Superhydrophobic ZnO Nanowire Surface: Chemical Modification and Effects of UV Irradiation

Abstract

We report a facile wet-chemical route for the fabrication of a superhydrophobic ZnO nanowire surface modified with fatty acids. A systematic study was performed on the relationship between carbon chain length of fatty acid and wetting states of well-aligned ZnO nanowire arrays. The wettability of the ZnO nanowire array was monotonically converted from hydrophilicity to hydrophobicity by increasing the carbon chain length of the chemisorbed fatty acid. The superhydrophobic surface obtained with stearic acid (SA, C18) showed a maximum water contact angle (CA) of 167°, which decreased gradually under UV illumination, due to UV-enhanced decomposition of SA monolayer. XPS analysis confirmed the photodecomposition of SA molecules through UV irradiation. Also, a selective area UV photopatterning was demonstrated using a photomask on the modified ZnO nanowire array.

Microstructure, wettability and electrical properties of n-ZnO/ZnO-SL/p-Cu2O heterojunction

“…The CA of the samples is *140°, *143°and *124°responding to Sample 1, Sample 2 and Sample 3, respectively. The results indicate that all the samples exhibit hydrophobicity, which indicates that the water droplet does not penetrate into the grooves of ZnO thin film and the wetting behavior of the sample can be explained by the Cassie-Baxter model [8]. For the hexagonal wurtzite structure ZnO crystal, each O 2-ion is surrounded by a tetrahedron of four Zn 2?…”

Biomimetic hierarchical ZnO structure with superhydrophobic and antireflective properties

“…The deposition method (MOCVD) used here, can produce ZnO NRs with intrinsic hydrophobicity. In contrast, ZnO NRs produced by hydrothermal method, usually show hydrophilic properties due to the existence of abundant of hydroxyl groups [35,36]. After modification by stearic acid, the CA further increases to 162° (Fig.…”

Metal oxide thin films and nanostructures for self-cleaning applications: current status and future prospects

“…According to the above-described mechanism, the induced superhydrophilic state in ZnO is unstable with time and may return to the initial hydrophobic state after a while. Consequently, the hydroxyl groups adsorbed on the defective sites can be replaced gradually by oxygen atoms when the UV irradiated films are placed in the dark [34][35][36][37][38]. The typical mechanism of photocatalysis in ZnO is shown below.…”