Identification and Characterization of Artists' Red Dyes and Their Mixtures by Surface-Enhanced Raman Spectroscopy

Abstract

Silver film over nanospheres (AgFONs) were successfully employed as surface-enhanced Raman spectroscopy (SERS) substrates to characterize several artists' red dyes including: alizarin, purpurin, carminic acid, cochineal, and lac dye. Spectra were collected on sample volumes (1 x 10(-6) M or 15 ng/microL) similar to those that would be found in a museum setting and were found to be higher in resolution and consistency than those collected on silver island films (AgIFs). In fact, to the best of the authors' knowledge, this work presents the highest resolution spectrum of the artists' material cochineal to date. In order to determine an optimized SERS system for dye identification, experiments were conducted in which laser excitation wavelengths were matched with correlating AgFON localized surface plasmon resonance (LSPR) maxima. Enhancements of approximately two orders of magnitude were seen when resonance SERS conditions were met in comparison to non-resonance SERS conditions. Finally, because most samples collected in a museum contain multiple dyestuffs, AgFONs were employed to simultaneously identify individual dyes within several dye mixtures. These results indicate that AgFONs have great potential to be used to identify not only real artwork samples containing a single dye but also samples containing dyes mixtures.

Revealing the invisible: using surface‐enhanced Raman spectroscopy to identify minute remnants of color in Winslow Homer's colorless skies

“…On the other hand, the sharp band at 1497 cm −1 has also been observed by Whitney et al in other samples of carminic acid and cochineal carmine lake manufactured by Weber, and so it should not be considered specific to Indian purple. [38] Thus, on the basis of the spectral evidence discussed above, it is concluded that grain 'a' is most likely composed of Indian purple. Other grains contained in the sample were observed to have a mixture of yellow, reddish purple, and bright red coloring (exemplified by grain 'b'); SERS spectra recorded for these grains (Fig.…”

Microanalysis of organic pigments and glazes in polychrome works of art by surface-enhanced resonance Raman scattering

“…With the exception of earlier work on pure anthraquinones using nanosphere lithography Ag nanoparticles (13), and silver nanoisland films (14,15), solution reduced Ag colloids [primarily Lee-Meisel (16) citrate reduced colloids] have been the SERS support of choice for analysis of dyes of artistic interest. The chief advantage of nanosphere lithography nanoparticles, the tunability of their plasmon resonance has been offset by a strong carbon background (11).…”

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

“…[16] SERS spectra on PUR obtained under different experimental conditions have also been described. [15,17,21,34,38] In the present case, and before trying to detect anthraquinone dyes using photoreduced Ag nanoparticles, it was necessary to obtain control SERS spectra using these SERS substrates. Figure 1 shows the SERS spectra from AZ, PUR and their mixed solutions at 514.5 nm.…”

“…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.…”