| Summary: | The catalytic activity of cobalt and iron nanoparticles for the growth of carbon nanotubes (CNTs) was studied by a specific reproducible and up-scalable fabrication method. Co and Fe catalysts were deposited over SiO<sub>2</sub> nanoparticles by a wet-impregnation method and two different annealing steps were applied for the catalyst formation/activation. The samples were calcined at an optimal temperature of 450 °C resulting in the formation of metal oxide nano-islands without the detection of silicates. Further reduction treatment (700 °C) under H<sub>2</sub> successfully converted oxide nanoparticles to Co and Fe metallic species. Furthermore, the catalytic efficiency of both supported-metal nanoparticles at 2 and 5% in weight of silica was evaluated through the growth of CNTs. The CNT structure, morphology and size dispersion were tailored according to the metal catalyst concentration.
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