In a lab in Krakow, Poland, a simple question about how we look at tiny things turned into a discovery that could reshape how scientists build materials at the nanoscale. Physicists at the Institute of Nuclear Physics, Polish Academy of Sciences (IFJ PAN) were watching a chemical reaction between copper oxide nanocubes and chloroauric acid. What they found depends entirely on how you choose to watch.
Here's the puzzle. When the team measured the reaction using a beam of photons (X-rays), the copper cubes seemed to dissolve away, leaving behind hollow, gold-rich nanoboxes — a material with a huge surface area that could make an excellent catalyst. But when they used an electron beam, the exact same reaction behaved differently. The gold simply coated the outside of the copper cubes, and the cubes never disappeared.
Same substances. Same reaction. Different outcome. The culprit turned out to be the beams themselves.
The team was led by Prof. Magdalena Parlinska and Dr. Joanna Depciuch-Czarny. They used two cutting-edge microscope techniques to observe the process. The first, liquid-cell transmission electron microscopy (LC-TEM), sends a beam of electrons through a tiny liquid-filled cell. The second, liquid-cell electrochemical scanning transmission X-ray microscopy (EL-STXM), uses a focused beam of soft X-rays instead. Both allow scientists to watch chemistry happen in real time, something ordinary microscopes can't do with liquids.
The key insight is that both electrons and photons react with water. When either beam hits the liquid, it creates reactive chemical species that change the local environment. The electron beam makes the solution more acidic, which slows the etching of the copper while speeding up the gold deposition. The photon beam does the opposite, allowing the copper to dissolve and the gold to form those hollow boxes.
"It is known that an electron beam creates a locally more acidic environment, which inhibits the oxidation and etching of copper oxide while simultaneously promoting the reduction of gold ions and their deposition," the researchers noted. In contrast, the photon beam doesn't cause the same drop in acidity.
This matters because scientists rely on these microscope techniques to understand how materials form. If the observation tool itself changes the result, then our pictures of the nanoworld may not always show what nature is really doing. It also opens a powerful new tool: by choosing which beam to use, researchers may be able to steer a reaction toward a particular nanoscale shape, building hollow boxes or coated cubes on purpose.
The X-ray experiments used the SOLARIS synchrotron at the Jagiellonian University in Krakow. The findings were published in the journal Small. For anyone working toward better catalysts or new nanomaterials, the lesson is hopeful and humbling: even the way we look can help build a better future.