The role of roughness and porosity on the self-cleaning and anti-biofouling efficiency of TiO2-Cu and TiO2-Ag nanocoatings applied on fired bricks

From the advent of nanotechnologies in building constructions, many materials were functionalized to create composite material with new properties. Titania (TiO2) is actually the most promising nanotechnology to create composite materials with self-cleaning and anti-microbial properties. TiO2 was able to limit algae adhesion and their growth, even if, in case of high porous and rough substrata, their inhibitory effect seems to be limited. This way, in this study, silver and copper nano-particulate enhanced an aqueous nano-titania solution were applied on brick specimens and their inhibitory effects were tested during accelerated laboratory tests. Extent of biofouling on specimens’ surface was assessed by measuring the aesthetical alteration and correlations between algal growth and key parameters of substrata were discussed. Results confirm the key role of porosity and roughness on the biofouling process on untreated specimens, and their effect on the photocatalytic power of the tested nano-coatings toward algal adhesion. Results from this study were compared with previous findings in the literature on the same types of specimens only treated with the same aqueous nano-titania solution. No significant improvements were detected by the addition of metal nanoparticles. Experimental curves were overlapped to analytical model calculated by Avrami’s law, and its validity was confirmed where latency time could be observed. Whereas no latency time was detected, that is a very fast adhesion of algal cells occurred, the experimental curves were modelled by using a four parametric logistic model that was able to describe numerically the biofouling process.