Photocatalytic activity of nanoneedles, nanospheres, and polyhedral shaped ZnO powders in organic dye degradation processes

• ZnO with acicular shape of nanoneedles were produced by an adapted thermal evaporation method.
• Nanoneedle-like ZnO shown the best photodegradation behavior for Methyl Orange and Safranin O.
• The photocatalytic performance has been related to the level of native point defects of samples.
• ZnO nanoneedle-like synthesis method is responsible for a high level of native point defects.

In this work acicular ZnO nanostructures were successfully produced by an adapted thermal evaporation method. The obtained material was compared with a commercial ZnO nanopowder of similar size and surface area but different morphology, and a commercial micro-powder of different morphology, size and surface area, in the degradation of Methyl Orange (MO) and Safranin O (SAF). Photoluminescence spectroscopy was used to evaluate the native point defects in the samples. It was observed that the nanostructured ZnO powder synthesized by the thermal evaporation process presented the highest amount of native point defects of all samples analyzed, which could be related with the better photocatalytic performance in despite of the specific surface area and crystallite size of the evaluated powders.

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