Inorganic Materials Form Nanotubes, Concentric Fullerenes

Daniel S. Burgess

Researchers investigating nanostructures of layered inorganic compounds have theorized that these materials should spontaneously form tubes and concentric fullerenes similar to those observed in graphite exposed to an electron beam. Now a team from Jawaharlal Nehru Centre for Advanced Scientific Research and from the Indian Institute of Science, both in Bangalore, India, has confirmed that GaS and GaSe do adopt such configurations when irradiated with laser light or when heated.

Exposing GaS and GaSe to pulsed laser light or to heat produces nanostructures similar to those formed in graphite. The electron microscope images have been colorized to expose details of the nanostructures. Courtesy of Ujjal K. Gautam.

The scientists used electron microscopy to examine the resulting nanostructures from the treatment of powders of the materials. For the laser experiments, they first dispersed the samples in various liquid media, including di-tert-butyl disulfide, n-octylamine and toluene, and illuminated them for two minutes with pulsed 532-nm light from a Q-switched Nd:YAG. For the thermal experiments, they sealed the samples in a quartz tube, which they heated so that one end was 900 °C and the other 400 °C.

The researchers found that the irradiated samples formed nanotubes and concentric fullerenes, in proportions that were dependent on the host medium. The structures are the result of rolling of sheets of the materials that are exfoliated by the laser light. Thermal treatment also yielded nanotubes, scroll-like formations and "nanoflowers."