Surface-NMR with quantum sensors

• Applicant: Professor Dr. Dominik Benjamin Bucher
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Analytical Chemistry
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 412351169

In recent years, color centers in diamond have been shown to be an outstanding atomic-scale sensor for magnetic fields. With these defects in diamond – more precisely nitrogen vacancy (NV) centers – nuclear magnetic resonance (NMR) signals from a few cubic nanometer sample volumes or even single protons have been detected. Although this innovative technique, originating from quantum optics, seems to be a very promising tool for chemical and life sciences, it has not been yet applied to solve scientific questions in these fields. Here, the diamond quantum sensors shall be used in an interdisciplinary research group to establish a surface sensitive NMR technology for (bio)chemical applications. In contrast to most of the previous studies in this field, which were based on single NV-centers, a high-dense NV-layer in diamond, located a few nanometers beneath the surface, will be used for this proposal, which increases sensitivity dramatically. This NV-layer probes NMR signals from a few nanometer-thick surface layer, which is not possible with traditional NMR methods. The surface NV-NMR technology shall be applied to three directions in chemical and life science applications: (1) Structural analysis of surface tethered molecules. Nanoscale NV-NMR results usually in broad resonance lines (kHz) due to short interaction times of the nuclear spin with the NV-sensor, as a consequence of the molecular diffusion of the sample. This diffusional line broadening will be overcome here by tethering molecules to the diamond surface, which will reduce the linewidth to 10-100 Hz. With this approach structures of surface immobilized catalysts shall be elucidated, a task which cannot be addressed with current methods. (2) Probing structure and dynamics of single lipid bilayers on the NV-diamond surface. After investigating surface supported lipid bilayers, the ultimate aim will be to determine membrane structures of living cells in a label free and microscopic way with NV-NMR. (3) Investigation of catalytic active surfaces. Thin platinum films on diamond will be sensed with NV-NMR and its material properties will be correlated with different film thicknesses. Moreover, surface molecular adsorption processes on platinum shall be probed. In summary, quantum sensors shall be established in chemistry for probing non-invasively (bio)molecular and material properties at surfaces, which cannot be addressed with traditional NMR techniques. This will be achieved through a unique and interdisciplinary combination of quantum technology and chemical (synthetic) methods.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: Electromagnet ; arbitrary waveform generator
• Instrumentation Group: 0110 Hochstabile Magnete (mit homogenem oder speziellem Feldverlauf) ; 6040 Frequenz-Umformer (statisch) und Hochfrequenzgeneratoren