PhD Thesis Defence Presentations - Maria Kotsidi

All art materials are prone to environmental degradation. Fading, yellowing, and discoloration are the most common degradation effects resulting from exposure to UV and visible light, and oxidizing agents. These effects of aging mechanisms lead to the severe and irreversible deterioration of the readability of works of art, which are the priceless heritage of humanity. Solvents and varnishes, which have long been used to protect artworks, turned out to be destructive solutions. The graphene-based materials can offer innovative solutions against the degradation of artworks due to natural aging. Since the discovery of graphene in 2004 (2010 Nobel Prize in Physics, Geim and Novoselov) it has been considered the ‘wonder material’. Graphene is one of several allotropes of Carbon and can be considered the ultimate aromatic hydrocarbon – existing as an infinite monolayer of carbon atoms joined together in a  two-dimensional, hexagonal sheet-like structure that gives rise to its many unique properties. Graphene shows protective abilities and, the properties of the hexagonal lattice arrangement of carbon atoms make it act as a flexible barrier to oxygen and other gases, damaging wavelengths of light and water vapor when applied to a surface. Graphene-related materials have been found to provide considerable ultraviolet shielding as coatings, while a single graphene layer absorbs up to 3 times more in the UV region (190-400 nm) than in the visible range. Additionally, it is known that chemical molecules such as water or oxygen cannot penetrate a continuous graphene membrane providing the ultimate shield against degradation. The aim of this thesis was the exploitation of all the derivatives of graphene to develop novel methods for the protection of art objects. The first part of this thesis focused on the deposition of a protective coating of monolayer or multilayer graphene on surfaces, such as papers, photos and paintings, with the roll-to-roll method, in order to protect them from fading over time. The assessment of the protection offered by the graphene veil was performed with Colorimetry and other spectroscopic techniques (Raman). The second part of this thesis focused on the reinforcement of commercial paints, inks, and pigments with two-dimensional materials, such as graphene, boron nitride, etc., which were produced via the liquid-phase exfoliation method. The coloured samples were subjected to accelerated aging to reassess the protection offered by the 2D materials against colour fading. Finally, the last part of the thesis includes the preparation of graphene-based aerogels from graphene oxide or ‘hybrid’ aerogels containing graphene oxide and other two-dimensional materials (hBN, MoS₂, WS₂). These samples were examined as adsorbent materials for harmful gaseous pollutants such as formaldehyde, acetic acid, hydrochloric acid, ammonia, etc., which usually are present inside the museums.