Diffusion Of Indigo Molecules Inside The Palygorskite Clay Channels

TL;DR

This study investigates how indigo molecules diffuse into palygorskite clay channels during heating, revealing their role in stabilizing the clay's structure and contributing to the durability of ancient Maya Blue pigment.

Contribution

It provides new insights into the microscopic diffusion process of indigo in palygorskite, explaining the pigment's durability through combined thermogravimetric and synchrotron X-ray analyses.

Findings

Indigo molecules diffuse into palygorskite channels during heating.

Diffusion replaces zeolitic water and stabilizes clay phases.

The process explains the durability of Maya Blue pigment.

Abstract

The search for durable dyes led several past civilizations to develop artificial pigments. Maya Blue (MB), manufactured in pre-Columbian Mesoamerica, is one of the best known examples of an organic-inorganic hybrid material. Its durability is due to the unique association of indigo molecule and palygorskite, a particular fibrous clay occurring in Yucatan. Despite 50 years of sustained interest, the microscopic structure of MB and its relation to the durability remain open questions. Combining new thermogravimetric and synchrotron X-ray diffraction analyses, we show that indigo molecules can diffuse into the channel of the palygorskite during the heating process, replacing zeolitic water and stabilizing the room temperature phases of the clay.