Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Molecular Hinges Open Pathways

28.02.2014
Exchange of bismuth atoms for chloride ions with retention of structure
 

Modern technology makes extensive use of ion exchangers. For example, they are commonly used to decalcify water by binding calcium ions and releasing sodium ions in return. Good exchangers tend to be materials with high surface areas, such as resins, zeolites, or clays. German scientists have now demonstrated that the compact, crystalline structures of intermetallic compounds, in which the diffusion pathways for efficient materials transport are actually absent, can also exchange ions. In the journal Angewandte Chemie, they report the full replacement of the chloride ions in Bi12Rh3Cl2 crystals by bismuth atoms.


The team working with Michael Ruck at the Technical University of Dresden noticed this unexpected phenomenon while researching bismuth subhalides. Subhalides are compounds that have fewer halogen ions than pure ionic metal halides. This results in regions that contain direct bonds between metal atoms. Subhalides with bismuth and rhodium are known to have intermetallic substructures that range from clusters to three-dimensional networks. Bi12Rh3Cl2  contains intermetallic networks consisting of edge-sharing [RhBi8] cubes and antiprisms.

The researchers planned to “pull” the halogen atoms out without destroying the intermetallic regions under gentle conditions using an n-butyllithium solution. The chloride ions were extracted just as the scientists hoped, even though they seemed to be tightly enclosed by the narrow channels of the intermetallic network. Even more surprisingly, the resulting voids in the crystal structure were filled by bismuth atoms. The bismuth atoms came from barely noticeable chemical decomposition of the surface of the crystal.

The resulting product is Bi12Rh3Bi2, a metastable superconductor with a structure identical to that of the subchloride. During the reaction, the morphology of the crystal remains unchanged. “The transformation must be based on efficient transport of chloride ions out and bismuth ions into the network,” says Ruck. Crystallographic studies revealed a small change in the torsion angle of the [RhBi8] antiprisms. “The antiprisms act as hinges in the network,” explains Ruck. “Transient changes in the angle allow wide diffusion pathways to open up parallel to all of the intermetallic strands. Since the diffusion paths intersect, the transport system is three-dimensional.”

Although the intermetallic network only changes very slightly, the electronic properties are significantly different: the subchloride only demonstrates metallic conductivity along special directions that are insulated by nonconducting parts of the structure. In the intermetallic compound, in contrast, the conducting strands are metallically connected through the additional bismuth atoms. They are thus electrically connected, resulting in a three-dimensional metal.

About the Author

Professor Dr. Michael Ruck conducts research and teaches chemistry and food chemistry at the Technical University of Dresden. He works in the area of solid-state chemistry and is particularly interested in metallic compounds and low-temperature synthesis of materials. He is also a Fellow of the Max Planck Institute of the Chemical Physics of solids in Dresden.

Author: Michael Ruck, Technische Universität Dresden (Germany), http://www.cpfs.mpg.de/

Title: The Topochemical Pseudomorphosis of a Chloride into a Bismuthide

Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201309460

| Angewandte Chemie
Further information:
http://pressroom.angewandte.org

Further reports about: Molecular bismuth Atoms chloride compounds ions pathways rhodium

More articles from Life Sciences:

nachricht New switch decides between genome repair and death of cells
27.09.2016 | University of Cologne - Universität zu Köln

nachricht A blue stoplight to prevent runaway photosynthesis
27.09.2016 | National Institute for Basic Biology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

Im Focus: Launch of New Industry Working Group for Process Control in Laser Material Processing

At AKL’16, the International Laser Technology Congress held in May this year, interest in the topic of process control was greater than expected. Appropriately, the event was also used to launch the Industry Working Group for Process Control in Laser Material Processing. The group provides a forum for representatives from industry and research to initiate pre-competitive projects and discuss issues such as standards, potential cost savings and feasibility.

In the age of industry 4.0, laser technology is firmly established within manufacturing. A wide variety of laser techniques – from USP ablation and additive...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

ICPE in Graz for the seventh time

20.09.2016 | Event News

 
Latest News

New switch decides between genome repair and death of cells

27.09.2016 | Life Sciences

Nanotechnology for energy materials: Electrodes like leaf veins

27.09.2016 | Physics and Astronomy

‘Missing link’ found in the development of bioelectronic medicines

27.09.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>