Abstract:
The mechanism involved in the modification of carbon nanotubes (CNTs) funtionalised using
diazonium salts has been investigated. Bamboo-like and hollow-tube multiwalled carbon nanotubes
(MWCNTs) were covalently modified using 4-nitrobenzenediazonium tetrafluoroborate. The
MWCNTs were derivatised in the presence and absence of hypophosphorous acid as a mild reducing
agent and the resulting materials were characterised using cyclic voltammetry. The observed peak
potentials for the modified materials were found to differ depending on the derivatisation conditions
(presence / absence of hypophosphorous acid, diazonium salt concentration and temperature) and these
defferences were interpreted mechanically. The experimental results suggest that, in the absence of
hypophosphorous acid, the derivatisation mechanism likely proceeds through a cationic intermediate,
whilst in the presence of the hypophosphorous acid the mechanism probably involves either a purely
radical intermediate or a mixture of radical and cationic species depending on the concentration of the
hypophosphorous acid reducing agent and the reaction temperature. Polymerisation of the nitrophenyl
groups on the surface of nanotubes was studied using different concentrations of 4-
nitrobenzenediazonium tetrafluoroborate and was found to increase with increasing concentration of
cationic intermediates. The effect of the reaction temperature on the derivatisation was explored over a
range of temperatures from 5 to 50
0C and the optimum derivatisation temperature was determined in
the presence and absence of hypophosphorous acid. It was found to be 20
0C and 35
0C in the presence
and absence of hypophosphorous acid respectively.
