Turning Gold to Purple to Harvest Sunlight

Professor Richard Watt and his chemistry students at Brigham Young University suspected that a common protein could potentially react with sunlight and harvest its energy — similar to what chlorophyll does during photosynthesis.

They started with citric acid from oranges and mixed it with the protein. Next they dissolved gold powder into the solution. Then they put vials of the yellow-colored mixture in direct sunlight and crossed their fingers in the hope that it would turn purple.

Here's the reason why: If it turned purple, that would signal that the gold atoms had received electrons and used the donated energy to bunch together as small, purple-colored nanoparticles. And that would mean that the protein used the sunlight to excite the citric acid and trigger a transfer of energy.

While direct sunlight did the trick in about 20 minutes, a high-powered tungsten mercury lamp worked much faster.

"We set the system up, turned on the light, and the solution turned purple," Watt said. "We knew that we'd proved the concept."

BYU chemists developed a method of artificial photosynthesis, and proved it by turning gold atoms (left) into purple-colored nanoparticles (right). (Image: Mark Philbrick/BYU)

The BYU researchers published their experiments in the Journal of Nanoparticle Research. The final step of this project will involve connecting the protein to an electrode to channel the energy into a battery or fuel cell. The BYU chemists will partner with Jae-Woo Kim of the National Institute of Aerospace for this next stage of the work.

Co-authors on the new study include BYU graduate Jeremiah Keyes, grad student Robert Hilton and Jeff Farrer, who runs an electron microscope lab at BYU.

For more information, visit: www.byu.edu