Dispersion of metal nanoparticles for aligned carbon nanotube arrays

We report that Co metal nanoparticles (an average diameter of 4 nm) chemically synthesized by a reverse micelle method catalyzes the growth of multiwall carbon nanotubes (MWNTs) aligned perpendicular to a substrate. The surface of the nanoparticles is covered with surfactants so that the nanoparticles can be dispersed in organic solvent. The dispersion of the nanoparticles was cast directly onto a plane Si substrate for thermal pyrolysis of acetylene. We have found that the pretreatment of the metal nanoparticles with hydrogen sulfide before the pyrolysis straightens the MWNTs, suggesting sulfurization of the nanoparticle catalyst plays an important role in regular growth of the MWNTs. The dispersion of the nanoparticles offers a conventional and processible approach to synthesize large area aligned MWNT arrays. (C) 2000 American Institute of Physics. [S0003-6951(00)05327-4].