Nanostructures and Super-Hydrophobic Properties on the Leaves of an Indigenous Australian Plant Eucalyptus Pleurocarpa

Abstract

This study presents the results of a topographical survey of the surface features found on the leaves of an indigenous Australian plant Eucalyptus pleurocarpa (Tallerack). Field emission scanning electron microscopy was used to examine the size and morphology of various micrometer and nanometre scale features presented on the leaf surface. In particular, the features formed by the epicuticular waxes were investigated and quantified. Analysis of water contact angle measurements carried out on the adaxial surface indicated that the leaf surface was super-hydrophobic (158.00 ± 4.30°), while the abaxial surface was found to be hydrophobic (150.20 ± 3.90°). Microscopy examination revealed that the leaf surfaces contained an array of stomata surrounded by a rugged surface region dominated by a rim and bumps. The stomata rims and surface bumps surrounding the stomata were adorned with nanometre scale pillar structures. On the adaxial surface the mean diameter of these pillar structures was estimated to be 300 ± 50 nm and lengths ranging from 1 to 7µm. While the self-cleaning experiments demonstrated that the Tallerack leaf could be effectively cleaned using a fine spray of water droplets that rolled over the surface picking up both hydrophilic (Ballotini microspheres) and hydrophobic (carbon black toner) contaminants.