The Dawn of the Fullerenes: A Research Adventure
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Curl, Robert Jr
Robert F. Curl Jr. was born in Alice, Texas in 1933. Quite remarkably, he stayed in Texas for almost his entire research career. After completing his PhD in Berkeley, California, he accepted an assistant professorship at the Texan Rice University in 1958 and remained there until his retirement, dealing with various problems from the field of physical chemistry. Still - and quite obviously, Curls scientific impulses reached far beyond Texan borders. When he received the 1996 Nobel Prize in Chemistry together with Richard E. Smalley (who also worked at Rice) and Sir Harold Kroto (at the time at the University of Sussex, UK), this was a true example of national and international scientific collaboration. In the present lecture, delivered in Lindau two years after the award, Curl gives a detailed, historical account of this collaboration, which led to the discovery of the Nobel Prize-winning, football-shaped C60 molecule, also known as the Buckminster fullerene or buckyball.In the 1980s, Curl and Smalley were studying metal clusters with an apparatus Smalley had developed in his laboratory. Using high-energy lasers, this apparatus could convert metals (or other materials) into a plasma. The latter was then allowed to expand into a vacuum, where chemical reactions took place. The products of these reactions could eventually be detected with an attached mass spectrometer. This laser-supersonic cluster beam apparatus attracted the attention of Harold Kroto, who was, at the time, studying the formation of carbon chains in space using microwave spectroscopy. Kroto believed that he could simulate the conditions in space using the equipment in Smalley’s lab (indeed, Curl mentions in his talk that ‘Kroto fell in love with this machine.’). Curl established the contact between the two scientists and Kroto came to Smalley’s laboratory in September 1985. Only 11 days after he arrived, the three scientists submitted a letter to the journal Nature reporting the discovery of a football-shaped C60 molecule, which they produced by vaporizing graphite using Smalley’s apparatus. This letter was the first of three publications that should lead to the the Nobel Prize, rendering Kroto’s 11 day visit to Rice the probably most efficient and rewarding scientific collaboration ever. However, Curl also mentions some other contributions to the C60 story, who were not rewarded by the Royal Swedish Academy of Sciences. In his autobiography Curl states that ‘Jim and Sean were equal participants in the scientific discussions that directed the course of this work and actually did most of the experiments.’ In his talk, he further mentions that the C60 molecule had been predicted theoretically by others long before its experimental detection. In concluding, Curl outlines some of the developments that were triggered by C60 research. If the transition metal nickel is added to the graphite being vaporized, for example, carbon nanotubes (‘buckytubes’) are obtained. In contrast to the fullerenes, which have remained largely devoid of practical applications, nanotubes are seen as a promising candidate in various areas of material science and are already being used in turbines, sports gear and scientific instruments, to name a few. In 2006, in the frame of the last of three talks Curl gave in Lindau so far, he should discuss these and other new developments in the field of carbon based materials. David_prizes/chemistry/laureates/1996/curl.html
 Good afternoon. I just wanted to tell you the story of how the fullerings were discovered because it was certainly the most fun time I ever had in life and I like to share it. In the early 1980s, my colleague Richard Smalley invented a machine to study clusters of atoms of very refractory elements. The machine's concept was very simple. You took refractor material, impacted the surface of it with a pulsed laser light, this would vaporize the material and the laser would atomize it and this plume of atoms would be then trained in a stream of helium gas mixed up with the helium, cooled off and the atoms that you would initially vaporize would come back together and form clusters. You could add various free agents to the stream of gas so that you could see what would react with the surfaces of these clusters. Then downstream, the gas expanded into a vacuum, into a supersonic jet, was cooled to a few degrees above absolute zero, skimmed into molecular beam and interrogated with a mass spectrometer. One got essentially a distribution of clusters sizes, that is, typically you'd have a big hump where a maximum would correspond to the most abundant clusters. Now may I have the first slide please? This is a picture of Rick Smalley atop this machine. He's about two meters above the floor. So this was for physical chemists at least, big science. You could get inside the main chamber of the machine with no difficulty. What he's doing at the moment is introducing a region where air could be excluded so that one could ionize clusters with a fluorine laser. May I have the next slide please? Now this is what Harry Croto was interested in. What happened was that there was a meeting in Austin, Texas in March of 1984, and Harry was there, and I was there, and I suggested to Harry that he come visit Rice. He came to Rice and he fell in love with our machine, with Rick's machine. And the reason he fell in love with the machine were these compounds he was interested in. His colleague David Walton would make compounds like this for him. He would investigate the rotational spectrum in a microwave spectrometry had determined the rest frequencies and then go to an observatory, a radio astronomy observatory, and try to observe the same rotational transitions in various interstellar clouds. And the amazing thing was that he found them because these things are fairly difficult to make in the laboratory. Polyacetylenes are notoriously tricky to work with. It's said that most polyacetylene chemists are missing a few fingers as a result of their endeavors. Now the reason that Harry became enthralled with this machine was that the question is if this is so hard to make in the laboratory, how does it get made in the interstellar medium? And Harry had the idea that, which he'll tell you about perhaps himself in a minute, that material was expelled from the surface of a carbon star. The carbon atoms would get together, make these chains, pick up a hydrogen at one end and a nitrogen at the other, and create the species that he was observing. So Rick and I and our colleague Frank Tittle were engaged in a program of investigation of semiconductor clusters in March of 1984, and we thought we were going to revolutionize the computer business and we were not too interested in getting off on this sidetrack. And it wasn't until August of 1985 that we finally decided there's a break in the action. We'll call Harry and ask him to come over and do his experiments. Next slide, please. And then we looked at the literature. And there was a group at Exxon, Roffing-Cox and Caldor, who had already examined carbon clusters in an apparatus identical with the one that we were working with and had proved that they