Dispersion of metal nanoparticles for aligned carbon nanotube arrays

We report that Co metal nanoparticles (an average diameter of 4 nm) chemica lly synthesized by a reverse micelle method catalyzes the growth of multiwa ll carbon nanotubes (MWNTs) aligned perpendicular to a substrate. The surfa ce of the nanoparticles is covered with surfactants so that the nanoparticl es can be dispersed in organic solvent. The dispersion of the nanoparticles was cast directly onto a plane Si substrate for thermal pyrolysis of acety lene. We have found that the pretreatment of the metal nanoparticles with h ydrogen sulfide before the pyrolysis straightens the MWNTs, suggesting sulf urization of the nanoparticle catalyst plays an important role in regular g rowth of the MWNTs. The dispersion of the nanoparticles offers a convention al and processible approach to synthesize large area aligned MWNT arrays. ( C) 2000 American Institute of Physics. [S0003-6951(00)05327-4].