Solubility and electrical transport properties of thiolated single-walled carbon nanotubes

Single-walled carbon nanotubes have been modified using dodecanethiol as the reaction agent. The thiolated nanotubes form a stable suspension in toluene, and can be used for Langmuir-Blodgett deposition of monolayers. The nanotube conductance decreases by three orders of magnitude and acquires a gate dependence with a memory effect. The conductance for the on and off states with $0V$ applied to the gate differs by more than two orders of magnitude. These effects are explained in terms of a chemical reaction between the tube wall and the thiol. The thiolation process is also observed on the exposure of the nanotubes to toluene solutions of dodecanethiol-stabilized Au nanoparticles. The nanoparticles can thus be used for labeling or manipulating the location of the chemical reaction sites on the tube wall. The reaction is followed using optical-absorption measurements.