could make chain-like species in this region that Harry was interested in, clusters of this size. So we called Harry back and said, looks like this experiment has been done, but if you'd like for us to do a few things, we'll do it and send you the data and Harry's responses. I'm kicking the next plane over there. I want to do this myself. So let me tell you a bit about this. This is the kind of data that this machine produced. What we have at the bottom is a number of carbon atoms. What we have going up this direction is a scale that tells you the relative number of clusters of a given size, so that in this particular diagram, the carbon 11 cluster has the greatest abundance. Now, this is not at all what a typical cluster diagram looks like. Typically, you would just have one single hump. There would be some, as I said, some cluster of maximum concentration or maximum amount. And this was very peculiar. Not at all like this. In this region, you have only odd-numbered clusters. In this region, there seems to be some sort of forbidden zone or gap. And in this region, you have only even-numbered clusters. And it's very difficult to come up with an explanation for how you can have only even-numbered clusters. This has never been seen in any other cluster distribution. This also shows various magic numbers, 11, 15, and 19 are magic numbers, 60, 70, perhaps, are also magic numbers. So, Herron came over. He worked with graduate students Jim Heath and Sean O'Brien to do the experiments to show that these carbon-chain compounds could be made by vaporizing carbon and mixing them with something like ammonia to provide the hydrogen atom for one end and the nitrogen atom for the other. And these experiments worked. You certainly could make these chains, and so the hypothesis seemed quite viable that that's the way these materials got made for the interstellar medium. However, in the course of doing these experiments, the whole distribution was looked at repeatedly under all sorts of conditions. And the relative intensity of the peak corresponding to 60 carbon atoms changed a lot depending on what the experimental conditions were. Sometimes it was quite prominent, perhaps maybe eight or nine times higher than its nearest neighbor. And so we reached the stage on a Friday afternoon where Harry was going back, I believe, on Monday, and we had to wrap things up. And we said, all right, we have a paper out of finding these chains. But we really ought to think about why this 60 peak fluctuates so much. I remember very clearly that we were sitting in Rick's office, and as a group of five of us, we agreed this ought to be done. And then the three professors looked at the two graduate students and said, why don't you work this weekend and see how intense you can make this carbon 60 peak? So now the next slide, please. So what happened is that on Monday morning, Jim Heath walked in with this spectrum. It's the same sort of thing except we were looking at only the region from 42 to 86 carbon atoms. There were, again, there were only even number clusters. And Jim Heath had found conditions where this peak was at least 30 times more prominent than its neighbors. So clearly you need to come up with an explanation for this. You can't ignore a result like this. It was a result sort of like this one that made us believe that we needed to investigate this further. So the main difference between these panels is that as you go from the bottom towards the top, there's been more chance for chemistry to take place in the expansion region, inside of the nozzle. And so what we knew about the chemical conditions implied that carbon 60 into a lesser extent carbon 70 was a survivor of chemical attack by carbon atoms. And so one wanted, therefore, to come up with some unique structure for the 60 carbon atom peak that would reflect this kind of inertness. Next slide, please. So here are the kinds of things one might work with. We've already seen the chains. The chains typically have a dangling bond at each end. And so this would be a site for chemical reaction just like the divalent carbon here would be a site for chemical reaction. You could get around the chain having a dangling bond at the end if you have a 60 carbon atom chain by making it into a hool hoop. But then there would be no reason to think that a 62 carbon atom hool hoop would be any different in reactivity from a 60 carbon atom hool hoop. The other alternative was the basis structure somehow or another on the structure of graphite. Graphite, after all, is the most stable form of carbon, these hexagons with the carbon atoms at the vertices. And you could imagine that somehow or another, if you made up a piece of chicken wire like this or hexagons like this, that you could fold it around, curve it around, and have a dangling bond on one side react with a dangling bond on the other side. And perhaps there would be some way of avoiding dangling bonds. Next slide. And there's precedent for this. The structures that Buckminster Fuller was so fond of making looked like chicken wire at first glance, looked like hexagons, and they're curved around and they look like they could ultimately close. And in fact, next slide, some of them like the Expo Dome at Montreal are virtually closed globes. Well, there's a little bit of a problem, and that is that Buckminster Fuller didn't tell you how to do this. The Rice Library has perhaps 100 books on the works of Buckminster Fuller. And if you look for those books, it's relatively difficult to find any kind of picture that tells you what to do. So there was a famous luncheon at the Mexican restaurant, which Harry can perhaps tell you a bit about in more detail, because I wasn't there. All I know is what I've been told. We're discussing how can we make a close form of this cage. We've been talking about that. And Harry said, well, a few years back, I made a thing out of cardboard to study the constellations. It was about so big and it was roughly a globin shape, but it was a polyhedron. It was made up of hexagons and I think pentagons. And it might have had 60 vertices. And so what happens in these discussions is everybody says, hmm, that's very interesting and changes the subject. And that's what happened on this occasion. But people don't forget these things. And this was around one o'clock in the afternoon, perhaps when this came up. And this began to knoll on Harry during the afternoon. And by a little bit after dinner time, I think around 6.30 or 7, he really wanted to see this straight thing he had made and he wanted to count the vertices on it to see if it had 60 vertices. And so he said, he called, came to me and he said, I want to call my wife, Laura, who's here today, and get her to get this thing out and count the vertices. And I said, Harry, it's 2.30 in the morning and writing. I don't know. And then I asked him the killing question, Harry, do you know where it is? Well, it's been a while since I've seen it. And so I said, it can wait till morning. What the heck? Why wake her up in the middle of the night to find this thing and count the vertices? Many wives would not appreciate this. So Harry agreed with me it could wait till morning, but it couldn't wait till morning. Because Rick hadn't forgotten about the