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Nanotube Research and Discoveries
The true identity of the discoverers of carbon nanotubes, or CNT, is a subject of some controversy. For years, scientists assumed that Sumio Iijima had discovered CNTs in 1991. Sumio Iijima, a Japanese physicist, published a paper describing his discovery. Iijima was a researcher at NEC Corporation when he made his discovery; his research area was in ultrafine particles. Iijima's paper initiated a flurry of excitement, and could be credited with inspiring the many scientists now studying applications of carbon nanotubes.
Though Iijima has been given much of the credit for discovering carbon nanotubes, it turns out that the timeline of CNTs goes back much further than 1991. The confusion over CNTs' discoverers arises from the fact that there are two different types of carbonanotubes: Single-walled (SWCNT) and multi-walled (MWCNT). Iijima's paper, which was published in Nature in 1993, offered the first conclusive proof of SWCNT. SWCNT have various important characteristics and were certainly a monumental discovery. Iijima's 1991 discovery of MWCNTs was also important; however, it turns out that researchers had repeatedly observed multi-walled CNTs for decades, going all the way back to 1952.
In 1952, two obscure Russian scientists gave the world its first clear look at carbon nanotubes. LV Radushkevich and VM Lukyanovich published clear images showing MWCNT with a 50 nm diameter. Unfortunately, their paper was in Russian, published in a Russian journal (Journal of PhysicalChemistry of Russia), and at the height of the Cold War. Because of the aforementioned facts, few (if any) scientists in the West took note of Radushkevich and Lukyanovich's accomplishment. These scientists' work represents the first known TEM (tunneling electron miscroscope) images of carbon nanotubes.
Image: Chiral Nanotube - Wikimedia Commons
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How Were Carbon Nanotubes Discovered?
Although the first pictures of carbon nanotubes date to 1952, it is probable that researchers had created them well before this date. In fact, one patent from 1889 discusses the use of "carbon filaments" produced by the combustion of methane in lightbulbs. These filaments were, in all likelihood, multi-walled carbon nanotubes; however, the technology to view nano-sized objects did not exist at the time.
Iijima's group discovered CNTs in the residue formed by burning graphite rods. In contrast, earlier scientists used a vapor deposition method that made use of a metallic catalyst. One theory for why it took so long for scientists to recognize the potential of CNTs is that the wrong scientists were studying the issue. Many of the scientists who studied CNTs, or "carbon filaments," as they were often called, were actually interested in avoiding the formation of carbon nanotubes. They were typically materials scientists who wanted to find out how to prevent the formation of carbon filament impurities during the production of steel.
As you by now know well, the discovery of carbon nanotubes is a messy affair. They have been discovered and re-discovered countless times, and many different parties have laid claim. However, the very first depiction of carbon nanotubes was by the Russian scientists Radushkevich and Lukyanovich. Iijima does deserve credit, though, for his discovery of single-walled nanotubes and for popularizing nanotubes at just the right time.