Morphology of C60 nanotubes fabricated by the liquid-liquid interfacial precipitation method

Single crystalline C60 fullerene nanowhiskers are formed by adding isopropyl alcohol gently to fullerene saturated solutions. The method is called the liquid-liquid interfacial precipitation method. In the present study, observation using transmission electron microscope was made for C60 nanowhiskers with hollow structure, i.e. C60 fullerene nanotubes fabricated by the modification of liquid-liquid interfacial precipitation method using pyridine as solvent. After adding isopropyl alcohol to the C60 solution in the glass bottles, ultrasonic dispersion was applied for 1 min and then the bottles were kept at 10 °C. Within 24 h, fibrous solids with the length larger than several millimeters and the diameters ranging from submicrons to 1 μm were precipitated. For the transmission electron microscope study, the samples were pulverized by the ultrasonic dispersion. Under the transmission electron microscope, tubular morphology was usually observed for the whiskers with the diameters larger than 200 nm and hardly observed for those with the diameters smaller than 200 nm; both the C60 fullerene nanotubes and the fullerene C60 nanowhiskers were in crystalline state. Since partly tubular structures were sometimes observed at the end of the C60 fullerene nanowhiskers, the mechanism for the formation of tubular morphology is suggested to be a dissolution process after the crystal growth. When the samples were kept in the glass bottles for several hours after the pulverization, closing of nanotubes at the ends was observed for relatively smaller nanotubes in diameter. For relatively larger nanotubes in diameter, zigzag thinning of tube wall edges was observed. It is thus expected that subsequent growth or dissolution occurred at the end of the pulverized C60 nanotubes, which may be an effective way to control the shape of tubes. The C60 nanotubes presented here will be useful as adsorbents, catalysts, and membranes.