Modeling Luminescence in Cultural Heritage: Theoretical Insight into the Luminescence of Dyes and Pigments

Both historic and modern synthetic pigments and dyes used in painting are susceptible to alteration due to their interaction with light, atmospheric moisture, oxygen, and other agents of degradation of the environment and of the painting substrate. Unfortunately, a severe and irreversible alteration process is taking place in many artworks of invaluable relevance in Cultural Heritage. For this reason, art conservation has turned to fundamental science, where modern analytical and spectroscopic techniques could revolutionize our approach to the preservation and restoration of world heritage artworks. Among the state-of-the-art experimental techniques, photoluminescence plays a central role, both to evidence the constituting materials and to individuate the degradation process based on the variations with respect to a pristine material. Theoretical simulations, which have been proven highly successful in the modeling, design, and characterization of materials is proposed as a “clean” and not invasive technique that can complement the experimental investigation in disclosing information on materials employed in works of art. The present chapter aims to emphasize the contribution of theoretical modeling to photoluminescence analysis on colorants in degraded artworks and to highlight its effectiveness in the interpretation of experimental measurements. We focus on both pigments and dyes that present completely different structural and electronic properties require different methodological approaches. In the chapter, a critical overview of the theoretical methods used to describe the luminescence of dyes and pigments is presented along with a discussion of the case studies of both classes of colorants present in the scientific literature.