Intercalation of indigo carmine anions into zinc hydroxide salt: A novel alternative blue pigment

• Indigo carmine anions were intercalated into a layered zinc hydroxide salt.
• The synthesis occurs by co-precipitation in slightly alkaline conditions.
• The obtained deeply blue material mimics the Maya Blue pigment.
• After dehydration at 200 °C, sulfonate groups are grafted to the layers.
• Intercalation is an alternative method to transform soluble dyes into pigments.

Zinc layered hydroxide salt was intercalated with indigo carmine (IC) anions, transforming a soluble dye into an insoluble pigment. The obtained material was characterized by X ray powder diffraction, where a basal distance of 19.07 Å was obtained. DFT simulation showed that the groups of the indigo carmine are held by electrostatic and hydrogen bonds to water molecules positioned in the tetrahedral zinc apex. Fourier transform infrared and UV–Vis spectra confirmed that the intermolecular bonds are broken, and intramolecular bonds prevail in the intercalated compound. Thermal analysis curves (thermogravimetry – TGA and differential scanning calorimetry – DSC) showed that the intercalated IC is stable up to 350 °C and the mass loss is consistent with the expected compound formula (Zn5(OH)8(IC)·H2O). The obtained material presents layered crystals with micrometer sizes, as shown by scanning electron microscopy, and consists of a novel blue pigment mimicking the Maya blue pigment, having potential industrial applications.

Indigo carmine anions were intercalated between the layers of a layered hydroxide salt, mimicking the Maya Blue pigment.Figure optionsDownload as PowerPoint slide