Influence of cationic composition and pH on the formation of metal stearates at oil-water interfaces.

We study the formation of layers of metal stearates at the interface between a decane solution of stearic acid and aqueous salt solutions of variable composition and pH by monitoring the evolution of their mechanical, optical, and chemical properties as a function of time after formation of the interface. For values of the pH below the pK(a) of stearic acid hardly any interfacial activity is observed. For pH > pK(a), stearic acid deprotonates at the interface and forms metal stearates, eventually leading to the formation of macroscopic solid layers.

Spatial extent of random laser modes.

We have experimentally studied the distribution of the spatial extent of modes and the crossover from essentially single-mode to distinctly multimode behavior inside a porous gallium phosphide random laser. This system serves as a paragon for random lasers due to its exemplary high index contrast. In the multimode regime, we observed mode competition.

Porous silicon as a stationary phase for shear-driven chromatography.

We report on the possibility to strongly increase the mass loadability and retention capacity of shear-driven chromatography (SDC) channels by growing a thin porous silicon layer on the stationary wall part. The thickness of the produced porous silicon layers was found to increase linearly with the anodisation time, and could easily be varied between 50 and 300 nm. Combining these layers with sub-microm thin flow-through channels, we believe it is the first time a sub-microm on-chip LC system with a phase ratio similar to that in packed column HPLC (i.

Macroporous germanium by electrochemical deposition.

Germanium is electrodeposited in a template formed from a dried suspension of silica spheres. The germanium completely fills the pores of the silica matrix. The semiconductor, as deposited, is amorphous but can be crystallized by annealing.