Bipolar phospholipids (bolalipids) represent an exciting class of amphiphilic molecules as they self-assemble in water to distinct structures of nanoscopic dimensions. Reported here are structural details of helical nanofibers, composed of achiral, symmetrical single-chain bolalipids with phosphocholine headgroups. These nanofibers are used as template for the fixation of gold nanoparticles (AuNPs) without prior functionalization. This realization of a metal array on bolalipid nanofibers is one of the rare examples of one-dimensional AuNP arrangements in solution. The loading and the heat of binding of AuNPs are determined applying transmission electron microscopy and isothermal titration calorimetry.
Using Derjaguin's approximation, we have evaluated the interaction energy associated with van der Waals, electrostatic, depletion, and capillary forces between colloidal spheroids. If the interaction range between spheroids is distinctly smaller than the lengths of their principal axes, then simple pair potentials that depend on particle distance and orientation can be derived. Attractive interactions between adjacent spheroids favor their parallel alignment. Parallel spheroids can be arranged into a variety of densely packed configurations. All of these configurations turn out to have the same lattice energy. We discuss the implications of this degeneracy with respect to the stability of photonic crystals consisting of spheroids.
We performed Monte Carlo simulations to study the adsorption behavior of a small flexible model
surfactant on hydrophilic surfaces. A coarse-grained lattice model was used to account for excluded-volume
effects and nearest-neighbor interactions. The model predicts adsorption isotherms that agree qualitatively
with experimental results. The results of the simulation complete and support experimental structure
investigations made with AFM, ellipsometry, and neutron reflectometry. Adsorbed bilayer structures
depend on the adsorption energy. The efficiency of hydrophobization and the shielding against small polar
molecules increase strongly with increasing surfactant concentration.
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