Microscopy is advancing in leaps and bounds these days. It was just last week that scientists produced the first image of a hydrogen atom’s orbital structure. Not to be outdone, Berkeley chemists have now captured a series of images showing molecules as they break and reform their chemical bonds. It looks almost... textbook.
It's always incredible when scientists present actual, tangible visual evidence to reaffirm theoretical models. As any chemistry student knows, molecular bonds, or covalent bond structures, are typically represented in science class with a stick-like nomenclature. But as the work of Felix Fischer, Dimas de Oteyza and their Berkeley Lab colleagues beautifully demonstrates, these models are startlingly accurate.
And like so many good scientific discoveries, it all happened somewhat by accident.
The Berkeley scientists were actually working on a way to precisely assemble nanostructures made from graphene using a new cutting-edge approach to chemical reactions. They were trying to build a single-layer material in which carbon atoms are arranged in repeating, hexagonal patterns — but they needed to take a closer look to see what was happening at the single-atom level. So, they pulled out a powerful atomic force microscope — and what they saw was “amazing,” to quote Fischer.
In this image you can see the positions of individual atoms and bonds in a molecule having 26 carbon atoms and 14 hydrogen atoms structured as three connected benzene rings.
Specifically, they managed to capture the specific outcomes of the reactions themselves — a totally unexpected and happy consequence of the research.
“Nobody has ever taken direct, single-bond-resolved images of individual molecules, right before and immediately after a complex organic reaction,” Fischer noted through a release.
To create the image, the researchers used the fine tip of the non-contact atomic force microscope to “feel” or read the electrical forces produced by the molecules. Each time the tip moved near a molecule’s surface, it was deflected by the different charges. The resulting movements of the stylus were detected by a laser beam, which in turn provided the data required to produce an image of how the atoms and bonds were aligned. What’s more, they were also able to visualize the bonds between them.
Taking a look at the top image, you can see the original molecule at left before the reaction takes place. At right, the two most common final products of the reaction are shown. The clumps are about a billionth of a meter across (3 angstroms).
You can read the entire study at the journal Science: “Direct Imaging of Covalent Bond Structure in Single-Molecule Chemical Reactions.”
Images: Berkeley Labs.