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Occurrence of the solid-state photo-CIDNP effect at earths magnetic field

Subject Area Analytical Chemistry
Biophysics
Physical Chemistry of Solids and Surfaces, Material Characterisation
Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
Term from 2017 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 367704943
 
Final Report Year 2023

Final Report Abstract

(i) Successfully lower fields were explored for the occurrence of the solid-state photo-CIDNP (photochemically induced dynamic nuclear polarization) effect which allows for dramatic enhancement of signals in NMR. A surprising observation, the positive signals in the stray-field range, led to an extension and unification of the theory. The present theory matches well to concepts used in the description of other hyperpolarization methods as DNP, ONP and PHIP. Therefore, the work presented here is remarkable brick in an arising unified theory of nuclear hyperpolarization. (ii) Successfully new systems were demonstrated able to show the solid-state photo-CIDNP effect. In particular, the study of the effect on LOV domains has a huge potential for further studies, for example towards the rational design of flavin-based artificial diads as well as for the development of photo-CIDNP MRI methodology. Diads can be optimized for lower fields, therefore sample design and methodology development will be hand-in-hand. In this respect, the observation of a 1H solid-state photo-CIDNP effect is a game changer. Until now, photo-CIDNP MRI would have to rely on 13C (or probably 2H and 19F). Carbon-13 would require isotope enrichment. That 1H can be pumped (and can even diffuse) might also be relevant for functional mechanisms in photosynthesis and animal navigation. (iii) Concerning the original question, the occurrence of the effect at earth’s magnetic field, the answer remains unclear: Until now, we were not able to demonstrate the effect at Earth’s magnetic field strength although the effect has been observed with in the stray field, i.e., in the milli-Tesla range but towards the micro-Tesla range, the effect disappeared. The reason might be that until now, all our samples were made for photo-CIDNP MAS NMR at high NMR fields. We also know that extending the distance between donor and acceptor, will allow for observation of the solid-state photo-CIDNP at lower fields. Photosynthetic systems did not allow for these experiments. Now, flavin-based systems are prepared providing sufficient distance for a new trial.

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