Physics of the Solid State, Vol. 44, No. 4, 2002, pp. 601–602. Translated from Fizika Tverdogo Tela, Vol. 44, No. 4, 2002, pp. 579–580. Original Russian Text Copyright © 2002 by Churilov, Isakova, Weisman, Bulina, Bachilo, Cybulski, Glushchenko, Vnukova. PROCEEDINGS OF THE V INTERNATIONAL WORKSHOP “FULLERENES AND ATOMIC CLUSTERS” (St. Petersburg, Russia, July 2–6, 2001) Synthesis of Fullerene Derivatives G. N. Churilov*, V. G. Isakova*, R. B. Weisman**, N. V. Bulina*, S. M. Bachilo**, D. Cybulski**, G. A. Glushchenko*, and N. G. Vnukova* * Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russia e-mail: [email protected] ** Rice University, Houston, TX 77005 USA e-mail: [email protected] Received April 1, 1999 Abstract—This paper presents the results of plasmochemical synthesis of fullerene derivatives with hydrogen, iodine, iridium, platinum, and scandium. The synthesis is carried out under atmospheric pressure in a carbon– helium plasma stream formed by an ac arc in the rf range. © 2002 MAIK “Nauka/Interperiodica”. The synthesis of fullerene derivatives with H2, I2, changes (as compared to the spectrum for a fullerene Sc, Ir, and Pt was carried out in a plasmochemical reac- mixture): a new band appeared at 434 nm and the band tor developed earlier in [1, 2]. The reactor differs con- at 334 nm was displaced to the UV region by 17 nm. siderably from the widely used Kretschmer reactor in This variation is usually attributed to fullerene com- that the synthesis occurs under atmospheric pressure in plexes with hydrogen of the C60H2 type [4, 5]. a stream of carbon–helium plasma generated by an ac Emission spectroscopy revealed the presence of Sc arc in the rf range. The reactor makes it possible for par- at a content of the order of 10–3% in the fullerene-con- ticles of the introduced substance to stay for a long time taining extract. in the carbon plasma jet and, hence, become atomized Highly effective chromatographic separation of the completely. Consequently, this reactor can be used for fullerene mixture prepared by extraction from Ir- and the synthesis of fullerenes both with light elements and Pt-containing soots was carried out in a Cosmosil with refractory metals. Buckyprep column. The mass spectra of the separated In accordance with the concept of the effect of the fractions were measured. It was found that the given electron concentration on the formation of fullerenes extract contains 55% C60, 25% C70, 15% higher and fullerene derivatives in a carbon plasma, which was fullerenes (mainly, C76, C78, C82, C84, and C86), and 5% developed in our earlier work [3], we synthesized oxidized fullerenes C and C . fullerene derivatives by adding both donors and accep- 60 70 tors of electrons (hydrogen, iodine, scandium, iridium, Mass spectrometry did not reveal the presence of and platinum). The initial metallic powder or metal any platinum or iridium derivatives in the extracts sep- wire was placed in a hole (d = 1.2 mm) made in one of arated from Ir- and Pt-containing soots. This can be due the electrodes between which the plasma jet of carbon to poor volatility of the formed metal compounds. with a metal was formed. Hydrogen and iodine were Moreover, Pt- and Ir-containing derivatives involved in introduced into the reactor in the form of a gas flow and soots may be insoluble in organic solvents. In this con- vapor, respectively, in different temperature regions of nection, we made an attempt to convert them into vola- the plasma. We tested fullerene-containing soot and tile chelate complexes of metals, which are soluble in fullerenes extracted from it. organic solvents and similar to those described in [6]. Fullerene-containing soots with Pt and Ir (samples I An analysis of the x-ray spectra revealed that Ir, Pt, and II, respectively) were treated with acetylacetone and Sc metals are present in a fullerene-containing soot (Hacac) in solutions of HF (a) and HCl (b) acids during only in the amorphous state. heating, and, then, reaction products (Ia, IIa, Ib, and The fullerene yield increased upon the introduction IIb) soluble in organic solvents were extracted from the of a metal from 4 to 12%. The introduction of iodine reaction systems. virtually nullifies the concentration of fullerenes in the The electronic absorption spectra of products Ia and soot. IIa are shifted to the UV region as compared to samples The electronic absorption spectra for the fullerene I and II. The x-ray diffraction pattern of the toluene extract from soots obtained during the synthesis with extract of the Ir-containing product IIa contains reflec- the introduction of hydrogen exhibited the following tions of fullerene (for small angles) and reflections of 1063-7834/02/4404-0601 $22.00 © 2002 MAIK “Nauka/Interperiodica” 602 CHURILOV et al. an unknown substance (for large angles); the latter the one hand, and the yield of the resulting fullerene reflections can be associated with Ir complexes. derivatives, on the other. This will be the next step Toluene extracts of the synthesis products contained toward the controlled synthesis of fullerene