Synthesis and Properties of Chemically Modified Carbon Nanotubes

Abstract

Since their discovery single-walled carbon nanotubes (SWNTs) have gained the interest of many scientists and engineers due to their prominent structural, mechanical and electronic properties which make them applicable in various areas including electronics, chemical and biological sensing and reinforced composite materials. Although SWNTs have many application areas their use can be limited since they are synthesised as a mixture of metallic and semiconducting species with different diameters and helicities and they have limited solubility in aqueous and non-aqueous solvents. Covalent modification of SWNTs is an important tool to introduce new functional groups onto the surface of nanotubes to improve their solubility and processability. It can also be used to separate metallic from semiconducting nanotubes.
The work presented here has concentrated on the non-disruptive covalent modification of SWNTs using pyridine diazonium salt addition, 1,3-dipolar cycloaddition and reductive alkylation.
The selectivitiy of the addition was probed by UV-vis-NIR and Raman spectroscopy where the metallic were found to be more selective than semiconducting SWNTs. The location and distribution of the functional groups was determined by AFM using electrostatic interactions with gold nanoparticles.
Rheological data showed that the pyridine modified SWNTs were able to act as crosslinkers and hydrogen bond to poly(acrylic acid) to form SWNT hydrogels. The indolizine modified SWNTs, emitted blue light when excited ca. 330 nm, were capable of sensing 4-nitrophenol, 3-nitrophenol, 2-nitrophenol, 2-nitrosotoluene and 2,4-dinitrotoluene with a detection limit of ca. 10-8 M.
The modified SWNTs were further characterised using FTIR, XPS, TGA-MS and optical microscopy.