Flame synthesis of aligned tungsten oxide nanowires

Aligned single-crystal WO2.9 nanowires are grown directly from tungsten substrates at high rates using a flame synthesis method. The nanowires have diameters of 20–50nm, lengths >10μm, coverage density of 109–1010cm−2, and growth rates >1μm∕min. Growth occurs by the vapor-solid mechanism, with local gas-phase temperature (∼1720K) and chemical species (O2, H2O, and H2) strategically specified at the substrate for self-synthesis. Advantages of this synthesis method are reduced processing times, absence of necessity for substrate pretreatment or catalysts, scalability for large-area surface coverage, high purity and yield of oriented nanowires, and continuous processing conditions.