Nanodiamonds Are a Researcher’s Best Friend

The forge that nature uses to make diamonds lies 100 miles below ground, where heat and pressure are so intense they crystallize carbon.

To make diamonds in his Case Western Reserve University lab, chemical engineer Mohan Sankaran simply needs a thin stream of argon gas, some ethanol and about 7 watts of electricity.

Size is the crucial difference between natural diamonds and the ones Sankaran makes. His diamonds are so small that it would take 50,000 of them to equal the width of a human hair.

This story is not about earrings, engagement rings or tennis bracelets. It’s about nanodiamonds and, more important, how to make them.

Sankaran’s method, which he recently described in the journal Nature Communications, has the potential to help create a new generation of super-tough or super-abrasive materials. It also could aid researchers who are testing nanodiamonds for use in promising new drug and cancer treatments.

“It’s the perfect crystal. It’s one of the hardest materials,” Sankaran said. “We can make them at room temperature.”

The field of nanoscience is all about the impossibly small. To work in it, scientists must employ electron microscopes and advanced engineering techniques to create and test the properties of infinitesimally small pieces of matter composed of a relative handful of atoms.

Within the field, nanodiamonds are important. In addition to being so tough, they are transparent and can conduct electricity. Chemicals and medical compounds attach easily to them.

Dean Ho, a professor of bioengineering at the University of California, Los Angeles, has used nanodiamonds in a variety of medical-research experiments.

Nanodiamonds coated with cancer drugs have dramatically reduced the size of brain tumors in rats, Ho said. They also helped keep the drug targeted on the tumors and away from healthy tissue.

And when nanodiamonds are coated with a dye called gadolinium, the ability of MRI machines to scan internal organs, tendons and other body parts increase by a factor of 10.

“So you can give a patient maybe one-tenth the gadolinium, which is nice, because it’s pretty toxic,” Ho said.

Since diamonds are nothing but carbon, human bodies tolerate them.

Ho said he’s excited about Sankaran’s research primarily because he could set up his own system to create nanodiamonds.

“The diamonds I use are processed in a lab but not made in a lab,” he said. “When they are made in the lab from the beginning, it’s nice to have control of the synthesis process.”

The traditional process to create nanodiamonds uses an intense pressure wave within a controlled explosion.

Heating pure carbon to a temperature of 1,832 degrees works, too, said Ajay Kumar, a Case Western research associate who worked on the project with Sankaran.

The process the two worked on was inspired by a 1990 theory that posed that nanodiamonds could be created with far less force and pressure. The theory was based in part on spectrographic analyses that detected nanodiamonds floating in outer space.

“In space, there are very cold temperatures and low pressures,” Sankaran said.

Kumar said it took about three years of experiments with different gases and compounds to get it right.

The process runs ethanol vapor past an electrode surrounded by argon gas. The reaction splits the carbon from the ethanol molecule and bonds it into spherical diamonds about the same width as DNA.

The material then was subjected to a number of tests to confirm that it did indeed exist. Yoke Khin Yap, director of engineering physics at Michigan Technological University, provided a key confirmation using a spectrographic analysis.

From: http://www.dispatch.com/content/stories/science/2013/12/15/nanodiamonds-are-a-researchers-best-friend.html