Synthesis and characterization of wires-like ZnO structures grown on a graphite support by microwave irradiation

• Synthesis of zinc oxide from a zinc nitrate hexahydrate oxidation.
• Synthesis of wires-like ZnO structures by microwave irradiation from a ZnO–C non-aqueous solid blend in a reduced reaction time.
• ZnO wires-like structures use carbon plates as a grow support medium inducing a preferential crystallographic orientation (101).
• A new “nucleation-aggregation” formation mechanism is proposed in this work.

Wires-like ZnO structures supported on graphite plates were synthesized by a microwave-assisted method using zinc oxide as precursor which was previously obtained from a chemical oxidation of zinc nitrate hexahydrate. Characterization was made by X-ray diffraction, scanning and high resolution transmission electron microscopy. X-ray diffraction results revealed that homemade ZnO showed the same diffraction peaks as its commercial counterpart, all reflections corresponds to a ZnO wurtzite hexagonal phase. After an irradiation process done at 2.45 GHz and an output power of 1200 W for 7 min, homemade ZnO showed a morphological transformation which can be appreciated in SEM micrographs resulting in the formation of the wires-like ZnO structures; these ones present a broadness between 150 to 200 nm and a variable length from 0.4 to 5 µm. Moreover, energy dispersive spectroscopy reveals that these structures present an entirely elemental zinc oxide composition. Wires-like ZnO structures use carbon plates as a support medium to perform their oriented growing. Finally, high resolution transmission electron microscopy showed that wires-like ZnO structures presents a crystalline arrangement with an interplanar distance of 2.4 Å corresponding to a preferential crystallographic orientation (101).