Thermodynamic, structural, and dynamic properties of supercooled water confined in mesoporous MCM-41 studied with calorimetric, neutron diffraction, and neutron spin echo measurements

Abstract

Thermodynamic, structural, and dynamic properties of heavy water (D(2)O) confined in mesoporous silica glass MCM-41 C10, C12, and C14 were investigated by differential scanning calorimetry, neutron diffraction, and neutron spin echo (NSE) measurements, respectively. The DSC data showed that no crystallization of D(2)O confined in C10 occurs in a temperature range between 298 and 180 K, and that crystalline ice is formed at 204 and 221 K for C12 and C14, respectively. For C10, the neutron radial distribution functions of confined D(2)O suggested a structural change in the supercooled state between 223 and 173 K. For C10 sample, it has been found that the tetrahedral-like water structure is partially enhanced in the central part of pores at 173 K. For all the samples, the intermediate scattering functions from the NSE measurements are fitted by the Kohlrausch-Williams-Watts stretched exponential function which implies that confined supercooled D(2)O exhibits a wide distribution of relaxation times. For C10, C12, and C14 samples, between 298 and 240 K, the relaxation times of supercooled D(2)O follow remarkably well the Vogel-Fulcher-Tamman equation; for C10 sample, below 240 K, the relaxation times of nonfreezing D(2)O show an Arrhenius type behavior. From the present experimental results on calorimetric, structural, and dynamic properties, it has been concluded that supercooled D(2)O confined in MCM-41 C10 experiences a transition from high-density to low-density hydrogen-bonded structure at around 229 K.

Specific cellular water dynamics observed in vivo by neutron scattering and NMR

“…Inelastic neutron experiments to study water dynamics were performed in the late 1950s, close to the very beginning of neutron beam applications to the study of liquids 2,3 and neutrons continue to contribute significantly in the field, the study by ref. 4 being a recent example.…”

Thermal Behavior and Structure of Low-temperature Water Confined in Sephadex G15 Gel by Differential Scanning Calorimetry and X-ray Diffraction Method

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Important findings from these studies are the supercooling of water, retardation of the motion of water molecules, distortion of tetrahedral-like hydrogen-bonded structure of water, and a fragile-to-strong dynamical crossover at around 220 K in confinement. Most of confined systems employed in previous studies were mesoporous materials, such as Vycor, 1,4,5 MCM-41, 3,6,[7][8][9][10][11][15][16][17][18][19] carbon nanotube 12 and activated carbon. 13,14 However, these materials have hard walls.…”

“…Thus, the thermal property and structure of confined water have drawn much attention for understanding the underlying mechanism of processes in confined systems. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] One of the recent topics of confined water is related to the fact that water confined in pores whose diameter is less than ~20 Å is not frozen in a temperature range of 235 -150 K, 7,8,[10][11][12][13][14][15][16][17][18][19] the so-called no-man's land, 20 where bulk water is always frozen below the homogeneous nucleation temperature (235 K) of water. Unfrozen water is particularly important, since it would provide us a key for understanding anomalous properties of water, the separation of solutes in chromatography, the survival of plants and insects under extreme conditions, etc.…”

Temperature and Size Effects on Structural and Dynamical Properties of Water Confined in 1 – 10 nm-scale Pores Using Proton NMR Spectroscopy

“…[16][17][18][19][20] Recent spectroscopic studies have reported that water molecules confined in pores smaller than 2 nm do not freeze even around 200 K and the transition from high-density to lowdensity hydrogen bonding structures occurs. [21][22][23][24][25] The slowing down of both rotational and/or translational motions of confined water molecules has been also verified to be promoted with decreasing pore sizes and temperatures. [26][27][28][29] These results have suggested that the specific hydrogen bonding network of water layer on surfaces differing from bulk water, i.e., the adsorbed water phase, is responsible for causing the freezing behavior of confined water in the supercooled state.…”