
2101-2110.
Dyke, C. A.; Stewart, M. P.; Tour, J. M. J. Am. Chem. Soc. 2005, 127, 4497-4509.