Synthetic strategies for Y-junction carbon nanotubes

Y-junction carbon nanotubes can be produced in relatively large quantities by the vapor phase pyrolysis of a mixture of cobaltocene or ferrocene with thiophene in a hydrogen atmosphere. Pyrolysis of Ni- and Fe-phthalocyanines or Fe(CO)(5) with thiophene also yields Y-junction nanotubes. Good yields of Y-junction nanotubes were obtained by pyrolyzing thiophene over an Ni(Fe )/SiO2 catalyst as well. Many of the nanotubes show multiple Y-junctions. O f the various methods employed by us, the pyrolysis of thiophene with metal locenes or over a Ni(Fe)/SiO2 catalyst yields the best results and the latt er is a less expensive route. The availability of large quantities of Y-jun ctions by the procedures employed here should render them useful for exploi tation in nanoelectronics. (C) 2001 Elsevier Science B.V. All rights reserv ed.