Herein, the first multi-purpose antifouling and foul-release photocatalytic coating based on ORMOSIL thin films doped with nanoflower-like Bi2 WO6 is described. Irradiation with visible light of the new films immersed in water produces significant amounts of H2 O2 by photocatalytic oxidation of water, and allows the degradation of (bio)organic pollutants at the outer surface of the xerogel film.
Prolonged testing of the new xerogel photocatalytic
coating AquaSun applied to a surface probe immersed in ocean water
irradiated with simulated solar radiation shows excellent action against
biofouling. Activated by moderate solar radiation, the organosilica
film has also good antimicrobial properties. Considering the high
stability, the environmental footprint, and the low cost of this sol–gel
marine coating, the technology has significant potential toward replacing
conventional antifouling and foul-release coatings with a single product
of broad applicability.
The hydrophilicity of titanium dioxide has been investigated for films, deposited on glass by e-beam evaporation, being exposed to UV radiation and subjected to thermal annealing. The wettability alteration has been showed to depend upon both treatments, and insights into how to introduce more stable hydrophilicity into these films have been presented for the sake of boosting their commercial value. Observations from multiple length scales to assess the wetting behavior of as-deposited and high-temperature annealed samples were assessed through macroscopic measurements, i.e., water contact angle measurements, showing that the annealed crystalline samples, treated at 500 °C, are much more hydrophilic (SCA ≈ 20°) than as-deposited TiO films (SCA ≈ 90°), and the nanoscopic experiments performed by amplitude modulation (AM) atomic force microscopy (AFM) indicated that this increased hydrophilicity is related to an enhanced adhesion force and surface energy, resulting in the partial crystallization of TiO and the consequent formation of crystals on its surface rather than being related to morphologic differences. XRD and Raman measurements have highlighted that the crystallinity of the TiO film is crucial in determining its hydrophilicity, in good agreement with the AFM study. The results also indicated that, after irradiation, the samples treated at 500 °C preserve their hydrophilicity for a significant time compared to previous studies.
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