Carbon nanotube (CNT)/europium hydroxide core-shell nanowires were prepared easily on a large scale under the boiling reflux of water assisted by the surfactant, sodium polystyrenesulfonate (SPS). The core-shell nanowires are characterized by transmission electron microscopy, X-ray diffraction, and Xray photoelectron spectrum. A possible formation mechanism has been suggested as follows: The phenyl rings of SPS can react with the carbon ring of CNTs to form the pi-pi noncovalent bond, which makes the SPS cover the surface of CNTs entirely, and thus the surface of modified CNTs is negatively charged, which repel with each other resulting in the good dispersion. In addition, the negatively charged surface of CNTs adsorbs europium ions (positive). The adsorbed europium ions in situ react with OH- ions to create europium hydroxide nanoparticles, and subsequently, the nanoparticles fuse together to form a dense coating layer on CNTs. (C) 2009 Elsevier B. V. All rights reserved.