Molecular Description of Grafted Supramolecular Assemblies on Gold Surfaces: Effect of Grafting Points and Chain Lengths.

The association of 4 aminoazobenzene (4AA) with two different water-soluble hosts, β-cyclodextrins (β-CD) and calixarenesulfonates (CnS), was studied in heterogeneous conditions using molecular simulations. This situation is achieved by immobilization of macrocycles onto a gold Au(111) surface. Several factors that can influence the binding properties are investigated here through the chain length of alkylthiols spacer of the surface-immobilized host and the number of attachment points to the surface.

Thermodynamics of Supramolecular Associations with Macrocyclic Water-Soluble Hosts.

The thermodynamic study of the complexation of the β-cyclodextrins and -sulfonatocalix[]arenes (CS) with the 4-aminoazobenzene was reported and was carried out by molecular dynamics simulations. We determined the whole thermodynamic properties (, Δ °, Δ °, and Δ °) using the potential of mean force (PMF) technique and more precisely the adaptive biasing force method. Depending on both the nature of the host molecule and the pH of the solution, the PMF profiles present different shapes and energy minima.

Associations of Water-Soluble Macrocyclic Hosts with 4-Aminoazobenzene: Impact of pH.

An investigation of the pH effect on the inclusion complexes of β-cyclodextrins and calixarenesulfonates with 4-aminoazobenzene was conducted both by experiments and molecular simulations. The whole thermodynamic characterizations of the association between hosts and 4-aminoazobenzene ( K, Δ G, Δ H, and TΔ S) were determined by UV-visible spectroscopy. β-Cyclodextrin inclusion complexes are not affected by pH change unlike those obtained with calixarenes.

Physics behind Water Transport through Nanoporous Boron Nitride and Graphene.

In this work, molecular dynamics simulations were used to determine the surface tension profile of water on graphene and boron nitride (BN) multilayers and to predict water permeation through nanoporous graphene and BN membranes. For both graphene and BN multilayers, a decrease in surface tension (γ) was evidenced as the number of layers increased. This lessening in γ was shown to result from a negative surface tension contribution due to long-range wetting of water, which also contributes to lower water permeation through a two-layer membrane with respect to permeation through a monolayer.