The goal of this chapter is to discuss the synthesis of carbon nanotubes via CVD using iron nanoparticles obtained from iron oxide precursors as the catalyst focusing on the possibility of high-yield syntheses on large-area substrates. The possibilities of using sol-gel methods to generate porous SiO2 and Al2O3 matrices that include iron nanoparticles are reported, and the advantage of an aluminum matrix over a silica matrix is discussed. The influence of both the sol drying-gelification temperatures on the carbon yield and conversion were discussed along with the influence the partial pressure of the carbon gas feedstock had on the CNT characteristics. The advantage of an aluminum matrix over a silica matrix is that it results in a hybrid material consisting of MWCNT with hercynite nanoparticles attached to their walls without purification. For silica matrices, several purifications steps after the CVD synthesis are necessary to remove amorphous carbon and other byproducts. Advanced oxidation techniques (AOTS) are new and interesting alternatives for the controlled oxidation of CNTs. With these techniques, controlling the degree of CNT oxidation is easy, environmentally friendly and allows for the formation of carboxylic groups,-OH or both, depending on the selected AOT. Iron nanoparticles can also be synthesized on different substrates using iron salt solutions. In addition, sold iron oxide nanoparticles dispersed in an adequate solvent can be deposited onto either conductive substrates or semiconductors using an appropriate technique. Both methods allow for the deposition of nanoparticles over large areas for the growth of carbon nanotubes. In addition, both methods can control the density of the catalyst on the substrate and for the synthesis of vertically aligned carbon nanotubes (VA-CNTs). Finally, the possibilities of a synthesis that uses metal substrates with its catalytic sites directly generated on the substrate surface without previous catalytic deposition was discussed. © 2013 Nova Science Publishers, Inc. All rights reserved.