Functional Surfaces with Photocatalytic Behavior and Reversible Wettability: ZnO Coating on Silicon Spikes

Multifunctional surfaces with reversible characteristics have gained great attention due to their various envisioned applications. We report on the development of surfaces exhibiting both photocatalytic activity and reversible wettability. Initially, irradiation of silicon wafers with femtosecond laser pulses produces a surface with dual-scale roughness in the micro- and nanoscale. Subsequently, the hierarchically roughened silicon surfaces are coated with ZnO following a simple sol gel process. The manufactured artificial surfaces exhibit reversible wettability from superhydrophilic (upon UV irradiation) to superhydrophobic (upon heating), while the specimens reveal high photocatalytic activity as illustrated by the decolorization of methylene blue utilized as a model dye. The surfaces exhibit reproducibility and stability over a number of cycles.