Traditional Venetian marmorino: Effect of zinc-based oxides on self-bleaching properties

The Venetian marmorino is a traditional material used for wall coating in Venice city, composed of hy- drated lime and marble powders, and is part of the cultural heritage of the city. Several surface dam- age processes can negatively affect its aesthetic properties, such as the formation of stain deposits of different origin (i.e. pollution, bio-deterioration, vandalism) which eventually change the colour of this material. An appealing way to avoid these deposits rely on inducing self-bleaching features by introduc- ing a photocatalyts on this material. In the present work, TiO 2 -based and ZnO-based photocatalysts were introduced within the marmorino , then evaluating how the addition of these materials influenced the compositional, structural and morphological properties though X-ray diffraction (XRD), N 2 physisorption and electron microscopy (SEM). ZnO-modified samples, which exhibited comparable morphological and structural properties, were further analyzed to get information concerning the surface compostion and the opto-electronic properties, through attenuated total reflectance (ATR) spectroscopy and photolumines- cence (PL), respectively, in turn related to the presence of defects and heterojunctions. The self-bleaching activity was evaluated by irradiation in mild condition (room temperature) in air using a dye as model stain compound. Finally, the morphological, surface and opto-electronic properties of the photocatalyst- modified marmorino were correlated to the activity results, aiming to understand how they can influence the material performances, and thus how to design an active self-bleaching Venetian marmorino .