Water repelling molecules are said to be hydrophobic. The hydration or formation of water interfaces around hydrophobic molecules is important for many biological processes: protein folding, membrane formation, transport of proteins across an interface, the transmission of action potentials across membranes. It is involved as well in the process of creating mayonnaise, or in the fact that you can get rid of fat with soap. Hydrophobic interfaces although long studied, are poorly understood.
Here's an amusing kitchen-table experiment to illustrate waters unusual properties: put a drop of pure insulating oil in a glass of pure, non-conducting water, and create an electric field using two wires hooked up to a battery. You'll see the oil move from the negative to the positive pole of the little circuit you've created. You have created charge in a mixture that was neutral, and a huge amount of it too, judging from the speed at which the droplets move. The same thing happens for gas bubbles in water; the phenomenon of charging applies to all hydrophobic/water interfaces.
- A century of debates -
It's not a new discovery; scientists have observed the phenomenon in the middle of the 19th century. But despite more than a century of research, the reason why such a huge electric charge exists is still the subject of heated debate.
In an article published this week in Angewandte Chemie a journal of reference in the field EPFL scientist Sylvie Roke challenges a hypothesis put forward last spring in the same journal. With experimental proof to back her up, the holder of the Julia Jacobi chair in photomedicine makes her case: the phenomenon is not caused by the inevitable "impurities" present in oils, as her colleagues claim, but rather by certain intrinsic properties of the water molecules involved.
- Show the unseeable -
For proof, Roke turns to the technologies in which she is an expert nonlinear optics
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| Contact: Sylvie Roke sylvie.roke@epfl.ch 41-216-931-191 Ecole Polytechnique Fdrale de Lausanne Source:Eurekalert |
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