Two effective methods for dispersion and alignment of single-walled carbon nanotubes (SWCNTs) were developed. One is the floating-potential dielectrophoresis (FPD) method, which can achieve the alignment of individual SWCNTs between two electrodes with high yield (more than 30%) and high repeatability. The second is the gas blow method. Using the shear forces associated with a rapidly moving fluid, SWCNTs were positioned in a direction corresponding to the flow vector of the fluid. This technique shows great potential for scaling up the displacement of SWCNTs with controlled orientations. Various dispersion agents including ethanol, dichlorobenzene, sodium dodecyl sulfate (SDS) and DNA were investigated with these two methods. It was found that SDS was the most effective dielectric medium used for FPD dispersion and alignment of SWCNTs. The result of electric measurement for the individual SWCNTs aligned between two electrodes suggests that, using the FPD method, both metallic and semiconducting SWCNTs could be aligned between the electrodes. The individual SWCNT resistances measured range from 20 KΩ to 5 MΩ suggesting a high contact resistance between an aligned SWCNT and metal electrodes. High resolution transmission electron microscopy (TEM) and scanning electron microscopy (SEM) characterization reveal DNA molecules wrapped around the SWNCTs after the dispersion process which may affect the intrinsic properties of SWCNTs.
Selective suspension in aqueous sodium dodecyl sulfate according to electronic structure type allows simple separation of metallic from semiconducting single-walled carbon nanotubes
