“Dry-state” surface-enhanced Raman scattering (SERS): toward non-destructive analysis of dyes on textile fibers

In the present work, we report the proof of concept of the possibility to identify natural dyes on textiles using surface-enhanced Raman scattering (SERS) detection by means of a simple “dry-state” SERS approach, i.e., exploiting the interactions between a solid nanometallic substrate and dye molecules present on textiles, thus avoiding any extraction or necessity to remove samples. The challenges associated with instrumental constraints related to SERS analysis of bulk materials and possible contamination of artworks with metallic nanoparticles were approached. Different silver nanosubstrates, i.e., nanoislands and films obtained starting from two different metal colloids, were tested for this aim. The study also investigates different parameters associated with the synthesis of nanosubstrates influencing the enhancement of the “dry-state” SERS signals obtained. SERS spectra of anthraquinone red dyes were successfully recorded from reference wool threads using this simple approach. The results illustrate the usefulness of the practical and rapid “dry-state” SERS approach that could open new opportunities toward the non-destructive analysis of dyes in artefacts.