Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Magic number colloidal clusters

13.12.2018

Complexity in nature, whether in chlorophyll or in living organisms, often results from self-assembly and is considered particularly robust. Compact clusters of elemental particles can be shown to be of practical relevance, and are found in atomic nuclei, nano particles or viruses. An interdisciplinary team of researchers led by professors Nicolas Vogel and Michael Engel at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have decoded the structure and the process behind the formation of one class of such highly ordered clusters. Their findings have increased understanding of how structures are formed in clusters and have now been published in the journal Nature Communications.

In physics, a cluster is defined as an independent material form at the transition area between isolated atoms and more extensive solid objects or liquids. Magic number clusters can be traced back to the work of Eugene Wigner, Maria Göppert-Mayer and Hans Jensen, who used this theory to explain the stability of atomic nuclei and won the Nobel prize for physics for their research in 1963.


Electron microscopic images of magic number colloidal clusters. Each cluster consists of tiny microscopic polymer balls which come together to form a drying water droplet (scale bar: 2 micrometres).

FAU/Junwei Wang

‘Until now, scientists have assumed that the effect is caused purely as a result of the attraction between atoms,’ says Prof. Dr. Nicolas Vogel, Professor for Particle Synthesis. Our research now proves that particles which don’t attract each other also form structures such as these. Our publication contributes to a greater understanding of how structures are formed in clusters in general.’

The research is based on an interdisciplinary collaboration: Prof. Dr. Nicolas Vogel, researcher at the Chair of Particle Technology, and Prof. Dr. Michael Engel, researcher at the Chair of Multi-scale Simulation – both from the Department of Chemical and Biological Engineering – have worked closely together with the materials science expert Prof. Dr. Erdmann Spiecker from the Chair of Materials Science (research into micro and nanostructures), pooling their expertise from the various areas. Vogel was responsible for synthesis, Spiecker for structure analysis and Engel for modelling clusters from colloidal polymer balls.

The term colloidal is derived from the ancient Greek word for glue and refers to particles or droplets which are finely distributed in a dispersion medium, either a solid object, a gas, or a liquid. ‘Our three approaches are particularly closely linked in this project,’ underlines Prof. Engel, ‘they complement each other and allow us to gain a deep understanding of the fundamental processes behind the forming of structures for the first time.’

Structures assemble themselves

The first step for the researchers in a process which covers several steps was to synthesise minute colloidal clusters, no larger than a tenth of the diameter of a single hair in total. ‘First of all, water evaporates from an emulsion droplet and the polymer balls are pushed together.

Over time, they assemble increasingly smoother sphere-shaped clusters and begin to crystallise. It is remarkable how several thousand individual particles independently find their ideal position in a precise and highly symmetrical structure in which all particles are placed in predictable positions,’ explains Prof. Vogel.

The researchers discovered more than 25 different magic number colloidal clusters of various shapes and sizes and were able to define four different cluster morphologies: where evaporation was fastest, buckled clusters were formed, as the droplet interface moved faster than the colloidal particles could consolidate. If the evaporation rate was lowered, the clusters were predominantly spherical.

Spherical clusters have a uniformly curved surface with only a weak pattern of crystals. Clusters with icosahedral symmetry were formed as the rate of evaporation decreased further. These clusters have a particularly high degree of symmetry and have numerous two, three or five fold symmetry axes.

Using high resolution microscopy to show the surface of the cluster does not provide sufficient proof of these symmetries. Even if the surface of a cluster appears highly ordered, that is no guarantee that the particles inside the cluster are arranged as expected. To verify this, the researchers used electron tomography, available at the Erlangen Centre for Nanoanalysis and Electron Microscopy (CENEM).

Individual clusters are bombarded with highly energised electrons from all directions and the images recorded. From more than 100 projections, researchers were able to reconstruct the three dimensional structure of the clusters and therefore the pattern of the particles within the clusters in a method reminiscent of computer tomography as used in medicine.

In the next step, the researchers conducted simulations and highly accurate numerical calculations. The analyses proved that clusters consisting of numbers of particles corresponding to a magic number are indeed more stable, as predicted on the basis of the theory. It is well known that the observed icosahedral symmetry can be found in viruses and ultra-small metal clusters, but it has never been investigated directly.

Now, with these results, a detailed and systematic understanding of how such magic number clusters are formed in the investigated model system is possible for the first time, allowing conclusions to be drawn for other natural systems where clusters tend to be formed.

Wissenschaftliche Ansprechpartner:

Further information:
Prof. Dr. Nicolas Vogel
Phone: +49 9131 8520357
nicolas.vogel@fau.de

Prof. Dr. Michael Engel
Phone: +49 9131 8520857
michael.engel@fau.de

Originalpublikation:

https://doi.org/10.1038/s41467-018-07600-4

Dr. Susanne Langer | idw - Informationsdienst Wissenschaft

More articles from Life Sciences:

nachricht Researchers discover vaccine to strengthen the immune system of plants
24.01.2020 | Westfälische Wilhelms-Universität Münster

nachricht Brain-cell helpers powered by norepinephrine during fear-memory formation
24.01.2020 | RIKEN

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Integrate Micro Chips for electronic Skin

Researchers from Dresden and Osaka present the first fully integrated flexible electronics made of magnetic sensors and organic circuits which opens the path towards the development of electronic skin.

Human skin is a fascinating and multifunctional organ with unique properties originating from its flexible and compliant nature. It allows for interfacing with...

Im Focus: Dresden researchers discover resistance mechanism in aggressive cancer

Protease blocks guardian function against uncontrolled cell division

Researchers of the Carl Gustav Carus University Hospital Dresden at the National Center for Tumor Diseases Dresden (NCT/UCC), together with an international...

Im Focus: New roles found for Huntington's disease protein

Crucial role in synapse formation could be new avenue toward treatment

A Duke University research team has identified a new function of a gene called huntingtin, a mutation of which underlies the progressive neurodegenerative...

Im Focus: A new look at 'strange metals'

For years, a new synthesis method has been developed at TU Wien (Vienna) to unlock the secrets of "strange metals". Now a breakthrough has been achieved. The results have been published in "Science".

Superconductors allow electrical current to flow without any resistance - but only below a certain critical temperature. Many materials have to be cooled down...

Im Focus: Programmable nests for cells

KIT researchers develop novel composites of DNA, silica particles, and carbon nanotubes -- Properties can be tailored to various applications

Using DNA, smallest silica particles, and carbon nanotubes, researchers of Karlsruhe Institute of Technology (KIT) developed novel programmable materials....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

„Advanced Battery Power“- Conference, Contributions are welcome!

07.01.2020 | Event News

 
Latest News

Researchers discover vaccine to strengthen the immune system of plants

24.01.2020 | Life Sciences

Brain-cell helpers powered by norepinephrine during fear-memory formation

24.01.2020 | Life Sciences

Engineered capillaries model traffic in tiny blood vessels

24.01.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>