Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Molecular Film on Liquid Mercury Reveals New Properties


A team of scientists from the U.S. Department of Energy’s Brookhaven National Laboratory, Harvard University, and Bar-Ilan University in Israel have grown ultrathin films made of organic molecules on the surface of liquid mercury. The results, reported in the November 15, 2002, issue of Science, reveal a series of new molecular structures that could lead to novel applications in nanotechnology, which involves manipulating materials at the atomic scale.

This schematic drawing shows how the stearic molecules of the film rearrange as they are added onto the surface of the liquid mercury support

Growing molecular films on liquid surfaces is part of an ongoing activity by Brookhaven scientists to create nanomaterials, which are a few billionths of a meter in thickness. Ultrathin films are becoming increasingly important for fast-developing applications, such as faster and smaller electronic and magnetic devices, advanced biotechnological membranes, and controlled drug release in the human body. The Brookhaven team is a leader in the field of liquid surface-supported film growth, with expertise gained over the past 20 years.

"When you grow a film on a solid surface, the molecules of the film tend to interlock with those of the underlying support," says Benjamin Ocko, the Brookhaven physicist who participated in the study. "But an underlying liquid surface is not ordered and provides an ideal setting for studying ultrathin states of matter without the complications of the solid support."

Ocko and his colleagues first filled a small tray with liquid mercury and then deposited on the surface a nanometer-thin film of stearic acid, an organic waxlike material that is a common component of cell membranes. Since stearic acid is not soluble in mercury, it floats on the surface.

To see how the molecules of the film organize on the surface, the scientists measured how x-rays produced by the National Synchrotron Light Source at Brookhaven scattered off the ultrathin molecular film. Key to the study was a unique instrument used for tilting the x-rays downward onto the liquid mercury surface, which was developed by Peter Pershan, a physicist at Harvard and one of the study’s authors, along with the Brookhaven team.

The scientists discovered that, as the number of molecules deposited on the surface increased, they formed four distinct patterns. "First, when a few molecules are deposited, they tend to take as much space as they can, by lying on the surface," explains Henning Kraack, a physics Ph.D. student from Bar-Ilan and the study’s lead author. "When more molecules are added, a second layer of molecules lies on top of the first one.

"Then, as even more molecules are deposited," Kraack continues, "they ’stand up’ to leave more space to neighboring molecules, allowing them to densely pack in one layer. But even then, before standing up straight, the molecules are first tilted to the side, and stand up completely only when they are ’squeezed’ by other molecules that ’elbow their way through.’"

These observations came as a surprise, since previous studies have shown that, when stearic molecules are deposited on water -- the only other liquid support studied so far -- they only stand up on the surface. "Patterns in which molecules lie flat on a liquid surface have never been observed before," Kraack says.

Moshe Deutsch, a physicist at Bar-Ilan and one of the authors of the study, notes that because the liquid mercury does not seem to influence too much the way the stearic molecules assemble, "growing films on a liquid surface is like growing them without support at all." It might be possible to choose a film pattern, he adds, simply by selecting the appropriate molecular coverage.

"This work shows that without an underlying lattice, we can control film growth," Deutsch says. "By growing other molecules on a liquid support, we will be able to control the size and properties of other films, and thus tailor them for different applications, in particular their use in nanoelectronics and nanosensor technology."

This work was funded by the U.S. Department of Energy, which supports basic research in a variety of scientific fields, the National Science Foundation, and the U.S.-Israel Binational Science Foundation in Jerusalem, Israel.

Karen McNulty Walsh | EurekAlert!
Further information:

More articles from Materials Sciences:

nachricht Heat energy leaps through empty space, thanks to quantum weirdness
12.12.2019 | University of California - Berkeley

nachricht How light a foldable and long-lasting battery can be?
12.12.2019 | Pohang University of Science & Technology (POSTECH)

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Cheers! Maxwell's electromagnetism extended to smaller scales

More than one hundred and fifty years have passed since the publication of James Clerk Maxwell's "A Dynamical Theory of the Electromagnetic Field" (1865). What would our lives be without this publication?

It is difficult to imagine, as this treatise revolutionized our fundamental understanding of electric fields, magnetic fields, and light. The twenty original...

Im Focus: Highly charged ion paves the way towards new physics

In a joint experimental and theoretical work performed at the Heidelberg Max Planck Institute for Nuclear Physics, an international team of physicists detected for the first time an orbital crossing in the highly charged ion Pr⁹⁺. Optical spectra were recorded employing an electron beam ion trap and analysed with the aid of atomic structure calculations. A proposed nHz-wide transition has been identified and its energy was determined with high precision. Theory predicts a very high sensitivity to new physics and extremely low susceptibility to external perturbations for this “clock line” making it a unique candidate for proposed precision studies.

Laser spectroscopy of neutral atoms and singly charged ions has reached astonishing precision by merit of a chain of technological advances during the past...

Im Focus: Ultrafast stimulated emission microscopy of single nanocrystals in Science

The ability to investigate the dynamics of single particle at the nano-scale and femtosecond level remained an unfathomed dream for years. It was not until the dawn of the 21st century that nanotechnology and femtoscience gradually merged together and the first ultrafast microscopy of individual quantum dots (QDs) and molecules was accomplished.

Ultrafast microscopy studies entirely rely on detecting nanoparticles or single molecules with luminescence techniques, which require efficient emitters to...

Im Focus: How to induce magnetism in graphene

Graphene, a two-dimensional structure made of carbon, is a material with excellent mechanical, electronic and optical properties. However, it did not seem suitable for magnetic applications. Together with international partners, Empa researchers have now succeeded in synthesizing a unique nanographene predicted in the 1970s, which conclusively demonstrates that carbon in very specific forms has magnetic properties that could permit future spintronic applications. The results have just been published in the renowned journal Nature Nanotechnology.

Depending on the shape and orientation of their edges, graphene nanostructures (also known as nanographenes) can have very different properties – for example,...

Im Focus: Electronic map reveals 'rules of the road' in superconductor

Band structure map exposes iron selenide's enigmatic electronic signature

Using a clever technique that causes unruly crystals of iron selenide to snap into alignment, Rice University physicists have drawn a detailed map that reveals...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

The Future of Work

03.12.2019 | Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

Latest News

Weizmann physicists image electrons flowing like water

12.12.2019 | Physics and Astronomy

Revealing the physics of the Sun with Parker Solar Probe

12.12.2019 | Physics and Astronomy

New technique to determine protein structures may solve biomedical puzzles

12.12.2019 | Life Sciences

Science & Research
Overview of more VideoLinks >>>