Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Illuminating the no-man's land of waters' surface

27.11.2012
Researcher at EPFL proves that the strong electric charge observed at the interface between oil and water is not due to impurities

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.


Nonlinear optics and light diffusion allow to see the unseeable.

Credit: © 2012 EPFL

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 and light diffusion. Using carefully filtered lasers channeled through a complex circuit of mirrors and lenses, she "hits" her sample – barely a drop – and measures the wavelength of the light that escapes from it. With this she can detect whether or not there are nanoscopic molecules on the interface between the oil and the water.

The precision of the observations "shows that negative charges exist even in a total absence of surface impurities, and thus the explanation put forward by my colleagues, which was derived from charge measurements and chemical titrations of the bulk liquids, doesn't hold up," says Roke. "We have developed a unique apparatus that can distinctly measure the interfacial structure of a layer on the sub-nanometer length scale that surrounds a droplet of oil in water. Thus, we can 'see' what is on the interface, and do not have to deduce it from comparing bulk properties, which is far less accurate."

Disproving a hypothesis isn't enough to explain a phenomenon, however. Roke is studying a promising avenue, that explores the intrinsic quantum nature of the water molecule itself, which might be responsible for the phenomenon. "The measurements we've made as part of this refutation could be used to try and prove this explanation," she says. "It's fascinating, because quantum effects (the smallest of the smallest) might be responsible for macroscopic charging effects that influence so many properties that relate to the functioning of the human body."

Sylvie Roke | EurekAlert!
Further information:
http://www.epfl.ch

More articles from Physics and Astronomy:

nachricht Structured light and nanomaterials open new ways to tailor light at the nanoscale
23.04.2018 | Academy of Finland

nachricht On the shape of the 'petal' for the dissipation curve
23.04.2018 | Lobachevsky University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Structured light and nanomaterials open new ways to tailor light at the nanoscale

23.04.2018 | Physics and Astronomy

On the shape of the 'petal' for the dissipation curve

23.04.2018 | Physics and Astronomy

Clean and Efficient – Fraunhofer ISE Presents Hydrogen Technologies at the HANNOVER MESSE 2018

23.04.2018 | Trade Fair News

VideoLinks
Science & Research
Overview of more VideoLinks >>>