Coating Alumina on Catalytic Iron Oxide Nanoparticles for Synthesizing Vertically Aligned Carbon Nanotube Arrays

To synthesize long and uniform vertically aligned carbon nanotube (VACNT) arrays, it is essential to use catalytic nanoparticles (NPs) with monodisperse sizes and to avoid NP agglomeration at the growth temperature. In this work, VACNT arrays were grown on chemically synthesized Fe₃O₄ NPs of diameter 6 nm by chemical vapor deposition. Coating the NPs with a thin layer of Al₂O₃ prior to CNT growth preserves the monodisperse sizes, resulting in uniform, thick and dense VACNT arrays. Comparison with uncoated NPs shows that the Al₂O₃ coating effectively prevents the catalyst NPs from sintering and coalescing, resulting in improved control over VACNT growth. © 2011 American Chemical Society.