The effect of solvent on electrical transport properties in single-wall carbon nanotubes

We have measured the temperature dependence of thermoelectric power, S(T), for Single-wall carbon nanotubes (SWNT) mat. The S(T) for high-temperature heat-treated SWNT samples shows a strong curved T-dependence. The results indicate the interaction between conduction electrons and transition metals; i.e. Kondo effect. For dried SWNT which contained solvent such as ethanol or DMF, on the contrary, the S(T) is almost proportional to T with intercept of nearly zero, indicating typical metallic behavior. The result indicates a metallic property in SWNT. We conclude that the Kondo effect is weakened when SWNT contain those solvents.