Because of their amphiphilic structure, surfactants adsorb at the water-air interface with their hydrophobic tails pointing out of the water and their polar heads plunging into the liquid phase. Unlike classical surfactants, metallabisdicarbollides (MCs) do not have a well-defined amphiphilic structure. They are nanometer-sized inorganic anions with an ellipsoidal shape composed of two carborane semicages sandwiching a metal ion. However, MCs have been shown to share many properties with surfactants, such as self-assembly in water (formation of micelles and vesicles), formation of lamellar lyotropic phases, and surface activity. By combining second harmonic generation and surface tension measurement, we show here that cobaltabis(dicarbollide) anion {[(C2B9H11)2Co](-) also named [COSAN](-)} with H(+) as a counterion, the most representative metallacarborane, adsorbs vertically at the water surface with its long axis normal to the surface. This vertical molecular orientation facilitates the formation of intermolecular and nonconventional dihydrogen bonds such as the B-H(δ-)···(δ+)H-C bond that has recently been proven to be at the origin of the self-assembly of MCs in water. Therefore, it appears here that lateral dihydrogen bonds are also involved in the surface activity of MCs.

The interface dynamic properties of a monoamide extractant with potential for application to the front end of the nuclear cycle and to waste treatment are examined by second harmonic generation. The results are compared with bulk nitric ion titration and surface pressure measurements. SH static studies show the extractant reaching the interface and accurately match the IFT measurements. The main feature of the SH dynamic studies is a chaotic fluctuation period, strongly related to intense extraction. Fluctuations are a signature of the interface behaviour during the extraction process. Vertical development of the interface, often called protrusion, remains the most probable origin of the measured fluctuation. Additionally, interfacial measurements show a non-monotonic lag time during extraction, probably related to cooperative effects not observed in the bulk at the working concentration. Such mutual behaviour could be a supplementary prerequisite for the ion transfer across this liquid-liquid interface.

The interfacial tension of water/dodecane interface is investigated by the pendant drop technique during the transfer of a surfactant molecule, the Triton X-100. This molecule is initially present in one of the liquid phases, and the measurement of the interfacial tension as a function of time permits us to probe the dynamic incoming and outgoing surfactant at the interface and to deduce a rate of transfer. As a rule, after the contact of both solutions, the interfacial tension exhibits a steep initial decrease, passes through a minimum, and then levels off at a value that depends on the initial surfactant concentration in the drop. The time delay before reaching the equilibrium state is due to the limitant step of the surfactant crossing over the liquid/liquid interface. Moreover, the interfacial tension evolution depends strongly on the phase where the Triton-X100 is initially dispersed. Indeed, the global kinetics is found to be faster when Triton X-100 transfers from dodecane toward water as compared to the reverse pathway. To quantify the limiting factors of the interfacial transfer mechanism, two theoretical models describing the time evolution of the system are presented and discussed. The first one is based on a diffusioncontrolled adsorption/desorption at the liquid/liquid interface, whereas the second one also takes into account an interfacial chemical adsorption/desorption reaction. This latter permits us to give an estimation of importance of the chemical processes, which occurs at the interface in the overall kinetics.

An analytical model is developed to analyze the fluctuations in the surface second harmonic generation (SHG) intensity from a Langmuir film. From the SHG autocorrelation analysis, also called nonlinear correlation spectroscopy (NLCS), the characteristic times of the phenomena occurring at the interface are determined. This method is then applied to monolayers of the amphiphilic chromophore dye 4-(4dihexadecylaminostyryl)-N-methylpyridinium iodide (DiA) at the air−water interface. This compound is known to spontaneously form aggregates at liquid interfaces. The aggregates characteristic size is estimated using the newly developed NLCS method and compared to Brewster angle microscopy (BAM) data for two experimental initial conditions leading to two different sizes, namely, a chloroform and a methanol DiA solution. This study combining the advantages of the surface specificity of SHG with the temporal analysis of intensity correlations demonstrates the potential of NLCS to investigate the dynamics of molecular aggregates at a liquid interface.

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The interaction of methyl orange dye with a layered double hydroxide colloidal material is investigated using real-time polarization-resolved second-harmonic scattering (SHS). Interlayer charge compensating anion exchange is studied from initial carbonate or nitrate anions to methyl orange negatively charged dye. A theoretical model, taking into account the field retardation effect, is presented to simulate the polarization-resolved SHS experiments. Various geometrical dye configurations inside or around the host material have been modeled. A comparison with the experimental data permits to give a microscopic description of the dye organization and its time evolution during the intercalation process in the material.

We report Montmorillonite (MMT) particles organization in aqueous solution using polarization resolved second harmonic scattering (SHS). This technique can probe specifically the organization of water in this system. The effect of the colloidal stability of the particle and the nature of the interlayer cations on the SHS Intensity is highlighted. The interlayer hydration has been probed and changes with the order Mg 2+ > Ca 2+ > Li + , Na + , K + > Cs +. Real time SHS evolutions during cesium exchange have been monitored, and different pathways are discussed in regards with the experimental results.