'The Red Solution'

C60 in tolune

A students view of the discovery of Buckminsterfullerene

(adapted from Jonathan Hare's PhD thesis, Sussex University, 1993.)


Brief reflections on the C60 experience

Its now 10 years since I got my PhD (1993). Busy people don't tend to look back much, I should do more. I forget sometimes the rather wonderful and exciting five years from 1990 to 1995 when I was lucky to be involved in the 'C60 affair'. Some memories from this period are rather like recalling a magical dream. I feel privileged to have been involved.

During this time I worked very closely with three great people at Sussex University; Harry Kroto, David Walton and Roger Taylor. There were also many others such as Amit Sarkar, John Dennis, Kuang Hsu and Maricio Terrones, Steve Firth and Gill Watson.

What memories that persists of this exciting time are good ones working in a dynamic, often happy and very creative team. I felt that my contribution was not only valued but that due to circumstances (my own set of skills fortuitously fitting in very well) was able to contribute uniquely to the 'life' of this group. It was therefore a very happy and exciting time.

Looking back, I can now see the experience not only enriched my life, but the confidence gained along with the enthusiasm and creativity that was shared has continued with me. I thank all those people for that gift.

The discernment that science creates offers much to humanity, perhaps never more so. However, on a more personal level, it is simply working with others where we can learn so much. This side of the scientific endeavour is not perhaps mentioned enough and I would therefore like to take this opportunity to thank all those people with whom I shared those times.


I will try to tell the story of the discovery of C60, Buckminsterfullerene, the third form of carbon. Its a wonderful discovery, not just because it will lead us from the enormous world of astronomy to the sub-microscopic world of atoms, but also because the basic ideas and experiments that lead up to the breakthroughs are relatively simple and straightforward to explain.

Carbon and Buckminsterfullerene
The ancient Greeks believed that all earthly objects were composed of four elements; earth, wind, water and fire. Over the next two thousand years these ideas were replaced by a far more complex (but less mystical) system of 92 elements. One of the first of these elements to be recognised was carbon. Indeed the pure forms of this element diamond and graphite, have been known for many thousand years stretching back before recorded history. Both these materials are of great importance in industry and in every day life, there importance can not be over estimated. Carbon is also the major atomic building block for life. All life on earth has carbon central to its composition and indeed the scientific study of carbon compounds, known as organic chemistry is a very large research field. As far as humans and life are concerned, carbon appears to be the most important element of them all, making up a large fraction of our composition. In the last 150 years or so carbon chemistry has therefore become one of the major avenues for scientific research. Bering in mind all this activity on carbon compounds it was very likely that if any of the basic elements were going to produce new surprises, it probably wouldn't be pure elemental carbon, we thought we knew just too much about it. It therefore came as a great surprise to many when, in 1985 a new, third form of carbon was discovered - Buckminsterfullerene.

Diamond and graphite are what is termed giant structures, that is if we could look deep into the structure with a powerful microscope, we would see millions and millions of atoms all connected together in a regular array. Graphite would appear to be made up of seemingly infinite planes of flat sheets of atoms lying one on top of another, while diamond would appear as a rigid and rather complex system, rather like some enormous scaffolding construction.

Buckminsterfullerene, on the other hand, is composed of just 60 atoms and its structure, although fairly complex, is in fact far more familiar. The atoms in this new form of carbon are arranged in exactly the same way (albeit much smaller !) to the patches of leather found on the common football, that is the structure is made up of pentagonal and hexagonal rings of carbon atoms. Buckminsterfullerene is a tiny molecular football of carbon as many times smaller than a real football, as the earth is to a football. Since its discovery Buckminsterfullerene has become known by various shorthand names including buckyball and C60, I shall use the later. A whole family of different size cage molecules were discovered (where C60 has the greatest stability), and these are known collectively as the fullerenes.

Its hard to imagine two solid substances having greater differences in properties than graphite and diamond. One is soft and lubricating, due to the ability of those microscopic flat sheets to slip over each other. The other is hard and rigid with the 'scaffolding' type structure making it the hardest naturally occurring substance. It appears then, that the properties of materials, (even when they are made up of identical building blocks, in this case carbon atoms) are dependant on there microscopic structure. Essentially it is the unique structure of buckminsterfullerene that makes it so interesting to the scientist. Nothing quite like this football molecule has ever been observed before, and so we therefore believe that this new form of carbon should possess exciting new properties.

