Controlled syntheses of aligned multi-walled carbon nanotubes: Catalyst particle size and density control via layer-by-layer assembling

Using the layer-by-layer assembly method, we have fabricated catalyst particles of a controlled size distribution and packing density for aligned carbon nanotube growth. Ill particular, poly(sodium-4-styrenesulfonate), PSS, and iron hydroxide colloid were layer-by-layer assembled via the electrostatic interaction onto an acetic-acid-plasma treated quartz plate. This multilayer catalyst precursor film was then calcined in Ar/H-2 at 750 degrees C to produce iron nanoparticles for the subsequent growth of carbon nanotubes at 750 degrees C Linder a combined flow of Ar/H-2 and C2H2. UV-vis absorption and X-ray photoelectron spectroscopic (XPS) measurements confirm the consecutive formation of the iron hydroxide colloid/PSS multilayer films. Atomic force and electron microscopic (AFM, SEM, TEM) imaging shows that the catalyst particles thus prepared possess a layer-number-dependent size distribution and packing density after calcination. Aligned multi-walled carbon nanotubes with a controlled structure and morphology were produced from judiciously designed layer-by-layer assembled multilayer catalyst precursor films with a desirable layer number and composition.