Identification of Natural Dyes in Ancient Textiles by Time-of-Flight Secondary Ion Mass Spectrometry and Surface-Enhanced Raman Spectroscopy

Abstract

The identification of dyes in archaeological remains is a long standing challenge. Major problems include contamination by environmental conditions over long periods of time, small amounts and limited availability of excavated samples, and low concentrations of dyestuff in the obtained samples. To address these issues, highly sensitive and non-destructive techniques are required. In response, in this work, two non-destructive analytical techniques, Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and Surface-Enhanced Raman Spectroscopy (SEAS), were used for dye detection and the analysis results are compared. TOF-SIMS provides high detection efficiency for the analysis of organic materials whereas SEAS is a useful technique for the detection of dyes in ancient textiles. An Ag colloid was employed to surmount the limitations of normal Raman measurement such as background fluorescence and weak Raman signals in small amounts of components. To identify the dyes used in ancient textiles, standard samples prepared using various dyestuffs and historical samples were analyzed with TOF-SIMS and Raman techniques. From the TOF-SIMS and the SEAS spectra, dyestuffs such as alizarin, berberine, an indigo were identified in ancient textiles. The results suggest that TOF-SIMS and SERS are efficient non-destructive techniques for the characterization of archaeological textiles.