Latest news with #JaniKotakoski
Yahoo
05-06-2025
- Science
- Yahoo
Single platinum atoms spotted in 2D lattice for first time unlock smarter gas sensors
Austrian scientists have achieved a breakthrough by embedding individual platinum atoms into an ultrathin material and pinpointing their positions within the lattice with atomic precision for the first time ever. The research team from the University of Vienna and the Vienna University of Technology (TU Wien), utilized a new method that combines defect engineering in the host material, the controlled placement of platinum atoms, and a cutting-edge, high-contrast electron imaging technique known as ptychography. Jani Kotakoski, PhD, an expert in the field of physics in nanostructured materials and research group leader, highlighted that the achievement sets the stage for tailoring materials with atomic precision. Active centers, which are tiny sites on the material's surface where chemical reactions occur or gas molecules can specifically bind, are crucial for enhancing the efficiency, selectivity, and overall performance of materials used in catalysis and gas detection. These centers are especially effective when made up of single metal atoms like platinum, which they aimed not only to produce, but also to visualize with atomic-level precision. Known for its highly tunable structure, the host material molybdenum disulfide (MoS₂) is an ultrathin semiconductor. To introduce new active sites, the scientists used helium ion irradiation to deliberately create atomic-scale defects on its surface, such as sulfur vacancies. These vacancy sites were then selectively filled with individual platinum atoms, allowing the team to engineer the material at the atomic level. This precise atomic substitution, known as doping, enables fine-tuning of the material's properties for specific applications, such as catalysis or gas detection. However, previous studies had not provided direct evidence of the exact positions of foreign atoms within the atomic lattice, as conventional electron microscopy lacks the contrast needed to clearly distinguish between defect types such as single and double sulfur vacancies. In a bid to address the challenge, the team has now used a state-of-the-art imaging method known as Single-Sideband Ptychography (SSB), which analyzes electron diffraction patterns to achieve atomic-level resolution. "With our combination of defect engineering, doping, and ptychography, we were able to visualize even subtle differences in the atomic lattice - and clearly determine whether a platinum atom had been incorporated into a vacancy or merely resting loosely on the surface," David Lamprecht, MSc, a student at the University of Vienna's institute for microelectronics, and lead author of the study, said. With the help of computer simulations, the scientists were able to precisely identify the different incorporation sites, such as positions originally occupied by sulfur or molybdenum atoms, marking a key advance toward targeted material design. The team believes that combining targeted atom placement with atomically precise imaging unlocks new possibilities for advanced catalyst design and highly selective gas sensing. While individual platinum atoms placed at precisely defined sites can serve as highly efficient catalysts, like in eco-friendly hydrogen production, the material can also be tailored to respond selectively to specific gas molecules. "With this level of control over atom placement, we can develop selectively functionalized sensors - a significant improvement over existing methods," Kotakoski concluded in a press release. According to the research team, the approach is not limited to platinum and molybdenum disulfide but can also be applied to a wide range of 2D materials and dopant atom combinations. By gaining more precise control over defect creation and incorporating post-treatment steps, the researchers now hope to further refine the technique. Their final goal is to develop functional materials with customized properties, in which every atom is positioned with absolute precision. The study has been published in the journal Nano Letters.
Yahoo
12-05-2025
- Science
- Yahoo
Groundbreaking accordion effect makes graphene more stretchable by removing atoms
Austrian researchers have unlocked a groundbreaking property of graphene, making it significantly more stretchable by manipulating its structure to ripple like an accordion using a one-of-a-kind method that has never been seen before. The unique technique, pioneered by scientists at the University of Vienna and the Vienna University of Technology, involved the meticulous manipulation of the atomic structure of graphene, a material extracted from graphite and is made up of pure carbon, in an ultra-clean, airless environment. This unique setup ensured that the graphene samples remained free from ambient air and foreign particles, which could interfere with the measurements and distort the results. Jani Kotakoski, PhD, a physics professor at the University of Wien and lead author of the research, believes the discovery opens up exciting new possibilities for the material, enabling its use in applications requiring enhanced flexibility, such as wearable electronics and advanced flexible devices. In 2004, the discovery of graphene by researchers Andre Geim, PhD, and Kostya Novoselov, PhD, from the University of Manchester, revolutionized science, introducing a new class of materials known as two-dimensional (2D) solids. These materials, just a single atom thick, possess unique properties that hold significant promise for various applications, with graphene being particularly celebrated for its exceptional electrical conductivity, flexibility, lightness and high resistance. However, its extreme stiffness, a result of its honeycomb-shaped arrangement of the atoms, has limited its use in many applications. Although removing atoms from its structure might be expected to reduce its stiffness, studies have yielded mixed results, with some research suggesting a slight decrease in rigidity, while others show an increase in stiffness. Now, to address the issue, the research team conducted experiments in an ultra-clean, airless environment, using state-of-the-art equipment to ensure that the graphene samples were completely isolated from external air and contaminants. The controlled setup allowed researchers to carry out precise measurements, eliminating interference from airborne particles that might have affected the accuracy of the results. "This unique system we have developed in the University of Vienna allows us to examine 2D materials without interference," Kotakoski explained. "For the first time this kind of experiment has been carried out with the graphene fully isolated from ambient air and the foreign particles it contains. Without this separation, these particles would quickly settle on the surface affecting the experiment procedure and measurements." According to Kotakoski, the breakthrough came from an intense focus on keeping the graphene surface completely clean during testing. The researchers discovered that removing just two neighboring atoms from the otherwise flat material caused it to bulge slightly. As more of these small bulges formed, they created a corrugated, wave-like structure, which the scientists have called the 'accordion effect.' "You can imagine it like an accordion," Joudi explained in a press release. "When pulled apart, the waved material now gets flattened, which requires much less force than stretching the flat material and therefore it becomes more stretchable." The findings were further backed by computer simulations from theoretical physicists Rika Saskia Windisch, MSc, and Florian Libisch, PhD, at the Vienna University of Technology, which confirmed the formation of these atomic ripples and the resulting increase in flexibility. The experiments also revealed that contamination from foreign particles on the material's surface completely suppresses the accordion effect. In fact, their presence can make the material seem stiffer, providing a likely explanation for conflicting data in earlier studies. "This shows the importance of the measurement environment when dealing with 2D materials," Joudi concluded. "The results open up a way to regulate the stiffness of graphene and thus pave the way for potential applications." The study has been published in the journal Physical Review Letters.
