The secondary growth of carbon nanotubes (CNTs) on the surface of CNTs to form the chemically connected CNTs structure was investigated. In order to grow the secondary CNTs, the catalyst FePt nanoparticles (NPs) were chemically synthesized as colloids and attached on the primary CNTs through the hydrophobic interaction between CNT and NPs as dispersed inside the solution. It was demonstrated that a bunch of secondary CNTs could grow from multiple NPs on the single primary CNTs by chemical vapor deposition. These secondary CNTs were entangled each other between primary CNTs, which provide the possible high density network with chemically connected structure. (C) 2013 Elsevier B.V. All rights reserved.