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Chemistry

Illuminating the Twist: Light-Controlled Supramolecular Chirality

In a striking demonstration of molecular control, a team of scientists has harnessed light to reverse the twist in self-assembling molecules. The study identifies how trace residual aggregates in photo-responsive azobenzene solutions can reverse helical chirality through secondary nucleation. By using precise control of ultraviolet and visible light, the researchers could switch between the rotation of helices, offering a breakthrough for novel materials with tunable properties.

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The self-assembly of molecules into complex structures is a crucial phenomenon in material science. Researchers from Japan have made a significant breakthrough by elucidating a technique where a small amount of residual aggregates drastically alters the self-assembly process of photo-responsive molecules. This study, led by Professor Shiki Yagai and his team, was published online in Nature Nanotechnology on April 11, 2025.

In recent years, there has been an increasing focus on controlling the size and hierarchical structures of self-assembled aggregates to achieve materials with desired properties. However, self-assembly is a dynamic process that requires precise control. As Professor Yagai explains, “During the process of self-assembly, molecules repeatedly associate and dissociate,” making it challenging to predict the final structure of the formed aggregates.

The research team focused on the self-assembly of a chiral, photoresponsive azobenzene molecule that naturally forms left-handed helical aggregates. They discovered that the presence of a small amount of residual aggregates within the solution induces a drastic change in the assembly process and leads to the formation of right-handed helical aggregates instead.

The team found that when the scissor-shaped azobenzene molecule is dissolved in an organic solvent at room temperature, it forms a closed scissor-like folded structure that further extends into a helical assembly. This is due to the chirality of the molecule, which causes it to fold like left-handed scissors and twist to form a left-handed helical stacking of the assembly.

The molecules are photoresponsive, meaning they can change their structure in response to light. When exposed to weak ultraviolet (UV) light, the helical assembly disassembles back into individual molecules, and upon subsequent exposure to visible light, the molecules reassemble into helical structures again.

Interestingly, under certain conditions, the resulting helical aggregates were found to be right-handed instead of left-handed, and exposure to stronger UV light followed by visible light led to the regeneration of the original left-handed helical aggregates. The team attributed this phenomenon to “secondary nucleation,” which explains why meta-stable right-handed aggregates are preferably formed instead of left-handed aggregates.

The researchers also discovered that the intensity of visible light affects the timing of the assembly, with strong visible light promoting rapid assembly while minimizing the influence of residual aggregates. By optimizing the intensities of UV and visible light, the team successfully controlled the switching between left- and right-handed helical structures which were dependent on the influence of residual aggregates.

Furthermore, it was found that the stable left-handed aggregates and meta-stable right-handed aggregates also exhibit opposite electron spin polarization, signifying the tuning of electronic characteristics of the helices. This study aims to explore the critical role of residual aggregates and explained how light-enabled fine-tuning can result in the fabrication of novel functional materials, giving promising insights into the field of material science.

Chemistry

Scientists Stunned by Record-Breaking, Watermelon-Shaped Nucleus: Breakthrough Discovery in Nuclear Physics

Scientists in Finland have measured the heaviest known nucleus to undergo proton emission, discovering the rare isotope 188-astatine. It exhibits a unique shape and may reveal a new kind of nuclear interaction.

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Scientists have made a groundbreaking discovery in nuclear physics, measuring the heaviest nucleus ever recorded to decay via proton emission. This achievement marks the first time such a feat has been accomplished in over 30 years, with the previous record set in 1996.

The research team from the University of Jyväskylä, Finland, successfully produced and measured the lightest known isotope of astatine, 188At, consisting of 85 protons and 103 neutrons. This exotic nucleus was created through a complex process involving a fusion-evaporation reaction and identified using a sophisticated detector setup.

“The properties of this nucleus reveal a trend change in the binding energy of the valence proton,” explains Doctoral Researcher Henna Kokkonen, who led the study. “This could be explained by an interaction unprecedented in heavy nuclei.”

The research team’s findings have significant implications for our understanding of atomic nuclei and their behavior. By expanding a theoretical model to interpret the measured data, scientists can now better comprehend the intricate mechanisms governing these complex systems.

Kokkonen notes that studying such exotic nuclei is extremely challenging due to their short lifetimes and low production cross sections. However, precise techniques like those employed in this study have made it possible to unlock new insights into the fundamental nature of matter.

The research article was published in Nature Communications as part of an international collaboration involving experts in theoretical nuclear physics. This breakthrough discovery not only pushes the boundaries of human knowledge but also has far-reaching implications for our understanding of the universe and its mysteries.

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Chemistry

Tiny Gold “Super Atoms” Could Spark a Quantum Revolution

Scientists have found that microscopic gold clusters can act like the world’s most accurate quantum systems, while being far easier to scale up. With tunable spin properties and mass production potential, they could transform quantum computing and sensing.

