Transmission electron microscopy investigation of fullerene nanowhiskers and needle-like precipitates formed by using C
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datomo Suga Department of Precision Engineering, School of Engineering, The University of Tokyo 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan (Received 22 February 2004; accepted 3 May 2004)
Nanowhiskers and needle-like precipitates obtained by the liquid-liquid interfacial precipitation method for the systems of isopropyl alcohol and toluene solutions of C60 and (2-C60)Pt(PPh3)2 were examined by transmission electron microscopy. Morphology of the C60 precipitates was remarkably changed by the addition of (2-C60)Pt(PPh3)2 in the C60 toluene solution, and capsular needle-like crystals of C60 were formed. C60 cages were found to be directly contacted along the growth axis of (2-C60)Pt(PPh3)2 needle-like crystals. I. INTRODUCTION
Recently we showed that single crystalline nanowhiskers of C60 and C70 can be produced through the liquid– liquid interfacial precipitation method (LLIP method) that uses a system of C60 (C70)-saturated toluene and isopropyl alcohol.1,2 The LLIP method can be applied to a system of C60-saturated m-xylene and isopropyl alcohol as well.3 The produced C60 nanowhiskers are shown in Fig. 1, for example. The C60 nanowhiskers have diameters of about 200 nm and lengths more than 500 m and may be called “C60 nanofibers.” In the LLIP method for C60, isopropyl alcohol is very slowly added to an organic (toluene, m-xylene) solution saturated with C60 to form a liquid–liquid interface of the C60 solution and isopropyl alcohol at room temperature. The temperature of C60 solvents and isopropyl alcohol is usually set lower than 25 °C in the process. The C60saturated organic solution is put into a transparent glass bottle and an equal amount of isopropyl alcohol (IPA) is added to the solution by using a pipette. Brownish, tiny precipitates of C60 are observed to nucleate by adding IPA. The nucleation of C60 precipitates can be understood by assuming that a supersaturated state of C60 occurs by the addition of IPA. The liquid-liquid interface between the C60-saturated toluene and IPA gradually disappears by diffusion, and fine C60 whiskers with constant diameters slowly grow in the bottle.
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2004.0304 2410
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J. Mater. Res., Vol. 19, No. 8, Aug 2004 Downloaded: 13 Mar 2015
Recently, it was found that the growth of the C60 whiskers is assisted by illumination of visible light.12 This fact suggests that the growth of C60 whiskers is promoted by the [2 + 2] cycloaddition across bonds, which is allowed in photoreaction of C60 molecules.13 The C60 nanowhiskers can be transformed into tubular structures by heating in vacuum.3 Figure 2 shows an example of the nano carbon tube (named “fullerene shell tube”) with an outer diameter of 240 nm and an inner diameter of 180 nm. The nano carbon tubes can be prepared by heating C60 nanowhiskers under rotary pump vacuum at temperatures higher than 600 °C.3 The LLIP method can be applied to synthesize the
FIG. 1. SEM image of C60 nanowhiskers
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