Last night I was reading a new book which claimed that we’ve never seen atoms or molecules. The point the author was making is that in evolutionary biology you don’t need to actually see evolution happening, you can infer it — just as we can confidently infer the existence of atoms and molecules. The point is correct, but the example is not.
We can actually see atoms and molecules. This morning I awoke to find out that a really spiffy molecule has been visualized using a new type of microscope.
It’s pentacene, with 22 carbons and 14 hydrogens. The molecule consists of five fused benzene rings, and is used, among other things, in solar panels.
IBM researchers in Switzerland imaged the molecule using a sophisticated new technology that includes a single molecule of carbon monoxide as an imaging device.
Fig. 1. Image of pentacene from the atomic force microscope
The AFM [atomic force microscope] 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.
Here’s the conventional molecular representation of pentacene:
Fig. 2. Pentacene as you might have seen it in O-chem
And, as I say in WEIT, we’ve been able to visualize atoms ever since the scanning tunnelling microscope was created in 1981. (Its inventors got a Nobel Prize five years later.)
Here’s a bunch of atoms, looking like little balls:
Fig. 3 : A photograph of about 500 atoms of Niobium (41) and Selenium (34) neatly arranged at the surface of a crystal (darker atoms are simply lying lower in the surface).