The buckminsterfullerene discovery is also important because the discovery spans many scientific disciplines. This interdisciplinary aspect not only appeals to the imagination but also brings scientists together who might not have otherwise shared there expertise. The benefits to science from this sort of collaboration are very great.

The Discovery of Buckminsterfullerene
The discovery of C60 was not made by scientists who were directly trying to make new materials. Rather, it was discovered almost be accident during experiments aimed at trying to understand chemistry in stars.

Despite the terrible loss of life and human creativity, the two world wars inevitably caused considerable improvements in technology. Before thinking too negatively on this point (for example atomic bombs etc.), one must remember the great advances in medicine and communications that have occurred because of 'war efforts'. My point is, that after the second world war, technology had improved dramatically. Advances in radio techniques were applied for peaceful research, and radar antenna once aimed at advancing enemy aircraft, where aimed at the stars instead. Since the war chemists have joined with astronomers to search for molecules in space. Certain molecules have a very characteristic spectra that allows the unambiguous detection of there presence in space once the same laboratory spectra can be recorded. A number of astronomical objects had been found to contain vast hoards of molecules in particular carbon chains called cyanoacetylenes.

In the 1970's David Walton and Harry Kroto at Sussex University, along with there respective students, had set up a programme to make cyanoacetynes in the lab, then by introducing these into a microwave spectrometer, measure there characteristic spectra. When the recorded spectra agreed with the theoretical predictions a search could be made using radio telescopes so that there presence in space could be verified. Usually the laboratory measurements would take place at Sussex while the astronomical measurements would take place at one of the number of radio telescopes dotted around the world. Interestingly, astronomical objects known as carbon stars, where found to be particularly good places to find these carbon chains, in fact there abundance in these objects were many hundreds of times greater than expected.

In 1985 an experiment was initiated by Kroto to investigate the carbon process occurring under similar conditions in the laboratory. In the lab of Richard Smalley at Rice University, Texas a Cluster Beam apparatus was used to vaporise carbon using a high intensity laser. The laser burns off carbon to form a plasma of several thousands of degrees not dissimilar to the temperatures of the surfaces of carbon stars. The molecules and particles that condensed from this hot plasma were then analysed by a mass spectrometer, sorting out the products into there corresponding mass. A more detailed description of this experiment and the results have been described elsewhere, but very briefly the carbon chains identified in space were detected by this apparatus, suggesting among other things that there was a very efficient formation mechanism for these species. The consequences of these results from a chemical and astronomical point view will not be discussed here because it turned out to be only a minor result of this unusual experiment.

Unexpectedly the cluster beam results also showed relatively large signals for the very large carbon molecules. The 60 atom specie in particular could be made almost dominant over the mass range explored by the machine. By adjusting the conditions carefully, even the carbon chains were swamped by the massive C60 signal, something rather incredible had been discovered. After careful analysis of the data, to check, among other things, weather it was not just an instrumental error, the only likely solution to the unexpected spectra was if carbon cages were being formed as well as the carbon chains. In particular C60 was proposed to have a football structure, known to mathematicians as the truncated icosohedron. The shape is composed of 12 pentagon and 20 hexagon rings. The molecule was named Buckminsterfullerene in honour of the architect, who designed geodesic domes based on similar pentagonal and hexagonal structures.

A Scientists Dream - Making Some C60
Over the next five years (1985-1990) the physical and chemical properties of C60 were investigated by analysis of the mass spectrometric data obtained from the cluster beams [5]. The cluster beam apparatus is an extremely sensitive machine, and as a result only very tiny amounts of C60 were actually being detected in the experiment. The machine that discovered C60 was therefore ideal for its initial study but in order to measure the fascinating properties of buckminsterfullerene a method for producing gram quantities was required.

Scaling up the cluster beam apparatus to make C60 was unfeasible, the amounts produced were really so small. It turned out that the discovery of a method of production was also made by a chance, again by scientists trying to understand astrophysical problems and not for work aimed at trying to make new materials. In 1990 a method was discovered for producing macroscopic amounts of this fascinating material [1]. This breakthrough has opened up a new field of chemistry allowing the properties of C60 to be determined directly.

