21ST CENTURY ALCHEMY

A platform of gold reveals the forces of nature’s invisible glue

Chalmers University of Technology

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Researchers at Chalmers University of Technology, Sweden, have discovered a quick and easy way to study the hidden forces that bind the smallest objects in the universe together. Using gold, salt water and light, they have created a platform on which the forces can be seen through colours. Two thin glass plates hold everything needed to study nature’s invisible glue.

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Credit: Chalmers University of Technology | Mia Halleröd Palmgren

When dust sticks to a surface or a lizard sits on a ceiling, it is due to ‘nature’s invisible glue’. Researchers at Chalmers University of Technology, Sweden, have now discovered a quick and easy way to study the hidden forces that bind the smallest objects in the universe together. Using gold, salt water and light, they have created a platform on which the forces can be seen through colours.  

In the lab at Chalmers, doctoral student Michaela Hošková shows a glass container filled with millions of micrometre-sized gold flakes in a salt solution. Using a pipette, she picks up a drop of the solution and places it on a gold-coated glass plate in an optical microscope. What happens is that the gold flakes in the salt solution are immediately attracted to the substrate but leave nanometre-sized optical spaces between them and the gold substrate. The cavities created in the liquid act as resonators in which light bounces back and forth, displaying colours.  When the microscope’s halogen lamp illuminates the platform and a spectrometer separates the wavelengths, the different colours of light can be identified. On the monitor which is connected to the lab equipment, it is now possible to see many flakes moving and changing to colours like red and green against the golden yellow background. 

Studying ‘nature’s glue’ using light trapped in tiny cavities

“What we are seeing is how fundamental forces in nature interact with each other. Through these tiny cavities, we can now measure and study the forces we call ‘nature’s glue’ – what binds objects together at the smallest scales. We don’t need to intervene in what is happening, we just observe the natural movements of the flakes,” says Michaela Hošková, a doctoral student at the Department of Physics at Chalmers University of Technology and first author of the scientific article in the journal PNAS in which the platform is presented.

Through the light captured in the cavities, the researchers can study the delicate balance between two forces – one pulling the tiny objects towards each other and one holding them apart. The joining force, the Casimir effect, makes the gold flakes connect to each other and the substrate. The second, electrostatic force, arises in the salt solution and prevents the flakes from sticking completely to the substrate. When those two forces balance each other, this is known as a self-assembly process and the result is the cavities that open up new research possibilities.

“Forces at the nanoscale affect how different materials or structures are assembled, but we still do not fully understand all the principles that govern this complex self-assembly. If we fully understood them, we could learn to control self-assembly at the nanoscale. At the same time, we can gain insights into how the same principles govern nature on much larger scales, even how galaxies form,” says Michaela Hošková. 

Gold flakes become floating sensors

The Chalmers researchers’ new platform is a further development of several years of work in Professor Timur Shegai’s research group at the Department of Physics. From the discovery four years ago that a pair of gold flakes creates a self-assembled resonator, researchers have now developed a method to study various fundamental forces.

The researchers believe that the platform, in which the self-assembled gold flakes act as floating sensors, could be useful in many different scientific fields such as physics, chemistry and materials science.

“The method allows us to study the charge of individual particles and the forces acting between them. Other methods for studying these forces often require sophisticated instruments which cannot provide information down to the particle level,” says research leader Timur Shegai. 

Can provide new knowledge on everything from medicines to biosensors

Another way to use the platform, which is important for the development of many technologies, is to gain a better understanding of how individual particles interact in liquids and either remain stable or tend to stick to each other. It can provide new insights into the pathways of medicines through the body, or how to make effective biosensors, or water filters. But it is also important for everyday products that you do not want to clump together, such as cosmetics.

“The fact that the platform allows us to study fundamental forces and material properties shows its potential as a truly promising research platform,” says Timur Shegai.

In the lab, Michaela Hošková opens a box containing a finished sample of the platform. She lifts it with tweezers and shows how easily it can be placed in the microscope. Two thin glass plates hold everything needed to study nature’s invisible glue.

