title: Solvation of a probe molecule by fluid supercooled water in a hydrogel at 200 K.
abstract: By combining electron paramagnetic resonance (EPR) measurements on a nitroxide probe and differential scanning calorimetry (DSC), we demonstrate existence of liquid supercooled water in a silica hydrogel with high hydration level down to temperatures of at least 198 K. Besides the major fraction of liquid supercooled water, a minor fraction crystallizes at about 236 K during cooling and melts at 246 K during heating. The liquid domains are of sufficient size to solvate the nearly spherical paramagnetic probe molecule TEMPO with a diameter of about 6 A. Analysis of EPR spectra provides the rotational correlation time of the probe that is further used to compare the viscosity of the supercooled water with the one of bulk water. In the temperature interval investigated, the supercooled water behaves as a fragile liquid and eventually solidifies at 120 K to a glass that incorporates the probe molecules.
authors.affiliation: Laboratory of Physical Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Santangelo
authors.forename: Matteo
authors.initials: M
authors.lastname: Levantino
authors.forename: Antonio
authors.initials: A
authors.lastname: Cupane
authors.forename: Gunnar
authors.initials: G
authors.lastname: Jeschke
mesh_terms: D002152:Calorimetry, Differential Scanning; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D015335:Molecular Probes / Q000737:chemistry*; D012995:Solubility; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D015335:Molecular Probes; D014867:Water; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate