Low-temperature ZnO atomic layer deposition on biotemplates: flexible photocatalytic ZnO structures from eggshell membranes

Macroporous ZnO membranes with a strong photocatalytic effect and high mechanical flexibility were prepared from inner shell membranes (ISM) of avian eggshells as templates after performing low-temperature ZnO atomic layer deposition (ALD). In order to evaluate the potential merits and general applicability of the ZnO structures, a comparative study of two membranes with coatings of either TiO2 or ZnO, processed under similar conditions, was performed. The study includes crystallographic features, mechanical and thermal stability and bactericidal efficiency. Both, the ZnO and the TiO2 coated membranes clearly exhibited bactericidal effects as well as mechanical flexibility and thermal stability even at relatively high temperatures. The ZnO membranes, even though prepared at fairly low temperatures (similar to 100 degrees C), exhibited polycrystalline phases and showed a good bactericidal efficiency as well as higher mechanical flexibility than the TiO2 coated membranes. This study shows the benefits of low-temperature ZnO ALD i.e., the thermally non-destructive nature, which preserves the mechanical stability and the native morphology of the templates used, together with an added functionality, i.e. the bactericidal effect.