Researchers at Hiroshima University, CNRS, and Université de Strasbourg synthesized crystals with magnetic properties that can change continuously and reversibly, a world first.
The study was highlighted as a cover article of the journal “Inorganic Chemistry,” a publication of the American Chemical Society in March 2016.
Recently, the scientific community has had immense interest in new types of magnets with the potential to create the next generation of energy efficient devices through innovations using materials science techniques.
Common magnets, like those holding reminders on home refrigerators or turning car motors, are made of metal and metal oxides. Newer magnets can be made with organic molecules and can have a range of magnetic behaviors because of variations in their molecular structure.
That range of behavior includes the strongly magnetic ferrimagnetic state and the very weakly magnetic spin glass state.
The different seasons in Hiroshima, Japan can affect the humidity inside office and research buildings throughout the year. Crystals prepared in different seasons showed different magnetic properties even though their crystal structures were almost identical.
“To find the source of the different magnetic states, we prepared the crystals under controlled conditions of temperature and humidity,” said Li Li, first author of the research paper and a Ph.D. student in the Department of Chemistry at Hiroshima University.
The crystals synthesized by the research team can exist in either the ferrimagnetic or spin glass state, depending on the conditions of how they are synthesized. This is the first material known to reversibly and continuously transition between magnetic states.
As the crystals absorb water from the air, they undergo subtle structural changes responsible for the continuous transformation between ferrimagnet and spin glass. By applying pressure, the effect can be reversed. This allows fine-tuning of the magnetic states, and explains why the humidity in the research lab can affect the crystals.
Using the research team’s synthesis methods, increasing the pressure on the crystal changes the spin glass state into the ferrimagnet state and drying the crystal changes ferrimagnet into spin glass. Pressure and humidity are like dimmer switches to slide the crystal back and forth between the two states.
Additionally, the crystal is chiral, meaning it can exist in either one orientation or its own mirror image. These mirror image versions of the molecule are not superimposable, like right and left human hands.
Both right-handed and left-handed versions of the crystals can transition between the ferrimagnet and spin glass states. However, there are valuable applications exclusive to chiral molecules due to their unique chemical and optical properties.
“Our laboratory primarily researches chiral magnets, but this is the first time we found one compound with multiple magnetic states,” said Katsuya Inoue, Ph.D., one of the researchers involved and the leader of Hiroshima University’s Center for Chiral Science.
Chiral magnets can be used in spintronics devices, which are the current state-of-the-art data storage technology that use less power, are faster, and can store more information than previous generations of computer hard drives.
“We imagine that a chiral material with two or more magnetic states will provide further technological advantages because of its handedness,” said Inoue.
“This is a brand new breed of molecular material and it requires finesse to synthesize. Our results might not lead directly to immediate practical applications, but advances made in the science of chiral magnets are generating properties not experienced before, opening a bright future of new innovations,” said Inoue.
Researchers from KU Leuven, the University of Strasbourg, and CNRS have discovered a new phosphor that could make next-generation fluorescent and LED lighting even cheaper and more efficient. The team used highly luminescent clusters of silver atoms and the porous framework of minerals known as zeolites.
Silver clusters consist of just a few silver atoms and have remarkable optical properties. However, current applications are limited, because the clusters tend to aggregate into larger particles, thus losing the interesting optical properties.
Professor Hofkens and his team from the Molecular Imaging and Photonics Unit have now found a way to keep the silver clusters apart by inserting them into the porous framework of zeolites. The result: stable silver clusters that maintain their unique optical properties.
The toxic and expensive phosphors used widely in fluorescent lighting could be eliminated thanks to a new study conducted by a materials scientist at Queen Mary University of London (QMUL).
Writing in the journal Nature Materials, the international group of scientists modified a mineral called zeolite, more commonly found in washing powder, to incorporate tiny clusters of silver atoms.
At this very small scale (less than 10 atoms), the silver clusters act very differently and can even emit light.
