Can EPR be used to probe solid-liquid phase transitions in confined systems?
Study of systems such as water under confined conditions is actively pursued because of its relevance to real systems, such as cells, microorganisms, etc. In this regard, EPR spectroscopy offers a convenient route due to its excellent sensitivity to micro viscosity and penetrability power. When used as a probe-based spectroscopy, however, the probe-system interactions need to be thoroughly examined beforehand. In this work, we consider a specific property: solid⇌liquid transition of water, and ask a fundamental question, “Can EPR detect the freezing of water at its conventional freezing point in bulk/confined conditions?” Our work convincingly demonstrates that the spin probe can itself induce liquid domains in ice, which could be mistaken as a depression in the freezing point. We propose a theory to account for these solute induced perturbations. Finally, it will be discussed how the proposed theory can be applied to the extreme dilution case of a solution containing a single solute molecule.
1.Thangswamy, M.; Maheshwari, P.; Dutta, D.; Rane, V.*; Pujari, P. K. J. Phys. Chem. A 2018, 122, 5177-5189.
2.Thangswamy, M.; Maheshwari, P.; Dutta, D.; Rane, V.*; Pujari, P. K. J. Phys. Chem. C 2019, 123, 11244-11256.