Carbon Nanotubes and Graphene - Research and Applications

Researchers studied thoroughly the forces involved in repeatedly kinking and buckling a single multi-walled carbon nanotube (MWCNT) using an atomic force microscope (AFM) operating inside a transmission electron microscope (TEM). The measured forces were correlated to the geometry of the nanotube. The compressive force sustained by the nanotube was determined as a function of its deflection from the initial state. The results are in good agreement with the classical elastic theory of buckling. The Young’s modulus of the nanotube determined by this method is consistent with values obtained by other techniques. The researchers have tested the limits of the elasticity of the nanotube and found a lower bound on its yield strength of 1.7 GPa, which is higher than that of steel. After kinking, the plastic deformation of the MWCNT was also observed.

Researchers report the development of a novel nanoelectronic platform based on single wall carbon nanotube nanoelectrodes for directly probing the dc conductivity in DNA at the single-molecule level. Potential application of this study would be the identification of specific genes. Stretching and positioning of DNA molecules to the nanotube electrodes was achieved by using dielectrophoresis (DEP). E-beam lithography was used to make electrical contacts to the individual single wall carbon nanotubes. Researchers measured current values of 25-40 pA when a double-stranded DNA molecule bridged the nanotube electrode. In comparison, a single-stranded DNA molecule carried much lower current (1 pA or less). The application of a back-gate voltage showed that the bridging DNA molecule forms a p-type semiconducting channel between the single wall nanotube electrodes. This research demonstrated that nanotubes can efficiently be employed as nanoelectrodes for probing charge transport in DNA.