Functionalization and solubilization of thin multiwalled carbon nanotubes

The reaction of thin multiwalled carbon nanotubes with a mixture of concentrated HNO3 and H2SO4 has been studied by IR absorption and x-ray photoelectron spectroscopies. The results indicate the attachment of -C(O)OH groups to nanotubes and subsequent conversion of these groups to -C(O)Cl groups via reaction with SOCl2 and then to -C(O)NR2 via reaction with didodecylamine. The yield of the carboxylated nanotubes is 53%, and that of the amidated nanotubes is 28%. The O : C atomic ratio in the carboxylated tubes is 1.0 : 9.0. The solubility of the carboxylated tubes in water is 3.13 g/l, and that of the amidated tubes in chloroform is 1.30 g/l.