On the Role of γ-Fe2O3 Nanoparticles and Reduced Graphene Oxide Nanosheets in Enhancing Self-Cleaning Properties of Composite TiO2 for Cultural Heritage Protection

Abstract

The durability of novel metallic artifacts and buildings is an open issue, and the role of smart protecting coatings in extending these artifacts’ lifetimes is crucial. In this paper, the role of γ-Fe2O3 nanoparticles and reduced graphene oxide (rGO) nanosheets on enhancing the self-cleaning properties of composite TiO2 films and reducing metal alterations due to contact with acid rain and pollutants is investigated. The photocatalytic assessment of the TiO2 based films indicates that there are optimum contents for γ-Fe2O3 and rGO, which confer the film lower bandgap and tune the TiO2 anatase/rutile ratio. By adding a proper content of γ-Fe2O3, wettability is reduced both in dark and under illumination, which could be related to higher roughness. γ-Fe2O3 overloading causes increasing crack density and eventually a fully cracked structure. Adding an appropriate amount of rGO causes a sharp increase in roughness, due to the stacking of rGO nanosheets, while simultaneously avoiding cracking. At higher contents of rGO, wettability further decreases due to higher amounts of hydroxyl groups bound onto rGO; also in this case, overloading causes film cracking. Evaluation of self-cleaning performance and discoloration resistance under soiling and acid rain simulated tests demonstrates that proper loadings of γ-Fe2O3 and rGO present higher efficiency thanks to higher superhydrophilic tendency and higher photocatalytic activities, as well as an efficient barrier effect.

Present Status and Perspectives of Graphene and Graphene‐related Materials in Cultural Heritage

“…Up to now, only a few experimental works on the use of rGO on historically relevant metal substrates have been reported, paving the way for extensive research and advanced studies. [177] Mokhtarifar et al proved that rGO nanosheets together with the 𝛾-Fe 2 O 3 nanoparticles enhance the self-cleaning properties of composite TiO 2 films deposited on metallic Ti specimens and, hence, reduce metal alterations due to contact with acid rain and pollutants. The role of rGO is mainly linked to the improvement in charge separation efficiency necessary for the photocatalytic process since the rGO layer acts as an electron acceptor, finally improving light harvesting and consequent light-induced wettability conversion.…”

“…Up to now, only a few experimental works on the use of rGO on historically relevant metal substrates have been reported, paving the way for extensive research and advanced studies. [ 177 ] Mokhtarifar et al. proved that rGO nanosheets together with the γ‐Fe 2 O 3 nanoparticles enhance the self‐cleaning properties of composite TiO 2 films deposited on metallic Ti specimens and, hence, reduce metal alterations due to contact with acid rain and pollutants.…”

Testing new graphene oxide‐coated glazing for papyrus manuscripts in museums: Part I

“…Discovered in the 21st century, graphene allowed new applications in different fields and showed outstanding thermal, optical, and electrical properties 17–19 . Graphene oxide (GO) coating has been used in touch screens of electronic devices and solar cells 20,21 and tested as a protective layer against the corrosion of industrial materials, including glass and metals 22–24 . Due to the strength of its 0.142‐nm‐long carbon bonds, graphene can be formed in a sheet.…”