When anthraquinone dyes meet pillared montmorillonite: Stability or fading upon exposure to light?

Abstract Hybrid pigments have attracted great interest due to their stability and physicochemical properties that can be used in paintings, artworks and in the field of cultural heritage. The study of new materials includes the search for new pigments by immobilization of the dyes in resistant substrates such clays minerals to get new colour fonts and materials with high stability. Organic-inorganic based lake pigments, at different pH, have been prepared. Ti- and Al-pillared montmorillonite were synthesized and loaded with carminic acid (CA) and alizarin (Aliz) organic dyes. The pillaring process was investigated by X-ray diffraction, textural analysis, transmission electronic microscopy and solid state nuclear magnetic resonance of 27 Al. The interactions between the organic guest and the inorganic host were highlighted by infrared, 13 C and 27 Al solid state magnetic nuclear resonance and time resolved fluorescence spectroscopies. The spectra support complex formation between the chromophores and the inorganic matrix. The colours of the pigments prepared were pH dependent. Lake pigments based on Al-Pillared Mt were more stable under light than Ti-based hybrid, even in oil painting formulations.