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Carbon Nanotube
The discovery of carbon nanotubes - Guided by serendipity
It all started in 1971, when I developed the world's first high-resolution electron microscope at Arizona State University. In the 1970s, I had the opportunity to study many different types of carbon materials. In 1980, I announced that I had seen "spherical graphite*," in a research paper I wrote related to carbon. I noticed that among the various forms of graphite, there were "onion-shaped" particles about 0.8 - 1 nanometer in diameter, and commented in my paper that "In order to explain the onion-like formation of this spherical graphite, in addition to hexagonal carbon graphenes**, 12 pentagonal graphenes were also required." This onion-like structure is in fact the fullerene (carbon-60 or C60) discovered in 1985 by Harold W. Kroto, Richard E. Smalley, and Robert F. Curl. At the time of that discovery, this fact was overlooked.
* Graphite is a flat crystal layer in which carbon molecules are arranged in a hexagonal shape. It is used in pencil lead and as a fiber in golf clubs and tennis racquets.
** "Hexagonal Graphene" refers to the state in which the molecules are arranged at the six apexes of a hexagon.
Based in part on this experience, when I heard about the discovery of C60 in 1985, I thought to myself, "So THAT was the onion-like structure that I saw." At the same time, I gained a new interest in the ways in which molecular structures with a perfect symmetrical shape like C60 are created.
From 1987, when I began working at NEC's Fundamental Research Laboratories, I decided to once again study these "onions" to reconfirm the research that I had conducted five years before.
Shortly after I began studying these onion structures, however, my attention was drawn not to C60, which demonstrated this onion structure, but rather to a needle-shaped material that appeared nearby. In the large-scale synthesis, using a method announced in 1990, C60 is generated using discharge from two carbon electrode rods (the arc discharge method). Within the soot that built up above the negative carbon pole, however, I found a needle-shaped material that had never been seen before. This needle-shaped material is the material to which I later gave the name "carbon nanotube."
>>See the Story Behind the Name
At the time, this discovery was seen as something of a "product of coincidence", but I prefer to think of this as necessity rather than coincidence. The thing that became clear to me when I saw this needle-shaped material was the connection between two factors: that one part of the theme of my doctoral thesis was the "needle crystals of silver," and that the asbestos which an assistant professor in the same laboratory at that time had been studying using an electron microscope had a tube-like crystal structure. In other words, that discovery was not simply "coincidence" - it was the power of "serendipity."
"Serendipity" is defined as "the ability to find valuable things," or "the faculty of discovery." I believe that I naturally came to have this ability through skills in using electron microscopes, which I had cultivated over many years, through my continued experience in working with carbon and my involvement with mineralogy in the United States, and, more than anything else, my strong determination to pursue research in unknown materials, for which the structures had not yet been clarified. Carbon nanotubes are nothing more than one of the things that I discovered through this continued process of searching for the truth.
>>See origin of the term "serendipity"
The Story Behind the Name
For some time after the discovery, I had used the term "micro-tubule," referring to microscopic tubes found in living organisms, and it was featured in the journal "Nature" on two occasions using this term. The Director of the Fundamental Research Laboratories at the time, Dr. Hiroyoshi Rangu (currently a Professor at the Tokyo University of Agriculture and Technology) said, "Don't you think you should pick a name that will be recognized worldwide? The name is very important, you know." I was in full agreement with Dr. Rangu, and decided upon the name "carbon nanotubes."
"Fullerenes" were named after the American architect Richard Buckminster Fuller, but the name "carbon nanotube" was selected from among several candidates, including "microtubules," which I used in my first paper, and "tubulin," originally the name of a protein, as well as "NEC tubes" and "Iijima tubes." Some people expressed the opinion that although the tubes were nano-sized, using "micro" was inappropriate, so I gave up on "microtubules," and I also decided against "Iijima tubes" because I felt embarrassed about using my own name. This is a type of "carbon," with a size on the "nano" scale, and shaped like a "tube" - so I settled on "carbon nanotubes."
Origin of the term "serendipity"
It is said that the English author Horace Walpole (1717-1797) coined the term "serendipity" in a letter to a friend written in 1754. He based the term on the title of a Sri Lankan fairy tale he had read, called "Three Princes of Serendip," Serendip being the former name of Sri Lanka. It was a story of three princes who "were always making discoveries, by accidents and sagacity, of things which they were not in quest of." He thus used the term to describe unexpected but valuable discoveries.