A Method of Production ?
In 1989 Krätschmer, Fostiropoulos and Huffman published a fascinating paper in the proceedings of an astronomical conference [6]. They claimed, on the basis of Infrared (IR) and Ultraviolet (UV) measurements, to have found C60 in a soot-like carbon layer deposited by arcing carbon rods in an inert gas atmosphere. Simple group theoretical analysis to determine the normal modes of vibration, predicts only four IR active bands for C60. These soot films showed the presence of four weak bands superimposed on a broad continuum and the intensities suggested that the carrier made up about 1 % of the soot. On the basis of these results the authors claimed that C60 could therefore be made in this very simple way.

To those not involved in the field it may come as a surprise to here that this paper was almost completely ignored probably for the following reasons. Analysis of the cluster beam data suggested that the amount of C60 being formed from the graphite was only about 1 part in 10,000 at best, and probably more like 1 part in 1,000,000. If one could obtain only this sort of production in the relatively sophisticated cluster beam equipment one would really not expect a simple carbon arc to be an efficient at all. Also the cage molecule C20H20, dodecahedron [7], had been made in the lab, in small quantities by a sixteen step synthesis from a suitable precursor. C60 (roughly three times the size) was therefore expected to be a difficult molecule to synthesis. Despite this Krätschmer et al. claimed that their technique was not only incredibly simple but also produced relatively high quantities of C60. It all seemed to good to be true.

My Interest in Astronomy
I studied for my first degree (in physics) at the University of Surrey between 1985-1989. For my final year project I designed, built and calibrated a magnetometer which I had intended to use for solar and terrestrial investigations. As far as I am aware no large magnetic storms occurred due to solar activity, during the period in which the magnetometer was in operation but, as luck would have it, in the last few days of the project, an electric storm passed very near the university allowing me to record magnetic fields created by the lightning. With this data I was able to make a rough estimate off the current flowing in the lightning discharges. My degree course also included an industrial year at the National Physical Laboratory (NPL) in Teddington. During this time I used atomic clocks for time transfer experiments. This rekindled my earlier interest in astronomy and inspired me to choose my own final year project developing the magnetometer.

Before I had finished my degree I wrote to Sussex University, enquiring about a D. Phil in Astronomy. My interests really lie in experimental science, unfortunately there are few opening in experimental astronomy. I was interviewed at Sussex where it was suggested that I would do better to try another university. A few weeks later however, I received a letter from the Astronomy department suggesting I contact Prof. Harry Kroto in the School of Chemistry and Molecular Sciences. I was interviewed by Prof. Kroto and he told me all about this fascinating new form of carbon - C60. I considered that I had quite a good idea of what was happening in other branches of science but I had never heard of this amazing discovery of a new form of carbon. This made me realise how important good communication between the sciences really is. The research seemed so fascinating, and Prof. Kroto was so enthusiastic that I really wanted to work in this field.

A New Post-Grad - The First Experiment
I started my D. Phil with Harry on 10-10-89. He was keen to try and reproduce the fascinating IR spectra obtained by Krätschmer et al. Two years earlier his group had made similar materials but had to abandon the investigation due to lack of financial support for the project.

The old, worn out carbon arc vaporiser used in these experiments was resurrected and Simon Balm (also a D. Phil student at the time) and myself spent a few days playing around getting it working. By the 17th October we vaporised carbon and obtained a deposit. Then Simon left to work on the cluster beam apparatus in another part of the building and I was joined by Amit Sarkar, a final year chemical-physics student. We worked together in order to try and reproduce the results of the Krätschmer paper which would also form Amits final year project.

During the next few weeks we found that the nature of the carbon deposited was critically dependant on the gas pressure under which the rods were vaporised. On the 22nd October we confirmed the IR results for the first time. However we could not reproduce these results consistently. During the following week, after continued use, the old equipment could take no more; the insulation on an old variac failed and burned out, the wiring left a lot to be desired and the pressure gauges and pump connections needed changing. To quote Harry Kroto, "you just start to get some results and the apparatus gives up, typical !" I spent the next week rebuilding the vacuum system and the electronics. Steve Wood (my British Gas CASE award supervisor) brought me a welding kit power supply to replace the old vaporiser transformer. When the apparatus was finally in working order we were allocated a small disused dark room in which to set it all up.

