Gainesville, FL--University of Florida engineering researchers have found they can ignite modified fullerenes using a low-power medical laser, a development they say opens the door to a wave of new technologies in health care, computing, and automotive design.1
The archetypal fullerene is C60--a single-molecule sphere of carbon atoms forming a pattern of pentagons and hexagons. Fullerene comes in other versions such as C70; in addition, non-carbon atoms and non-fullerene molecules can be attached (often distorting the fullerenes). If those atoms or molecules turn the fullerene into a tool that is useful in some biologically or chemically reactive way, then the fullerene is said to have been "functionalized."
The researchers used lasers with power in the range of 500 mW, which, when focused to an intensity of 100 W/cm2, is enough to initiate the uncoiling or unraveling of the functionalized fullerenes. That process, they believe, rapidly releases the energy stored when the molecules are formed into their distorted shapes, causing light, heat, or burning under different conditions.
Killing cancer cells
In one possible application, the researchers infused cancer cells in a laboratory with a variety of functionalized fullerenes called polyhydroxy fullerenes, which are known to be biologically safe. They then used the laser to heat the fullerenes, destroying the cancer cells from within.
"It caused stress in the cells, and then after ten seconds we just see the cells pop," said Vijay Krishna, a postdoctoral associate.
He said the finding suggests doctors could dose patients with the polyhydroxy fullerenes, identify the location of cancers, then treat them using low-power lasers, leaving other tissues unharmed. Another application would be to image the locations of tumors or other areas of interest in the body using the fullerenes' capability to light up.
Efficient explosive triggers
The paper also reports the researchers used fullerenes to ignite a small explosive charge. The weak laser contained far less energy than standard electrical explosive initiators, the researchers said, yet still ignited a type of functionalized fullerenes called carboxy fullerenes. That event in turn ignited comparatively powerful explosives used in traditional blasting caps.
Mining, tunneling, or demolition crews currently run electrical lines to explosives, a time-consuming and expensive process if the explosives are far away. The experiment suggests crews could use blasting caps armed with the fullerenes and simply point a laser to set them off.
"Traditional bursting caps require a lot of energy to ignite--they use a hot tungsten filament," said Nathanael Stevens, a postdoctoral associate. "So it is interesting that we can do it with just a low-powered laser."
Lithography
The researchers coated paper with polyhydroxy fullerenes, then used a high-resolution laser to write a miniature version of the letters "UF." The demonstration suggests the technique could be used for many applications that require precise lithography. The researchers had developed one promising application involving creating the patterns on computer chips, said Brij Moudgil, professor of materials science and engineering at the University of Florida and director of the engineering college's Particle Engineering Research Center, where the research was conducted.
Other uses
Although not discussed in the paper, other potential applications include infusing the fullerenes in gasoline, then igniting them with lasers rather than traditional spark plugs in car engines, Moudgil said. Because the process is likely to burn more of the gasoline entering the cylinders, it could make cars more efficient and less polluting.
REFERENCE
1. Vijay Krishna et al., Nature Nanotechnology, Published online: 14 March 2010 | doi:10.1038/nnano.2010.35
