Extractionless non‐hydrolysis surface‐enhanced Raman spectroscopic detection of historical mordant dyes on textile fibers

Abstract

Alizarin and carminic acid have been detected in reference wool and linen fibers dyed with madder and cochineal, respectively, through surface-enhanced Raman scattering (SERS) measurements carried out directly on the fiber, without previous hydrolysis of the mordant-dye complex. For such purpose, Ag nanoparticles were produced and immobilized in situ via the laser photoreduction of a silver nitrate aqueous solution in contact with the fiber. Control SERS spectra of pure dyes (alizarin, purpurin and carminic acid, as well as of mixtures of the first two) on similar Ag nanoparticles were also obtained. The method has been applied to one archeological Coptic textile (6th-8th A.D.) of Egyptian origin, where alizarin has been clearly identified. Other mordant dyes of the flavonoids family (luteolin, apigenin and flavonols) have also been identified by the same SERS method in wool fibers dyed with natural plants, mainly used in Central and South America (Dyer's greenweed, old fustic, onion and chilca) following pre-Columbian dying recipes.

Raman spectroscopy in art and archaeology

“…A new SERS method carried out directly on the fibre of historical textiles, without the need of the standard hydrolysis of the mordant-dye complex, has been developed by Jurasekova et al [13] to detect historical mordant dyes. In this case, alizarin and carminic acid have been detected in reference wool and linen fibres dyed with madder and cochineal respectively; the method has been applied to one archaeological Coptic textile (sixth to eighth century AD) of Egyptian origin, where alizarin has been clearly identified.…”

Chemometric Analysis of Raman and IR Spectra of Natural Dyes

“…SERS is a popular method in a dye analysis especially in the field of art conservation. there is a few reports with the application of this technique for the analysis of natural dyes in textiles [31][32][33][34]. the use of SERS to the in situ analyses of natural samples is still discussed and developed [35].…”

A Colorful History: The Evolution of Indigoids

“…The roots of Rubia tinctoria Salisb. (Rubiaceae) or madder were used by the Egyptians to produce the so-called "alizarin red" (4). This red pigment has been found in the Tutankhamun tomb and owes its color to the presence of the anthraquinone alizarin (2) (Fig.…”