ZnO mesocrystals from solvothermal synthesis

Abstract

Mesocrystals represent a new class of nanostructured materials, made of crystallographically aligned nanoparticles. Due to their unique structural features they have many physicochemical properties, different from nanoparticulate materials and single crystal materials, which can provide better performance in some applications. Zinc oxide mesocrystals have been synthesized by the solvothermal method at 200 °C during 4 hours from slightly basic (pH = 8) precursor (ethanolic zinc acetate solution in the presence of lithium hydroxide). XRD analysis showed that precursor solution consists of zinc acetate and zinc-hydroxy-acetate. Structural and microstructural properties were analyzed using X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. ZnO mesocrystals are hexagonal prisms with diameters of 80 – 200 nm and lengths of 100 – 200 nm, but several larger prisms have a hole in the center. Based on characterization results we have discussed the growth mechanism of ZnO mesocrystals. Dipolar nature of ZnO and planar structure of zinc-hydroxy-acetate with free position of the acetate ions between positively charge planes play crucial role in the formation of the ZnO mesocrystals during the solvothermal reaction.