Fabrication of solid cylindrical-shaped microtowers of ZnO/C core-shell hexagonal nanorods by thermolysis

Solid cylindrical-shaped (SCS) microtowers composed of hexagonal ZnO/C core-shell nanorods were fabricated through a facile sealed thermolysis route. The microtowers were simultaneously grown along both the axial and radial directions. Dilute acid treatment of the ZnO/C core-shell nanorods led to the formation of carbon nanotubes in the insoluble phase, and ZnO plates were produced by precipitation of the soluble phase upon addition of a base. The as-prepared products were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The electrical conductivity of the SCS microtowers and carbon nanotubes was measured. A microtower growth mechanism was proposed based on observation of the temperature-dependent shape changes.