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    Mind the band gap! — researchers create new nanoscale forms of elementary semiconductor with tunable electronic properties

    Researchers have demonstrated that by using a semiconductor with flexible bonds, the material can be moulded into various structures using nano containers, without altering its composition, the discovery could lead to the design of a variety of customised electronic devices using only a single element.
    Semiconductors are vital to our daily lives, as they are found in nearly every electronic device. One of the key characteristics of semiconductors is their band gap, which determines how they conduct electric current. The band gap is typically engineered for specific applications by breaking chemical bonds or introducing additional elements into the material. However, these processes can be complex and energy-intensive.
    Researchers from the University of Nottingham, the EPSRC SuperSTEM facility, Ulm University in Germany, and BNNT LLC in the USA imaged new forms of selenium using transmission electron microscopy, employing nanotubes as tiny test tubes. The study has been published today in Advanced Materials.
    Dr Will Cull, research fellow in School of Chemistry, Univesity of Nottingham, who carried out the experimental work, said, ‘Selenium is an old semiconductor with a rich history, having been used in the first solar cells. In our research, we have revitalised selenium by discovering new forms that can emerge when confined to the nanoscale.’
    Selenium can exist as nanowires, with its structure and bonding varying by diameter. Below a certain size, the bonding between selenium atoms changes, increasing bond angles. This causes straightening of the initially helical structure, ultimately constricting it into atomically thin wires.
    Dr Will Cull said, ‘We successfully imaged new forms of selenium using transmission electron microscopy, employing nanotubes as tiny test tubes. This approach allowed us to create a new phase diagram that connects the atomic structure of selenium to the diameter of the nanowires.’
    The Nottingham group previously reported using nano test tubes to image chemical reactions of individual molecules and to observe phase transitions in semiconductors. This approach enables real-time filming of chemistry at the atomic level.

    Dr Will Cull said, ‘To our astonishment, we observed that the nano test tube became thinner as we imaged it! Before our very eyes, we witnessed the selenium nanowire inside the nanotube being squeezed like toothpaste, stretching and thinning. This serendipitous discovery allowed us to establish mechanisms for the transformation of one type of nanowire to another, which have implications for their electronic properties, with near-atomic precision.’
    The band gap is a crucial property of semiconductors that significantly impacts their use in various devices, including solar cells, transistors, and photocatalysts. Professor Quentin Ramasse, director of EPSRC SuperSTEM, said, ‘By utilising atomically resolved scanning transmission electron microscopy coupled with electron energy loss spectroscopy, we were able to measure the band gaps of individual chains of selenium. These measurements enabled us to establish a relationship between the diameter of these nanowires and their corresponding band gaps.’
    Professor Quentin Ramasse said, ‘Traditionally, carbon nanotubes have been used as nano test tubes; however, their outstanding energy absorption properties can obscure the electronic transitions of the material inside. In contrast, a newer type of nano test tube, boron nitride nanotubes, is transparent, allowing us to observe the band gap transitions in selenium nanowires contained within them.’
    The famous Moore’s Law states that the number of transistors on an integrated circuit doubles approximately every two years. As a result, electronic components must become smaller. Professor Andrei Khlobystov, School of Chemistry, University of Nottingham, said, ‘We have investigated the ultimate limit for nanowire size while preserving useful electronic properties. This is possible for selenium because the phenomenon of quantum confinement can be effectively balanced by distortions in the atomic structure, thus allowing the band gap to remain within a useful range.’
    The researchers hope that these new materials will be incorporated into electronic devices in the future. Accurately tuning the band gap of selenium by changing the diameter of the nanowire could lead to the design of a variety of customised electronic devices using only a single element. More

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    A new AI-based weather tool surpasses current forecasts

    Weather forecasting is getting cheaper and more accurate. An AI model named Aurora used machine learning to outperform current weather prediction systems, researchers report May 21 in Nature.

    Aurora could accurately predict tropical cyclone paths, air pollution and ocean waves, as well as global weather at the scale of towns or cities — offering up forecasts in a matter of seconds.

    The fact that Aurora can make such high-resolution predictions using machine learning impressed Peter Dueben, who heads the Earth system modeling group at the European Centre for Medium-Range Weather Forecasts in Bonn, Germany. “I think they have been the first to push that limit,” he says. More

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    New color-changing sensor detects alcohol with a smartphone snap

    Determining how strong your drink is doesn’t need to be either guesswork or lab work. New research has made it as simple as checking your messages — and more colorful, too.
    Osaka Metropolitan University researchers have developed a smartphone-compatible alcohol sensor that can visually detect a full range of ethanol concentrations, without the need for complex electronics or lab tools. Their technology allows for a broad array of potential applications in environmental monitoring, healthcare, industrial processes, and alcohol breath analysis.
    Ethanol is used widely in food, pharmaceuticals, and fuel. It is also the intoxicating ingredient in many alcoholic beverages. Accurate detection of ethanol concentration, particularly in products containing both ethanol and water, is crucial for product hygiene management and quality maintenance.
    “Conventional sensors typically require power sources and complex electronics, limiting their accessibility for everyday use,” said Kenji Okada, an associate professor at Osaka Metropolitan University’s Graduate School of Engineering and lead author of this study.
    Seeking both selectivity and practicality, the team fabricated a portable and highly sensitive ethanol sensor built from a copper-based metal-organic framework (MOF) thin film called Cu-MOF-74.
    These MOFs contain nanometer-sized pores that absorb ethanol molecules and respond with a visible color change — a phenomenon known as solvato/vapochromism. Thanks to its low light-scattering properties and high transparency, the Cu-MOF-74 film enables precise optical measurements without the need for complex lab equipment.
    “Our sensor changes color in response to varying ethanol levels across the full concentration range, even at low concentrations,” Okada said.

    What truly sets this technology apart is its integration with a smartphone app. Users can simply snap a photo of the film to measure ethanol concentration, making it a portable and accessible tool for use in the field, factories, or healthcare settings.
    The researchers’ findings offer a smarter, simpler, and more reliable approach to alcohol sensing. From the quality of your drink to the potential future of portable breath tests, this new sensor technology brings us a colorful step closer to real-time alcohol monitoring in everyday life.
    “We hope our study could open up a wide range of applications, from the food and beverage industry to environmental monitoring, industrial exhaust gas detection and alcohol breath analysis,” Okada said.
    The study was published in Small Science. More

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    The unsung women of quantum physics get their due

    Senior physics writer Emily Conover has a Ph.D. in physics from the University of Chicago. She is a two-time winner of the D.C. Science Writers’ Association Newsbrief award and a winner of the Acoustical Society of America’s Science Communication Award. More

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    As quantum mechanics turns 100, a new revolution is under way

    Senior physics writer Emily Conover has a Ph.D. in physics from the University of Chicago. She is a two-time winner of the D.C. Science Writers’ Association Newsbrief award and a winner of the Acoustical Society of America’s Science Communication Award. More

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    New audio tech could let you listen privately without headphones

    Controlling sound has long been a staple of science fiction and fantasy. In Dune, the cone of silence allows characters to converse privately, even in open spaces. The eerie billboards of Blade Runner 2049 whisper advertisements into the ears of those passing by.

    In the real world, quirks of architecture, intentional or not, can direct where sound goes. In the U.S. Capitol’s hall of statues, for example, a whisper can travel silently across the room from one spot to another. The sound waves interact with curved surfaces to focus the audio. Now, scientists are looking to precisely control sound, perhaps one day resulting in a world without earbuds, but directing sound waves is a challenge. More

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    Seafloor amber may hold hints of a tsunami 115 million years ago

    Wavelike patterns in 115-million-year-old amber suggest that a long-ago tsunami inundated what is now northern Japan, researchers report May 15 in Scientific Reports.

    Tsunamis can be destructive and, to anything alive nearby, often terrifying. But the physical damage wrought by these giant waves eventually erodes away, typically leaving behind little evidence of their passage. As a result, there’s scant records of tsunamis stretching back beyond the current geologic epoch, which began roughly 12,000 years ago. More

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    This tool-wielding assassin turns its prey’s defenses into a trap

    Add a little-known species of assassin bugs to the list of animals that can fashion and wield tools. And true to their name, the insects use that tool to draw their prey into an ambush, researchers report May 12 in Proceedings of the National Academy of Sciences.

    Found in Thailand and China, Pahabengkakia piliceps is a species of predatory insects called assassin bugs that has a taste for the region’s stingless bees. When researchers at Xishuangbanna Tropical Botanical Garden in China began studying the assassin bugs in 2021, they became intrigued by how P. piliceps hunt. While lying in wait at a hive’s entrance, the assassin bugs use their front legs to proficiently pick off bees that fly by. More