For most of human history, diamonds were extraordinarily rare, and there was no way to artificially produce them. Scientists have learned to make diamonds in laboratories, but the process had numerous drawbacks. Researchers from Stanford University and SLAC National Accelerator Laboratory have been working on a new technique. According to a new study, the team has succeeded in producing pure diamonds using a trace material found in fossil fuel deposits.
Diamonds have always been prized for their appearance, but their unique combination of optical clarity and hardness means they’re also useful today in medicine, biological sensing, manufacturing, and even quantum computing. Natural diamonds form deep in the Earth’s crust, where temperatures and pressure squeeze carbon into a diamond lattice. Recreating that in the lab has always required a great deal of energy, time, or the addition of a metal catalyst that leaves impurities in the final product.
Scientists have long studied a class of molecules called diamondoids to better understand the properties of diamonds. Diamondoids occur naturally in fossil fuel deposits like crude oil and natural gas and consist of carbon and hydrogen. When isolated, diamondoids look like a fine, white powder, but on the molecular level, they contain the smallest “cage” unit structure of the diamond crystal lattice. The researchers collected three different forms of diamondoid to test.
Diamondoid structures. Triamantane is a three-cage molecule.
Fittingly, you need diamonds to make diamonds from diamondoids. The team loaded the samples into a diamond anvil cell, which can subject small objects to incredible pressure. Next, they heated the compressed samples with a laser. Under these conditions, the carbon bonds reorient into the standard diamond lattice, and the hydrogen atoms fall away. A three-cage diamondoid called triamantane turned out to be the best at forming diamonds. It took 20 gigapascals of pressure and a temperature of 1,160 degrees Fahrenheit (626 degrees Celsius) to transform triamantane powder into a pure diamond.
This process is faster and cheaper than other methods of producing diamonds, but it has one major drawback: scale. A diamond anvil cell can only compress very small samples, so you can only make microscopic diamonds from diamondoids — at least for now. This process could help scientists better understand what it takes to make a diamond and improve the way they’re produced in the lab.
Top image credit: Andrew Brodhead/Stanford University
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