Suitability of Ag‐agar gel for the micro‐extraction of organic dyes on different substrates: the case study of wool, silk, printed cotton and a panel painting mock‐up

Abstract

A surface‐enhanced Raman spectroscopy (SERS) substrate made of agar gel coupled with silver nanoparticles has been applied to the micro‐extraction and the ultra‐sensitive detection of dyes on pieces of textile of different nature (silk, wool, and printed cotton) and on a mock‐up panel painting. In particular, the Ag‐agar gel substrate previously developed has been improved by the addition of the chelating agent ethylenediaminetetraacetic acid (EDTA), which has been found to play an important role as a stabilizer of the nanocomposite matrix and for the improvement of the micro‐extractive performances of the gel. The system has been confirmed to be non‐destructive and minimally invasive, showing a better capability of trapping the dye molecules inside its structure. Ag‐agar gel‐EDTA has been an invaluable and powerful tool for the characterization of the dye present in a printed cotton sample of unknown chemical composition. SERS analyses, performed on the dried cube of gel following extraction on the sample, have allowed for the identification of the dye. SERS results have been corroborated by high‐performance liquid chromatography analyses. The possibility of easily detecting compounds at very low concentration coupled with the high sensitivity of SERS makes this technique a valid and versatile method for the non‐destructive recognition of chemicals in works of art. Copyright © 2014 John Wiley & Sons, Ltd.

Tailored micro-extraction method for Raman/SERS detection of indigoids in ancient textiles

“…A further dyeing example regards the case of anthraquinonic mordant dyes, which are (partially) water soluble, and are attached to the fiber attributable to the presence of metal ions. We have already reported in a previous work that it is possible to extract anthraquinonic dyes by adopting as a solvent for the extraction, an aqueous solution of a chelant reagent [11].…”

“…Moreover, degradation processes or bad state of conservation of the art object may further affect the analyses of the blue dye. In the last decade, the successful application of the high sensitive surface enhanced (resonance) Raman spectroscopy [SE(R)RS] for the detection of organic dyes in works of art has strongly improved the possibility of identifying fluorescent organic dyes according to minimal invasive [10][11][12][13][14] and microdestructive approaches [15][16][17]. Up to the present, the majority of the developed SERS procedures dealt mainly with the detection of red and yellow dyes [15][16][17][18][19][20][21][22][23][24][25][26], whereas only a few works have investigated the characterization of indigoids by means of SERS/SERRS.…”

Surface-Enhanced Raman Spectroscopy: Using Nanoparticles to Detect Trace Amounts of Colorants in Works of Art

“…Although many of the technical and methodological improvements in the field of SERS for cultural heritage have only been tested on mock-up paint layers (Doherty et al 2011(Doherty et al , 2014Platania et al 2014;Retko et al 2014), SERS is becoming increasingly popular in real-world case studies to detect and identify red dyes and lake pigments in samples from actual paintings. The first application in this context, reported in 2009, concerns the analysis of a 50-µm red glaze sample from St. John the Baptist Bearing Witness (ca.…”

“…Both groups incorporated the silver colloid directly in the gel substrate to be put in contact with the work of art. The agar gel approach was further refined by Platania et al (2014) by adding ethylenediaminetetraacetic acid (EDTA)-a chelating agent-to the gel, thus improving the extraction of a variety of dyes from substrates such as oil paints, printed and dyed textiles. The agar gel seems to be one of the most promising approaches because, due to its shrinking upon drying, it causes the nanoparticles to come into close contact, inducing the occurrence of SERS active hot spots.…”

Raman Spectroscopy of cultural heritage Materials: Overview of Applications and New Frontiers in Instrumentation, Sampling Modalities, and Data Processing

“…To this end, a small but growing number of papers have been published demonstrating the use of flexible substrates based on acrylic gels [182,183], methylcellulose pastes [119], gelatin [120], or agar-agar gel [187,241], optionally loaded with a mild micro-extractant, often based on ethylenediaminetetraacetic acid (EDTA) [240]. The analytical procedure either involves mixing the gel with nanoparticles, or using the gels to extract a minute and nearly invisible amount of dye for later analysis with SERS after deposition of colloidal silver particles on the face that was previously in contact with the artifact.…”