Liquid-solid interactions advancing

A proper solvated electron is a particle localized in the potential well of a polar medium, the well being created by the interaction of electron charge with the permanent and induced dipole moments of the nearest as well as remote neighbours. This notion of the nature of a solvated electron, based on the idea that the Landau-Pekar theory initially advanced for solid bodies can be applied also to liquid systems, was advanced in 1948 since then considerable efforts have been made to develop it and verify it experimentally. In most liquid systems, localization of an electron is followed by the formation of a cavity where most of the density of the solvated electrons is concentrated. The cavity is surrounded by the orientated dipoles of the solvent. Usually, the radius of this cavity equals about 3-3.5 A which conforms to a solvated-electron molar volume of 70-100 cm . This is the reason why solutions with large concentrations of solvated electrons have a lower density. 

L-H. Lee, in Interaction of liquids at Solid Substrates , Advances in Chemistry Series No. 87, American Chemical Society, Washington, DC, 1968, p. 106. 

Figure 6.1 schematically depicts the three interactions between a liquid droplet and a surface. These three interactions are actually governed by the movement of the contact line. When the liquid first wets the surface, the contact line advances outward, and the first information one seeks is wettability. The adjectives to describe the surface are wettable and non-wettable. As for the liquid, it will either wet or partially wet the surface or repel from it. As discussed in Chap. 5, wettability is measured by the advancing angle Oa- Once the liquid partially wets the surface, a static sessile drop is formed. There exist two interactions between the sessile drop and the surface. In the vertical direction, it is the adhesion and it is measured by the receding angle 0r. The only motion for the contact line is receding, and an interface (liquid-solid) is eliminated when the liquid droplet is detached from the surface. 

The principal dilTerence from liquid-state NMR is that the interactions which are averaged by molecular motion on the NMR timescale in liquids lead, because of their anisotropic nature, to much wider lines in solids. Extra infonnation is, in principle, available but is often masked by the lower resolution. Thus, many of the teclmiques developed for liquid-state NMR are not currently feasible in the solid state. Furthemiore, the increased linewidth and the methods used to achieve high resolution put more demands on the spectrometer. Nevertheless, the field of solid-state NMR is advancing rapidly, with a steady stream of new experiments forthcoming. 

This chapter simnnarizes the interactions that affect the spectrum, describes the type of equipment needed and the perfomiance that is required for specific experiments. As well as describing the basic experiments used in solid-state NMR, and the more advanced teclmiques used for distance measurement and correlation, some emphasis is given to nuclei with spin / > dsince the study of these is most different from liquid-state NMR. 

Schick, M.J. Harvey, E.N., Jr. In "Interaction of Liquids at Solid Substrates" Alexander, A.L., Symposium Chairman ADVANCES IN CHEMISTRY SERIES, No. 87, American Chemical Society Washington, D.C. 1968 p. 63. 

The first MC (16) and MD (17) studies were used to simulate the properties of single particle fluids. Although the basic MC (11,12) and MD (12,13) methods have changed little since the earliest simulations, the systems simulated have continually increased in complexity. The ability to simulate complex interfacial systems has resulted partly from improvements in simulation algorithms (15,18) or in the interaction potentials used to model solid surfaces (19). The major reason, however, for this ability has resulted from the increasing sophistication of the interaction potentials used to model liquid-liquid interactions. These advances have involved the use of the following potentials Lennard-Jones 12-6 (20), Rowlinson (21), BNS... 

For nondeformable particles, the theories describing the interaction forces are well advanced. So far, most of the surface force measnrements between planar liquid surfaces (TFB) have been conducted under conditions such that the film thickness is always at equilibrium. In the absence of hydrodynamics effects, the forces are correctly accounted considering classical theories valid for planar solid surfaces. When approached at high rate, droplets may deform, which considerably complicates the description it is well known that when the two droplets are sufficiently large, hydrodynamic forces result in the formation of a dimple that flattens prior to film thinning. Along with the hydrodynamic interactions, the direct... 

Infrared spectroscopy was widely used in the second half of the 20th century, and this technique has allowed some advances to be made in awareness of functionalities in, and of complexes formed by, humic molecules. However, the greatest advances in determinations of functionalities, in aspects of compositions and structures, and now in aspects of humic interactions have been made since the introduction of solid-state 13C NMR spectroscopy (Wilson, 1987 Malcolm, 1989). Chapter 15 in this book (by Simpson and Simpson) has reviewed in detail the applications of NMR in the solid and liquid states to studies of compositions and interactions of NOM. We now have a good indication of the types of functionalities that compose HS, and combinations of modem NMR technologies and principal component analysis (PCA) techniques allow us to deduce the origins of some of the functionalities (Novotny et al., 2007). 

In Interaction of Liquids at Solid Substrates Alexander, A. Advances in Chemistry American Chemical Society Washington, DC, 1968. 

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