Researchers Create Short-lived Nanodiamonds in the Lab

Posted on May 23, 2014

Rice University scientists created short-lived nanodiamonds in the lab by hitting hydrogenated coal with an electron beam. The diamonds only last seconds before falling back into less-structured forms of carbon. The dark spots in these images are the nanodiamonds formed in hydrogenated anthracite coal when hit by beams from an electron microscope.

The researchers took close-ups of the coal with an electron microscope, which fires an electron beam at the point of interest. Unexpectedly, the energy input congealed clusters of hydrogenated carbon atoms, some of which took on the lattice-like structure of nanodiamonds.

Rice chemist Ed Billups says in a statement, "The beam is very powerful. To knock hydrogen atoms off of something takes a tremendous amount of energy."

The researchers say the smallest of the nanodiamonds were seen to fade away under the power of the electron beam in a succession of images taken over 30 seconds.

Billups says, "The small diamonds are not stable and they revert to the starting material, the anthracite."

Billups turned to Rice theoretical physicist Boris Yakobson and his colleagues at the Technological Institute for Superhard and Novel Carbon Materials in Moscow to explain what the chemists saw. Yakobson, Pavel Sorokin and Alexander Kvashnin had already come up with a phase diagram that demonstrated how thin diamond films might be made without massive pressure. They used similar calculations to show how nanodiamonds could form in treated anthracite and subbituminous coal. In this case of nanodiamonds, the electron microscope's beam knocks hydrogen atoms loose from carbon layers. Then the dangling bonds compensate by connecting to an adjacent carbon layer, which is prompted to connect to the next layer. The reaction zips the atoms into a matrix characteristic of diamond until pressure forces the process to halt.

The research was published here in the Journal of Physical Chemistry Letters.

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