Solution plasma synthesis of ZnO flowers and their photoluminescence properties

ZnO nanoflowers, amorphous ZnO nanospheres and metallic Zn particles have been controllably synthesized using solution plasma technique at different reaction temperatures and agitation. X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that ZnO nanoflowers were synthesized at a high electrolyte temperature in a static system (no agitation). On the other hand, the use of agitation led to both amorphous ZnO nanospheres and spherical metallic zinc particles. The excitation temperature of plasma was 4000 K from the light emission using spectrometer. From these result, melting and vaporization of the Zn electrode produced particles. ZnO nanoflowers grew on the surface of spherical particles by precipitation from Zn(OH)42− ions. Photoluminescence (PL) measurement indicated that as-synthesized ZnO flowers and amorphous ZnO nanospheres showed strong green emissions, which was attributable to their surface defect structure. Furthermore, the annealing at 700 °C led to a reduction in green emissions, attributable to a decrease in the number of surface defects. Photocatalytic activity of ZnO nanoflowers was increased by the annealing.

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