Biomorphic tubular nickel oxide structures: Effect of the synthesis parameters on their structural and functional properties, surface-related applications

Abstract A cheap, reproducible and facile method for synthesis of 1D high specific surface area biomorphic NiO crystalline microstructures by using natural fibers (cotton, hemp and flax) as templates, is reported. The effect of synthesis temperature and of fiber type on the structural and functional properties of biomorphic oxide in comparison with one produced without template is presented. A comparative (HR)TEM study performed on the ultrasonicated samples evidenced that, irrespective of the kind of fibers, fractions of tubular morphologies, fractions of mesoporous walls and fine nanoparticles populations are found. Such morphologies are never obtained in the absence of biotemplates and were induced by the carbonization and thermal decomposition of organic fiber constituents. A remarkable increase of the specific surface (between 20 and 50 times higher) than for template-free NiO (0.64 m2g-1) was reached when using fibers templates for synthesis at 600 °C/2 h. Due to the peculiar generated nanoporosity and ultrafine particle population, gas sensing tests demonstrated a higher sensitivity when templates were employed. The magnetic properties of tubular structures depend on their nanoscale arrangement and the magnetization values confirmed the Ni/NiO ratio determined by structural analysis.