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BP: Fachverband Biologische Physik

BP 7: Single Molecule Biophysics

BP 7.5: Vortrag

Montag, 17. März 2025, 16:30–16:45, H44

Label-Free Photothermal Infrared Correlation Spectroscopy — •Arthur Markus Anton and Frank Cichos — Leipzig University, Peter Debye Institute for Soft Matter Physics, Linnéstr. 5, 04103 Leipzig

Correlation spectroscopy is an indispensable method in modern life science. It allows for retrieving analyte properties in solution like it’s concentration or diffusion coefficient, and thus enables to calculate the hydrodynamic radius of proteins or the viscosity of membranes, for instance. Common techniques are based on fluorescence or scattering, such as fluorescence correlation spectroscopy or dynamic light scattering respectively, and therefore need fluorescent labeling of analytes or lack of molecular specificity.

In this contribution we present a novel spectroscopic correlation technique on the basis of pumping with IR light but probing by means of visible light. The absorption of IR light is highly specific and allows us for label-free addressing of specific vibrational modes within the analyte molecules via the particular pump wavelength. Upon absorption, energy is dissipated and transferred into heat which alters the refractive index of the medium surrounding the absorbing species. This transient refractive index change is then probed by means of visible light providing a similar probe focal volume as conventional correlation spectroscopy techniques. Consequently, on the basis of IR pumping and visible probing we calculate the analyte’s concentration and diffusion coefficient.

Keywords: Correlation spectroscopy; Photothermal microscopy