It may look like a piece of honeycomb, but this lattice-shaped image is the first ever close-up view of a single molecule. Scientists from IBM used an atomic force microscope (AFM) to reveal the chemical bonds within a molecule. ‘This is the first time that all the atoms in a molecule have been imaged,’ lead researcher Leo Gross said.
The researchers focused on a single molecule of pentacene, which is commonly used in solar cells. The rectangular-shaped organic molecule is made up of 22 carbon atoms and 14 hydrogen atoms. In the image above the hexagonal shapes of the five carbon rings are clear and even the positions of the hydrogen atoms around the carbon rings can be seen. To give some perspective, the space between the carbon rings is only 0.14 nanometers across, which is roughly one million times smaller than the diameter of a grain of sand.
‘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.
The team from IBM Research Zurich said the results could have a huge impact of the field of nanotechnology, which seeks to understand and control some of the smallest objects known to mankind. The AFM uses a sharp metal tip that acts like a tuning fork to measure the tiny forces between the tip and the molecule. This requires great precision as the tip moves within a nanometer of the sample. ‘Above the skeleton of the molecular backbone (of the pentacene) you get a different detuning than above the surface the molecule is lying on,’ Mr Gross said. This detuning is then measured and converted into an image. To stop the tip from absorbing the pentacene molecule, the researchers replaced the metal with a single molecule of carbon monoxide. This was found to be more stable and created weaker electrostatic attractions with the pentacene, creating a higher resolution image.
The experiment was also performed inside a high vacuum at the extremely cold temperature of -268C to avoid stray gas molecules or atomic vibrations from affecting the measurements. ‘Eventually we want to investigate using molecules for molecular electronics,’ Mr Gross said. 'We want to use molecules as wires or logic switches or elements.