Zurich, Switzerland – IBM scientists have imaged the ‘anatomy’ of a molecule with greater resolution than ever before.
The scientists used an atomic force microscope (AFM) operated in an ultrahigh vacuum and at very low temperatures ( -268oC or – 451oF) to image the chemical structure of individual pentacene molecules.
For the first time ever, it was possible to look through the electron cloud and see the atomic backbone of an individual molecule. Here’s a video of the process:
“Though not an exact comparison, if you think about how a doctor uses an x-ray to image bones and organs inside the human body, we are using the atomic force microscope to image the atomic structures that are the backbones of individual molecules,” said IBM researcher Gerhard Meyer. “Scanning probe techniques offer amazing potential for prototyping complex functional structures and for tailoring and studying their electronic and chemical properties on the atomic scale.”
The AFM uses a sharp metal tip to measure the tiny forces between the tip and the sample, such as a molecule, to create an image. In this case, the molecule investigated was pentacene.
Pentacene is an oblong organic molecule consisting of 22 carbon atoms and 14 hydrogen atoms measuring 1.4 nanometers in length. The spacing between neighboring carbon atoms is only 0.14 nanometers. In the experimental image, the hexagonal shapes of the five carbon rings as well as the carbon atoms in the molecule are clearly resolved. Even the positions of the hydrogen atoms of the molecule can be deduced from the image.
“The key to achieving atomic resolution was an atomically sharp and defined tip apex as well as the very high stability of the system,” said IBM scientist Leo Gross.
The scientists were also able to derive a complete three-dimensional force map of the molecule. “To obtain a complete force map the microscope needed to be highly stable, both mechanically and thermally, to ensure that both the tip of the AFM and the molecule remained unaltered during the more than 20 hours of data acquisition,” explained Fabian Mohn.