By the 11th of December we had conducted more experiments and we were able to reproduce the spectra a second time, it really did look as if the soot contained something interesting. Amit and I continued the experiments but we could still not get reliable spectra from the films; only about one in every ten produced a positive result.

Amit finished his project with two positive IR spectra confirming the results of Krätschmer et al. [8]. Meanwhile I pressed on with trying to make reproducible films so that I could pin-point the exact conditions which would give rise to the 4 bands. To do this I varied every parameter I could think of while trying to keep all else constant. While I was conducting these experiments I was also building equipment for the cluster beam experiments. On the 28th of February 1990, I wrote to Krätschmer telling him of the results we had obtained and received a friendly positive reply.

After some time I found that the separation of the depositing surface from the arc was the important factor once the pressure of the gas was greater than the value noted by Krätschmer et al. (10 Torr for helium). This allowed me to detect the bands routinely and thus be able to see, for example, how gas pressure or separation effected the spectra. (With hindsight, it is probable that in the case of films deposited too near the hot arc, most of the fullerene content may sublime away, and therefore no bands are detected). The results of these measurements were presented at a Conference on Molecular Clouds in Manchester on 25 - 29 March 1990 [9]. A lot of interest was shown and several reprints were requested. One encouraging comment came from the astronomer Patrick Thaddeus who said, "I think you really have got something there".

The next few months were spent analysing some data obtained by the Giotto space probe which passed through the tail of Halley's Comet. As time permitted every few days I 'fired up' the vaporiser and made more soot. Every time the correct spectra were recorded the soot's were scraped off and collected. In this way I managed to collect a small stock of the precious (C60 containing ?) material.

By the 29th of May we thought we might have enough to run the solid state NMR. Three samples were submitted, so that any differences in the materials could be recorded. Unfortunately the NMR equipment had a faulty spinner and there seemed to be some confusion over the timing pulses needed to probe such samples - consequently no results were obtained.

The Halley Comet paper was written up by the 12th July and sent off. I was looking forward to a holiday in Scotland the following week, however before I left a friend of mine Nick Blagden (also a postgrad) suggested I submit a sample of the soot for mass spectrometric analysis. I gave a sample to Ala'a Abdul-Sada a post-doctoral fellow who has great expertise in mass spectrometry. He seemed very keen and said he would run the sample as soon as possible.

The following week was spent walking with Guy Nobel, and old school friend of mine through 80 miles of the Scottish mountains along the beautiful West Highlands Way, in gorgeous sunshine. This was a great experience and a time for a well-earned break. When I returned to Sussex Ali immediately contacted me saying he had some very exciting results, however in his own words "we have peaks at the correct positions Jon, but the machine has broken down so we can't repeat the measurements" (!). The spectrum showed the peak profile and isotope intensities expected for C60 (however the calibration was in error by 2 mass units). The importance of this spectrum cannot be over-emphasised because it was the first experimental evidence, apart from the IR results, to confirm the presence of C60 in the soot.

The Red Solution
On the 26th of July I read Krätschmer et al. paper in Chemical Physics Letters showing that pure 13C rods gave the same UV and IR spectra but with the expected isotope shifts [10]. This showed that the spectra originated from carbon and not from 'junk' evaporated into the arc, and also that the molecule was carbon rich. Krätschmer et al. also referenced our findings in their paper. This paper was important because it reminded me that the world was moving-on out there and that someone might actually make C60 very soon. This niggling worry didn't help things but it pushed me along.

On the following Friday I thought again about trying to extract the C60 from this soot. Over the past months I had made about 10 mg of soot that I knew contained the substance that produced the IR and mass spectra. To try and extract C60 seemed the next logical step. Benzene seemed the obvious choice. I took about half of the soot I had made and added it to about 20 ml of benzene in a small vial. I put it on the shelf and left it over the weekend. To be honest I didn't expect much to happen, but it was well worth a try. When I came in to the lab on Monday morning (6th August) the soot had settled and the benzene had turned red !, albeit very faint. On filtering and evaporation the liquid colour became far more intense as one would expect. I went round the lab proclaiming (although somewhat half-heartedly), " C 60's in here ! " shaking the small vial infront of peoples eyes, "Yes, OK Jon.....", but it turned out that this was exactly what it was. A red solution (or any other colour for that matter) from pure carbon was a totally unexpected result, infact the solubility of C60 remains one of its most important properties, allowing chemistry, for example, to be carried out relatively strightforwardly. Later we were to show that one could extract a whole family off fullerenes just by washing the soot in benzene.

