TiO2 Nanowire Growth Driven by Phosphorus-Doped Nanocatalysis

Ni-catalyzed single-crystal TiO 2 nanowire growth was observed to occur well below the bulk Ni melting point when a small amount of P was present. TEM, SAED, EDXS, and EELS analyses as well as consideration of the Ni/P phase diagram point to a previously unreported mechanism of nanowire growth catalyzed by a liquid Ni/P eutectic shell surrounding a solid Ni core. High-resolution elemental analysis supports the conclusion that the active catalyst is the outer liquid Ni/P layer with P present at a 3−8% level surrounding a solid Ni core. Growth proceeds by precursor adsorption onto the liquid layer followed by diffusion to the growing surface of the nanowire. This catalyst system produces rutile TiO 2 nanowires efficiently. We believe that the technique is generalizable to other metal/dopant systems which could lead to the synthesis of other hard-to-synthesize nanowires.