Pozzi F.,Solomon R. Guggenheim Museum |
Leona M.,Metropolitan Museum of Art
Journal of Raman Spectroscopy | Year: 2016
Since its introduction in the cultural heritage field, nearly 30 years ago, surface-enhanced Raman spectroscopy (SERS) has emerged as a promising analytical technique that is particularly suitable for the detection and identification of organic colorants. Its great molecular selectivity and specificity, and unparalleled sensitivity compared to other instrumental methods, have allowed researchers to successfully characterize a wide number of natural dyes and a few synthetic ones in microscopic samples from objects of artistic, historical, and archaeological significance. Continued research over the course of the past decade has led to the construction of comprehensive databases of dyes, whose adsorption and spectral properties have been investigated at length; to the comparative study of the efficiency and performance of various metal substrates; and to the evaluation of several sample treatment methods and ad-hoc analytical protocols. In addition, recent literature in the field of SERS for art and archaeology has described instrumentation and technique advancements aimed at solving the unique challenges posed by the analysis of irreplaceable objects, namely, quasi non-destructive sampling, spatial resolution improvement, examination of insoluble compounds, and resolution of dye mixtures. Reviewing the most salient methodological and technological milestones that have traced the history of SERS for cultural heritage to date, the present article is intended as a practical resource for those researchers who would like to undertake systematic characterization of organic colorants from artworks using this powerful technique. Copyright © 2015 John Wiley & Sons, Ltd.
Casadio F.,School of the Art Institute of Chicago |
Leona M.,Metropolitan Museum of Art |
Lombardi J.R.,City University of New York |
Van Duyne R.,Northwestern University
Accounts of Chemical Research | Year: 2010
Organic dyes extracted from plants, insects, and shellfish have been used for millennia in dyeing textiles and manufacturing colorants for painting. The economic push for dyes with high tinting strength, directly related to high extinction coefficients in the visible range, historically led to the selection of substances that could be used at low concentrations. But a desirable property for the colorist is a major problem for the analytical chemist; the identification of dyes in cultural heritage objects is extremely difficult. Techniques routinely used in the identification of inorganic pigments are generally not applicable to dyes: X-ray fluorescence because of the lack of an elemental signature, Raman spectroscopy because of the generally intense luminescence of dyes, and Fourier transform infrared spectroscopy because of the interference of binders and extenders. Traditionally, the identification of dyes has required relatively large samples (0.5-5 mm in diameter) for analysis by high-performance liquid chromatography. In this Account, we describe our efforts to develop practical approaches in identifying dyes in works of art from samples as small as 25 μm in diameter with surface-enhanced Raman scattering (SERS). In SERS, the Raman scattering signal is greatly enhanced when organic molecules with large delocalized electron systems are adsorbed on atomically rough metallic substrates; fluorescence is concomitantly quenched. Recent nanotechnological advances in preparing and manipulating metallic particles have afforded staggering enhancement factors of up to 1014. SERS is thus an ideal technique for the analysis of dyes. Indeed, rhodamine 6G and crystal violet, two organic compounds used to demonstrate the sensitivity of SERS at the single-molecule level, were first synthesized as textile dyes in the second half of the 19th century. In this Account, we examine the practical application of SERS to cultural heritage studies, including the selection of appropriate substrates, the development of analytical protocols, and the building of SERS spectral databases. We also consider theoretical studies on dyes of artistic interest. Using SERS, we have successfully documented the earliest use of a madder lake pigment and the earliest occurrence of lac dye in European art. We have also found several examples of kermes and cochineal glazes, as well as madder, cochineal, methyl violet, and eosin lakes, from eras ranging from ancient Egypt to the 19th century. The ability to rapidly analyze very small samples with SERS makes it a particularly valuable tool in a museum context. © 2010 American Chemical Society.
Agency: NSF | Branch: Standard Grant | Program: | Phase: Chemical Measurement & Imaging | Award Amount: 481.90K | Year: 2010
With support from the Chemical Measurement and Imaging program, Julie Arslanoglu of New Yorks Metropolitan Museum, of Art and John Loike of Columbia University seek to develop and improve methodologies such as enzyme-linked immunosorbent assay (ELISA) for the detection, identification, and localization of proteins and gums in art. Identification of these diverse biological materials (found in paints, coatings, and adhesives) will improve understanding essential for informed treatment, preservation, and authentication. The approaches developed will improve specificity in identification, enabling for example distinction between use of whole egg or only egg white as a gilding adhesive, or the use of sturgeon?s glue or goat?s milk explicitly as a paint binder. Parallel mass spectrometric studies should enable identification of specific targets for improved characterization, and aptamer technology is being used to identify organic molecules in art. The complementary nature of these techniques is being explored. Finally, the localization of proteins and polysaccharide in paint or coating layers in cross-sections is being characterized using Surface Enhanced Raman (SERS)-labeled antibodies. This will greatly enhance knowledge of an artist?s technique as well as conservation treatment.
In addition to important insights into the preservation and authentication of cultural heritage objects, methods developed in these studies should contribute to other fields affected by similar limitations (low concentration of highly degraded organic materials with interfering inorganic ions), such as environmental monitoring or forensic analysis. The research entails teaching and training of students and postdocs interested in the science of preservation of cultural heritage. Results will be widely disseminated to the general public through websites and presentations in the museum setting, as well as scholarly conferences and publications.
Agency: NSF | Branch: Standard Grant | Program: | Phase: Chemical Measurement & Imaging | Award Amount: 375.00K | Year: 2010
With support from the Chemical Measurement and Imaging Program (via the SciArt solicitation), Drs. Marco Leona of the Metropolitan Museum of Art and John Lombardi of CUNY are devising means of identifying the materials present in works of art - complex assemblages of inorganic and organic materials, often with unknown histories. The work is essential to understanding the history and improving the conservation of artworks. The problem is challenging because many materials of interest (e.g., markers for provenance, attribution, and use history) are present in very low concentrations and/or are affected by degradation processes. Strict sampling limitations further complicate the undertaking. The team is adapting surface-enhanced Raman spectroscopy (SERS) for the identification of organic colorants, an important class of artists materials found in textiles, paintings, and other polychrome works of art. Specifically, they are developing sensitive and reproducible SERS substrates and new sample preparation methods, and using a broadband tunable laser to enable resonant excitation for increased sensitivity. They are investigating computational modeling in parallel with experimental adsorption measurements to address important problems affecting SERS, such as variations in response among closely related dyes and the influence of interfering compounds.
The high-sensitivity non-destructive techniques being developed should have applicability beyond the confines of cultural heritage research, in areas such as biochemical, pharmaceutical, environmental, and forensic, and homeland security. The increased understanding of the SERS phenomenon will be helpful in elucidating the relative importance of electromagnetic and chemical contributions to the SERS mechanism. The work will thus have broad impact through improved understanding and conservation of works of art and cultural heritage; enhanced cross-disciplinary research training for undergraduate, graduate, and postdoctoral chemists with case studies from art conservation and art historical studies; and science outreach through inclusion of scientific results in museum publications and public programs.
Centeno S.A.,Metropolitan Museum of Art
Journal of Raman Spectroscopy | Year: 2016
The aim of the present article is to highlight publications that illustrate some advances in the application of Raman spectroscopy to investigate materials typically observed in manuscripts, drawings, prints, and paintings in museums' and cultural institutions' collections, and to discuss some of the challenges and future prospects. Copyright © 2015 John Wiley & Sons, Ltd.