derivatives. fractions of greenish yellow and yellow color which were soluble in protogenic solvents (acetone and alco- hol). The electronic absorption spectra of compounds ACKNOWLEDGMENTS obtained from fullerene-containing soots and the spec- This work was supported by the American Founda- tra of halogenated iridium acetylacetonates contain tion CRDF, grant no. RE1-2231. The foundation is not bands at 270–280 nm, which are similar to the bands of responsible for the concepts, ideas, and results pre- iridium γ-fluoroacetylacetones but are displaced by 10– sented in this paper. This work was also partly sup- 15 nm toward the long-wavelength range. The presence ported by the Russian State Program “Fullerenes and of other bands can be associated with the presence of Atomic Clusters” (project no. 5-3-00) and the Program fullerenes in the metal complexes; in addition, the for- “University Research Work in Priority Trends of Sci- mation of carbon-bonded acetylacetonates and mixed ence and Technology,” the Ministry of Education of the halogenacetylacetonates of metals is also possible. Russian Federation (project nos. 201.05.01.001 and The results obtained demonstrate that, in the irid- 203.02.05.007). ium- and platinum-based fullerene-containing soots, iridium and platinum are in the chemically active form. This follows from the fact that the aforementioned reac- REFERENCES tions with acetylacetone do not occur with the familiar 1. G. H. Churilov, L. A. Soloviev, Ya. N. Churilova, et al., metallic forms of iridium and platinum (compact metal, Carbon 37, 427 (1999). metallic sponges, and powders). It can be assumed that 2. G. N. Churilov, Prib. Tekh. Éksp., No. 1, 5 (2000). the active form of Ir and Pt is their oxidized state in the 3. G. N. Churilov, P. V. Novikov, and N. G. Vnukova, in form of insoluble fullerides; however, the results of Proceedings of the XV International Winterschool on x-ray diffraction analysis indicate the presence of Electronic Properties of Novel Materials “Molecular amorphous particles of a metal in soots, which proba- Nanostructures,” Kirchberg, Austria, 2001. bly exhibit a high chemical activity. 4. D. Mandrus, M. Kele, R. L. Hettich, et al., J. Phys. The experiments described here indicate that the Chem. B 101, 123 (1997). synthesis of metallocomplexes of fullerenes in prepara- 5. C. C. Henderson and P. A. Cahill, Science 259, 1885 tion amounts is a complex problem associated with the (1993). donor and acceptor properties of the substances being 6. V. G. Isakova, I. A. Baidina, N. B. Morozova, and introduced. Further investigations are required for I. K. Igumenov, Polyhedron 19, 1097 (2000). determination of the relation between the magnitude and the variation of the electron concentration in a plasma upon the introduction of various elements, on Translated by N. Wadhwa PHYSICS OF THE SOLID STATE Vol. 44 No. 4 2002 Physics of the Solid State, Vol. 44, No. 4, 2002, pp. 603–606. From Fizika Tverdogo Tela, Vol. 44, No. 4, 2002, pp. 581–584. Original English Text Copyright © 2002 by Mordkovich, Shiratori, Hiraoka, Takeuchi. PROCEEDINGS OF THE V INTERNATIONAL WORKSHOP “FULLERENES AND ATOMIC CLUSTERS” (St. Petersburg, Russia, July 2–6, 2001) Synthesis of Multishell Fullerenes by Laser Vaporization of Composite Carbon Targets1 V. Z. Mordkovich, Yosuke Shiratori, H. Hiraoka, and Yoshimasa Takeuchi International Center for Materials Research, East 601, KSP, Takatsuku, Kawasaki, 213-0012 Japan e-mail: [email protected] Abstract—Multishell fullerenes are the smallest among multishell carbon clusters, such as the larger graphitic onions or multishell nanotubes. Unlike classical fullerenes, which have a cage structure and are known to have been synthesized in a variety of sizes (C60, C70, C84, C102, etc.), multishell fullerenes have a cage-inside-cage concentric structure, such as double-shell C60@C240 or triple-shell C60@C240@C560. We report on the synthesis of multishell fullerenes by laser vaporization of C60-containing composite carbon targets. Transmission elec- tron microscopy, Raman scattering spectroscopy, and other methods were used for characterization of the prod- uct. The yield of the process reaches up to 40%, which permits production in gram amounts even in laboratory conditions. © 2002 MAIK “Nauka/Interperiodica”. 1 Multishell fullerenes are the smallest among multi- Also, it seems reasonable to suggest that the actual shell carbon clusters, such as the larger graphitic onions growth of additional shells around C60 cores takes place [1, 2] or multiwall nanotubes [2, 3]. Unlike classical not during 3000°C treatment but during the cooldown fullerenes, which have a cage structure and are known after the heat treatment. If this suggestion is correct, the to have been synthesized in a variety of sizes (C60, C70, successful synthetic route should be comprised of at C84, etc.), multishell fullerenes have a cage-inside-cage least two steps: (1) the formation of carbon vapor con- concentric structure, such as double-shell C60@C240 or taining many C60 molecules and (2) cooling down at the triple-shell C60@C240@C560.