Novel optical-photothermal infrared (O-PTIR) spectroscopy for the sub-micron molecular characterization of cultural heritage : oral presentation at CHEMCH 2022 conference, Ravenna, Italy, July 4-8 2022
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Optical-photothermal infrared (O-PTIR) spectroscopy is a recently developed molecular spectroscopy technique, which allows to obtain chemical information on organic and inorganic samples at a submicrometric scale. The high spatial resolution (≈450nm), potential lack of sample preparation and comparability of the spectral results to traditional FTIR spectroscopy, make it a promising candidate for application in heritage science. This work presents the first use of O-PTIR for the study of cultural heritage, focusing on the identification of both original materials and degradation products. Two types of objects were considered: an extremely small fragment from a painting (L’Arlésienne by Van Gogh) and a series of small, degraded 16th-century brass and glass objects. Both cases presented intrinsic analytical challenges, linked to the limited size and/or chemical nature of the samples, or to the complex geometry of the objects. This made it impossible to answer crucial research questions on these unique pieces with traditional state-of-the-art speciation techniques (including SR-μFTIR, μRaman and MA-XRPD). O-PTIR, on the contrary, allowed to overcome these limitations, unraveling key chemical information which would have otherwise remained hidden. In particular, the results obtained on the paint fragment, include the sub-micrometric chemical imaging of the complete stratigraphy of the painting, and the detection of geranium lake pigments in the paint layers, failed with other high-end techniques . The analysis of glass and metal objects further confirmed the great potential of O-PTIR, with the implementation of this technique in a multianalytical approach enabling the successful non-invasive characterization of original materials and degradation products. This ultimately uncovered markers of glass-induced metal corrosion processes on the surface of both glass and metal objects . Building upon these striking results, advantages and disadvantages of this novel spectroscopic technique compared to other state-of-the-art methods currently employed in heritage science will be thoroughly discussed.
Marchetti, V. Beltran, F. Borondics, C. Sandt, G. Nuyts, M. Leeuwestein, M. Debulpaep, K. De Wael, Novel optical-photothermal infrared (O-PTIR) spectroscopy for the sub-micron molecular characterization of cultural heritage. Oral presentation at CHEMCH 2022 conference, Ravenna, Italy, July 4-8 2022