Needle- and cross-linked ZnO microstructures and their photocatalytic activity using experimental and DFT approach

Thermal oxidation is a simple and cost-effective method that allows the production for large-scale of ZnO microstructures. By modifying the etching conditions (with HNO₃) of the precursor, the morphology of the as-oxidized samples can be controlled, giving way to needle- and cross-linked ZnO microstructures. Electron microscopy results revealed that the (1 0 0) are dominating planes in the cross-linked structures, while the (1 0 1) are dominating planes in the needle structures. Density functional theory studies demonstrated that the ZnO interaction with HNO₃ is a selective process which depends on the ZnO surfaces involved, whereas the reactivity of such surfaces can be attributed to the p orbitals associated with oxygen. Finally, photocatalytic results proved that these ZnO microstructures can be applied to degrade organic pollutants; i.e., methylene blue.