To make the fibers, Sotzing and his colleagues make a solution of salmon DNA and mix in the two types of dye. The solution is pumped slowly out from a fine needle, and a voltage is applied between the needle tip and a grounded copper plate covered with a glass slide. As the liquid jet comes out, it dries and forms long nanofibers that are deposited on the glass slide as a mat. The researchers then spin this nanofiber mat directly on the surface of an ultraviolet LED to make a white-light emitter.
During the fiber-spinning process, the two different dye molecules automatically attach themselves to two different locations on the DNA. The researchers have found in previous work that the nanofiber mats produce 10 times brighter light than thin films of the dye-containing DNA.
“It’s really very cool [work], and I think that it has practical promise,” says Aaron Clapp, a professor of chemical and biological engineering at Iowa State University. “[But] it seems like an overly dramatic way of doing it.”
Clapp speculates that instead of relying on energy transfer between the two fluorescent dyes, you could just change their ratios and get the colors you want.
However, each dye would then require a different input energy source as opposed to just one UV source, Sotzing points out. What’s more, energy transfer between two dyes gives better control over the color of the output light.
Walt says that it may be possible to use the first dye to transfer energy to multiple dyes and get an even wider range of colors. “The results reported here suggest DNA-[energy transfer] light emitters are promising,” Walt says, “but the ultimate utility will depend on factors such as lifetime and power efficiency.”