“What I find most exciting is that the measurement itself is so beautiful and easy. The method is simple and fast, based only on the movement of gold flakes and the interaction between light and matter,” says Michaela Hošková, zooming the microscope in on a gold flake, the colours of which immediately reveal the forces at play.

 

How the researchers study ‘nature’s invisible glue’

Gold flakes approximately 10 micrometres in size are placed in a container filled with a salt solution, i.e. water containing free ions. When a drop of the solution is placed on a glass substrate covered with gold, the flakes are naturally attracted to the substrate and nanometre-sized cavities (100-200 nanometres) appear. Self-assembly occurs as a result of a delicate balance between two forces: the Casimir force, a directly measurable quantum effect that causes objects to be attracted to each other, and the electrostatic force that arises between charged surfaces in a salt solution.

When a simple halogen lamp illuminates the tiny cavities, the light inside is captured as if in a trap. This allows the researchers to study the light more closely using an optical microscope connected to a spectrometer. The spectrometer separates the wavelengths of the light so that different colours can be identified. By varying the salinity of the solution and monitoring how the flakes change their distance to the substrate, it is possible to study and measure the fundamental forces at play. To prevent the saline solution with the gold flakes from evaporating, the drop of gold flakes and saline are sealed and then covered with another glass plate.

The platform was developed at Chalmers’ Nanofabrication Laboratory, Myfab Chalmers, and at the Chalmers Materials Analysis Laboratory (CMAL).

 

More about the research

The scientific article Casimir self-assembly: A platform for measuring nanoscale surface interactions in liquids has been published in PNAS (Proceedings of the National Academy of Sciences). It was written by Michaela Hošková, Oleg V. Kotov, Betül Küçüköz and Timur Shegai at the Department of Physics, Chalmers University of Technology, Sweden, and Catherine J. Murphy at the Department of Chemistry, University of Illinois, USA.

The research was funded by the Swedish Research Council, the Knut and Alice Wallenberg Foundation, the Vinnova Centre 2D-Tech and Chalmers University of Technology’s Nano Area of Advance.

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Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2505144122 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Casimir self-assembly: A platform for measuring nanoscale surface interactions in liquids

Video: The platform on which the forces can be seen through colours. [VIDEO] 

On the monitor, which is connected to the lab equipment, it is possible to see many gold flakes moving and changing to colours like red and green against the golden yellow background. The colours reveal the forces at play.

  

The Chalmers researchers’ new platform makes it possible to measure and study the forces that are usually referred to as nature’s invisible glue – what binds objects together at the smallest scales. When light is captured between two gold flakes, the researchers can study the delicate balance between two forces – one pulling the tiny objects towards each other and the other holding them apart. The joining force, the Casimir effect, makes the gold flakes connect to each other.  The second, electrostatic force, arise in the salt solution and prevents the flakes from sticking together completely. When those two forces balance each other, this is known as a self-assembly process, and the result is the cavity that opens up new research possibilities.

Credit

​​​​​​​Illustration: Chalmers University of Technoogy | Michaela Hošková

A platform of gold reveals the forces in nature’s invisible glue. Researchers at Chalmers University of Technology, Sweden, have discovered a quick and easy way to study the hidden forces that bind the smallest objects in the universe together. Using gold, salt water and light, they have created a platform on which the forces can be seen through colours.

When light is captured between micrometre-sized gold flakes in a salt solution, it is possible to study the delicate balance between two forces – one pulling the tiny objects towards each other and the other holding them apart. The joining force, the Casimir effect, makes the gold flakes connect to each other. The second, electrostatic force, arises the salt solution and prevents the flakes from sticking together completely. When those two forces balance each other, this is known as a self-assembly process and the result is the cavity that opens up new research possibilities.

In the lab at Chalmers, doctoral student Michaela Hošková shows a glass container filled with millions of micrometre-sized gold flakes in a salt solution. Using a pipette, she picks up a drop of the solution and places it on a gold-coated glass plate in an optical microscope. What happens is that the gold flakes in the salty solution are immediately attracted to the substrate but leave nanometre-sized optical spaces between them and the gold platform. The cavities created in the liquid act as resonators in which light bounces back and forth, displaying colours.  When the microscope’s halogen lamp illuminates the platform and a spectrometer separates the wavelengths, the different colours of light can be identified. On the monitor, which is connected to the lab equipment, it is now possible to see many flakes moving and changing to colours like red and green against the golden yellow background. The colours reveal the forces at play.

