Ternary single-crystalline NaV6O15 nanoneedles were synthesized on a large scale by a novel in situ reaction-crystallization-etching process using bulk V2O5 powders and poly(styrene-alt-maleic acid) sodium salt (PSMA-Na) as raw materials and HF as a catalyst under hydrothermal treatment at 180 degrees C for 24 It. HF not only catalyzes the formation of NaV6O15 nanowires but also promotes the transition of nanowires to nanoneedles. The synthesized nanostructures appeared needle-shaped, with sharp tips about 3-50 nm in diameter and wide butts of tens to 250 nm at the other end, while the lengths of the nanoneedles normally ranged from 5 to similar to 20 mu m. (c) 2007 Elsevier B.V. All rights reserved.