Application of surface-enhanced Raman scattering (SERS) for the identification of anthraquinone dyes used in works of art

Abstract

Surface-enhanced Raman scattering (SERS) was investigated for applications in the analysis of anthraquinone dyes used in works of art. Two SERS procedures were developed and evaluated with three frequently used anthraquinone dyes, alizarin, carminic acid and lac dye. The first procedure involves coating a layer of silver nanoparticles directly on pieces of filter paper stained with the dyes of interest by thermal evaporation to induce SERS effect. In the second procedure, a SERS-active Ag-Al 2 O 3 substrate was prepared by spin-coating an alumina-nanoparticle layer onto a glass slide to provide the nanostructure of the substrate, followed by thermally evaporating a layer of silver nanoparticles on top of the alumina layer. Aliquots of dye solutions were delivered onto this substrate to be analyzed. Intense SERS spectra characteristic of alizarin, carminic acid and lac dye were obtained using both SERS procedures. The effects of two parameters, the concentration of the alumina suspension and the thickness of the silver nanoparticle layer on the performance of the Ag-Al 2 O 3 substrate were examined with alizarin as the model compound. Comparative studies were conducted between the Ag-Al 2 O 3 substrate and the SERS substrate prepared using Tollens reaction. The Ag-Al 2 O 3 substrate was shown to offer larger enhancement and improved reproducibility than the Tollens substrates. Finally, the potential applicability of the Ag-Al 2 O 3 substrate for the analysis of real artifact objects was illustrated by the identification of alizarin extracted from a small piece of textile dyed using traditional methods and materials. The limit of detection for alizarin was estimated to be 7 × 10 −15 g from tests performed on solutions of known concentration.

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

“…Different SERS substrates have been employed, mostly silver colloids reduced with citrate, [14,15,17 -19,21 -34] hydroxylamine [16,22,23,28] or borohydride. [33] But other substrates have been tested as well: electrodes, [13,26] Ag-Al 2 O 3 35 , Tollens mirrors, [31,35] vacuum-evaporated silver nano-island films (AgIF), [31,36] e-beam-deposited AgIF, [37] silver films over nanospheres (AgFON), [38] and Ag nanoparticles obtained in situ by laser photoreduction. [20,39] SERS spectra of dyestuffs other than anthraquinones and flavonoids (redwoods, naftoquinones and orchil dyes, [31,37] melanin sepia [33] ) have been recorded using such SERS substrates.…”

“…Different proof-of-concept experiments, carrying out previous hydrolysis and extraction treatments, [35,37] only hydrolysis [31] or no pretreatment at all, [18,20,21] have been published, attempting to demonstrate the capabilities of SERS for the detection of dyestuffs on real artworks. Most of them, as well as some of the case studies described, [19,25,29] were devoted to dyed textiles, but dyes in other materials have also been explored.…”

Application of surface‐enhanced Raman scattering techniques to the ultrasensitive identification of natural dyes in works of art

“…With the exception of of Guineau, 1 who used electrochemically roughened Ag electrodes, and of Chen et al, 5 who compared a nanoengineered substrate with a chemically deposited silver film, most of the work on alizarin has been done using solution-reduced Ag colloids. Other SERS supports, such as silver nanoisland films or chemically deposited silver mirrors have not yet been investigated for the detection of natural dyes of artistic importance.…”

Analysis of alizarin by surface‐enhanced and FT‐Raman spectroscopy

“…[5 -7] An effect that can significantly enhance the Raman intensity is surface-enhanced Raman scattering (SERS). [1,6,7] SERS is a technique in which lasers are used to excite vibrational transitions in molecules adsorbed on noble metal nanostructures (e.g. on metal colloids, island films or roughened metal surfaces).…”