Water Solution Interface Research Articles

Laser interferometry analysis of ciprofloxacin and ampicillin diffusion from liposomal solutions to water phase

The paper presents experimental investigations of diffusion of antibiotics (ciprofloxacin or ampicillin) into the water phase from mixtures of neutral or negatively charged liposomes, and antibiotic–liposome interactions. Using the laser interferometry technique, the amounts and fluxes of released antibiotics, concentration field evolution, and the velocity of the concentration boundary layer’s “growth” were determined. To avoid the limitations of membranes, a measurement system without the artificial boundary of phases with a free water–solution interface has been proposed. It was found that the diffusion of anionic and neutral liposomes into the water phase was insignificant and mainly the diffusion of antibiotics was measured. Differences in the diffusion kinetics of ciprofloxacin and ampicillin from liposomal solutions to the water phase were observed. Ampicillin diffused more efficiently than ciprofloxacin regardless of the liposomal solution type. Moreover, the amount of ampicillin and ciprofloxacin released from the anionic liposomal phase was higher than that from the neutral one. Our results confirm that ciprofloxacin at neutral pH shows little tendency to bind neutral liposomes. Additionally, it was also observed that ciprofloxacin disrupts negatively charged liposomes as a final effect of antibiotic–lipid interactions.

Biophysical effects of electric fields on membrane water interfaces: a mini review

Lipid-water interfaces are dielectric transition regions. Their local organizations are highly sophisticated. They are sensitive to electric field with dramatic consequences on the global membrane organization and function. The importance of using local values of parameters (e.g. dielectric constant) near water-solution interface due to hydration and different electrostatic effects is often neglected in the description of cellular functions. Structural changes in the lipid layer are induced by minute changes in the electric properties of the interface. They bring alterations in the structure and oligomerization of membrane proteins.

Motion of Fine Particles under Interfacial Tension Gradient in Relation to Continuous Casting Process

In front of the solidifying interface of a water solution, in the case of NaCl water solution, fine bubbles (10~100 μm in diameter) were just moving upward, no matter how close they were from the solidifying interface. However, in front of the solidifying interface of C8H17SO3Na water solution, once the distance between the bubbles and the solidifying interface became less than 90~100 μm, rising bubbles were found to move horizontally toward the solidifying interface quickly, and then to be engulfed by the interface. This effect can be attributed to the surface tension gradient around the bubbles induced by the concentration gradient in the boundary layer formed in front of the solidifying interface. The phenomenon is taken as a kind of the Marangoni effect in a broad sense. The movement of fine particles driven by the interfacial tension gradient is found to have a close relationship to certain phenomena in continuous casting processes, such as the occurrence of bubble or inclusion‐related defects in steel and nozzle clogging.

Behaviors of Bubbles in Front of a Solidifying Interface

By means of a solidifying water model, we investigated the influence of the concentration boundary layer on the behavior of fine bubbles (less than 60 μ m in diameter) near the solidifying interface. The solidifying interface of water solution was moved horizontally from the left to the right side of the solidifying cell. In the vicinity of the solidifying interface of a non-surfactant (NaCl) water solution, fine bubbles were moving upward, no matter how close they were from the solidifying interface. However, in the case of a surfactant (C 8 H 17 SO 3 Na) water solution, once the distance between bubbles and the solidifying interface was less than 90∼100 μ m, bubbles were found to move horizontally toward the solidifying interface, and then were entrapped by it. This phenomenon can be attributed to the surfactant concentration gradient inside the boundary layer, which results in a surface tension gradient around the surface of bubbles. Experimental results can be quantitatively explained fairly well with theoretical analysis.

Estimation of Dielectric Constants of Adsorbed Monolayers for Some Sodium Soap Solutions

The interfacial tensions of lauric and myristic acid sodium salt water solutions were measured at the air/water interface at 20°C and at the air/0.01 M NaOH water solution interface at 20° and 40°C. On the basis of these results the dependence of standard free energy of adsorption (ΔG0) on the interface coverage (Θ) was determined from the Blomgren–Bockris isotherm. According to these dependencies the interactions of adsorbed molecules were discussed and dielectric constants of the adsorbed monolayer were estimated.

Surface laser light scattering studies of the air/poly(N-vinyl-2-pyrrolidone)-water solution interface

An experimental study of poly(N-vinyl-2-pyrrolidone) (PVP) in water solution has been carried out by using the surface laser light scattering (SLLS) technique. The concentration dependence data of the peak frequency and linewidth are obtained from the SLLS spectra of the PVP/water solutions with two PVP molecular weights over a wide concentration range varying from the dilute to semidilute regime. The equilibrium surface tension of the solution is also measured as a function of polymer concentration and molecular weight. In the dilute solution, the peak frequency and surface tension show only a small decrease with increasing concentration. However, in the semidilute concentration regime, the surface tension and the frequency shift decrease rapidly with increasing concentration, accompanied by the dramatic increase in the spectral linewidth. The surface tension, SLLS spectral peak frequency and linewidth show an important molecular weight dependence. Over the entire concentration range investigated, the SLLS data of the PVP/water solutions do not show evidence of the capillary to Rayleigh wave evolution.

Highly ordered Langmuir–Blodgett films based on semi-amphiphilic phthalocyanines

Semi-amphiphilic phthalocyanines can be built via ion exchange at a fatty acid monolayer–water solution interface and be transferred onto solid substrates to give well-ordered Langmuir–Blodgett films.

Capacitance measurements of the silicon—silicon dioxide—potassium chloride water solution interface as a method to determine the fixed charge value and its centroid

An attempt is made to describe measurements of the differential capacitance of silicon—silicon dioxide—electrolyte structures. Experimental data are given for silicon electrodes covered with oxide layer of various thickness in 0.1 M KCl water solution. The measurements reveal that the differential capacitance is always a series combination of space charge layer capacitance in silicon and the capacitance of a thin dielectric layer on the electrode surface even in the case of carefully etched electrodes. The results obtained enable an evaluation of the interface charges within the oxide. It is stated that the surface roughness coefficient of a electrode covered with oxide has a slightly lower value than that in case of an electrode without oxide. Es wird versucht, die Messungen der differentiellen Kapazitat einer Silizium—Siliziumdioxid—Elektrolyt—Struktur zu beschreiben. Experimentelle Werte werden fur Siliziumelektroden, die mit einer Oxidschicht unterschiedlicher Dicke bedeckt sind, in einer wasrigen 0,1 Mol-KCl-Losung angegeben. Die Messungen zeigen, das die Differentialkapazitat auch im Falle von sorgfaltig geatzten Elektroden immer eine Serienschaltung der Raumladungskapazitat im Silizium und der Kapazitat einer dunnen dielektrischen Schicht an der Elektrodenoberflache ist. Die erhaltenen Ergebnisse ermoglichen eine Berechnung der Grenzflachenladungen innerhalb des Oxids. Es wird angenommen, das die Oberflachenrauhigkeit einer mit Oxid bedeckten Oberflache etwas geringer ist als die einer Elektrode ohne Oxid.