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Numerous water characteristics are essentially ascribed to its peculiarity to form stronghydrogen bonds that become progressively more stable on decreasing the temperature. However, thestructural and dynamical implications of the molecular rearrangement are still subject of debate andintense studies. In this work, we observe that the thermodynamic characteristics of liquid water arestrictly connected to its dynamic characteristics. In particular, we compare the thermal behaviourof the isobaric specific heat of water, measured in different confinement conditions at atmosphericpressure (and evaluated by means of theoretical studies) with its configurational contribution obtainedfrom the values of the measured self-diffusion coefficient through the use of the Adam-Gibbsapproach. Our results confirm the existence of a maximum in the specific heat of water at about 225K and indicate that especially at low temperature the configurational contributions to the entropy aredominant.

The hydrogen density of states (DOS) in confined water has been probed by inelastic neutron scattering spectra in a wide range of its P - T phase diagram. The liquid-liquid transition and the dynamical crossover from the fragile (super-Arrhenius) to strong (Arrhenius) glass forming behavior have been studied, by taking into account the system polymorphism in both the liquid and amorphous solid phases. The interest is focused in the low energy region of the DOS ( E < 10 meV) and the data are discussed in terms of the energy landscape (local minima of the potential energy) approach. In this latest research, we consider a unit scale energy (EC) linked to the water local order governed by the hydrogen bonding (HB). All the measured spectra, scaled according to such energy, evidence a universal power law behavior with different exponents ( γ ) in the strong and fragile glass forming regions, respectively. In the first case, the DOS data obey the Debye squared-frequency law, whereas, in the second one, we obtain a value predicted in terms of the mode-coupling theory (MCT) ( γ ≃ 1.6 ).

Water is one of the most important compounds on Earth, yet its material properties are still poorly understood. Here, we use a recently developed two-state, two-(time)scale (TS2) dynamic mean-field model combined with the two-state Sanchez–Lacombe (SL) thermodynamic theory in order to describe the equation of state (density as a function of temperature and pressure) and diffusivity of liquid water. In particular, it is shown that in a relatively wide temperature and pressure range (160 K < T < 360 K; 0 < P < 100 MPa), density and self-diffusion obey a special type of dynamic scaling, similar to the "τTV" scaling of Casalini and Roland, but with the negative exponent γ. The model predictions are consistent with experimental data. The new equation of state can be used for various process models and generalized to include multicomponent mixtures. [ABSTRACT FROM AUTHOR]

Abstract: A novel approach to synthesize Au/TiO2 nanostructures with interesting optical properties is presented and discussed. It is based on the nanoparticle “cold” or “hot” nanosoldering occurring when two water suspensions of Au and TiO2 nanoparticles are merely mixed at room temperature or laser irradiated after mixing. Thanks to the high fraction and mutual reactivity of surface species, immediately after the mixing process, the encounters between Au and TiO2 nanoparticles in liquid phase are enough for “cold” nanosoldering of gold nanoparticles onto TiO2 nanoparticles to occur. The optical characterizations show that this fast process (timescale less than 1min) is followed by a slower process, attributable to some change of the Au nanoparticles. This latter process is significantly accelerated by the 532nm laser light illumination. The structural and optical properties of “cold” and “hot” nanosoldered Au–TiO2 nanoparticles were investigated by TEM, UV–vis and fluorescence spectroscopies. Interesting optical limiting response was detected at laser fluences above 0.8J/cm2. The nature of the nonlinear effect was investigated by the Z-scan technique, determining both the nonlinear absorption coefficient and the refraction index. Such interesting non-linear optical properties are worth to be tailored for specific applications. [Copyright &y& Elsevier]

The current devices used to produce massive amounts of snow (i.e., snow machines) can be improved with concern to both the energy efficiency and the quality of snow. Here we investigate an alternative snow production method based on the ultrasonic nebulization of water and its subsequent condensation on the cold surfaces of a refrigerator. Inspection of the snow samples with a stereo optical microscope shows both dendritic and granular snow morphologies. The characterization of the samples by Raman spectroscopy shows a behavior consistent with that of a natural, low-density snow. Our results indicate that ultrasonic nebulization of water is an effective strategy for producing natural-like snow at the laboratory scale. [ABSTRACT FROM AUTHOR]

In this review we discuss the role of hydrophilic/hydrophobic interplay in several processes involving water–surface interactions. For this purpose, we describe the self-organization architecture of biomacromolecules, the design of artificial biocompatible nano-devices able to deliver poorly water-soluble drugs, and the engineering of packaging materials capable to preserve food from water, dust, and microorganisms contamination. Material properties together with mutual-cooperative interactions play a crucial role to match the complexity of biological environments and desired functional products. Therefore, the comprehension and description of hydrophilic/hydrophobic interactions at molecular level represent the main steps towards the development of new biosystems with improved functionality. [Display omitted] • H 2 O polymorphic properties tune its interaction with molecular/macroscopic surfaces. • WMI pilot surface functionalization and self-organization of biomolecules. • WMI are crucial in improving drug delivery systems and food packaging materials. [ABSTRACT FROM AUTHOR]