The structural and electronic charge distributions of single-wall carbon nanotubes (SWNTs) chemically modified with Ag and CrO3 were investigated by ab initio methods. Using first-principles spin-polarized calculations, we studied the structural and electronic behavior of Ag atoms and CrO3 molecules interacting with an (8, 0) semiconducting SWNT. We have found that the Ag atom behaves as an electron donor and the CrO3 as an electron acceptor in the presence of the SWNT. Resonance Raman experiments performed on Ag and CrO3-adsorbed SWNTs confirm the donor and acceptor behavior, respectively. (c) 2005 Elsevier B.V. All rights reserved.