A facile method to identify anthraquinone dyes in textile artworks using galvanic displacement based-SERS substrates

We present here a novel strategy for textile sample treatment, using galvanic displacement-based substrates, to identify anthraquinone dyes by surface enhanced Raman spectroscopy (SERS). This global procedure of SERS analysis, using several silver microparticles , in particularly those of dendritic shape, formed by reducing silver nitrate with zinc or copper, can be accomplished within 20 min. Compared to the synthesis of standard Lee-Meisel colloids, the preparation of silver dendrites provides a simple, fast and cost-effective route to produce reliable SERS substrates. The most fascinating feature is that the textile fibers analyzed are almost simultaneously covered with the substrates once the galvanic displacement reaction is triggered. This method was successfully applied to discriminating between alizarin and purpurin in a 6th-9th century samite with bird roundels, and carminic acid and laccaic acid in a 1740s chinoiserie brocade. However, as is the case with other silver substrates, the Raman signals of the insect dyes normally overlapped those of the plant dyes in the SERS profiles.