idea that this thing was made of hexagons and maybe pentagons. So he went home and he cut out a bunch of hexagons out of paper and he cut some pentagons with the same length edges out of paper. And he tried to put them together and to make some closed structure with 60 vertices. And from what he tells me, once he started working with pentagons, it turned out to be trivial. You start with one pentagon and you put five hexagons around it and you already have a bowl-shaped object. And so the next morning, he lived at that time far away from Rice, the next morning he called me and said, I'm on my way to work, get everybody together in my office, I found the solution. Next slide please. And he came in and he threw this object on the table in the office. And of course, none of us bothered to count the vertices. We knew it had 60 vertices or he wouldn't have come in claiming that this was a solution. But I'm always one not to give up too easily. So I said, well, we really got to see if the bonding of carbon works out. And so we pasted these little pieces of extra paper that had double bonds on them to see if we started out making the number of bonds from each carbon before on one side. If when we got around to the other side, it would work out. There would still be, there would be no carbons with either three bonds or five bonds. And it worked out and so I said, oh, I believe this must be the right structure. So we called the chairman of the math department at Rice. We didn't know what this was. And said, we've got this object that's got 20 hexagons and 12 pentagons, 60 vertices. What is it? He said, well, let me look it up and I'm sure I can find out the answer. And in about five minutes he called back and I happened to be the one that picked up the phone and he said, what you've got there is a soccer ball. And I was somewhat taken aback by this comment and I pretended, you know, you'd try to somehow another shift your ground to be. I said, well, what's this technical name? You know, like I knew it was a soccer ball on the log. And he said, well, it's a truncated icosahedron and you guys haven't discovered anything new. We mathematicians have known about this for quite a while. So anyway, we got a computer model made. Next slide, please. This molecule, this is what it is with the bonding of course, the carbon atoms of the vertices. This particular teculate structure, that is, you could move the double bonds around in many different ways, actually 12,500 different ways. But the ones for all the double bonds are only in the pentagon. There's only one structure where the double bonds are only in the hexagons and no double bonds are in the pentagon. And that is by far the dominant structure. So this particular material, it was discovered sometime later, reacts like a polyolefin and not like an aromatic compound. As it looks, this looks like benzene, but it really isn't benzene. So we wrote a paper for nature, a letter to nature, and we claimed that this new material that no one had ever thought of before would be wonderful. It would do all sorts of things. It would be the carrier of the diffuse interstellar bands. It would be a wonderful lubricant. I don't think we claimed it would cure the common cold, but we quivered on the edge of doing that. And we sent the paper off to nature and we were really happy. Next slide, please. And we had our team photo made. This is Sean O'Grine and this is Jim Heath. And you've met the other characters in this play. This is our mystery woman. No good story. Every good story needs a mystery woman. We still don't know who she is. Anyway, we were very happy about this. We finally found, next slide, please, how about Mr. Fuller made domes? He put pentagons in them by Goliath. So this is a picture of Mr. Fuller revealing a secret. Now, as I said, we thought we were the first people to ever think of this. Next slide, what we were. E.C. Ozawa in Japan had thought of this molecule in 1971 by the simple expedient of taking a close look at a soccer ball that his son was playing with. And apparently, this was the idea of this compound was really quite well known to a large number of chemists. For example, the Russians had done a theoretical calculation on it. Next slide, please. And the synthetic organic chemist, Orville Chapman, who's at UCLA, had looked around for a suitable target for his considerable synthetic organic skills, asked himself supposedly this question, if God would give me the grace to make one molecule, what would that molecule be? And answered his own question with soccer ball C60. And this was around 1980. He went further than that. He wrote a proposal to the National Science Foundation in the United States. It was funded to make the soccer ball C60. And he set to work with several graduate students to make it. And unfortunately, he was not able to make it. No organic chemist has synthesized this molecule by the traditional methods of organic chemistry, at least so far. Now, in this period of time, when we were discovering that, hey, this isn't such a revolutionary new idea, after all, things were very interesting because Harry had gone back to England, and we were in the United States. And so we'd sent out a lot of reprints, or preprints of our paper, and we began to get information back. And we were getting slightly different information that us in Houston and Harry in Sussex that were pointing in the same direction. What we got was a preprint of a paper by Tony Heyman, who had considered once again, done this theoretical calculation on soccer ball C60. This was actually the third time it was published, but no one knew that. But he had in his paper a lot of thoughts that have not been sufficiently appreciated. One thought that he had, one thing that he showed was he considered an alternative closed-cage structure for carbon-60, and concluded that it wouldn't be a good structure because it had five-membered rings that were bonded together, and he thought this would be a high-energy, possibly chemically reactive side. The other thing that he knew was that Euler had, in about 1764, explained the rules for how you make polyhedra. And when these rules were applied to a system that contained only six-membered rings and five-membered rings, what it said was that as long as you had 24 or more even number of atoms, you could make a closed-cage solution, which would have exactly 12 pentagons in it, and the rest would be hexagons. Now, what Harry was getting, please slide, please, was somebody pointed out this beautiful little article by David Jones, which was published in 1966 saying Daedalus, he wrote, David Jones had a column for the new scientist where he essentially said, crazy ideas that I've had about chemistry. And he published under the name of Daedalus because I guess he didn't want people to think he was crazy for having crazy ideas. He says, Daedalus has conceived a hollow molecule, a closed spherical shell of sheet polyglyc graphite whose molecules or flat sheets have been signed hexagons. He proposes to modify the high-temperature graphite process by introducing suitable impurities into the sheets to work them, reasoning that it will ultimately close on itself. And almost immediately people told him the suitable impurities ought to be