Credit

Chalmers University of Technology | Mia Halleröd Palmgren

21ST CENTURY ALCHEMY

Nanoparticles supercharge vinegar’s old-fashioned wound healing power

The University of Bergen

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Vinegar and cobalt-containing nanoparticles - animation

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Credit: QIMR Berghofer

Wounds that do not heal are often caused by bacterial infections and are particularly dangerous for the elderly and people with diabetes, cancer and other conditions.

Acetic acid (more commonly known as vinegar) has been used for centuries as a disinfectant, but it is only effective against a small number of bacteria, and it does not kill the most dangerous types.

New research led by researchers at University of Bergen in Norway, QIMR Berghofer and Flinders University in Australia has resulted in the ability to boost the natural bacterial killing qualities of vinegar by adding antimicrobial nanoparticles made from carbon and cobalt. The findings have been published in the international journal ACS Nano.

Molecular biologists Dr Adam Truskewycz and Professor Nils Halberg found these particles could kill several dangerous bacterial species, and their activity was enhanced when added to a weak vinegar solution.

As part of the study, Dr Truskewycz and Professor Halberg added cobalt-containing carbon quantum dot nanoparticles to weak acetic acid (vinegar) to create a potent antimicrobial treatment. They used this mixture against several pathogenic species, including the drug resistant Staphylococcus aureus, Escherichia coli (E. coli) and Enterococcus faecalis. 

Dr Truskewycz said the acidic environment from the vinegar made bacterial cells swell and take up the nanoparticle treatment.

"Once exposed, the nanoparticles appear to attack dangerous bacteria from both inside the bacterial cell and also on its surface, causing them to burst. Importantly, this approach is non-toxic to human cells and was shown to remove bacterial infections from mice wounds without affecting healing," he said.

The anti-bacterial boost in vinegar found in the study could potentially be an important contribution towards the ongoing battle against the rising antimicrobial resistance levels worldwide, with an estimated 4.5 million deaths associated with a direct infectious disease.

Professor Halberg said this study showed how nanoparticles could be used to increase the effectiveness of traditional bacterial treatments.

“Combination treatments such as the ones highlighted in this study may help to curb antimicrobial resistance. Given this issue can kill up to 5 million people each year, it’s vital we look to find new ways of killing pathogens like viruses, bacteria and fungi or parasites,” he said.

Link to the study: https://pubs.acs.org/doi/10.1021/acsnano.5c03108

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Journal

ACS Nano

21st  CENTURY ALCHEMY

Revolutionary ‘Breathing’ Crystal Could Transform the Clean Energy Industry

By Haley Zaremba - Aug 24, 2025

• Scientists in South Korea and Japan created a man-made crystal (SrFe0.5Co0.5O2.5) that absorbs and releases oxygen repeatedly at moderate temperatures without breaking down.
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• The discovery could revolutionize clean energy by advancing solid oxide fuel cells, smart windows, and oxygen-based electronics.
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• Early tests show applications ranging from boosting electric vehicle range to dramatically improving building energy efficiency.

A new man-made crystal that can “breathe” oxygen may be a game changer for energy efficiency and the clean energy transition. The material is made from an oxide of strontium, iron, and cobalt, and when heated in a simple gas environment, the thin film crystal has been observed to release and then reabsorb oxygen, much like a human lung. Moreover, it can repeat the action over and over without breaking down. The potential applications of such a material are vast, and could be instrumental in the clean energy transition.

"It is like giving the crystal lungs and it can inhale and exhale oxygen on command," says Professor Hyoungjeen Jeen. Jeen, a physics professor at  Pusan National University in South Korea, co-authored the study along with Professor Hiromichi Ohta from the Research Institute for Electronic Science at Hokkaido University in Japan. Their remarkable findings of the crystal, which has the formula SrFe0.5Co0.5O2.5, were published in a scientific paper in the journal Nature Communications earlier this month.

