Characteristics of Hybrid Pigments Made from Alizarin Dye on a Mixed Oxide Host

This paper describes the fabrication of a new hybrid pigment made from 1,2-dihydroxyanthraquinone (alizarin) on a mixed oxide host (aluminum-magnesium hydroxycarbonate, LH). Various tools were applied to better understand the interactions between the organic (alizarin) and inorganic (LH) components, including ion mass spectroscopy (TOF-SIMS), 27-Aluminm solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). TOF-SIMS showed that modification of the LH had been successful and revealed the presence of characteristic ions C₁₄H₇O₄Mg⁺ and C₁₄H₆O₅Al^-, suggesting interactions between the organic chromophore and both metal ions present in the mixed oxide host. Interactions were also observed between Al³⁺ ions and Alizarin molecules in ²⁷Al NMR spectra, with a chemical shift detected in the case of the modified LH matrix. Any changes in color following reactions with Mg²⁺ and Al³⁺ ions were observed. Some of the physicochemical properties of alizarin, such as resistance to dissolution and color stability at elevated temperatures, were improved in comparison to the pure dye. This effect can be attributed to strong dye-LH interactions and the effective transformation of alizarin into an insoluble form. Moreover, the pigments exhibited higher thermal resistance and greater color stability in comparison to commercially available alizarin lakes (Alizarin Crimson).