Materials research is elementary

An Ohio State University chemist and his colleagues are taking new, high-tech materials for a spin inside a nuclear magnetic resonance (NMR) instrument.

The American, French And Danish researchers recently discovered that they can quickly obtain more precise data about a material’s atomic structure if they spin the material at just the right speed inside the NMR instrument.

Philip Grandinetti, associate professor of chemistry at Ohio State, and his research partners have named their new technique FASTER, short for ‘FAst Spinning gives Transfer Enhancement at Rotary resonance.’

FASTER is said to eliminate the signal interference that plagues traditional techniques for studying materials using NMR.

The chemists recently reported that spinning samples at speeds of up to 30,000 cycles per second can, in many cases, boost the signal strength of the NMR measurements more than ten times over.

‘This is a big advance for people who want to study the atomic level structure of almost any solid material — ceramics, plastics, glasses, or catalysts,’ said Grandinetti. ‘Even for peptides, proteins, or DNA, FASTER could shorten the time necessary for studying a substance from weeks to mere hours.’

Grandinetti explained that NMR works by tuning into the radio waves emitted by atoms within materials.

Grandinetti likened the interference that confounds NMR signals to interference between stations on an FM radio. When a station is far away, music from other stations can drown it out.

In the case of atoms and molecules, the radio information that is lost concerns the environment of the atoms because each atom emits radio waves at a particular frequency, depending on the type of atoms that surround them.

‘The problem is, when we tune in our NMR ‘radios,’ we receive a lot of static,’ Grandinetti said. ‘We try our best to reduce the noise, but these tiny signals from atomic nuclei are weak to begin with, so it’s a battle to get a good signal.’

The idea of spinning materials in an NMR instrument to improve the signal isn’t new. The original technique, magic-angle spinning (MAS) spins materials at a certain angle with respect to the NMR’s magnetic field but it doesn’t work for 70 percent of known elements.

For these elements the rules of quantum mechanics prevent certain nuclear transitions from taking place, and it is those transitions that would reveal a clearer NMR signal.

Typically, researchers must average the test results for these elements over several weeks to reduce the noise. They also must employ expensive high-power amplifiers to boost the magnetic field.

Performing their experiments on commercially available equipment, Grandinetti and his partners used FASTER to produce the same results in a matter of hours without having to use a high-power amplifier.

Any NMR machine with an MAS probe can use FASTER, said Grandinetti. High-power, one-kilowatt amplifiers typically cost about $20,000, but FASTER requires an investment of only a few thousand dollars for a low-power amplifier.

Grandinetti plans to apply this advance to several different projects; one involves a study of the geochemistry under nuclear waste storage tanks at the US Department of Energy site in Hanford, Washington. Millions of gallons of radioactive waste from decades of nuclear weapons production are stored at the site, in tanks that are now leaking into the ground.