In this work, first, we aim to present a catalyst-free protocol to fabricate doped carbon nanotubes (CNTs) by S, P and S/P elements and with controlled physical and chemical properties. Then, we have explored the effect of S concentration on the morphology of CNTs. The structural and chemical composition of fabricated CNTs/NAA composites were analysed by various characterisation techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), EDXS and high resolution transmission electron microscopy (HRTEM). (C) 2016 Elsevier B.V. All rights reserved.