Single-walled carbon nanotube bundles intercalated with semiconductor nanoparticles

Nanoparticles of CdSe, CdS and ZnSe have been incorporated in the inter-tubular gaps of single-walled carbon nanotube (SWNT) bundles. Electron microscope, X-ray diffraction (XRD), electronic spectroscopy and Raman studies have been employed to characterize these systems. The lengths of the intercalate inside the bundles could be varied by changing the reaction conditions. Electronic absorption and photoluminescence studies from the semiconductor intercalates show the expected blue-shift with respect to the corresponding bulk samples in CdS and ZnS samples. The SWNT lattice is expanded on incorporating CdSe as confirmed by XRD in the low-angle range. The expansion in the lattice is also corroborated by the Raman measurements which show a considerable red-shift for both the radial and the tangential modes of the SWNT signal, thus signifying an increase in the van der Waals gap between the tubes in the bundle. The red-shift of the Raman signal is due to the decrease in the inter-tube interactions as well as due to doping effects.