Research article

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Photoreactive composite thin layers with tunable wetting properties from superhydrophilic to superhydrophobic nature were prepared. To achieve extreme wetting properties, the adequate surface roughness is a crucial factor, which was achieved by the incorporation of plasmonic Ag-TiO₂ particles, as polymer filler, into the smooth polymer film with adjusted hydrophilicity. The initial copolymer films were synthesized from hydrophilic 2-hydroxyethyl-acrylate (HEA) and hydrophobic perfluorodecyl-acrylate (PFDAc) monomers. In the case of hydrophobic PFDAc, the photocatalyst- roughened thin films displayed superhydrophobic behavior (γ_s^tot ~ 2.3±1.7 mJ/m2, Θ > 150°), while the roughened hydrophilic pHEA layers possessed superhydrophilicity (γ_s^tot ~ 72.1 ±0.2 mJ/m2, Θ ~ 0°). The photoactivity of the composites was presented both in solid/gas (S/G) and solid/ liquid (S/L) interfaces. According to the light-emitting diode (LED) light photodegradation tests on ethanol (EtOH) as volatile organic compound (VOC) model- molecules at the S/L interface, the superhydrophobic hybrid layer was photooxidized 88.3% of the initial EtOH (0.36 mM). At S/L interface the photocatalytic efficiency was depended on the polarity of the model pollutant molecules: the photooxidation of hydrophobic SUDAN IV (c₀ = 0.25 mg/mL) dye reached 80%, while in the case of the hydrophilic Methylene Blue dye (c₀ = 0.002 mg/mL) it was only 17.3% after 90 min blue LED light (λ = 405 nm) illumination.