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Chemistry

Breaking Down Redox Reactions: Unraveling the Secrets of Proton-Coupled Electron Transfer with High Pressure

Chemists reveal method for differentiating PCET mechanisms — a key step for steering fundamental energy conversion and redox catalysis processes.

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Redox reactions are the backbone of many vital processes that sustain life on Earth. From cellular respiration to photosynthesis, these chemical reactions play a crucial role in harnessing energy and converting it into forms that can be used by living organisms. In addition to their importance in biology, redox reactions also have significant implications for various fields such as chemistry, biochemistry, and the use of light for energy generation.

A team of researchers led by Professor Ivana Ivanović-Burmazović from LMU Munich and Professor Dirk Guldi from FAU Erlangen-Nürnberg has made a groundbreaking discovery in understanding the fundamental principles of redox reactions. Using an innovative approach based on high pressures, they have successfully differentiated between two related reaction mechanisms: concerted and stepwise proton-coupled electron transfer (PCET).

In PCET reactions, electrons are transferred between molecules while protons are moved simultaneously to prevent changes in charge, making it the most efficient way for a redox reaction to occur. However, there were previously no direct methods to distinguish between the two mechanisms with certainty.

The researchers investigated the effect of pressure on the light-induced reaction of a photosensitive molecule in solution. They applied pressures up to 1,200 atmospheres and observed changes in the reaction rate. If the reaction rate remained unchanged under high pressure, it indicated a concerted mechanism, where electrons and protons are transferred simultaneously without changing the charge or solvation sphere.

Conversely, if the reaction rate changed under high pressure, it suggested a stepwise process, where electrons and protons were transferred separately, causing changes in the charge and solvation sphere. To their surprise, the researchers found that they could influence the process by increasing the pressure, steering the reaction from a stepwise mechanism toward a concerted one.

This breakthrough discovery has significant implications for research areas dealing with electron and proton motion, offering new insights into fundamental chemical processes. The findings could also contribute to advancing technologies concerned with converting and storing chemical energy, such as redox catalysis for solar fuel generation or hydrogen production.

Chemistry

Defying Physics: Atacamite’s Rare Magnetic Cooling Property

Deep in Chile’s Atacama Desert, scientists studied a green crystal called atacamite—and discovered it can cool itself dramatically when placed in a magnetic field. Unlike a regular fridge, this effect doesn’t rely on gases or compressors. Instead, it’s tied to the crystal’s unusual inner structure, where tiny magnetic forces get tangled in a kind of “frustration.” When those tangled forces are disrupted by magnetism, the crystal suddenly drops in temperature. It’s a strange, natural trick that could someday help us build greener, more efficient ways to cool things.

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Atacamite, a vibrant emerald-green mineral found in the Atacama Desert in Chile, has been discovered to possess a rare property that defies conventional physics. The mineral exhibits magnetocaloric behavior at low temperatures, meaning its temperature changes significantly when subjected to a magnetic field. A team of researchers from TU Braunschweig and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has been investigating this phenomenon, and their findings could lead to the development of new materials for energy-efficient magnetic cooling.

The researchers found that atacamite’s unique geometric structure, consisting of long chains of small, linked triangles known as sawtooth chains, is responsible for its magnetocaloric behavior. This arrangement creates “magnetic frustration,” where the spins in the copper ions cannot align themselves antiparallel to one another due to the triangular structure. As a result, the spins only arrange themselves at very low temperatures (under 9 Kelvin) in a static alternating structure.

When the researchers applied an extremely high magnetic field to the atacamite crystal, something surprising occurred: the material exhibited a significant cooling effect, with its temperature dropping to almost half of its original value. This strong magnetocaloric effect has fascinated the researchers, as it is unusual for magnetically frustrated materials to exhibit such behavior.

Further studies using magnetic resonance spectroscopy have revealed that the magnetic order in atacamite is destroyed when a magnetic field is applied. This destruction of magnetic order explains why the material’s temperature changes significantly in response to the magnetic field. The team has also conducted complex numerical simulations, which have provided an explanation for the mineral’s unexpected behavior: the magnetic moments on the tips of the sawtooth chains mediate a weak coupling to neighboring chains, leading to the removal of long-range magnetic order.