five-membered rings, and you need exactly 12 of them. And essentially what we discovered was you didn't really have to do much to modify the high-temperature graphite process. All you had to do was let carbon condense, carbon atoms condense from a high temperature, and you would spontaneously make this closed-cage compound. And next slide, please. And he had, in some of his subsequent work, he had some pictures of this beautiful radiolara animals which have skeletons that are made of hexagons and pentagons primarily, although if you look carefully you can see some heptagons in there. And this picture comes out of a book by Dorsey Thompson on growth and form. Dorsey Thompson had considered the relationship between geometry and symmetry and the structure of organisms. For example, we have bilateral symmetry, a starfish has five-fold symmetry, and these little animals have sort of spherical symmetry. And so this turns out to be, in some ways, related to biology. Next slide, please. So this led us back to this distribution and the thought that perhaps the reason that there are only even clusters here is because all of these clusters are closed-cage compounds. That's they've already been subjected to considerable chemical attack and only the ones that were already closed-cages survive. Next slide, please. Well, that makes it a little hard because if these are all closed-cages, why are they reacting away? And there is something unique about carbon-60. It's the smallest-cage compound that has no adjacent pentagons in it. And so almost simultaneously, Harry and quite independently, the group at Galveston, Thomas Schmalz and Doug Klein, Bill Seitz, the reason that maybe the five-membered rings that are adjacent to each other are particularly susceptible to chemical attack, and maybe what's going on here is that C70 is the next smallest closed-cage reform that has no adjacent pentagons. Now, it turns out to prove this as a formidable challenge. And in fact, the group at Galveston, who are quite talented mathematicians, finally proved it in about 1993. But it's like a... This is the only one that you can make a non-adjacent pentagon structure for easily. Harry tried to make some in this region and never could succeed and was forced essentially to guess. And it is true that this is the next one that has no adjacent pentagons. Next slide, please. So what's happening? Here's a seafority. What's happening is if you have a pair of pentagons that are adjacent, these two particular carbon atoms that bridge the two pentagons are particularly susceptible to chemical attack, and no fullerene has ever been isolated which had adjacent pentagons. Next slide, please. Now, there are many different isomers. Once you get up in the neighborhood of C60, there are 1,812 closed-cage forms of C60. And this is a... They're all but one of the isomers. A soccerball isomer has adjacent pentagons in it. This is just one of them. Well, we had a lot of fun in 1985. Almost all the ideas that we had were on the table by the end of 1985. We spent a couple of years defending ourselves and trying to do new experiments to test the fullerene hypothesis. By about 1988 or 89, we were running out of gas. You go to give a talk, the organic chemist would say, let's see your vial of substance, and we'd say, we don't have it. We just have a few molecules in a molecular beam. And it was clear there was no Nobel Prize in what we had done. And we couldn't figure out what to do next. Next slide, please. And these two guys came to our rescue. This is Wolfgang Prechmer from Heidelberg, and this is Don Huffman from the University of Arizona in Tucson. They are physicists who have been interested in carbon particles in space for a long time. And they had a machine for making carbon, essentially for making carbon soot and then looking at it. And this machine consisted of a couple of graphite rods that you ran a current through, heated up the graphite, vaporized the carbon, and then they had a little disc that they put above it to collect the soot on. And they had some peculiar soot, and they wondered what was going on. They usually had an inert atmosphere in here. They wondered what was going on with this peculiar soot. And after kidding each other around for years, they finally decided, well, maybe it really is C60. Maybe we ought to look for it. And sure enough, they discovered that if you had about half an atmosphere of argon in this bell jar and collected soot here, that that soot was about 5% a mixture of C60 and C70. And so people around the world started – this was essentially August of 1990, September of 1990. People around the world started vaporizing carbon rods and collecting the soot from inside the container. You notice it doesn't land just here. It lands everywhere on the inside of the container. And so most of the research groups look kind of like this. Next slide, please. It was a nasty work. And scraping the soot out and shaking it up and dissolving the C60 and the C70 out of it. Next slide, please. Once the chemists knew how they could get this material out, then they separated this material. And actually, Harry's group was one of the first groups to separate the material. This is C60 in a toluene solution. This is a thin film of C60. This is C70, pure C70 in a toluene solution and C84 in a toluene solution. And so there are about, I don't know, perhaps eight or nine different pure fullerines that have been isolated. And there was a tremendous amount of excitement and a very large number of papers that came out in the year right after 1990 as people worked on this. And so where do we stand today? And have the next slide, please. Well, first of all, there's this material has come out since about 1992. If you add, this is a fullerine that's been elongated and was only capped with pentagons on one end, if you do your vaporization of carbon and add a little bit of metallic iron cobalt or nickel, particularly nickel, to the system, the catalyst takes over the system and converts all the fullerine production into the production of these carbon nanotubes, bucky tubes. And a lot of the current excitement is, can we do something with these bucky tubes? I mean, for example, if you could take millions or billions of them and put them together into a cable, all parallel to each other, you would have the strongest cable imaginable, perhaps a hundred times stronger than steel at perhaps a quarter of the weight for the same cross-section. Unfortunately, no one knows how to do that. But the effort to make something out of these materials, also the material is electrically conducting, so you would have electrically conducting extremely strong cable. So just recently, people have wondered whatever became of bucky ball. Next slide, please. This is what we have, I've got my slide out, I apologize, this is what we have come out of this in terms of the morphology of carbon. We started out with diamond as a three-dimensional network of carbon atoms. So this is basically a three-dimensional material. One other form of carbon is graphite, which is basically a two-dimensional material, these sheets of six-membered rings. Then the nanotubes are one-dimensional materials, and the bucky balls would correspond to a zero-dimensional material. So