杏吧原创

Blink and you might miss it. Researchers have captured the rapid formation of buckyballs 鈥� carbon spheres just 1 nanometre in diameter 鈥� on film for the first time.

The footage shows how buckyballs, or C60 fullerenes, form in a new process where a thin sheet of graphite exposed to high temperatures shrinks and loses carbon atoms, says at Rice University in Houston, Texas, US.

鈥淚t鈥檚 a bit like polishing a diamond,鈥� he says. 鈥淭he starting point is a large, angular carbon sheet, and heat helps remove the imperfections and form symmetrical C60 spheres.鈥�

Buckyballs could have a wide range of potential applications, from medical imaging to toxic waste clean鈥搖p, although there are also concerns over their potential toxicity.

Yakobson and his colleagues at Rice University teamed up with Jianyu Huang at Sandia National Laboratories in New Mexico, US, to study buckyball formation. Their starting point was a much thicker carbon nanotube.

Yakobson鈥檚 team fired an electric current through the tube, heating it to over 2000 潞C. At this temperature some of the carbon evaporated from inside the tube and reassembled into a large, single-layer graphite sheet.

Maintaining the graphite at high temperature caused it to start losing carbon atoms through evaporation, before gradually shrinking to form a stable C60 fullerene. Eventually, even the C60 fullerenes shrank and disappeared. The process involved made it possible for researchers to monitor the buckyball鈥檚 development using a transmission electron microscope.

鈥楴ice experiment鈥�

The experiment is the first to demonstrate that buckyballs form through a 鈥渟hrink-wrap鈥� process, says Yakobson.

Harry Kroto discovered buckyballs in 1985 while at the University of Sussex. 鈥淭his is a nice experiment,鈥� he says. 鈥淚t indicates one mechanism to produce C60 fullerenes. But I鈥檓 not convinced it is necessarily the only way.鈥�

Kroto thinks buckyballs may form through 鈥渟elf-assemblage鈥� as well as through 鈥渟hrink-wrapping鈥�. He suggests that fullerenes could also begin life as small carbon molecules that gradually grow through the 鈥渋ngestion鈥� of carbon atoms.

Yakobson says both processes may actually be at work during the fullerene formation recorded by his team. 鈥淭he problem with our approach is we only see one half of the process,鈥� he says. 鈥淲e start from the moment that we see big, ugly graphite sheets shrinking into C60 fullerenes.鈥�

These graphite sheets may themselves form through a process of self-assemblage, he says: 鈥淲e are still missing the first act of the drama.鈥�

Journal reference: Physical Review Letters (DOI: )

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