The researchers believe that their work could inspire further research into innovative magnetocaloric materials within the class of magnetically frustrated systems. While atacamite itself is unlikely to be mined for use in cooling systems, its unique properties provide valuable insights into the fundamental mechanisms governing magnetic behavior in solids. The discovery of this rare property could potentially lead to breakthroughs in energy-efficient magnetic cooling technologies, revolutionizing the way we think about and use refrigeration.

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Chemistry

Mapping Platinum Atoms for a Greener Future in Catalysis

A precious metal used everywhere from car exhaust systems to fuel cells, platinum is an incredibly efficient catalyst—but it’s costly and carbon-intensive. Now, a serendipitous collaboration between scientists at ETH Zurich and other European institutions has opened a new frontier in understanding and optimizing platinum-based catalysts at the atomic level.

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The field of catalysis has revolutionized industries and everyday life, with around 80% of all chemical products relying on this principle. One particularly effective catalyst is platinum, but its rarity and expense make it essential to use it efficiently. Researchers at ETH Zurich have made a groundbreaking discovery by mapping the atomic environments of single platinum atoms in solid supports, paving the way for optimized production of single-atom catalysts.

Using nuclear magnetic resonance (NMR), a team led by Javier Pérez-Ramírez and Christophe Copéret was able to study the individual platinum atoms in detail. This method, typically used for investigating molecules, allowed them to show that the atomic environments of these atoms can have very different properties, influencing their catalytic action.

The researchers found that each platinum atom has a unique combination of neighboring atoms and spatial orientation, similar to the distinct tones in an orchestra. By developing a computer code with the help of a simulation expert, they were able to filter out the different “tones” and create a map of the atomic environments surrounding the platinum atoms.

This breakthrough enables the optimization of production protocols for single-atom catalysts, where all platinum atoms can have tailored environments. The researchers aim to develop more efficient catalytic materials, which is crucial for a greener future in industries such as fuel cells and exhaust catalysts.

The discovery has significant intellectual property implications, allowing the precise description of catalysts at the atomic level and enabling patent protection. This innovation has far-reaching consequences for the development of more sustainable technologies and could transform the field of catalysis forever.

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Chemistry

Revolutionizing Magnetic Field Technology: A Breakthrough Design for MRI and Magnetic Levitation

Two German physicists have reimagined how to create powerful and uniform magnetic fields using compact permanent magnets. By overcoming the limitations of the well-known Halbach array, which works only with infinitely long magnets, they engineered innovative 3D magnet arrangements that work in practical, finite-size setups. Their designs not only boost field strength but also enhance homogeneity, verified through real-world experiments. This game-changing advancement could help bring affordable MRI technology to underserved regions and power applications like particle accelerators and magnetic levitation systems.

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Physicists at the University of Bayreuth and Johannes Gutenberg University Mainz have made a groundbreaking discovery that could transform the way we generate magnetic fields. Prof. Dr. Ingo Rehberg and Dr. Peter Blümler developed an innovative approach to create homogeneous magnetic fields using compact, permanent magnets. This breakthrough design outperforms the traditional Halbach arrangement, which is ideal only for infinitely long and therefore unrealizable magnets.

The new approach presents optimal three-dimensional arrangements of very compact magnets, idealized by point dipoles. The researchers investigated the optimal orientation of the magnets for two geometries relevant to practical use: a single ring and a stacked double ring. This “focused” design allows the generation of homogeneous fields outside the magnet plane, enabling applications such as magnetic levitation systems.

To validate their theoretical predictions, Rehberg and Blümler constructed magnet arrays from 16 FeNdB cuboids mounted on 3D-printed supports. The resulting magnetic fields were measured and compared with theoretical calculations, revealing excellent agreement. In terms of both magnetic field strength and homogeneity, the new configurations clearly outperform the classical Halbach arrangement.

The potential applications of this breakthrough design are vast. Conventional MRI technology relies on powerful superconducting magnets, which are technically complex and extremely costly. The new approach offers a promising alternative for generating homogeneous magnetic fields using permanent magnets. Additionally, this innovation could lead to advancements in particle accelerators and magnetic levitation systems.

This study was published in the renowned interdisciplinary journal Physical Review Applied, showcasing significant advances at the intersection of physics with engineering, materials science, chemistry, biology, and medicine. The implications of this breakthrough design are far-reaching, and further research is expected to uncover new possibilities for its applications.

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