Evaluation of inhibitory effect of TiO2 nanocoatings against microalgal growth on clay brick façades under weak UV exposure conditions

• Effect of TiO2 on algal growth under low UV radiation is studied.
• TiO2 is not able to fully prevent the biofouling of microorganism on the material.
• TiO2 greatly enhances the self-cleaning ability of the brick surface due to water.

Microalgal growth largely affects the aesthetical properties of building façades worldwide. It causes biodeterioration of building materials and, in a later stage, it can compromise integrity of the elements and their durability. Recently, the use of nanotechnology to prevent the growth of microalgae is rising. One of the most widespread and promising material is titanium dioxide (TiO2). Photocatalytic properties of TiO2 inhibit biofouling of microalgae when this coating is stimulated by UV radiation coming from the sun or from artificial light. In this study, the biocide effect of TiO2 coatings applied on clay brick specimens under weak UV radiation was assessed. Results revealed that TiO2 nanocoating was not able to fully prevent microalgal biofouling, but under optimal UV exposure conditions for the growth of microalgae it efficaciously prevented the adhesion of these microorganisms on the treated substrates through the formation of a superficial water film. This property resulted in a good self-cleaning efficiency of TiO2.