Harry's response was one of excited caution. We were both worried that the colour may be due to a colloidal suspension of tiny soot particles - we must obtain a mass spec. of the liquid, however due to malfunctioning equipment the spectrometer gave no signal.

The Birth of Fullerene Science
On the morning of the 10th August Harry asked me to go down to the chemistry stores and pick up a Fax that had just come through from the journal Nature. On the way back I nosed through the papers intently. By the time I reached Harrys office I could tell he must have known what was in the paper. In the following silent minutes, that seemed to last for ever, I watched as Harry flicked through the pages with such concentration, "Oh my God, they've done it !".

The Nature paper was great, Krätschmer et al. had made the soots in the way described above and sublimed a solid from it which showed, by IR and UV spectroscopy and X - ray diffraction, results consistent with a molecular structure of small balls 7 Å across, AND it was found to be soluble in benzene to give a red solution (!) [1]. The following days were not what one could call easy, one can imagine what it must be like to spend years working on an idea and then be proved correct by someone ELSE.

Personally my feelings were mixed, on the one hand all this work I had been doing was not in vain; C60 really did exist in the soots, which was rather satisfying. On the other hand it looks like we had been so close ! My view is that we could have proved the structure of C60 at Sussex but I would have done it cautiously in my own time, probably in the remaining two years of my degree. However this was not to be the case because the fullerene story had entered a new phase.

After what must have been an indigestible lunch, Harry sent a Fax back to Nature expressing his congratulations to the authors. Soon everyone in the School came to know about the discovery. I meet Chup Yew Mok, a visiting professor, he said "Jon, everyone is talking about your work !"

The Nature paper described a classic example of a new discovery in science and because of this it deserves all the fame it has received, and rightly so. However the next crucial step in the story was carried out here at Sussex with Roger Taylor joining the team. The next day Roger came up to talk to Harry, he had some ideas on how to extract and possibly separate the material more effectively. He asked for all the material I had made, I was very reluctant to let this precious stuff go, so initially I gave him half my total stocks. Meanwhile I pressed on making as much material as possible. Roger used the soxhlet method to extract much more material from the soot, we got an 8 % yield of C60 ! However a really exciting discovery came when Roger chromatographed this extracted material. He obtained at least three coloured bands of material separated on the chromatography column, one was the characteristic red colour but the first fraction was magenta, what was this first fraction ?

One result from the initial 1985 discovery was that whenever C60 formed then so should C70. Could this first band be C70 ? The Nature paper FAX focused only on C60. The one measurement that would prove the structure without doubt was the 13C NMR spectra - there were no NMR measurements in the Nature paper, if we could record this all would not be lost ! Gerry Lawless and Tony Avent of the Sussex NMR lab ran these fractions for solution NMR. Because of the high symmetry of C60 the NMR should give one resonance, and if C70 had the proposed (D5h) structure then it should produce a 5 line spectra of predictable intensities (having a 1 : 2 : 1 : 2 : 1 ratio). The results were exactly as expected, we were the first group to measure the NMR of pure C60 and C70 and prove unambiguously there structures by this powerful method. All was not lost.

We were still having problems with the mass spec. at Sussex so I took the two (now very, very precious) samples up to VG Analytical in Manchester to run on their superb machines. Harry, Roger and David Walton (a major team member of the Sussex C60 group) waited by the phone at Sussex for me to ring them with any news. After much trying we did eventually record the mass spectra we needed.

It turns out that C60 is magenta in solution and that the red seen in the extract was in fact due to the more strongly coloured (but less abundant) C70. These results were published very soon in our paper to the journal Chemical Communications [11]. Roger continued the chromatography and I converted an old pyrolysis chamber into a more efficient fullerene soot generator [12].

As a group we worked very long hours, I remember on many occasions toiling through the night to make more soot and trying various experiments to improve the yields. It was a very exciting time, new things were being discovered daily and working the long hours just didn't matter. Overall it felt like a great team effort.

