Flame synthesis of zinc oxide nanowires

Single-crystalline ZnO nanowires are grown directly on zinc-plated-steel substrates at high rates (microns/minute) using a flame-synthesis method, with no catalysts. The growth of the nanostructures is very sensitive to local gas-phase chemical species concentrations (O2, H2, CO2, H2O) and temperature (800–1500 K) as measured by laser-based spontaneous Raman spectroscopy. Larger-diameter (>100 nm) hexagonal-cross-section nanowires, with [0 0 0 1] growth direction, are produced at higher temperatures; while smaller-diameter (25–40 nm) nanowires, with [ 1 1 2 ¯ 0 ] growth direction, are produced at lower temperatures, and only on the fuel side of the reaction zone (with no oxygen present). Nanoribbons and other nanowire-based morphologies are also found and discussed.