We have used chemical vapor deposition (CVD), for the synthesis of carbon nanotubes (CNTs) by the sublimation of iron phthalocyanines (FePcs); by the catalytic decomposition of acetylene over iron nanoparticles, supported on a thermal Si oxide and also by a Pd catalyst supported on alumina. We have explored different means of growing multiple wall CNTs and other carbon materials. Transmission and scanning electron microscopy have been used to characterize the synthesis products. We have also performed inverse photoemission spectroscopy (IPS), to explore the unoccupied electronic states above the Fermi level of CNTs and describe the peculiarities of the nanotubes electronic structure. We have examined by different CNTs samples and determined the origin of the main IPS spectral features. (C) 2007 Elsevier Ltd. All rights reserved.