Thermodynamics glassy water

Many classic explanations for the behavior of liquid bulk water have been developed [16-18]. A truly coherent picture of the thermodynamics of metastable water should make clear (a) the anomalous behavior of the thermodynamic parameters in the supercooled region, (b) the properties and nature of the transition between the two glassy phases LDA and HDA, and (c) the relationship between supercooled and glassy water. 

Most of the structural and dynamic studies in solutions have been carried out at ambient temperature and atmospheric pressure or not far from it. An increasing number of papers is devoted to supercooled [16-19] and glassy [18,20,21] water and solutions as well as to studies of water [22] and of aqueous solutions [23,24] at high temperature and/or pressure. Computer simulation methods are very flexible and are suitable for various studies at almost any thermodynamic conditions, and therefore a new strategy of the research can be established easily simulations may predict some properties of the solutions at conditions which can be later verified when the appropriate experimental conditions become available. 

Copper (I) complexes exhibit catalytic activity for the four-electron (4-e) reduction of O2 to water. Natural occurring enzymes like Cu-containing fungal laccase reduce O2 directly to water very efficiently at very positive potentials, not far from the thermodynamic standard potential of the O2/H2O couple. These enzymes involve a trinuclear Cu active site [149-153]. For this reason some authors have investigated the catalytic activity of Cu(I) complexes for ORR, in particular Cu phenanthrolines confined on graphite or glassy carbon surfaces [154-169], with the aim of achieving the total reduction of O2 via the transfer of four-electrons. 

Figure 4. The relationship between temperature, water content, and stability (after Franks, F.f In a dilute aqueous suspension, a biochemically active molecule is structural stabile but is vulnerable to a wide range of environmental degradative forces such as hydrolysis, oxidation and racemization. In a surface immobilized or dehydrated state, a biochemically active molecule achieves peater kinetic stability at a cost of thermodynamic instability. From a dilute state (A) through supersaturation (S) with progressive water loss on the way to a solid glassy state (B), a biochemcially active molecule passes through a thermodynamically defined (entropic loss of water and enthalpy of adsorption) transition zone (stippled) where irreversible conformational changes may occur. We have observed that the disaccharides used to fabricate Aquasomes appear to stabilize biochemically active molecules in this zone during surface-induced dehydration. The dashed line represent the freeze-drying pathway between the eutectic point and Tg.

---