Lead author Dr Oliver Fenwick from QMUL’s School of Engineering and Materials Science, said: “We’ve shown that silver atoms can be assembled in the porous framework of minerals known as zeolites with a level of control not reported previously. This has allowed us to tailor very precisely the properties of the silver clusters to meet our needs – in this case an efficient phosphor.
“The high efficiency of the materials along with cheap, scalable synthesis makes them very attractive as next generation emitters for fluorescent lamps, LEDs and for biological imaging, for example for highlighting tumours or cell division.”
The University of Strasbourg in Strasbourg, Alsace, France, is the second largest university in France (after Aix-Marseille University), with about 43,000 students and over 4,000 researchers.
The present-day French university traces its history to the earlier German-language Universität Straßburg, which was founded in 1538, and was divided in the 1970s into three separate institutions: Louis Pasteur University, Marc Bloch University, and Robert Schuman University. On 1 January 2009, the fusion of these three universities reconstituted a united University of Strasbourg, which is now amongst Europe’s best in the League of European Research Universities.
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University of Strasbourg research articles from Innovation Toronto
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Viruses are able to redirect the functioning of cells in order to infect them. Inspired by their mode of action, scientists from the CNRS and Université de Strasbourg have designed a “chemical virus” that can cross the double lipid layer that surrounds cells, and then disintegrate in the intracellular medium in order to release active compounds.
To achieve this, the team used two polymers they had designed, which notably can self-assemble or dissociate, depending on the conditions. This work, the result of collaborative efforts by chemists, biologists and biophysicists, is published in the 1st September issue of Angewandte Chemie International Edition.
Biotechnological advances have offered access to a wealth of compounds with therapeutic potential. Many of these compounds are only active inside human cells but remain unusable because the lipid membrane surrounding these cells is a barrier they cannot cross. The challenge is therefore to find transfer solutions that can cross this barrier.
By imitating the ability of viruses to penetrate into cells, chemists in the Laboratoire de Conception et Application de Molécules Bioactives (CNRS/Université de Strasbourg) sought to design particles capable of releasing macromolecules that are only active inside cells. To achieve this, these particles must comply with several, often contradictory, constraints. They must remain stable in the extracellular medium, they must be able to bind to the cells so that they be internalized, but they must be more fragile inside the cells so that they can release their content.
Using two polymers designed by the team, the scientists succeeded in creating a “chemical virus” that meets the conditions necessary for the direct delivery of active proteins into cells.
In practice, the first polymer (pGi-Ni2+) serves as a substrate for the proteins that bind to it. The second, recently patented polymer (?PEI), encapsulates this assembly thanks to its positive charges, which bind to the negative charges of pGi-Ni2+. The particles obtained (30-40 nanometers in diameter) are able to recognize the cell membrane and bind to it. This binding activates a cellular response: the nanoparticle is surrounded by a membrane fragment and enters the intracellular compartment, called the endosome. Although they remain stable outside the cell, the assemblies are attacked by the acidity that prevails within this new environment. Furthermore, this drop in pH allows the ?PEI to burst the endosome, releasing its content of active compounds.
Thanks to this assembly, the scientists were able to concentrate enough active proteins within the cells to achieve a notable biological effect. Thus by delivering a protein called caspase 3 into cancer cell lines, they succeeded in inducing 80% cell death1.
The in vitro results are encouraging, particularly since this “chemical virus” only becomes toxic at a dose ten times higher than that used during the study. Furthermore, preliminary results in the mouse have not revealed any excess mortality. However, elimination by the body of the two polymers remains an open question. The next stage will consist in testing this method in-depth and in vivo, in animals. In the short term, this system will serve as a research tool to vectorize2 recombinant and/or chemically modified proteins into cells. In the longer term, this work could make it possible to apply pharmaceutical proteins to intracellular targets and contribute to the development of innovative drugs.
Read more: Imitating viruses to deliver drugs to cells