Nanotechnology Now

Our NanoNews Digest Sponsors


Heifer International

Wikipedia Affiliate Button

Home > Press > Molecular "propellers" may rotate very slowly

Abstract:
The experiments conducted in the Institute of Physical Chemistry of the Polish Academy of Sciences on super-thin liquid-crystal films created on water surface allowed the surprisingly slow and continuous rotational motion of molecules, rotating "in unison", to be observed nearly with the naked eye.

Molecular "propellers" may rotate very slowly

Poland | Posted on September 9th, 2010

Scientists from the Institute of Physical Chemistry of the Polish Academy of Sciencies (IPC PAS) established that in the liquid-crystal layers that are several nanometers thick and created on water surface, molecules may rotate with extremely low speed, just one revolution per several minutes. Such slow rotational motion is a real surprise since it was expected that rotation would be quickly destroyed by thermal fluctuations. "The slowdown in rotation of molecules is nothing unexpected in liquid crystals usually formed of thousands of layers. However, in our experiments we have monolayers and we can observe the effects of very slow rotational motion of chemical molecules nearly with the naked eye," emphasises Prof. Robert Holyst from the IPC PAS.

The experiment conducted in the IPC PAS is distantly related to famous experiments carried out by Benjamin Franklin and connected with quieting agitated water by spilling oil on it. During one of the attempts Franklin noticed that oil spilled on the surface of a pond became so thin at a certain point that it stopped spreading. "We do something similar but on a smaller scale: we spill microlitres of liquid crystal on water surface. Its molecules form a monolayer, that is a layer which is one-molecule thick," explains PhD Andrzej Zywocinski from the IPC PAS.

Molecules of the liquid crystals that are examined have amphiphilic character - the hydrophilic group of a chain attaches to water surface, over which the hydrophobic tail protrudes making dissolution impossible - and they freely move across the water surface, which means they behave like gas in two-dimensional space. However, researchers were interested in the behaviour of liquid crystals in a liquid phase. A gas may be transformed into a liquid or solid as a result of changes in temperature or pressure. If we use the latter, solidification is achieved at high pressures of at least several dozens of atmospheres. Fortunately, in the case of monolayers a suitably high pressure can be easily obtained with a device called the Langmuir balance. It is a shallow tank filled with water, with two hydrophilic barriers between which there is a film of the liquid crystal several nanometers thick. "It is sufficient to decrease the distance between the barriers in order to achieve an increase in surface pressure that will cause the liquid crystal to become liquid or even solid," says Patrycja Niton, a PhD student from the IPC PAS.

The surface of a liquid-crystal film in a liquid phase was observed with the Brewster angle microscope at relatively small enlargement. The Brewster angle is an angle at which light falling on the surface of a dielectric reflects off fully linearly polarized, which means that the component of the electric field oscillates in one plane. If a polarizer is placed in the way of such polarized light so that the light goes through it, it will stop the entire reflected light and under the Brewster angle microscope clean water will look black. However, if on the water surface there is something which twists the plane of polarization, bright reflections will appear.

In the experiments conducted in the Institute of Physical Chemistry of the PAS it was analysed how a monolayer of a ferroelectric SmC* liquid crystal behaved on water surface. It is typical for SmC* phase that molecules spontaneously arrange themselves into layers and each subsequent layer is slightly twisted in relation to the others. "We have only one layer which we can imagine to be a forest of molecules inclined in the same direction at certain angle," explains PhD Zywocinski. When water molecules evaporate, they hit into groups of atoms of various sizes which are connected with an asymmetric (chiral) carbon atom in each molecule of the liquid crystal. Due to the asymmetry, the fragments of molecules of liquid crystals protruding over the water surface act as the sails of a windmill and they start to rotate collectively (this effect was for the first time observed by Prof. Hiroshi Yokoyama from Japan). A molecule must be constructed in an appropriate way to be able to rotate. The polar group that keeps it at the water surface should not be too big as it would be immersed too deeply and would hinder the rotation caused by the asymmetric chiral group which is hit by the molecules of evaporating water. The chiral group, on the other hand, must remain distinctly above the surface.

Rotating molecules change the polarization plane of the reflected light and in the field of view of the Brewster angle microscope there are areas of periodically changing brightness. The quickest rotation of molecules observed in this way lasted five seconds and the slowest as long as eight minutes. It is probably possible to achieve even slower rotational motion but not through the decrease of temperature (as liquid crystals become solid then) but by saturating the air with water vapour, which would decrease the pace of evaporation and thus the frequency of collision of water molecules and "sails" of liquid crystals.

Slowly rotating molecules of liquid crystals can be used to construct nanodevices. "It is possible to construct a molecule in which a group of atoms playing the role of a sail would be a kind of a nanodrive. Then we would create a real molecular nanoengine driven by a water vapour stream," says PhD Zywocinski, and he adds that scientists are now working on the possibility to transfer this collective rotation of single molecules to larger objects.

