Surface wetting of superhydrophobic aluminum oxide nanostructures investigated using the fiber-optic spectrometer and quartz crystal microbalance

Abstract

We synthesized an anodic aluminum oxide nanostructure with a pore diameter of 80 nm (AA080) directly on a quartz crystal substrate and deposited a thin gold film onto the AA080 (Au/AA080). The nanostructure surfaces were rendered hydrophobic via different chemical modifications to yield partially or fully superhydrophobic surfaces; only the top gold surface was hydrophobic (T-Au/AAO), or both the gold and AAO surfaces were hydrophobic (TS-Au/AAO). The surface wetting properties of each nanostructure-grown quartz substrate immersed in water were investigated using a novel integrated system consisting of a fiber optic spectrometer and a quartz crystal microresonator (QCM). A QCM was used to measure the changes in the dissipation factor and the resonance frequency during surface wetting. A fiber optic UV-vis spectrometer was used to measure the changes in the wavelength and peak intensities of the interference fringes. Synchronous QCM and spectrometer measurements permitted in situ discrimination between the permeation of water into the nanopores and the replacement of air interlayer with water for the first time to the best of our knowledge. (C) 2015 Elsevier B.V. All rights reserved.