Track Molecular Fingerprints with Spectroscopy - dummies

Track Molecular Fingerprints with Spectroscopy

By Earl Boysen, Nancy C. Muir, Desiree Dudley, Christine Peterson

When nanotechnology researchers build a new nanomaterial, they want to verify its structure. Microscopes such as SEMs and AFMs can give them visual information about the structure of the new material, but other techniques can easily provide additional information, such as what types of atoms are bonded to each other in the material and how many electrons are shared among these atoms.

It turns out that molecules, and portions of molecules (the pairs of atoms that bond together to form molecules), have fingerprints, just as people do. However, their fingerprints consist not of little swirls in the skin but of the wavelength of the light that atoms and molecules absorb.

The wavelengths of light absorbed by various atoms and molecules produce a spectrum. Generating a spectrum to determine the structure of molecules is called spectroscopy.

For example, the simplified spectrum labeled A shows that carbon nanotubes absorb infrared light at a wavelength of 6452 nm and 8403 nm. The spectrum labeled B has all the absorption points shown in spectrum A, plus a peak at 5838 nm, which indicates the bonding of oxygen to some of the carbon atoms in the nanotube.

Therefore, if researchers take an infrared spectrum of an unknown material and see the peaks shown in spectrum B, they know that the material consists of carbon nanotubes functionalized by adding oxygen atoms.

The spectrum of carbon nanotubes with and without oxygen bonded to them.
The spectrum of carbon nanotubes with and without oxygen bonded to them.