Microspheric organization of multilayered ZnO nanosheets with hierarchically porous structures

Novel superstructures of multilayered ZnO nanosheets with hierarchically porous structures are successfully synthesized from a hydrothermal preparation and thermal decomposition of a layered precursor of zinc hydroxide carbonate (denoted as ZnHC). Nanosheet-based ZnHC microspheres are self-assembled by the hydrothermal process by using zinc nitrate hexahydrate and urea as the starting materials. The corresponding microspheric organizations of multilayered ZnO nanosheets with hierarchically porous structures are obtained by the thermal decomposition ZnHC precursor at 573 K. SEM images show that the average diameter of ZnO assembled microspheres is about 15 μm, and the length of a ZnO nanosheet building block which is made up of thin mutilayered sheets is around ∼7 μm. Studies also show well-crystallized pores with hierarchically distributed pore sizes are embedded in the multilayered ZnO nanosheets building blocks. A plausible dissociation-deposition mechanism using in situ formed Zn(OH)₂ nuclei as the "sacrificial" templates for the microsphere assembly is also proposed.