Degradation of chromogenic photoworks.
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Photographic artworks, especially those where photographs are combined with other materials, so called photoworks, show signs of aging through color shift which results in value loss of the artworks. In order to find more suitable ways to store them, an investigation is made of possible chemical reactions which may result in this change in color. Evidence is found for the presence of acetic acid, this pollutant will be a focus in this research. The generalized forms of three basic yellow, magenta and cyan dyes found in photographs are synthesized and treatment with acid was performed. UV-Vis spectroscopy and NMR spectroscopy were used to investigate the influence of acid on the dyes. Cyclovoltammetric measurements and DFT calculations were done in order to gather more information about the reactivity of the dyes and more specific, about the reactivity of the Schiff base. The dyes are changed irreversibly when treated with acid. Absorption of visible light happens at the same wavelength but with a lower intensity. Several derivatives of dyes were synthesized in order to investigate the degradation mechanism. The hypothesis of the hydrolysis of the Schiff base was tried to be approved but due to lack of evidence this hypothesis cannot be established.