Novel superhydrophilic and hydrophobic nanostructured agar-like zirconia thin films: manipulating of morphology with PEG/CTAB

Abstract

In this paper, a thorough study is dedicated to the manipulating of nanostructured zirconia thin films prepared by a sol–gel process with the focus on the wetting properties. It is observed that by engineering the amount of cetyltrimethylammonium bromide [[N(CH3)3] Br] (CTAB) and polyethylene glycol (PEG) in zirconium chloride precursor solution, the novel agar-like morphology with random orientation can be grown. Different morphologies are observed by changing the amount of PEG in the solution. All the prepared samples in this method show tetragonal phase after annealing at 500 °C for 1 h. The crystallite sizes have a direct correlation with the ratio of lattice parameters. The optical band gap is estimated by Kubelka–Munk method. Modified ZrO2 thin films at an optimum ratio of PEG to CTAB annealed at 500 °C and present water contact angle lower than 3° (without UV illumination) which indicates their superhydrophilic properties. The analytical results of SEM images of samples annealed at 500 °C are also reported. Spreading and wicking of liquid through the nanochannels which are formed in the vacant spaces between nanorods lead to superior wetting property. Annealing temperature also strongly affects the wettability of agar-like zirconia thin films. Agar-like ZrO2 thin films are obtained with superhydrophilic behavior by annealing at 500 °C. Similar agar-like morphology is also observed with hydrophobic character by annealing at 200 °C. The introduced preparation method in this paper provides an easy route to fabricate superhydrophilic agar-like ZrO2 thin films without further processing.