According to What do Thomas Edison and the 2010 Nobel Prize in Physics winners Konstantin Novoselov and Andre Geim have in common? recent publications From the Rice University Lab james tourit could be graphene. The answer that may have confounded Edison died almost 20 years before physicist P.R. Wallace proposed that such a substance might exist, and almost 80 years before Novoselov and Geim won the Nobel Prize for their isolation and characterization.
Graphene is a transparent, extremely strong material that is as thin as a single atom, making it useful in many modern applications such as semiconductors. A type of graphene called turbostratic graphene can be produced by applying a voltage to a durable carbon-based material and rapidly heating it to 2,000 to 3,000 degrees Celsius.
In modern terminology, the method is called flash Joule heating. But for Edison in 1879, the only method available to him was to light one of his newly patented stable light bulbs. Unlike modern incandescent light bulbs, which rely on tungsten filaments, early versions often used durable carbon-based filaments like Japanese bamboo. Flip the switch and a voltage is applied, rapidly heating the filament and producing light. Or maybe graphene. It depends on the century.
“I was developing a way to mass-produce graphene using readily available and affordable materials,” explains Lucas Eddy, lead author of the paper and a former Rice graduate student in Tour’s lab. “I was looking at everything from an arc welder that was more efficient than anything I’d ever built to a lightning-struck tree that was completely dead-ended.” But then, as a lab colleague said, he had a lightbulb moment. “I was trying to find the smallest and simplest device that could be used for flash Joule heating, and I remembered that early light bulbs often used carbon-based filaments.”
Why Edison’s light bulb? Unlike many other early light bulbs, Edison’s patented design reached a critical temperature of 2,000 degrees Celsius. As a bonus, Edison’s 1879 patent gave Eddy a precise blueprint for replicating his experiments.
Eddie’s first few attempts to procure an Edison-type light bulb failed when the “carbon” filament turned out to be tungsten. “You can’t fool a chemist,” laughs Eddie. “But I finally found a small art store in New York City that sold artisan Edison-style light bulbs.” The artisan-made light bulbs were exactly like Edison’s, right down to the Japanese bamboo filament. The filaments were also close in diameter, with Eddy’s filament only 5 micrometers larger than Edison’s.
Like Edison, Eddy connected his light bulb to a 110-volt DC power source. I turned it on for just 20 seconds. Longer heating times can result in the formation of graphite rather than graphene, he explains.
Modern lenses in the optical microscope, a tool centuries older than Edison, showed that the carbon filament had changed from a dark gray color to a “shiny silver color.” A change may have occurred, but what is it?
To characterize this change, Eddy used Raman spectroscopy, a technique developed in the 1930s. This technology uses lasers to identify materials through their atomic characteristics, similar to reading barcodes. Advances over the past century have made it possible to do so with great precision. Spectroscopy confirmed what Eddie expected. Part of the filament transformed into turbostratic graphene. In his quest to develop a practical light bulb for everyday use, Edison may have created a substance that would quickly become key to the technology-dependent 21st century.
Of course, there’s no way to know what actually happened in Edison’s old experiments. Even if the original light bulb used by Edison was available for analysis, the graphene produced could have turned into graphite during the first 13 hours of testing.
“Replicating what Thomas Edison did using the tools and knowledge we now have is extremely exciting,” said Tour, TT and WF Chao Professor of Chemistry and corresponding author of the paper. “The discovery that he could have produced graphene raises curiosity about what other information is buried in historic experiments. What questions would our scientific ancestors ask if they could join us in our laboratories today? What questions could we answer when we revisited their work through a modern lens?”
This research was supported by the Air Force Office of Scientific Research (FA9550-22-1-0526, JMT), the U.S. Army Corps of Engineers Research and Development Center (W912HZ-21-2-0050 and W912HZ-24-2-0027, JMT), and the Welch Foundation (C-2065-20210327, YH). We are solely responsible for the content of this press release. These are the views of the authors and do not necessarily represent the official views of any funding bodies or institutions.