Magnetic Resonance Force Microscopy

The rich myriad of microscopic methods used to investigate processes on an atomic scale has been greatly influenced by AFM (Atomic Force Microscopy). Based on this technique, many new methods have been developed that aim to obtain the highest possible resolution. One of these advancements is MRFM (Magnetic Resonance Force Microscopy), which has great potential to specifically resolve single electron spins in a spatial manner. However, current MRFM-based methods need extreme measurement conditions like temperatures in the milli-Kelvin range and vacuum. Hence, they only have limited application to biological systems.

Our group has established a new microscopy method called LIMRFM (Light-Induced Magnetization sensed via magnetic Resonance Force Microscopy) within the framework of the DFG-funded project SPP 1601 "New frontiers in sensitivity for EPR spectroscopy: from biological cells to nano materials". Our cooperation partners in this project include the groups of Prof. Stefan Weber (Institut für Physikalische Chemie, Albert-Ludwigs-University Freiburg) and of Prof. Thomas Musch (Elektronische Schaltungstechnik, Ruhr-Universität Bochum). The method itself combines MRFM and EPR (Electron-Paramagnetic Resonance)-spectroscopy and employs the magnetic field of light-inducible molecules to achieve spatial resolution.

Pentacene has recently attracted much attention as a molecule that can be excited with light. After excitation, it exhibits very specific magnetic and electronic properties under ambient conditions. This is due to a highly polarised, inducible paramagnetic triplet state, of which we made use to establish LIMFM. With help of the magnetised pentacene, a localized detection becomes possible under ambient conditions even with small sample concentrations. Non-invasive measurement conditions make LIMRFM an exciting method for the future, thus, pushing back boundaries in this field. Applications to biological problems where pentacene is used as a spin-label at room temperature and without a vacuum are being developed.

Raman and FT-IR microscopy

Two complementary spectroscopy techniques, Raman and IR (infrared), are used to probe the chemical fingerprint spectrum of molecules. Any changes in molecular structure and composition will alter the vibrational response of the sample. To map the chemical composition of a sample, IR and Raman spectroscopic methods are combined with microscopic techniques in the form of microspectroscopy.

CRM (Confocal Raman Microscopy) allows one to acquire information on the molecular composition of a sample in the three spatial dimensions, thus providing both a lateral- and depth-profile of the sample. The spatial resolution of the setup is limited only by the Abbe limit of the laser used to excite the sample molecules. Using visible lasers, a resolution of 300 nm can be achieved, enabling single cells to be studied on a compartmental level.


Most relevant publications

Gruenerpfeil"Metal-carbonyl-complexes as a new modality for label-free live cell imaging by Raman-microspectroscopy", K. Meister, J. Nielsen, U. Schatzschneider, N. Metzler-Nolte, D.A. Schmidt and M. Havenith,  Ang. Chem. Int. Ed. 49, 3310-3312 (2010).

"Detection of hybridization on nanografted oligonucleotides using scanning near-field infrared microscopy", I. Kopf, C. Grunwald, E. Bründermann, L. Casalis, G. Scoles and M. Havenith, J. Phys. Chem. C 114 (2), 1306-1311 (2010).

Gruenerpfeil"Chemical imaging of micro-structured self assembled monolayers (SAMs)", I. Kopf, J. S. Samson, G. Wollny, C. Grunwald, E. Bründermann and M. Havenith, J. Phys. Chem. C 111 (23), 8166 (2007).

Gruenerpfeil"SNIM-scanning near-field infrared microscopy", E. Bründermann, M. Havenith, Annual Reports Prog. Chem. Section C: Phys. Chem 104, 235 (2008).

Gruenerpfeil"Unraveling the interactions between cold atmospheric plasma and skin-components with vibrational microspectroscopy", K. Kartaschew, M. Mischo, S. Baldus, E. Bründermann, P. Awakowitz and M. Havenith, Biointerfaces 10, 029516 (2015).

Gruenerpfeil"Graphene Multilayer as Nanosized Optical Strain Gauge for Polymer Surface Relief Gratings", G. Di Florio, E. Bründermann, N.S. Yadavalli, S. Santer, and M. Havenith, Nano Lett. 14 (10), 5754-5760 (2014).