one of the things that's come out of this is that we can think of carbon as satisfying virtually all forms, in one form or another satisfying virtually all morphologies that are possible in three-dimensional space. Next slide, please. So this is what I thought was coming up. In the May 4, 1998, Wall Street Journal, this question was asked by Susan Warren, and the obvious answer is no commercial product has been made out of bucky balls. And her reasoning was that it cost too much, $11,000 a pound for C60, same inputted outside the scope of something that would be useful, and the highest utility material pharmaceuticals have to cost less than $2,500 a pound. I don't think this is actually the reason. It is true that it's hard to scale up the manufacture of C60 because of this basic, the fundamental batch nature of the process in digging in there and getting a sit-out. But no one has come up with this killer application that's going to be some great commercial value, and therefore there's been no reason to drive this price down. Now, next slide, please. That's not because people aren't trying. There's areas of research or producing fullerines, particularly in the hydro-metallic fullerines, fullerines with metals inside. There's a lot of work on the organic chemistry of fullerines, efforts to find applications in biology and medicine, efforts to find applications in optics and electronic devices, but no one, as far as I know, has come up with that practical application that we're all thinking of. So in the words of Rick Smalley, we all wonder whether the kid will ever get a job. Thank you.
 Good afternoon. I just wanted to tell you the story of how the fullerings were discovered  because it was certainly the most fun time I ever had in life and I like to share it.  In the early 1980s, my colleague Richard Smalley invented a machine to study clusters  of atoms of very refractory elements. The machine's concept was very simple. You took  refractor material, impacted the surface of it with a pulsed laser light, this would vaporize  the material and the laser would atomize it and this plume of atoms would be then trained  in a stream of helium gas mixed up with the helium, cooled off and the atoms that you  would initially vaporize would come back together and form clusters. You could add various free  agents to the stream of gas so that you could see what would react with the surfaces of  these clusters. Then downstream, the gas expanded into a vacuum, into a supersonic jet, was  cooled to a few degrees above absolute zero, skimmed into molecular beam and interrogated  with a mass spectrometer. One got essentially a distribution of clusters sizes, that is,  typically you'd have a big hump where a maximum would correspond to the most abundant clusters.  Now may I have the first slide please? This is a picture of Rick Smalley atop this machine.  He's about two meters above the floor. So this was for physical chemists at least, big  science. You could get inside the main chamber of the machine with no difficulty. What he's  doing at the moment is introducing a region where air could be excluded so that one could  ionize clusters with a fluorine laser. May I have the next slide please?  Now this is what Harry Croto was interested in. What happened was that there was a meeting  in Austin, Texas in March of 1984, and Harry was there, and I was there, and I suggested  to Harry that he come visit Rice. He came to Rice and he fell in love with our machine,  with Rick's machine. And the reason he fell in love with the machine were these compounds  he was interested in. His colleague David Walton would make compounds like this for him.  He would investigate the rotational spectrum in a microwave spectrometry had determined  the rest frequencies and then go to an observatory, a radio astronomy observatory, and try to  observe the same rotational transitions in various interstellar clouds. And the amazing  thing was that he found them because these things are fairly difficult to make in the  laboratory. Polyacetylenes are notoriously tricky to work with. It's said that most polyacetylene  chemists are missing a few fingers as a result of their endeavors.  Now the reason that Harry became enthralled with this machine was that the question is  if this is so hard to make in the laboratory, how does it get made in the interstellar medium?  And Harry had the idea that, which he'll tell you about perhaps himself in a minute,  that material was expelled from the surface of a carbon star. The carbon atoms would get  together, make these chains, pick up a hydrogen at one end and a nitrogen at the other, and  create the species that he was observing. So Rick and I and our colleague Frank Tittle  were engaged in a program of investigation of semiconductor clusters in March of 1984,  and we thought we were going to revolutionize the computer business and we were not too  interested in getting off on this sidetrack. And it wasn't until August of 1985 that we  finally decided there's a break in the action. We'll call Harry and ask him to come over  and do his experiments. Next slide, please. And then we looked at the literature. And  there was a group at Exxon, Roffing-Cox and Caldor, who had already examined carbon clusters  in an apparatus identical with the one that we were working with and had proved that they  could make chain-like species in this region that Harry was interested in, clusters of  this size. So we called Harry back and said, looks like this experiment has been done,  but if you'd like for us to do a few things, we'll do it and send you the data and Harry's  responses. I'm kicking the next plane over there. I want to do this myself. So let me  tell you a bit about this. This is the kind of data that this machine produced. What we  have at the bottom is a number of carbon atoms. What we have going up this direction is a  scale that tells you the relative number of clusters of a given size, so that in this  particular diagram, the carbon 11 cluster has the greatest abundance. Now, this is not  at all what a typical cluster diagram looks like. Typically, you would just have one single  hump. There would be some, as I said, some cluster of maximum concentration or maximum  amount. And this was very peculiar. Not at all like this. In this region, you have only  odd-numbered clusters. In this region, there seems to be some sort of forbidden zone or  gap. And in this region, you have only even-numbered clusters. And it's very difficult to come  up with an explanation for how you can have only even-numbered clusters. This has never  been seen in any other cluster distribution. This also shows various magic numbers, 11,  15, and 19 are magic numbers, 60, 70, perhaps, are also magic numbers. So, Herron came over.  