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Preparation and characterization of superhydrophobic surfaces based on hexamethyldisilazane-modified nanoporous alumina

Nevin Tasaltin1*, Deniz Sanli2, Alexandr Jonáš1, Alper Kiraz1* and Can Erkey2

Author affiliations

1 Department of Physics, Koç University, RumelifeneriYolu, 34450 Sariyer, Istanbul, Turkey

2 Department of Chemical and Biological Engineering, Koç University, RumelifeneriYolu, 34450 Sariyer, Istanbul, Turkey

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Citation and License

Nanoscale Research Letters 2011, 6:487  doi:10.1186/1556-276X-6-487

Published: 9 August 2011

Abstract

Superhydrophobic nanoporous anodic aluminum oxide (alumina) surfaces were prepared using treatment with vapor-phase hexamethyldisilazane (HMDS). Nanoporous alumina substrates were first made using a two-step anodization process. Subsequently, a repeated modification procedure was employed for efficient incorporation of the terminal methyl groups of HMDS to the alumina surface. Morphology of the surfaces was characterized by scanning electron microscopy, showing hexagonally ordered circular nanopores with approximately 250 nm in diameter and 300 nm of interpore distances. Fourier transform infrared spectroscopy-attenuated total reflectance analysis showed the presence of chemically bound methyl groups on the HMDS-modified nanoporous alumina surfaces. Wetting properties of these surfaces were characterized by measurements of the water contact angle which was found to reach 153.2 ± 2°. The contact angle values on HMDS-modified nanoporous alumina surfaces were found to be significantly larger than the average water contact angle of 82.9 ± 3° on smooth thin film alumina surfaces that underwent the same HMDS modification steps. The difference between the two cases was explained by the Cassie-Baxter theory of rough surface wetting.

Keywords:
superhydrophobic surfaces; surface modification; hexamethyldisilazane; nanoporous alumina