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As researchers from Penn State and Colorado State have demonstrated, tiny gold “super atoms” could revolutionize the field of quantum computing. These clusters, which have a core of gold surrounded by other molecules called ligands, can mimic the properties of trapped atomic ions in a gas, allowing scientists to take advantage of these spin properties in a system that can be easily scaled up.

The researchers found that gold clusters can exhibit spin polarization, a property that is usually fixed in a material. This means that electrons in the cluster can be aligned with each other, making it possible to maintain their correlation for a longer time and remain accurate for much longer periods. The current state-of-the-art system for high accuracy and low error in quantum information systems involve trapped atomic ions — atoms with an electric charge — in a gaseous state.

The gold clusters, which can be synthesized relatively large amounts at one time, have the key properties needed to carry out spin-based operations. They can mimic the super-positions that are done in the trapped, gas-phase dilute ions, and have been identified as having 19 distinguishable and unique Rydberg-like spin-polarized states.

The researchers determined the spin polarization of the gold clusters using a similar method used with traditional atoms. While one type of gold cluster had 7% spin polarization, a cluster with different ligands approached 40% spin polarization, which is competitive with some of the leading two-dimensional quantum materials.

This research has opened up new possibilities for chemists to use their synthesis skills to design materials with tunable results, and could lead to breakthroughs in quantum computing and other fields. The researchers plan to explore how different structures within the ligands impact spin polarization and how they could be manipulated to fine tune spin properties.

In conclusion, tiny gold “super atoms” have the potential to revolutionize the field of quantum computing and could lead to breakthroughs in various fields.

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Chemistry

From Lead to Gold in a Fraction of a Second at the Large Hadron Collider

At the Large Hadron Collider, scientists from the University of Kansas achieved a fleeting form of modern-day alchemy — turning lead into gold for just a fraction of a second. Using ultra-peripheral collisions, where ions nearly miss but interact through powerful photon exchanges, they managed to knock protons out of nuclei, creating new, short-lived elements. This breakthrough not only grabbed global attention but could help design safer, more advanced particle accelerators of the future.

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The Large Hadron Collider (LHC), a 17-mile particle accelerator buried under the French-Swiss border, has achieved the centuries-old dream of alchemists: transforming lead into gold. However, this accomplishment was not without its limitations – it happened within a fraction of a second. The scientists reported their results in Physical Reviews.

The achievement was made possible by the sophisticated and sensitive detector called ALICE, which is roughly the size of a McMansion. It was scientists from the University of Kansas, working on the ALICE experiment, who developed the technique that tracked “ultra-peripheral” collisions between protons and ions that resulted in gold creation at the LHC.

According to Daniel Tapia Takaki, professor of physics and leader of KU’s group at ALICE, these ultra-peripheral collisions involve near misses between particles. The ions racing around the LHC tunnel are heavy nuclei with many protons, each generating powerful electric fields. When accelerated, these charged ions emit photons – they shine light.

“When you accelerate an electric charge to near light speeds, it starts shining,” Tapia Takaki said. “One ion can shine light that essentially takes a picture of the other. When that light is energetic enough, it can probe deep inside the other nucleus, like a high-energy flashbulb.”

During these ultra-peripheral collisions, surprising interactions can occur, including the creation of gold through photon-photon collisions. These events are incredibly clean, with almost nothing else produced. They contrast with typical collisions where sprays of particles flying everywhere.

However, the ALICE detector and the LHC were designed to collect data on head-on collisions that result in messy sprays of particles. These clean interactions were hard to detect with earlier setups.

Tapia Takaki’s KU co-authors on the paper are graduate student Anna Binoy; graduate student Amrit Gautam; postdoctoral researcher Tommaso Isidori; postdoctoral research assistant Anisa Khatun; and research scientist Nicola Minafra. The KU team at the LHC ALICE experiment plans to continue studying the ultra-peripheral collisions.

Tapia Takaki said that while the creation of gold fascinated the public, the potential of understanding the interactions goes deeper. This light is so energetic, it can knock protons out of the nucleus, sometimes one, sometimes two, three or even four protons. We can see these ejected protons directly with our detectors.

Each proton removed changes the elements: One gives thallium, two gives mercury, three gives gold. These new nuclei are very short-lived, they decay quickly, but not always immediately. Sometimes they travel along the beamline and hit parts of the collider – triggering safety systems.

That’s why this research matters beyond the headlines. With proposals for future colliders even larger than the LHC – some up to 100 kilometers in Europe and China – you need to understand these nuclear byproducts. This ‘alchemy’ may be crucial for designing the next generation of machines.

This work was supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics.

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