It is not unusual for natural substances to bond with and release oxygen, which is a highly reactive element. This is why oxygen is such a critical building block for human and plant life – it’s a relatively low-hanging fruit in evolutionary terms. But replicating such processes in science isn’t always easy. The process frequently degrades materials quickly, or requires extreme temperatures to cause the absorption or release, making such processes inconvenient for any potential commercial application. 

This is what makes this newest breakthrough so exciting – the oxygen absorption and release cycle is sustained without breaking down the crystal at moderate temperatures –  approximately 752 °F (400 °C). “This finding is striking in two ways: only cobalt ions are reduced, and the process leads to the formation of an entirely new but stable crystal structure,” Jeen explained. And, when oxygen is reintroduced, the original crystal structure is restored. 

“This tackles the challenge of operating in harsher conditions involving much higher temperatures for oxygen control, and replaces other materials used in this process that were too fragile to use repeatedly,” reports New Atlas.

Due to these characteristics, these man-made crystals could be extremely useful in technologies such as solid oxide fuel cells, which can be used to produce electricity from hydrogen with minimal emissions if oxygen is controlled. The solid oxide fuel cells could be instrumental in extending the range of electric cars, especially if they are able to operate at relatively low temperatures. 

The ability to control oxygen “also plays a role in thermal transistors—devices that can direct heat like electrical switches—and in smart windows that adjust their heat flow depending on the weather,” according to Phys.org. These smart windows can help to maintain indoor temperatures, greatly enhancing buildings’ energy efficiency. This could have an enormous impact on climate goals – at present, incredibly, buildings consume more energy than transportation and industry combined.The research team has already tested out the application of the crystal in smart windows. “They’ve found out that the material changes transparency based on its oxygen content, with the oxygen-rich version appearing less transparent while the oxygen-depleted version showing increased transparency,” reports Design Boom. The scientific team also foresees potential applications in electronics, including oxygen sensors and gas separation systems. 

"This is a major step towards the realization of smart materials that can adjust themselves in real time," says Professor Ohta. "The potential applications range from clean energy to electronics and even eco-friendly building materials."

For now, however, next steps for the scientific process are to continue to refine the crystals’ composition and processing methods to optimize performance and durability. The team is continuing to test different metal ratios to see if they can improve upon SrFe0.5Co0.5O2.5. 

By Haley Zaremba for Oilprice.com

21ST CENTURY ALCHEMY

Techniques honed by Kansas nuclear physicists helped detect creation of gold in Large Hadron Collider collisions

University of Kansas

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ALICE experiment at CERN's Large Hadron Collider, where KU nuclear physicists helped detect gold, briefly, during ultra-peripheral collisions. 

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Credit: CERN

LAWRENCE — Nuclear physicists working at the Large Hadron Collider recently made headlines by achieving the centuries-old dream of alchemists (and nightmare of precious-metals investors): They transformed lead into gold.

At least for a fraction of a second. The scientists reported their results in Physical Reviews.

The accomplishment at the Large Hadron Collider, the 17-mile particle accelerator buried under the French-Swiss border, happened within a sophisticated and sensitive detector called ALICE, a scientific instrument 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 made gold in the LHC.

“Usually in collider experiments, we make the particles crash into each other to produce lots of debris,” said Daniel Tapia Takaki, professor of physics and leader of KU’s group at ALICE. “But in ultra-peripheral collisions, we’re interested in what happens when the particles don’t hit each other. These are near misses. The ions pass close enough to interact — but without touching. There’s no physical overlap.”

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.”

The KU researcher said during these UPC “flashes” surprising interactions can occur, including the rate event that sparked worldwide attention.

“Sometimes, the photons from both ions interact with each other — what we call photon-photon collisions,” he said. “These events are incredibly clean, with almost nothing else produced. They contrast with typical collisions where we see 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 said. “Our group at KU pioneered new techniques to study them. We built up this expertise years ago when it was not a popular subject.”

These methods allowed for the news-making discovery that the LHC team transmuted lead into gold momentarily via ultra-peripheral collisions where lead ions lose three protons (turning the speck of lead into a gold speck) for a fraction of a second.

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,” he said. “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,” he said. “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,” Tapia Takaki said. “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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DOI

10.1103/PhysRevC.111.054906