Since the discovery that C60 can be extracted from the arc processed carbon the field of fullerene research has grown spectacularly. This almost 'epidemic' resulted in over 600 papers on fullerene research in the first year since the 1991 breakthrough. Fullerene research now has important implications for many branches of science from physics and chemistry, to astronomy. Fullerenes can be made by; sooting hydrocarbon flames, evaporating graphite by RF induction heating, they have been made by evaporating graphite using sunlight concentrated by a large mirror, infact almost anywhere were carbon can nucleate from a plasma. The likely hood for finding C60 in space, produced for example by the hot surface of carbon stars (along with other carbon rich objects) therefore appears to be promising.

>From a technical point of view C60 has been found to be superconducting when doped with metal atoms. Light Emitting Diodes (LED's) have been fabricated from similarly doped material and solutions of C60 show interesting optical phenomena. The list of possible applications and novel properties increase all the time, and who knows we may eventually find these molecules even in house hold appliances.

The interdisciplinary aspect of the C60 story certainly appeals to the imagination which must be good for science promotion and education. Recently the BBC television programme, Tomorrow's World has presented articles on Buckminsterfullerene and inperticular the science series Horizon have covered the whole story (Molecules with Sun glasses, 1992).

Finally a nice aspects of the whole story is that it shows how a student can become involved in very important and exciting research without the need for a great expertise or the purchase of expensive equipment. In this day-and-age of super computers and vast particle physics laboratories, its nice to know that science can also be done with just a few pounds worth of equipment. Natures secrets may be hard to uncover but this does not mean that they are always costly to discover. Our future depends on science and we must therefore make sure that suitable encouragement continues in all avenues.

Its not easy to know where to start when trying to thank the many people who, not only made this work possible, but have also made it such an enjoyable time.

First of all, thanks must go to Harry Kroto for being enthusiastic, inspirational, motivating and honest. I must also thank David Walton, Steve Woods and Roger Taylor for all their help and kindness throughout the C60 saga.

I am also grateful to the following people; Amit Sarkar, Steve Firth, Ali Abdul-Sada, John Dennis, Wahab Allaf, Simon Balm, Chup Yew Mok, Wolfgang Krätschmer, John Lynch (BBC) and Saul Nassé (BBC).

I especially thank my father and my brother, without there enthusiasm and love I would have never have overcome my problems with reading and writing. In a way I suppose this article is dedicated to all those kids who are categorised as having 'spelling difficulties'.

1. Krätschmer, W.; Lamb, L. D.; Fostiropoulos, K.; Huffman, D. R.Nature 1990, 347, 354-358.

2. Braun, T. Angew. Chem. Int. Ed. Engl. 1992, 31, 588-589.

3. H. W. Kroto, Angew. Chem. Int. Ed. Engl. 1992, 31, 111., Krätschmer, W., Huffman, D. R. Carbon 1992, 30, 1143. and Huffman, D.R. Physics Today Nov. 1991.

4. Kroto, H. W.; Heath, J. R.; O'Brien, S. C.; Curl, R. F.; Smalley, R. E. Nature 1985, 318, 162-163.

5. Kroto, H. W.; Allaf, A. W.; Balm, S. P. Chem. Rev. 1991, 91, 1213-1235.

6. Krätschmer, W.; Fostiropoulos, K.; Huffman, D. R. Dusty Objects in the Universe; Bussoletti, E.; Vittone, A. A.; Eds.; Kluwer: Dordrecht, 1990 (Conference in 1989).

7. Paquette, L. A.; Ternansky, D. W.; Balogh, G.; Kentgen, Science, 1983, 105, 5446.

8. Sarkar, A., Final Year project, University of Sussex, Mols., 1990.

9. 7th Manchester Astronomical Conference on Molecular Clouds, Confirmation of the detection of discreet IR bands in deposited carbon. 26 - 30 March 1990.

10. Krätschmer, W.; Fostiropoulos, K.; Huffman, D. R. Chem. Phys. Letters 1990, 170, 167.

11. Taylor, R; Hare, J. P.; Abdul-Sada, A. K.; Kroto, H. W. J. Chem. Soc. , Chem. Commun. 1990, 1423-1425.

12. Hare, J. P.; Kroto, H. W.; Taylor, R. Chem. Phys. Letters 1991, 177, 394-398. 7


Dr Jonathan Hare, The University of Sussex
Brighton, East Sussex. BN1 9QJ.

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