Solute-interface interaction

L. Berthelot, V. Rosilio, M. L. Costa, S. Chierici, G. Albrecht, P. Boullanger, and A. Baszkin, Behavior of amphiphilic neoglycolipids at the air solution interface. Interaction with a specific lectin, Colloids Surf., B Biointerfaces, 11 (1998) 239-248. 

In this book, the processes at solid/liquid interfaces of soil and rock, in most cases under environmental conditions, will be discussed. A scientifically correct description of interfacial processes requires the study of the properties of solid and liquid phases and the interface, as well as the interactions of these phases. Previous books typically focused on selected aspects of the subject, such as, for example, the properties of the solid phase or the interactions of selected substances such as heavy metal ions with soil/rock. We intend to present a comprehensive treatment of the soil-liquid-interface system, emphasizing the importance of the chemical species produced in a geological material/solution/interface interaction. We recommend the book to all chemists, geologists, and soil scientists working in interfacial, environmental, and soil sciences. 

The processes pictured take place at the magnesium-solution interface. Interaction of the cyclopropyl halide and the magnesium in reaction step (1) involves electron transfer from the metal into the antibonding orbital of the carbon-halogen bond. This results in the formation of a radical-anion which is closely associated with a univalent magnesium cation. 

The adsorption of nonelectrolytes at the solid-solution interface may be viewed in terms of two somewhat different physical pictures. In the first, the adsorption is confined to a monolayer next to the surface, with the implication that succeeding layers are virtually normal bulk solution. The picture is similar to that for the chemisorption of gases (see Chapter XVIII) and arises under the assumption that solute-solid interactions decay very rapidly with distance. Unlike the chemisorption of gases, however, the heat of adsorption from solution is usually small it is more comparable with heats of solution than with chemical bond energies. 

Figure 8 shows an example of the most common behavior of AEam/0 as a function of adsorbate coverage. Linear behavior, if ever observed, is seen at the air/solution interface.93 At metal/solution interfaces, if chemical interactions with the metal can be ruled out, electrostatic interactions cannot be avoided, and these are responsible for the downward curvature.91 Upward curvatures are often observed at air/solution interfaces as a consequence of lateral interactions.95... 

A macroscopic model for regular air/solution interfaces has been proposed by Koczorowski et al 1 The model is based on the Helmholtz formula for dipole layers using macroscopic quantities such as dielectric constants and dipole moments. The model quantitatively reproduces Ax values [Eq. (37)], but it needs improvement to account for lateral interaction effects. 

Later we will describe both oxidation and reduction processes that are in agreement with the electrochemically stimulated conformational relaxation (ESCR) model presented at the end of the chapter. In a neutral state, most of the conducting polymers are an amorphous cross-linked network (Fig. 3). The linear chains between cross-linking points have strong van der Waals intrachain and interchain interactions, giving a compact solid [Fig. 14(a)]. By oxidation of the neutral chains, electrons are extracted from the chains. At the polymer/solution interface, positive radical cations (polarons) accumulate along the polymeric chains. The same density of counter-ions accumulates on the solution side. 

Obviously AGad depends on the strength of the solvent-surfaee and the adsorbate-surfaee interaction in addition S-S-, A-A- and S-A-interactions contribute. Various simplifications are possible [74Tra]. As a further complication the electrical field being always present (except at at the electrode/solution-interface has to be considered. Consequently the free enthalpy of adsorption can be split into a chemical part and an electrical part ... 

In 1997, a Chinese research group [78] used the colloidal solution of 70-nm-sized carboxylated latex particles as a subphase and spread mixtures of cationic and other surfactants at the air-solution interface. If the pH was sufficiently low (1.5-3.0), the electrostatic interaction between the polar headgroups of the monolayer and the surface groups of the latex particles was strong enough to attract the latex to the surface. A fairly densely packed array of particles could be obtained if a 2 1 mixture of octadecylamine and stearic acid was spread at the interface. The particle films could be transferred onto solid substrates using the LB technique. The structure was studied using transmission electron microscopy. 

According to Frumkin and Damaskin, A% at the air/solution interface changes linearly with composition, i.e., the interface behaves as two condensers in series. "" On a molecular basis, this model is tantamount to assuming that an adsorbate and solvent do not interact in the interfacial zone, but create two homogeneous surface layers. 

