Van derWaals interactions

Figure 6.34. Schematic, strongly simplified potential energy diagram along the reaction coordinate of a molecule X2 approaching a metal surface. First the molecule feels the weak Van derWaals interaction, leading to physisorption. The next stage is associative...

Figure 5.12 Van derWaals interaction between two hydrogen molecules and the resulting Lennard-Jones potential, V(r).

Sheet silicates (mica and clay minerals) strong Si-0 bonds within sheets, weaker ionic or (less common) van derWaals interactions... 

Figure 1.2.6 Diagram representing the electronic structure of the ionic, hydrogen bond and van derWaals interactions.

A preliminary analysis of the detailed summations of van derWaals interactions between a film and a semi-infinite solid indicates that if e9j has the same interpretation as in the preceding section, in Equations 14 through 23 x sl is actually ( sl - ll)-The expression for cos 6 now becomes ... 

Yellow field points represent an attractive van derWaals interaction and gold field points represent hydrophobic centroids. Oxygen atoms are shown in red, nitrogen in blue, and fluorine in pale green. The size of the points is related to the strength of the interaction. 

Surfactants act as solubilizers to disperse CNTs via physical adsorption, and the procedures of solubilization are very simple. CNTs are placed in a solution containing solubilizer and then subjected to sonication treatment for a while. During sonication, the provided mechanical energy can overcome the van derWaals interactions between the CNT bundles and leads to the exfoliation of CNTs. At the same time, solubilizer molecules adsorb onto the surfaces of the CNT walls. Solubility of CNTs in a solvent depends on the type, the concentration of the solubilizer, and the purity of the CNTs. The mechanism for dispersion of CNTs by the solubilizer is believed to be an unzipping mechanism proposed by Strano and co-workers at Rice University in 2003. 

This section illustrates that the thermodynamic principles we have learned so far can be applied to electrochemical systems. However, to solve Equation (9.28) in general, we need to determine the activity coefficients of the species in solution. The treatment of activity coefficients markedly differs from the nonelectrolyte solutions we have been discussing so far in the text. Charged species in solution have strong ionic interactions that are very different from other interactions in the solution. Recall from Chapter 4, these interacts vary as (l/r) in comparison to van derWaals interactions that vary as 1/ r , even in a dilute solution. 

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