Exploring the low cell adhesion of photoinduced superhydrophilic surfaces for improving the effect of antifouling protective coatings on porous building materials

Abstract

The susceptibility of building materials to biological colonization is associated with accelerated decay processes, aesthetical alterations and health risks. Thus, preventive measurements involving the use of coatings with passive (bioreceptivity decrease) and active (biocides) antifouling mechanisms are common. Hydrophobic and superhydrophobic coatings that decrease water availability are the most common anti-fouling strategies, although they can promote cell adhesion under the right circumstances and lose effectiveness after the initial biofilm setting. In this work, we explore an innovative alternative strategy to improve the anti-fouling effect of a hydrophobic coating through surface modification to grant low cell-adhesion superhydrophilic properties (while preserving its low water absorption) and its combination with nano-biocides. This is achieved by the incorporation of Ag or CuO-modified TiO2 into an ormosil sol–gel matrix. Irradiation with UV–Vis light activates the superhydrophilic surface while maintaining a decrease in capillary water absorption of >90% and accelerated algal exposure tests showed a markedly lower colonization rate compared to the superhydrophobic surface, owing to the modifications in cell-water-surface interfacial tensions. The nano-biocides showed a dual effect, promoting the transition to superhydrophilic and further decreasing colonization. Furthermore, the superhydrophilic surfaces enhance the biocide effect by promoting the interaction of the nanoparticles with the surrounding media.