Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Liquid crystals form nano rings

07.02.2018

Quantised self-assembly enables design of materials with novel properties

At DESY's X-ray source PETRA III, scientists have investigated an intriguing form of self-assembly in liquid crystals: When the liquid crystals are filled into cylindrical nanopores and heated, their molecules form ordered rings as they cool – a condition that otherwise does not naturally occur in the material. This behavior allows nanomaterials with new optical and electrical properties, as the team led by Patrick Huber from Hamburg University of Technology (TUHH) report in the journal Physical Review Letters.


Quantized Self-Assembly of Discotic Rings in a Liquid Crystal Confined in Nanopores

Photo: A. Zantop, M. Mazza, K. Sentker, P. Huber, Max-Planck Institut für Dynamik und Selbstorganisation und Technische Universität Hamburg

'Physical Review Letters', 2018; CC BY 4.0

The scientists had studied a special form of liquid crystals that are composed of disc-shaped molecules called discotic liquid crystals. In these materials, the disk molecules can form high, electrically conductive pillars by themselves, stacking up like coins. The researchers filled discotic liquid crystals in nanopores in a silicate glass. The cylindrical pores had a diameter of only 17 nanometers (millionths of a millimeter) and a depth of 0.36 millimeters.

There, the liquid crystals were heated to around 100 degrees Celsius and then cooled slowly. The initially disorganized disk molecules formed concentric rings arranged like round curved columns. Starting from the edge of the pore, one ring after the other gradually formed with decreasing temperature until at about 70 degrees Celsius the entire cross section of the pore was filled with concentric rings. Upon reheating, the rings gradually disappeared again.

This change of the molecular structure in confined liquid crystals can be monitored with X-ray diffraction methods as a function of temperature and with high accuracy,” says co-author and DESY scientist Milena Lippmann, who prepared and participated in the experiments at the High-Resolution Diffraction Beamline P08 at PETRA III. “The combination of symmetry and confinement gives rise to unexpected, new phase transitions,” says Marco Mazza from the Max Planck Institute for Dynamics and Self-Organization in Göttingen where the process was modelled with computer simulations. For this purpose, MPI scientist Arne Zantop devised a theoretical and numerical model for the nanoconfined liquid crystals that confirmed the experimental results and helps to interpret them.

The individual rings formed stepwise at characteristic temperatures. “This makes it possible to turn individual nanorings on and off by small changes in temperature,” emphasizes main author Kathrin Sentker from TUHH. She had noticed this phenomenon through surprisingly step-like signal changes in laser-optical experiments. While such quantized changes usually only occur at very low temperatures, the liquid crystal system shows this quantum behavior already well above room temperature.

As the opto-electrical properties of discotic liquid crystals change with the formation of molecular columns, the nanopore-confined variant is a promising candidate for the design of new optical metamaterials whose properties can be controlled stepwise through temperature. The investigated nanostructures could also lead to new applications in organic semiconductors, such as temperature-switchable nanowires, explains co-author Andreas Schönhals from the Bundesanstalt für Materialforschung und -prüfung (BAM), the German Federal Institute for Materials Research and Testing, who is interested in the thermal and electrical properties of these systems.

“The phenomenon constitutes a fine example how versatile soft matter can adapt to extreme spatial constraints and how this can lead to new insights in physics as well as new design and control principles for the self-organisation of functional nanomaterials,” explains principal investigator Huber.

Scientists from Helmholtz-Zentrum Berlin (HZB) and from Czestochowa University of Technology in Poland were also involved in this study. Sentker and Huber are members of the Collaborative Research Initiative SFB 986 “Multi-Scale Materials Systems” dedicated to the design of materials with tailor-made mechanical, electrical, and photonic properties. It brings together the materials research competences in the Hamburg metropolitan area and is funded by Deutsche Forschungsgemeinschaft (DFG), the central self-governing research funding organisation in Germany.

Reference:
Quantized Self-Assembly of Discotic Rings in a Liquid Crystal Confined in Nanopores; Kathrin Sentker, Arne W. Zantop, Milena Lippmann, Tommy Hofmann, Oliver H. Seeck, Andriy V. Kityk, Arda Yildirim, Andreas Schönhals, Marco G. Mazza, and Patrick Huber; Physical Review Letters, 2018;

DOI: 10.1103/PhysRevLett.120.067801

Contact

Prof. Dr. Patrick Huber
Hamburg University of Technology (TUHH)
Institute of Materials Physics and Technology
+49 42878 3235
patrick.huber@tuhh.de
http://huberlab.wp.tuhh.de

Dr. Milena Lippmann DESY
+49 40 8998 4691
milena.lippmann@desy.de

Dr. Marco G. Mazza
Max Planck Institute for Dynamics and Self-Organization
+49 551 5176-233
marco.mazza@ds.mpg.de

Jasmine Ait-Djoudi | idw - Informationsdienst Wissenschaft
Further information:
http://www.tuhh.de

More articles from Materials Sciences:

nachricht Scientists develop low-cost energy-efficient materials
24.04.2019 | National University of Science and Technology MISIS

nachricht Modified 'white graphene' for eco-friendly energy
23.04.2019 | Tomsk Polytechnic University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Energy-saving new LED phosphor

The human eye is particularly sensitive to green, but less sensitive to blue and red. Chemists led by Hubert Huppertz at the University of Innsbruck have now developed a new red phosphor whose light is well perceived by the eye. This increases the light yield of white LEDs by around one sixth, which can significantly improve the energy efficiency of lighting systems.

Light emitting diodes or LEDs are only able to produce light of a certain colour. However, white light can be created using different colour mixing processes.

Im Focus: Quantum gas turns supersolid

Researchers led by Francesca Ferlaino from the University of Innsbruck and the Austrian Academy of Sciences report in Physical Review X on the observation of supersolid behavior in dipolar quantum gases of erbium and dysprosium. In the dysprosium gas these properties are unprecedentedly long-lived. This sets the stage for future investigations into the nature of this exotic phase of matter.

Supersolidity is a paradoxical state where the matter is both crystallized and superfluid. Predicted 50 years ago, such a counter-intuitive phase, featuring...

Im Focus: Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter

  • Coolest and smallest star to produce a superflare found
  • Star is a tenth of the radius of our Sun
  • Researchers led by University of Warwick could only see...

Im Focus: Quantum simulation more stable than expected

A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.

Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...

Im Focus: Largest, fastest array of microscopic 'traffic cops' for optical communications

The technology could revolutionize how information travels through data centers and artificial intelligence networks

Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

Fraunhofer FHR at the IEEE Radar Conference 2019 in Boston, USA

09.04.2019 | Event News

 
Latest News

Proteins stand up to nerve cell regression

24.04.2019 | Life Sciences

New sensor detects rare metals used in smartphones

24.04.2019 | Life Sciences

Controlling instabilities gives closer look at chemistry from hypersonic vehicles

24.04.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>