A designed UV-vis light curable coating nanocomposite based on colloidal TiO2 NRs in a hybrid resin for stone protection

The modification of a UV-vis light curable hybrid methacrylic siloxane resin with organic coated TiO2 nanorods (NRs) has been carried out, in order to fabricate a functional coating for protection of stone artefacts of artistic and cultural relevance. The nanocomposite, formulated without using any harmful and high volatile monomer components, has been deposited onto the surface of stone samples made of a porous carbonate stone, namely Lecce stone. Such a building material, specifically selected as a relevant example of porous and light coloured stone, is widely used in monuments and constructions of cultural and historic interest of the Apulia region (Italy). The protective ability of the nanocomposite against the water vapour capillarity absorption and its self-cleaning properties have been investigated as a function of the TiO2 NR loading, the applied amount of the formulation and the curing conditions. A reliable protocol for the application of the nanocomposite has been implemented, and, remarkably, a single UV-vis light curing step has resulted in a uniform and hydrophobic coating layer, able to preserve the water vapour permeability, the pristine colour and surface morphology of the stone samples. Moreover, the nanocomposite coated stone surface has demonstrated self-cleaning ability when tested for the degradation of an organic molecule, used as a model compound, under both solar light simulated and real sun irradiation. The achieved nanocomposite has ultimately proven to be technologically advantageous as a functional coating, suited to protect surfaces of artistic, archaeological monuments of historical interest, also under outdoor conditions.