The dependence of surface tension on surface properties of ionic surfactant solution and the effects of counter-ions therein.

In the present paper, we aim to investigate the dependence of surface tension on the surface properties and reveal the counter-ion effects on the adsorption of ionic surfactants on the solution surface. The surface tension, surface excess and surface concentration (defined as the amount of surfactant adsorbed in the surface phase divided by the surface area) of two anionic surfactants, namely dodecyl sulfate sodium and dodecyl sulfate caesium, dissolved in non-aqueous polar solvent formamide have been separately measured at 6 °C through independent experiments. Then, the correlation of surface tension with surface concentration and that of surface tension with surface excess is inspected in detail.

The competitive adsorption of counter-ions at the surface of anionic surfactants solution.

We have determined the surface excess of surface active anion and counter-ions in a non-aqueous polar solution of anionic surfactants blends, as well as their distributions near the solution surface. The blends of two anionic surfactants, sodium dodecyl sulfate (SDS) and cesium dodecyl sulfate (CDS), with different contents were used as solutes to prepare the solutions. According to the isotherms that are separately fitted to the pure SDS and the pure CDS solutions (C.

Behavior of 1,2-dioleoyl-sn-glycero-3-phosphocholine at the surface of 3-hydroxypropionitrile near the critical micelle concentration.

The existence of a local minimum of surface tension near the critical micelle concentration has been reported for various surfactant solutions. In some cases, this is interpreted as an indication for the presence of impurities. Recently, this phenomenon has been interpreted as an inhibition of the aggregation for POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) in HPN (3-hydroxypropionitrile).

Influence of the aliphatic chain length of imidazolium based ionic liquids on the surface structure.

The molecular surface structure of four imidazolium based ionic liquids was studied with two surface sensitive techniques. Angle resolved neutral impact collision ion scattering spectroscopy (ARNICISS) allows us to determine elemental concentration depth profiles and to obtain information about the topography of the surface. Angle resolved X-ray photoelectron spectroscopy (ARXPS) can be used to study the chemical composition of the surface.

Effects of counterions on adsorption behavior of anionic surfactants on solution surface.

The goal of the present paper concerns the effects of counterions on adsorption behavior of anionic surfactants. The surfactants chosen are sodium dodecyl sulfate and cesium dodecyl sulfate, and the polar solvent is formamide. In the investigations, the surface excess and surface tension have been measured independently.

Orientation of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine at the surface of formamide and hydroxypropionitrile.

Phospholipids are a main component of cell membranes. Therefore, the experimental investigation of the self-organization of phospholipids is of great interest. Here we present results concerning the orientation of the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) at the surface of the polar solvents formamide and 3-hydroxypropionitrile (HPN), which we investigated by means of neutral impact collision ion scattering spectroscopy.

Behavior of surfactant molecules near the critical micelle concentration: a statistical treatment.

Several studies report the existence of a local minimum of the surface tension near the critical micelle concentration (CMC) of surfactant solutions. The interpretation of this phenomenon is not unambiguous. While some authors conceive this observation as a normal feature, others consider it to be a clear indication of the presence of an impurity which is more surface active than the surfactant itself.

Chemical potential of a nonionic surfactant in solution.

The chemical potential of a surfactant in solution can be calculated from the Gibbs adsorption equation when the surface excess of the surfactant and the surface tension of the solution as a function of surfactant concentration are known. We have investigated a solution of the nonionic surfactant 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in the polar solvent 3-hydroxypropionitrile at concentrations below and above the critical micelle concentration (cmc). Neutral impact collision ion scattering spectroscopy was applied for the direct measurement of the surface excess of POPC as a function of concentration.

Increased layer interdiffusion in polyelectrolyte films upon annealing in water and aqueous salt solutions.

As-deposited films of multilayered polyelectrolytes are considered to be non-equilibrium structures. Due to the strong attraction between oppositely charged polyions, polyelectrolyte interdiffusion is thought to be suppressed during the adsorption process. Equilibration is promoted by a decrease of the electrostatic attraction between polyion pairs.

Binary liquid mixtures. The relation between surface tension and surface composition as studied by MIES (metastable induced electron spectroscopy).

For a binary liquid mixture, we define the surface fraction of a component as the fraction of the surface which is covered by this species. The perfectly surface-sensitive electron spectroscopy MIES (metastable induced electron spectroscopy) allows to derive this quantity in a very direct manner from experiment with no model assumption needed. We find for several binary mixtures that the surface tension depends linearly on the surface fraction with striking accuracy.

Angle resolved ion scattering spectroscopy reveals the local topography around atoms in a liquid surface.

Neutral impact collision ion scattering spectroscopy under normal incidence is known to yield the concentration depth profiles of all elements except hydrogen at the surface of liquids and other amorphous material. In the evaluation of the data one tactically has to assume that the top surface layer and the adjacent layers are laterally homogeneous. In the present paper we establish that the angular resolved mode of this spectroscopy is able to test with high accuracy whether the lateral homogeneity is valid and-if this is not the case-in which way the top layer is structured.

Internal structure of polyelectrolyte multilayers probed via neutral impact collision ion scattering spectroscopy.

Layering in polyelectrolyte multilayer films has been studied by neutral impact collision ion scattering spectroscopy. The method affords a direct look at vertical ordering within these films at the nanometer scale. By labeling certain polyelectrolyte layers with heavy atom (Ru) probes, sufficient contrast has been obtained to visualize and quantify the distribution of these labeled polyelectrolytes throughout the film.

Activity of surface active substances determined from their surface excess.

Commonly, the surface excess is determined from surface tension measurements via the Gibbs equation. This equation relates the activity (chemical potential), the surface excess, and the surface tension. When knowing two out of the three quantities, the third one can be calculated.