Séminaire ISTerre

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Characterization of natural materials using infrared spectroscopy at the 50 nm scale: breaking the diffraction limit with photo-thermal AFM-IR

mercredi 21 juin 2023 - 10h00

Van Phan THI HAI - post-doc IGE, en lien avec l'équipe Minéralogie
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Extra-terrestrial samples are often a fine mixture of organic matters (OM), silicates, sulphides, carbonates and water ice. Their analysis using vibrational spectroscopy has been particularly challenging using vibrational spectroscopy because of strong fluorescence background (Raman) and because constituents are mixed at scale much smaller than the spatial resolution (Raman & IR). Conventional IR spectrometers are limited by diffraction, and typical spatial resolution is around 5-µm. As part of the SOLARYS funded ERC project, we have developed a recent technique that combines IR spectroscopy and atomic force spectroscopy (AFM), that enables to probe optical absorption properties at a scale much smaller than the wavelength. This new technique requires to develop new protocol for analysing natural samples, and to assess the capability of the technique to natural, often complex materials. We will present in this seminar the principle of the method and its application to the analysis of coals and carbon-bearing extra-terrestrial samples (carbonaceous chondrites and samples from asteroid Ryugu). We will show that the spatial resolution is indeed <50 nm and that IR signatures of organics can be mapped within a sample, providing access to the spatial relationship between mineral and organics, as well as to the chemical functionalities of the carbon species.

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Equipe organisatrice : Organisation labo

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères