Wetting Modification by Photocatalysis: A Hands-on Activity To Demonstrate Photoactivated Reactions at Semiconductor Surfaces

We present a hands-on activity designed for advanced physical chemistry courses for Master’s students on the application of photocatalysis to the modification of the surface properties of a semiconductor (titanium dioxide). The wetting properties of TiO2 films, deposited from commercial powders, are studied before and after UV irradiation. Irradiation-induced superhydrophilicity is exploited to provide antifogging properties. The TiO2 films are then functionalized with a perfluorinated alkylsilane to impart superhydrophobicity and subsequently lithographed by irradiation through a photomask: the photocatalytic degradation of the organic chains in the irradiated areas leads to a wetting contrast that can be revealed using dye solutions. This experience can be easily adapted to be suited for undergraduates or high-school students as well as to demonstrations for science festivals.