Using a novel.. low-cost approach based an aerosol technique, highly branched, Y-junction nanotubes were synthesised. A catalyst-precursor solution composed of metal salts in water was sprayed into a furnace. A heated mixture of carbon reactant gas and hydrogen creates an atmosphere in which the catalyst particles are formed in situ and nanotube growth occurs. Controlled by several parameters, the catalyst induces the growth of different carbon nano-structures. This is the first time that Y-branched nanotubes have been synthesised in high quality and purity. A mechanism involving a one catalyst particle process is proposed to rationalise the formation of junction tubes. (c) 2005 Elsevier B.V. All rights reserved.