Modeling hydration-mediated ion-ion interactions in electrolytes through oscillating Yukawa potentials.

Classical Poisson-Boltzmann theory represents a mean-field description of the electric double layer in the presence of only Coulomb interactions. However, aqueous solvents hydrate ions, which gives rise to additional hydration-mediated ion-ion interactions. Experimental and computational studies suggest damped oscillations to be a characteristic feature of these hydration-mediated interactions.

Saddle-curvature instability of lipid bilayer induced by amphipathic peptides: a molecular model.

Amphipathic peptides that partition into lipid bilayers affect the curvature elastic properties of their host. Some of these peptides are able to shift the Gaussian modulus to positive values, thus triggering an instability with respect to the formation of saddle curvatures. To characterize the generic aspects of the underlying mechanism, we employ a molecular lipid model that accounts for the interfacial tension between the polar and apolar regions of the membrane, for interactions between the lipid headgroups, and for the energy to stretch or compress the hydrocarbon chains.

Influence of spontaneous curvature on the line tension of phase-coexisting domains in a lipid monolayer: A Landau-Ginzburg model.

The line tension between two coexisting phases of a binary lipid monolayer in its fluid state has contributions not only from the chemical mismatch energy between the two different lipid types but also from the elastic deformation of the lipid tails. We investigate to what extent differences in the spontaneous curvature of the two lipids affect the line tension. To this end, we supplement the standard Landau-Ginzburg model for the line tension between coexisting phases by an elastic energy that accounts for lipid splay and tilt.

Role of Transmembrane Proteins for Phase Separation and Domain Registration in Asymmetric Lipid Bilayers.

It is well known that the formation and spatial correlation of lipid domains in the two apposed leaflets of a bilayer are influenced by weak lipid-lipid interactions across the bilayer's midplane. Transmembrane proteins span through both leaflets and thus offer an alternative domain coupling mechanism. Using a mean-field approximation of a simple bilayer-type lattice model, with two two-dimensional lattices stacked one on top of the other, we explore the role of this "structural" inter-leaflet coupling for the ability of a lipid membrane to phase separate and form spatially correlated domains.

Differential capacitance of ionic liquids according to lattice-gas mean-field model with nearest-neighbor interactions.

The Bragg-Williams free energy is used to incorporate nearest-neighbor interactions into the lattice gas model of a solvent-free ionic liquid near a planar electrode. We calculate the differential capacitance from solutions of the mean-field consistency relation, arriving at an explicit expression in the limit of a weakly charged electrode. The two additional material parameters that appear in the theory-the degree of nonideality and the resistance to concentration changes of each ion type-give rise to different regimes that we identify and discuss.

Debye-Hückel theory of weakly curved macroions: Implementing ion specificity through a composite Coulomb-Yukawa interaction potential.

The free energy of a weakly curved, isolated macroion embedded in a symmetric 1:1 electrolyte solution is calculated on the basis of linear Debye-Hückel theory, thereby accounting for nonelectrostatic Yukawa pair interactions between the mobile ions and of the mobile ions with the macroion surface, present in addition to the electrostatic Coulomb potential. The Yukawa interactions between anion-anion, cation-cation, and anion-cation pairs are independent from each other and serve as a model for solvent-mediated ion-specific effects. We derive expressions for the free energy of a planar surface, the spontaneous curvature, the bending stiffness, and the Gaussian modulus.

Au Exchange or Au Deposition: Dual Reaction Pathways in Au-CsPbBr Heterostructure Nanoparticles.

We have designed a facile synthetic strategy for the selective deposition of Au metal on all-inorganic CsPbBr perovskite nanocrystals that includes the addition of PbBr salt along with AuBr salt. PbBr is necessary because the addition of Au to solutions of CsPbBr nanocrystals otherwise results in the exchange of Au ions from solution with Pb cations within the nanocrystal lattice to produce CsAuAuBr nanocrystals with a tetragonal crystal structure and a band gap of about 1.6 eV, in addition to Au metal deposition.