He worked with graduate students Jim Heath and Sean O'Brien to do the experiments to  show that these carbon-chain compounds could be made by vaporizing carbon and mixing them  with something like ammonia to provide the hydrogen atom for one end and the nitrogen  atom for the other. And these experiments worked. You certainly could make these chains,  and so the hypothesis seemed quite viable that that's the way these materials got made  for the interstellar medium. However, in the course of doing these experiments, the whole  distribution was looked at repeatedly under all sorts of conditions. And the relative  intensity of the peak corresponding to 60 carbon atoms changed a lot depending on what  the experimental conditions were. Sometimes it was quite prominent, perhaps maybe eight  or nine times higher than its nearest neighbor. And so we reached the stage on a Friday afternoon  where Harry was going back, I believe, on Monday, and we had to wrap things up. And  we said, all right, we have a paper out of finding these chains. But we really ought  to think about why this 60 peak fluctuates so much. I remember very clearly that we were  sitting in Rick's office, and as a group of five of us, we agreed this ought to be done.  And then the three professors looked at the two graduate students and said, why don't  you work this weekend and see how intense you can make this carbon 60 peak? So now the  next slide, please. So what happened is that on Monday morning, Jim Heath walked in with  this spectrum. It's the same sort of thing except we were looking at only the region  from 42 to 86 carbon atoms. There were, again, there were only even number clusters. And  Jim Heath had found conditions where this peak was at least 30 times more prominent than  its neighbors. So clearly you need to come up with an explanation for this. You can't  ignore a result like this. It was a result sort of like this one that made us believe  that we needed to investigate this further. So the main difference between these panels  is that as you go from the bottom towards the top, there's been more chance for chemistry  to take place in the expansion region, inside of the nozzle. And so what we knew about the  chemical conditions implied that carbon 60 into a lesser extent carbon 70 was a survivor  of chemical attack by carbon atoms. And so one wanted, therefore, to come up with some  unique structure for the 60 carbon atom peak that would reflect this kind of inertness.  Next slide, please. So here are the kinds of things one might work with. We've already  seen the chains. The chains typically have a dangling bond at each end. And so this would  be a site for chemical reaction just like the divalent carbon here would be a site for  chemical reaction. You could get around the chain having a dangling bond at the end if  you have a 60 carbon atom chain by making it into a hool hoop. But then there would be  no reason to think that a 62 carbon atom hool hoop would be any different in reactivity  from a 60 carbon atom hool hoop. The other alternative was the basis structure somehow  or another on the structure of graphite. Graphite, after all, is the most stable form of carbon,  these hexagons with the carbon atoms at the vertices. And you could imagine that somehow  or another, if you made up a piece of chicken wire like this or hexagons like this, that  you could fold it around, curve it around, and have a dangling bond on one side react  with a dangling bond on the other side. And perhaps there would be some way of avoiding  dangling bonds. Next slide. And there's precedent for this. The structures that Buckminster Fuller  was so fond of making looked like chicken wire at first glance, looked like hexagons,  and they're curved around and they look like they could ultimately close. And in fact, next  slide, some of them like the Expo Dome at Montreal are virtually closed globes. Well,  there's a little bit of a problem, and that is that Buckminster Fuller didn't tell you  how to do this. The Rice Library has perhaps 100 books on the works of Buckminster Fuller.  And if you look for those books, it's relatively difficult to find any kind of picture that  tells you what to do. So there was a famous luncheon at the Mexican restaurant, which  Harry can perhaps tell you a bit about in more detail, because I wasn't there. All I  know is what I've been told. We're discussing how can we make a close form of this cage.  We've been talking about that. And Harry said, well, a few years back, I made a thing out  of cardboard to study the constellations. It was about so big and it was roughly a globin  shape, but it was a polyhedron. It was made up of hexagons and I think pentagons. And  it might have had 60 vertices. And so what happens in these discussions is everybody  says, hmm, that's very interesting and changes the subject. And that's what happened on this  occasion. But people don't forget these things. And this was around one o'clock in the afternoon,  perhaps when this came up. And this began to knoll on Harry during the afternoon. And  by a little bit after dinner time, I think around 6.30 or 7, he really wanted to see  this straight thing he had made and he wanted to count the vertices on it to see if it had  60 vertices. And so he said, he called, came to me and he said, I want to call my wife,  Laura, who's here today, and get her to get this thing out and count the vertices. And  I said, Harry, it's 2.30 in the morning and writing. I don't know. And then I asked him  the killing question, Harry, do you know where it is? Well, it's been a while since I've  seen it. And so I said, it can wait till morning. What the heck? Why wake her up in the middle  of the night to find this thing and count the vertices? Many wives would not appreciate  this. So Harry agreed with me it could wait till morning, but it couldn't wait till morning.  Because Rick hadn't forgotten about the idea that this thing was made of hexagons and maybe  pentagons. So he went home and he cut out a bunch of hexagons out of paper and he cut  some pentagons with the same length edges out of paper. And he tried to put them together  and to make some closed structure with 60 vertices. And from what he tells me, once he  started working with pentagons, it turned out to be trivial. You start with one pentagon  and you put five hexagons around it and you already have a bowl-shaped object. And so  the next morning, he lived at that time far away from Rice, the next morning he called  me and said, I'm on my way to work, get everybody together in my office, I found the solution.  Next slide please. And he came in and he threw this object on the table in the office. And  of course, none of us bothered to count the vertices. We knew it had 60 vertices or he  wouldn't have come in claiming that this was a solution. But I'm always one not to give  up too easily. So I said, well, we really got to see if the bonding of carbon works out.  And so we pasted these little pieces of extra paper that had double bonds on them to see  if we started out making the number of bonds from each carbon before on one side. If when  we got around to the other side, it would work out. There would still be, there would  be no carbons with either three bonds or five bonds. And it worked out and so I said, oh,  I believe this must be the right structure. So we called the chairman of the math department  at Rice. We didn't know what this was. And said, we've got this object that's got 20  hexagons and 12 pentagons, 60 vertices. What is it? He said, well, let me look it up and  I'm sure I can find out the answer. And in about five minutes he called back and I happened  to be the one that picked up the phone and he said, what you've got there is a soccer  ball. And I was somewhat taken aback by this comment and I pretended, you know, you'd  try to somehow another shift your ground to be. I said, well, what's this technical name?  