Thermo-optical response of colloidal metallic and semiconducting single-walled carbon nanotubes

The thermo-optical responses of aqueous solutions of semiconducting and metallic carbon nanotubes were investigated using thermal-lens technique. The colloids thermal diffusivity, thermal lens strength and thermo-optical coefficient were measured. The results suggest that the presence of carbon nanotubes at low concentration does not change significantly the thermal diffusivity and conductivity of the colloidal system in comparison with pure water. However, the thermal lens strength presented a huge enhancement due to the presence of carbon nanotubes. It was also observed that the colloid containing semiconducting carbon nanotubes presents a larger thermo-optical coefficient than the system containing metallic tubes. The thermal contribution to the nonlinear refraction of the colloidal systems was characterized by Z-scan technique and their parameters of nonlocality were also evaluated.