Control of Fe catalyst nanoparticle density for carbon nanotube growth using Langmuir-Blodgett deposition of mixtures of Fe nanoparticles and arachidic acid

•Fe nanoparticles (NPs) were mixed with arachidic acids.•FeNPs and arachidic acids were deposited on substrates by Langmuir-Blodgett method.•The vertically-aligned (VA) CNTs were synthesized from FeNPs by thermal CVD method.•Thermal aggregation of FeNPs was prevented by mixing arachidic acids.•We report a relationship between thermal aggregation of FeNPs and VA-CNT growth.

Vertically-aligned carbon nanotubes (VA-CNTs) have been attracting attention as the electrode material of polymer electrolyte fuel cell. Fe nanoparticles (FeNPs) were used as catalyst for VA-CNT growth. FeNP monolayer film was deposited on substrates by Langmuir-Blodgett (LB) technique. VA-CNTs were synthesized from FeNP LB films by thermal chemical vapor deposition (CVD) method. Number density of VA-CNTs was lowered because of thermal aggregation of FeNPs during thermal CVD. We mixed FeNPs with arachidic acids (C20) as filler molecules, and synthesized VA-CNTs from FeNPs-C20 LB films, therefore we could reduce thermal aggregation and control the number density of FeNPs.