Ion-specific clustering of metal-amphiphile complexes in rare earth separations.

The nanoscale structure of a complex fluid can play a major role in the selective adsorption of ions at the nanometric interfaces, which is crucial in industrial and technological applications. Here we study the effect of anions and lanthanide ions on the nanoscale structure of a complex fluid formed by metal-amphiphile complexes, using small angle X-ray scattering. The nano- and mesoscale structures we observed can be directly connected to the preferential transfer of light (La and Nd) or heavy (Er and Lu) lanthanides into the complex fluid from an aqueous solution.

Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces.

Anions are expected to be repelled from negatively charged surfaces. At aqueous interfaces, however, ion-specific effects can dominate over direct electrostatic interactions. Using multiple surface sensitive experimental techniques, we show that surface affinities of SCN anions are so strong that they can adsorb at a negatively charged floating monolayer at the air-aqueous interface.

Transient Phase of Ice Observed by Sum Frequency Generation at the Water/Mineral Interface During Freezing.

We observed a transient noncentrosymmetric phase of ice at water/mineral interfaces during freezing, which enhanced the intensity of the IR-visible sum frequency generation intensity by up to 20-fold. The lifetime of the transient phase was several minutes. Since the most stable form of ice, hexagonal and cubic ice, are centrosymmetric, our study suggests the transient existence of stacking-disordered ice during the freezing process at water/mineral interfaces.