Discovering the effect of alum on UV photo-degradation of gelatin binder via FTIR, XPS and DFT calculation

Abstract

In the field of cultural heritage, a growing interest is focused on the UV photo-degradation of organic binders induced by mineral pigments. But the effect of alum on the UV photo-degradation of gelatin binder remains unclear, which are two of the most common materials in traditional Chinese painting and calligraphy. This paper investigated alterations in composition, the secondary structure and morphology of gelatin under the individual or compound action of UV light and alum. Results showed that alum can obviously accelerate the alterations in the secondary structure and morphology of gelatin. The results of FTIR, XPS and DFT calculation confirmed that alum can directly or indirectly provide active hydrogen atom and O2· radicals, so the initiation and propagation process of gelatin photodegradation were promoted. The paper discovered the mechanism of the degradation of protein binders in Chinese traditional cultural heritage, and provided important theoretical basis for find suitable treatments for conservation or targeted materials for protection.