You know, like I knew it was a soccer ball on the log. And he said, well, it's a truncated  icosahedron and you guys haven't discovered anything new. We mathematicians have known  about this for quite a while. So anyway, we got a computer model made. Next slide, please.  This molecule, this is what it is with the bonding of course, the carbon atoms of the  vertices. This particular teculate structure, that is, you could move the double bonds around  in many different ways, actually 12,500 different ways. But the ones for all the double bonds  are only in the pentagon. There's only one structure where the double bonds are only  in the hexagons and no double bonds are in the pentagon. And that is by far the dominant  structure. So this particular material, it was discovered sometime later, reacts like  a polyolefin and not like an aromatic compound. As it looks, this looks like benzene, but  it really isn't benzene. So we wrote a paper for nature, a letter to nature, and we claimed  that this new material that no one had ever thought of before would be wonderful. It would  do all sorts of things. It would be the carrier of the diffuse interstellar bands. It would  be a wonderful lubricant. I don't think we claimed it would cure the common cold, but  we quivered on the edge of doing that. And we sent the paper off to nature and we were  really happy. Next slide, please. And we had our team photo made. This is Sean O'Grine  and this is Jim Heath. And you've met the other characters in this play. This is our  mystery woman. No good story. Every good story needs a mystery woman. We still don't know  who she is. Anyway, we were very happy about this. We finally found, next slide, please,  how about Mr. Fuller made domes? He put pentagons in them by Goliath. So this is a picture of  Mr. Fuller revealing a secret. Now, as I said, we thought we were the first people to ever  think of this. Next slide, what we were. E.C. Ozawa in Japan had thought of this molecule  in 1971 by the simple expedient of taking a close look at a soccer ball that his son  was playing with. And apparently, this was the idea of this compound was really quite  well known to a large number of chemists. For example, the Russians had done a theoretical  calculation on it. Next slide, please. And the synthetic organic chemist, Orville Chapman,  who's at UCLA, had looked around for a suitable target for his considerable synthetic organic  skills, asked himself supposedly this question, if God would give me the grace to make one  molecule, what would that molecule be? And answered his own question with soccer ball  C60. And this was around 1980. He went further than that. He wrote a proposal to the National  Science Foundation in the United States. It was funded to make the soccer ball C60. And  he set to work with several graduate students to make it. And unfortunately, he was not  able to make it. No organic chemist has synthesized this molecule by the traditional methods of  organic chemistry, at least so far. Now, in this period of time, when we were discovering  that, hey, this isn't such a revolutionary new idea, after all, things were very interesting  because Harry had gone back to England, and we were in the United States. And so we'd  sent out a lot of reprints, or preprints of our paper, and we began to get information  back. And we were getting slightly different information that us in Houston and Harry in  Sussex that were pointing in the same direction. What we got was a preprint of a paper by Tony  Heyman, who had considered once again, done this theoretical calculation on soccer ball  C60. This was actually the third time it was published, but no one knew that. But he had  in his paper a lot of thoughts that have not been sufficiently appreciated. One thought  that he had, one thing that he showed was he considered an alternative closed-cage structure  for carbon-60, and concluded that it wouldn't be a good structure because it had five-membered  rings that were bonded together, and he thought this would be a high-energy, possibly chemically  reactive side. The other thing that he knew was that Euler had, in about 1764, explained  the rules for how you make polyhedra. And when these rules were applied to a system that  contained only six-membered rings and five-membered rings, what it said was that as long as you  had 24 or more even number of atoms, you could make a closed-cage solution, which would have  exactly 12 pentagons in it, and the rest would be hexagons. Now, what Harry was getting,  please slide, please, was somebody pointed out this beautiful little article by David  Jones, which was published in 1966 saying Daedalus, he wrote, David Jones had a column  for the new scientist where he essentially said, crazy ideas that I've had about chemistry.  And he published under the name of Daedalus because I guess he didn't want people to think  he was crazy for having crazy ideas. He says, Daedalus has conceived a hollow molecule, a  closed spherical shell of sheet polyglyc graphite whose molecules or flat sheets have been signed  hexagons. He proposes to modify the high-temperature graphite process by introducing suitable impurities  into the sheets to work them, reasoning that it will ultimately close on itself. And almost  immediately people told him the suitable impurities ought to be five-membered rings, and you  need exactly 12 of them. And essentially what we discovered was you didn't really have to  do much to modify the high-temperature graphite process. All you had to do was let carbon  condense, carbon atoms condense from a high temperature, and you would spontaneously make  this closed-cage compound. And next slide, please. And he had, in some of his subsequent  work, he had some pictures of this beautiful radiolara animals which have skeletons that  are made of hexagons and pentagons primarily, although if you look carefully you can see  some heptagons in there. And this picture comes out of a book by Dorsey Thompson on  growth and form. Dorsey Thompson had considered the relationship between geometry and symmetry  and the structure of organisms. For example, we have bilateral symmetry, a starfish has  five-fold symmetry, and these little animals have sort of spherical symmetry. And so this  turns out to be, in some ways, related to biology. Next slide, please. So this led us  back to this distribution and the thought that perhaps the reason that there are only  even clusters here is because all of these clusters are closed-cage compounds. That's  they've already been subjected to considerable chemical attack and only the ones that were  already closed-cages survive. Next slide, please. Well, that makes it a little hard  because if these are all closed-cages, why are they reacting away? And there is something  unique about carbon-60. It's the smallest-cage compound that has no adjacent pentagons in  it. And so almost simultaneously, Harry and quite independently, the group at Galveston,  Thomas Schmalz and Doug Klein, Bill Seitz, the reason that maybe the five-membered rings  that are adjacent to each other