The film made at the Institute of Physical Chemistry of the PAS shows water surface covered with a liquid crystal monolayer. Rotating molecules change the polarization plane of the reflected light and cause periodic changes in brightness, which are particularly well noticeable in the spiral at the bottom of the monitor. The field of view is 4.8 x 6.4 mm. (Source: IPC PAS)

ichf.edu.pl/press/2010/09/IChF100908c_mov01.avi

####

About Polish Academy of Sciences
The Institute of Physical Chemistry of the Polish Academy of Sciences was established in 1955 as one of the first chemical institutes of the PAS. The Institute's scientific profile is strongly related to the newest global trends in the development of physical chemistry and chemical physics. Scientific research is conducted in nine scientific departments. CHEMIPAN R&D Laboratories operating as part of the Institute implement, produce and commercialise specialist chemical compounds to be used, in particular, in agriculture and pharmacy. The Institute publishes approximately 300 original research papers annually.

For more information, please click here

Contacts:
Prof. Robert Hołyst
Institute of Physical Chemistry of the Polish Academy of Sciences
tel. +48 22 3433123


Ph.D. Andrzej Żywociński
Institute of Physical Chemistry of the Polish Academy of Sciences
tel. +48 22 3433247

Copyright © Polish Academy of Sciences

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Ultra-flat circuits will have unique properties: Rice University lab studies 2-D hybrids to see how they differ from common electronics July 25th, 2016

Attosecond physics: Mapping electromagnetic waveforms July 25th, 2016

Borrowing from pastry chefs, engineers create nanolayered composites: Method to stack hundreds of nanoscale layers could open new vistas in materials science July 25th, 2016

Integration of novel materials with silicon chips makes new 'smart' devices possible July 25th, 2016

Thin films

Cambridge Advanced Imaging Centre praises support film consistency and quality from EM Resolutions July 5th, 2016

Novel capping strategy improves stability of perovskite nanocrystals: Study addresses instability issues with organometal-halide perovskites, a promising class of materials for solar cells, LEDs, and other applications June 13th, 2016

New nanomaterial offers promise in bendable, wearable electronic devices: Electroplated polymer makes transparent, highly conductive, ultrathin film June 13th, 2016

Perovskite solar cells surpass 20 percent efficiency: EPFL researchers are pushing the limits of perovskite solar cell performance by exploring the best way to grow these crystals June 13th, 2016

Possible Futures

Designing climate-friendly concrete, from the nanoscale up: New understanding of concrete’s properties could increase lifetime of the building material, decrease emissions July 25th, 2016

Ultra-flat circuits will have unique properties: Rice University lab studies 2-D hybrids to see how they differ from common electronics July 25th, 2016

Attosecond physics: Mapping electromagnetic waveforms July 25th, 2016

Borrowing from pastry chefs, engineers create nanolayered composites: Method to stack hundreds of nanoscale layers could open new vistas in materials science July 25th, 2016

Academic/Education

News from Quorum: The College of New Jersey use the Quorum Cryo-SEM preparation system in a project to study ice crystals in high altitude clouds July 19th, 2016

Leti and Korea Institute of Science and Technology to Explore Collaboration on Advanced Technologies for Digital Era July 14th, 2016

SUNY Poly Celebrates Its 10th Year Exhibiting at SEMICON West with Cutting Edge Developments in Integrated Photonics and Power Electronics July 8th, 2016

FEI and King Abdullah University of Science and Technology Establish New Electron Microscopy ‘Centre of Excellence’: Centre of Excellence involves materials and life sciences research and technical collaboration July 5th, 2016

Molecular Machines

New remote-controlled microrobots for medical operations July 23rd, 2016

Pushing a single-molecule switch: An international team of researchers from Donostia International Physics Center, Fritz-Haber Institute of the Max Planck Society, University of Liverpool, and the Polish Academy of Sciences has shown a new way to operate a single-molecule switch July 19th, 2016

Researchers harness DNA as the engine of super-efficient nanomachine: New platform detects traces of everything from bacteria to viruses, cocaine and metals July 10th, 2016

On the path toward molecular robots: Scientists at Japan's Hokkaido University have developed light-powered molecular motors that repetitively bend and unbend, bringing us closer to molecular robots. July 8th, 2016

Announcements

Borrowing from pastry chefs, engineers create nanolayered composites: Method to stack hundreds of nanoscale layers could open new vistas in materials science July 25th, 2016

Integration of novel materials with silicon chips makes new 'smart' devices possible July 25th, 2016

Accurate design of large icosahedral protein nanocages pushes bioengineering boundaries: Scientists used computational methods to build ten large, two-component, co-assembling icosahedral protein complexes the size of small virus coats July 25th, 2016

XEI Scientific Partners with Electron Microscopy Sciences to Promote and Sell its Products in North and South America July 25th, 2016

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







Car Brands
Buy website traffic