Preparation of photocatalytic thin films with composition dependent wetting properties and self-healing ability

Abstract

This paper presents the preparation of a multifunctional coating with triplet photoreactive, superhydrophobic and intelligent self-healing properties. Beside the structural and morphological behaviors of the hybrid thin films consist of fluoropolymer matrix and Ag-TiO2 photocatalyst particles, the wetting properties were also studied by static (Θ) and dynamic water contact angle measurements. The photoactivity of layers was evidenced both at solid/gas (S/G) and solid liquid (S/L) interfaces. The surface roughness (Rq = 3.7 ± 0.9 μm to 15.2 ± 1.2 μm) and thus the wetting properties and apparent surface free energy values (γstot) of the layers were adjustable from superhydrophilic (Θ = 0°; γstot = 70.2 mJ m−2) to superhydrophobic properties (Θ = 150.9°; γstot = 13.1 mJ m−2). At S/G interface the photoactivity of the layers was increased with the Ag-TiO2 photocatalyst content, however, at S/L interface the photocatalytic properties were tailored by the wetting of the films: 90% of the apolar SUDAN IV dye was photodegraded, while the aqueous Methylene Blue dye was not decomposed due to the inadequate surface adsorption. Moreover, it was also presented that the ambient moister catalysed hydrolysis/self-condensation reaction of the hydrophobic dodecyltrichlorosilane (DDSiCl3) molecules resulted self-assembled micro-protrusions on the surface of low energy photoreactive film and this mechanism resulted self-healing superhydrophobic surfaces with photocatalytic properties.