Mild synthetic routes to high-surface zinc oxide nanopowders

ZnO nanostructured powders have been prepared at low temperature and atmospheric pressure by thermal decomposition of solid precursors. Two alternative methods have been explored by using: (i) commercial zinc acetate dihydrate and (ii) a solid mixture obtained after the evaporation of a solution of zinc acetate in aqueous ammonia at 90 °C. Powder X-ray diffraction characterization shows that in both cases crystalline ZnO was obtained after precursor treatment at 90°C over 150 h. According to attenuated total reflection Fourier transform infrared analysis, powders obtained by both routes retain a small percentage of adsorbed acetate. Elemental analysis proves that almost 98 wt.-% of acetate was removed during the low-temperature treatment. Low-temperature nitrogen adsorption-desorption characterization shows the existence of two types of pores: intra-aggregate mesopores and interaggregate macropores. The specific surface area reached a value of 35 m2 g -1 for materials obtained following the direct route (i) and increased to 60 m2 g-1 for powders obtained by the ammonia route (ii). TEM characterization confirms the presence of a hierarchical pore structure as a result of the formation of sub-micrometric porous aggregates (50-200 nm.) composed of nanocrystals smaller than 20 nm. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA,.