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

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.

Sponge-like carbon thin films: The dealloying concept applied to copper/carbon nanocomposite

“…3c) are selected to synthesize np-C films. It is expected that upon exposure to nitric acid, Cu oxidizes and dissolves into the solution according to (2) leaving behind a skeleton of solid carbon:…”

“…The high specific surface area of this kind of material confers them exceptional properties such as super-hydrophobicity [1,2], enhanced catalysis activity [3][4][5][6], and very selective filtering ability [7,8]. Various materials were used to synthesize nanoporous structures including metals (e.g., Au [6,[9][10][11][12][13][14], Pt [15][16][17][18], and Ag [19,20]), oxides (e.g., TiO 2 [21][22][23] and SiO 2 [24,25]) and carbon [26][27][28][29][30][31][32][33][34][35][36].…”

Graphoepitaxial Directed Self‐Assembly of Polystyrene‐Block‐Polydimethylsiloxane Block Copolymer on Substrates Functionalized with Hexamethyldisilazane to Fabricate Nanoscale Silicon Patterns

“…The substrates to be modifi ed were placed in a sieve at the top of the beaker and exposed to vapour for various times (0.3 -48 h). This followed procedure reported by Tasaltin et al [ 24 ] Samples were subsequently washed with ethanol and then dried under a stream of nitrogen.…”

“…The surfaces increase in hydrophobicity due to the formation of the low energy methyl-terminated surface layer. [ 24 ] The HMDS functionalized surfaces were further analyzed using ellipsometery and the results are presented in Table 1 . Minor thickness increases are observed as the HMDS exposure increases, again consistent with increased HMDS coverage.…”

Highly stable superhydrophobic surfaces under flow conditions

“…22 The increases in the contact angle with pore size can be attributed to decreases in the contact line between water and the nanostructure surfaces. [23][24][25] Figure 3(a) shows the variations with time in the resonance frequencies of the hydrophobic AAO-grown quartz crystals upon immersion in water. These variations are quite different from those of the hydrophilic AAO nanostructures, in two significant ways.…”