title: Low-Density Water Structure Observed in a Nanosegregated Cryoprotectant Solution at Low Temperatures from 285 to 238 K.
abstract: The structure of liquid water is defined by its molecular association through hydrogen bonding. Two different structures have been proposed for liquid water at low temperatures: low-density liquid (LDL) and high-density liquid (HDL) water. Here, we demonstrate a platform that can be exploited to experimentally probe the structure of liquid water in equilibrium at temperatures down to 238 K. We make use of a cryoprotectant molecule, glycerol, that, when mixed with water, lowers the freezing temperature of the solution nonmonotonically with glycerol concentration. We use a combination of neutron diffraction measurements and computational modeling to examine the structure of water in glycerol-water liquid mixtures at low temperatures from 285 to 238 K. We confirm that the mixtures are nanosegregated into regions of glycerol-rich and water-rich clusters. We examine the water structure and reveal that, at the temperatures studied here, water forms a low-density water structure that is more tetrahedral than the structure at room temperature. We postulate that nanosegregation allows water to form a low-density structure that is protected by an extensive and encapsulating glycerol interface.
authors.affiliation: Faculty of Engineering, University of Nottingham , Nottingham NG7 2NR, U.K.
authors.forename: J J
authors.initials: JJ
authors.lastname: Towey
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory , Chilton, Didcot, Oxon OX11 OQX, U.K.
authors.forename: A K
authors.initials: AK
authors.lastname: Soper
authors.affiliation: School of Physics and Astronomy, University of Leeds , Leeds LS2 9JT, U.K.
authors.forename: L
authors.initials: L
authors.lastname: Dougan