Atoms are known for forming bonds and breaking apart, a process that’s crucial to basically everything in the universe. But because it happens on such a tiny scale, it’s difficult to study and record. Now, researchers from the Universities of Nottingham and Ulm have managed to capture atoms forming and breaking bonds on video for the first time.
The team used transmission electron microscopy (TEM) to image a pair of rhenium atoms, as they “walked” hand in hand along a carbon nanotube. With a quadruple bond between them, the two atoms form a molecule of Re2.
“It was surprisingly clear how the two atoms move in pairs, clearly indicating a bond between them,” says Kecheng Cao, an author of the study. “Importantly, as Re2 moves down the nanotube, the bond length changes, indicating that the bond becomes stronger or weaker depending on the environment around the atoms.”
The researchers then saw the atoms move apart, stretching themselves into more of an elliptical shape, straining and eventually breaking the bond. And finally, after a while they combined once again into an Re2 molecule.
“To our knowledge, this is the first time when bond evolution, breaking and formation was recorded on film at the atomic scale,” says Andrei Khlobystov, an author of the study. “We are now pushing the frontiers of molecule imaging beyond simple structural analysis, and towards understanding dynamics of individual molecules in real time.”
Of course, imaging this stuff is made tricky by just how small it all is – the chemical bond between two atoms measures just 0.1 to 0.3 nanometers long, or about 500,000 times smaller than the width of a human hair. With plenty of mysteries still lurking down on the atomic scale, this new technique could help provide some answers.
The research was published in the journal Science Advances. Check out the atoms bonding and unbonding in the video below.
Source: University of Nottingham
I'm curious about the effect of the electron beam on this kind of analysis. This is almost certainly a 200kV microscope. One would think that the energy of the incoming beam would have a huge effect on the sample. That is most likely the reason the pair of atoms is moving around.
I did analysis of small Pt particles on carbon nanotubes using a 30kV STEM. It sounds paradoxical but the lower energy beam probably affected the sample more than in their work. I could analyze particles down to about 3nm in diameter. Below that the energy of the incoming electrons caused the particles to move about making them impossible to be analyzed. (I was doing x-ray spectroscopy of small particles at the time.) A roughly 3nm particle of Pt probably contains something like 600 or so atoms.
I never got a chance to try it but it was suggested to me that I try working with large molecules that contained a heavy metal atom. The large molecule would hold the atom and prevent it from moving about as in the video. Maybe they could try something like that with a pair of Re atoms trapped in a molecular cage of some sort.