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Keywords:

  • SERS;
  • mordant dyes;
  • textiles;
  • alizarin;
  • flavonoids

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. Copyright © 2010 John Wiley & Sons, Ltd.