Work

Identification of Coexisting Indigo Species in an Ancient Green Thread Using Direct Plasmon-enhanced Raman Spectroscopy

Year: 2020

Type: article

Abstract: A green ancient thread sample from a Chilean mummy turban was analyzed by plasmon-enhanced Raman scattering spectroscopy using a direct drop-colloidal method.The enhanced-Raman signals in the sample are associated with biomolecules from the thread and two coexisting dyes, indigo and leuco-indigo.The presence of indigo (blue colour) was identified from its most characteristic vibrational bands.Leuco-indigo (yellow colour) was identified for the first time in an ancient textile; its SERS signals are coincident with the SERS bands of a synthesized leuco-indigo.The interconversion leuco-indigo to indigo was followed by UV-visible spectroscopy.Based on theoretical calculations it is proposed that the interconversion involves a  electron delocalization mainly around the NC-CN bridge.The mixture of both dyes (indigo and leuco-indigo) is the responsible for the green colour observed.

Source: Journal of the Chilean Chemical Society

DOI: 10.4067/s0717-97072020000204798

Authors: Freddy Celis, Cristian Tirapegui, Macarena García, Andrés Aracena, Álvaro. E. Aliaga, Marcelo Campos-Vallette

Institutions: Universidad de Playa Ancha de Ciencias de la Educación, Universidad Autónoma de Chile, University of the Americas, University of Chile

Language: English

Topic: Cultural Heritage Materials Analysis

Subfield: Archeology

Field: Arts and Humanities

Domain: Social Sciences

Open Access status: diamond

Funders: Universidad de Tarapacá, Universidad de Playa Ancha

Award: G7112040507