SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 62: Poster Session V: Organic molecules on inorganic substrates: electronic, optical and other properties I
O 62.2: Poster
Mittwoch, 3. März 2021, 10:30–12:30, P
Application of laser PEEM to a biological system: Geobacter sulfurreducens — •Franz Niklas Knoop, Gerhard Lilienkamp, and Winfried Daum — Institute of Energy Research and Physical Technologies, TU Clausthal, Leibnizstraße 4, 38678 Clausthal-Zellerfeld, Germany
Recently, multi-photon photoelectron emission microscopy (nP-PEEM) was successfully applied to the spectromicroscopy of porphyrin thin films and exciton-plasmon coupling in nanoplasmonic-porphyrin hybrid systems by tuning the laser wavelength for multi-photon excitation in resonance with the molecular S0 -> S2 transition (Soret band) [1]. Here, we report on our laser-PEEM study of a biological system, the bacterium Geobacter sulfurreducens. This anaerobic bacterium features membrane-associated and extracellular cytochromes containing iron porphyrins. In contrast to porphyrin films of ZnTPP or MgTPP, near-Soret excitation of photoelectrons from Geobacter sulfurreducens results in pronounced dependencies of the photoemission on irradiation time indicating laser-induced, irreversible changes of the bacteria. An initial decrease of the photoemission can be related to an irreversible photo-induced oxidation of the cytochromes while a strong increase for longer periods of irradiation is shown to be caused by thermal effects. PEEM excitation spectra of the exposed bacteria also show the degenerative effect of the exciting laser pulses.
[1] K. Stallberg, G. Lilienkamp, W. Daum, J. Phys. Chem. C 121, 13833 (2017).