Controlling the morphology of Vertically-aligned carbon nanotubes using Langmuir-Blodgett deposited CoFe2O4, Fe3O4, and Fe nanoparticles with palmitic acid

The synthesis of Vertically-aligned carbon nanotubes (VA-CNTs) from Langmuir-Blodgett (LB) films of laboratory made CoFe2O4 nanoparticles (NPs), Fe3O4 NPs, and commercially available Fe NPs was performed to compare the catalytic activity of these catalyst NPs. VA-CNT films synthesized of CoFe2O4 NPs were approximately 2-3 times thicker than these synthesized of Fe3O4 NPs and Fe NPs. Palmitic acid (C16) molecules were mixed with the above catalyst NPs to control the distance between catalyst NPs in LB films, and adjust the number density of VA-CNTs synthesized from these LB films. Catalyst NPs were not dispersed uniformly and composed the domain of catalyst NPs in the C16 mixed L films. From optimizing the area ratio of catalyst NPs to C16 molecules, VA-CNT films synthesized of the catalyst NPs and C16 mixture exhibited large thicknesses compared with these synthesized of only catalyst NPs. VA-CNT films synthesized of CoFe2O4 NP-C16 LB films exhibited the largest thicknesses among these synthesized of three types of catalyst NP-C16 LB films, and enable to obtain a VA-CNT film up to 136 μm. We also performed the evaluation of VA-CNT diameters to investigate how the catalyst types, sizes, distributions, and area ratios affect CNT diameters. The mean inner and outer diameters were almost constant regardless of the catalyst types and area ratios. The mean coefficients of variation (CVs) of the CNT outer diameters synthesized of CoFe2O4 NPs, Fe3O4 NPs, and Fe NPs were 19.5%, 20.5%, and 28.9%, respectively.