Application of the Lattice-Boltzmann method to wetting on anisotropic textured surfaces: Characterization of the liquid-solid interface.

HYPOTHESIS: To understand the relationship between topography and wetting, it is not enough to study the contact angle. Indeed, the liquid-solid interface plays an important role in wetting. However, data such as the total triple line length, the wetting area and the anchoring depth are inaccessible or difficult to obtain experimentally. This work proposes to overcome the experimental limitations by using a numerical approach to characterize the wetting behavior on textured surfaces. METHODS: The wetting behavior of an anisotropic textured surface was compared for both experimental and numerical approaches. The experimental wetting is characterized by sessile drop experiments. The simulations were performed by applying the pseudo-potential Lattice-Boltzmann method. The numerical approach was then used to predict the wetting behavior of different materials. FINDINGS: The simulations capture both the wetting state and the contact angle, in accordance with the experimental observation. Without making any assumptions about the interfacial shape and anchoring, the simulation allows to characterize the liquid-solid interface by quantifying the total length of the triple line and the wetting area. Simultaneously, the simulations enable the characterization of impregnation within textures for complex mixed regimes.

A neutral zwitterionic molecular solid.

We report on the acid ethylenedithiotetrathiafulvaleneamidoglycine (EDT-TTF-CO-NH-CH(2)-CO(2)H; 1; EDT-TTF=ethylenedithiotetrathiafulvalene) and the 1:1 adduct [(EDT-TTF)(·+)-CO-NH-CH(2)-(CO(2))(-)][(EDT-TTF)-CO-NH-CH(2)-(CO(2)H)]·CH(3)OH (2), a new type of hydrogen-bonded, 1:1 acid/zwitterion hybrid embrace of redox peptidics into a two-dimensional architecture, an example of a system deliberately fashioned so that oxidation of π-conjugated cores toward the radical-cation form would interfere with the activity of the appended ionizable residues in the presence of a templating base during crystal growth. First-principles calculations demonstrate that, notwithstanding preconceived ideas, a metallic state is more stable than the hole-localized alternatives for a neat 1:1 neutral acid/zwitterion hybrid. The inhomogeneous Coulomb field associated with proton-shared, interstacks O-H···O hydrogen bonds between the ionizable residues distributed on both sides of the two-dimensional π-conjugated framework leads, however, to a weak hole localization responsible for the activated but high conductivity of 1 S cm(-1). This situation is reminiscent of the role of the environment on electron transfer in tetraheme cytochrome c, in which the protonation state of a heme propionate becomes paramount, or ion-gated transport phenomena in biology. These observations open rather intriguing opportunities for the construction of electronic systems at the interface of chemistry and biology.

Electronic structure of the A(8)Tr(11) (A = K, Rb, Cs; Tr = Ga, In, Tl) Zintl phases: possible chemical reasons behind their activated versus non activated conductivity.

The electronic structure of the A(8)Tr(11) (A = K, Cs; Tr = Ga, In, Tl) Zintl phases has been studied by means of first-principles density functional theory (DFT) calculations. It is shown that the hypoelectronic Tr(11) cluster in these phases must be considered as Tr(11)(8-) even if it would require just a 7- charge to maximize its bonding, filling all its bonding and nonbonding levels. Our calculations show that the lowest empty orbital of the isolated Tr(11)(7-) clusters is an a(1)-type orbital. However, a degenerate e-type set of orbitals is higher but quite close in the case of the Ga(11)(7-) clusters. Thus, for the isolated Tr(11)(8-) clusters, the extra electron occupies always an a(1)-type antibonding orbital that contains, however, some Tr-Tr bonding component thus leading to a weak global antibonding character. In the solid, cluster-alkali-metal bonding interactions occur and spread the cluster levels into bands, but the extra electron still fills the a(1)-type cluster level for most of the A(8)Tr(11) phases. The cluster-alkali-metal interactions have a minor role in stabilizing this orbital but they provide the necessary delocalization to lead to the metallic character of these phases. In contrast, the e-type antibonding levels of the Ga(11)(7-) isolated cluster are those which become filled by the extra electron in the Cs(8)Ga(11) solid. This phase should be metallic, but occupation of this degenerate pair of cluster levels would lead to a structural instability that may be avoided by reducing the interactions of the alkali-metal atoms with the cluster levels. In that way the occupation appropriate for the isolated cluster is restored (i.e., one electron fills the a(1) cluster orbital), but the extra electron now remains localized on the cluster, thus leading to the unexpected activated conductivity observed for the Cs(8)Ga(11) phase.