Interfacial water molecules play important roles in many physical, chemical and biological processes. A molecular-level understanding of the structural arrangement of water molecules at electrode/electrolyte solution interfaces is one of the most important issues in electrochemistry. The presence of oriented water molecules, induced by interactions between water dipoles and electrode and by the strong electric field within the double layer has been proposed [39-41]. It has also been proposed that water molecules are present at electrode surfaces in the form of clusters [42, 43]. Despite the numerous studies on the structure of water at metal electrode surfaces using various techniques such as surface enhanced Raman spectroscopy [44, 45], surface infrared spectroscopy [46, 47[, surface enhanced infrared spectroscopy [7, 8] and X-ray diffraction [48, 49[, the exact nature of the structure of water at an electrode/solution interface is still not fully understood. 

Table 8.76 shows the main characteristics of voltammetry. Trace-element analysis by electrochemical methods is attractive due to the low limits of detection that can be achieved at relatively low cost. The advantage of using standard addition as a means of calibration and quantification is that matrix effects in the sample are taken into consideration. Analytical responses in voltammetry sometimes lack the predictability of techniques such as optical spectrometry, mostly because interactions at electrode/solution interfaces can be extremely complex. The role of the electrolyte and additional solutions in voltammetry are crucial. Many determinations are pH dependent, and the electrolyte can increase both the conductivity and selectivity of the solution. Voltammetry offers some advantages over atomic absorption. It allows the determination of an element under different oxidation states (e.g. Fe2+/Fe3+). 

Since this capacitance is supposed to be in series with that of the solution and since capacitances of mercury-solution interfaces are much larger than 2 F/cm2, this number is too low. The Thomas-Fermi theory as well as the neglect of interactions between metal electrons and the electrolyte are at fault. To reduce the metal s contribution to the inverse capacitance, a model must include6 penetration of the electron tail of the metal into the solvent region, where the dielectric constant is higher, as the models discussed below do. 

McBride M.B. Processes of heavy and transition metal sorption by soil mineral. In Interactions at the Soil Colloid-Soil Solution Interface, G.H. Bolt, M.F. De Boodt, M.H.B.Hayes, M.B. McBride, eds. NATO ASI Series (Series E Applied Sciences-Vol 190). Dordrecht, Netherlands Kluwer Academic Publishers, 1991. 

Real polymer processes involved in polymer crystallization are those at the crystal-melt or crystal-solution interfaces and inevitably 3D in nature. Before attacking our final target, the simulation of polymer crystallization from the melt, we studied crystallization of a single chain in a vacuum adsorption and folding at the growth front. The polymer molecule we considered was the same as described above a completely flexible chain composed of 500 or 1000 CH2 beads. We consider crystallization in a vacuum or in an extremely poor solvent condition. Here we took the detailed interaction between the chain molecule and the substrate atoms through Eqs. 8-10. 

Subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS), has been used extensively to examine interactions of species at the electrode/electrolyte interface. In the present work, the method has been extended to probe interactions at the mercury solution interface. The diminished potential dependent frequency shifts of species adsorbed at mercury electrodes are compared with shifts observed for similar species adsorbed at d-band metals. 

Several different approaches can be used to model the interaction of solutes with reactive mineral surfaces. The conceptual approaches differ in the degree to which they account for observed or postulated solution and surface reactions. Whatever the approach, the description of interactions at the particle/solution interface must inevitably take into account the effect of pH on solute adsorption. 

General Observations About x. its Relationship to the Overall Partitioning Coefficient and to the Concept of Surface-Site Heterogeneity. One approach to metal/particle surface interactions which has been developed, historically, in a variety of forms, is a conceptual model that assumes only two conditions for surface sites occupied by an adsorbate or unoccupied. In applying this approach to the solid/aqueous solution interface, the adsorption... 

The electrical double layer has been dealt with in countless papers and in a number of reviews, including those published in previous volumes of the Modem Aspects of Electrochemistry series/ The experimental double layer data have been reported and commented on in several important works in which various theories of the structure of the double layer have been postulated. Nevertheless, many double layer-related problems have not been solved yet, mainly because certain important parameters describing the interface cannot be measured. This applies to the electric permittivity, dipole moments, surface density, and other physical quantities that are influenced by the electric field at the interface. It is also often difficult to separate the electrostatic and specific interactions of the solvent and the adsorbate with the electrode. To acquire necessary knowledge about the metal/solution interface, different metals, solvents, and adsorbates have been studied. 

The value of the electric permittivity of water in the inner part of the double layer is commonly accepted as equal to 6. A much higher capacity of the inner layer at the Ga/solution interface was explained by the weak interaction of gallium with water, leading to a high value of As shown... 

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