are particularly susceptible to chemical attack, and maybe  what's going on here is that C70 is the next smallest closed-cage reform that has no adjacent  pentagons. Now, it turns out to prove this as a formidable challenge. And in fact, the  group at Galveston, who are quite talented mathematicians, finally proved it in about  1993. But it's like a... This is the only one that you can make a non-adjacent pentagon  structure for easily. Harry tried to make some in this region and never could succeed  and was forced essentially to guess. And it is true that this is the next one that has  no adjacent pentagons. Next slide, please. So what's happening? Here's a seafority. What's  happening is if you have a pair of pentagons that are adjacent, these two particular carbon  atoms that bridge the two pentagons are particularly susceptible to chemical attack, and no fullerene  has ever been isolated which had adjacent pentagons. Next slide, please. Now, there  are many different isomers. Once you get up in the neighborhood of C60, there are 1,812  closed-cage forms of C60. And this is a... They're all but one of the isomers. A soccerball  isomer has adjacent pentagons in it. This is just one of them. Well, we had a lot of  fun in 1985. Almost all the ideas that we had were on the table by the end of 1985. We  spent a couple of years defending ourselves and trying to do new experiments to test the  fullerene hypothesis. By about 1988 or 89, we were running out of gas. You go to give  a talk, the organic chemist would say, let's see your vial of substance, and we'd say,  we don't have it. We just have a few molecules in a molecular beam. And it was clear there  was no Nobel Prize in what we had done. And we couldn't figure out what to do next. Next  slide, please. And these two guys came to our rescue. This is Wolfgang Prechmer from  Heidelberg, and this is Don Huffman from the University of Arizona in Tucson. They are  physicists who have been interested in carbon particles in space for a long time. And they  had a machine for making carbon, essentially for making carbon soot and then looking at  it. And this machine consisted of a couple of graphite rods that you ran a current through,  heated up the graphite, vaporized the carbon, and then they had a little disc that they  put above it to collect the soot on. And they had some peculiar soot, and they wondered  what was going on. They usually had an inert atmosphere in here. They wondered what was  going on with this peculiar soot. And after kidding each other around for years, they  finally decided, well, maybe it really is C60. Maybe we ought to look for it. And sure  enough, they discovered that if you had about half an atmosphere of argon in this bell jar  and collected soot here, that that soot was about 5% a mixture of C60 and C70. And so  people around the world started – this was essentially August of 1990, September of 1990.  People around the world started vaporizing carbon rods and collecting the soot from inside  the container. You notice it doesn't land just here. It lands everywhere on the inside  of the container. And so most of the research groups look kind of like this. Next slide,  please. It was a nasty work. And scraping the soot out and shaking it up and dissolving  the C60 and the C70 out of it. Next slide, please. Once the chemists knew how they could  get this material out, then they separated this material. And actually, Harry's group  was one of the first groups to separate the material. This is C60 in a toluene solution.  This is a thin film of C60. This is C70, pure C70 in a toluene solution and C84 in  a toluene solution. And so there are about, I don't know, perhaps eight or nine different  pure fullerines that have been isolated. And there was a tremendous amount of excitement  and a very large number of papers that came out in the year right after 1990 as people  worked on this. And so where do we stand today? And have the next slide, please. Well, first  of all, there's this material has come out since about 1992. If you add, this is a fullerine  that's been elongated and was only capped with pentagons on one end, if you do your  vaporization of carbon and add a little bit of metallic iron cobalt or nickel, particularly  nickel, to the system, the catalyst takes over the system and converts all the fullerine  production into the production of these carbon nanotubes, bucky tubes. And a lot of the current  excitement is, can we do something with these bucky tubes? I mean, for example, if you could  take millions or billions of them and put them together into a cable, all parallel to  each other, you would have the strongest cable imaginable, perhaps a hundred times stronger  than steel at perhaps a quarter of the weight for the same cross-section. Unfortunately,  no one knows how to do that. But the effort to make something out of these materials,  also the material is electrically conducting, so you would have electrically conducting  extremely strong cable. So just recently, people have wondered whatever became of bucky  ball. Next slide, please. This is what we have, I've got my slide out, I apologize, this  is what we have come out of this in terms of the morphology of carbon. We started out  with diamond as a three-dimensional network of carbon atoms. So this is basically a three-dimensional  material. One other form of carbon is graphite, which is basically a two-dimensional material,  these sheets of six-membered rings. Then the nanotubes are one-dimensional materials, and  the bucky balls would correspond to a zero-dimensional material. So one of the things that's come  out of this is that we can think of carbon as satisfying virtually all forms, in one  form or another satisfying virtually all morphologies that are possible in three-dimensional space.  Next slide, please. So this is what I thought was coming up. In the May 4, 1998, Wall Street  Journal, this question was asked by Susan Warren, and the obvious answer is no commercial  product has been made out of bucky balls. And her reasoning was that it cost too much,  $11,000 a pound for C60, same inputted outside the scope of something that would be useful,  and the highest utility material pharmaceuticals have to cost less than $2,500 a pound. I don't  think this is actually the reason. It is true that it's hard to scale up the manufacture  of C60 because of this basic, the fundamental batch nature of the process in digging in there  and getting a sit-out. But no one has come up with this killer application that's going  to be some great commercial value, and therefore there's been no reason to drive this price  down. Now, next slide, please. That's not because people aren't trying. There's areas  of research or producing fullerines, particularly in the hydro-metallic fullerines, fullerines  with metals inside. There's a lot of work on the organic chemistry of fullerines, efforts  to find applications in biology and medicine, efforts to find applications in optics and  electronic devices, but no one, as far as I know, has come up with that practical application  that we're all thinking of. So in the words of Rick Smalley, we all wonder whether the  kid will ever get a job. Thank you.
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