In the last hundred years or so, people have been trying to simulate the working principles of nature. Flying is one of the most dreamed-of, and recently we are trying to mimic green plants and their way to capture the Sun’s energy.
Kane Jennings and Peter Ciesielski, along with a team of scientists from the Vanderbilt University in Nashville, Tennessee, have been working to create the world’s first artificial leaf, that can do what natural leaves do: capture the light. More, their leaves transform that light into electricity. So, the nature’s 3.5 billion years work is now to be synthesized in a lab experiment. Here’s how they do it.
Elias Greenbaum (is this his real name?) from the Oak Ridge National Laboratory discovered a protein in the 1990s, known as the PS1. He extracted the protein from spinach leaves, and observed that it remained active when immobilized on a gold surface.
The researchers built their device using a commercially available gold-silver alloy sheet. They poured nitric acid on the sheet to dissolve the silver from the surface and leave the gold sheet with nano-sized pored. This way they increased the useful contact surface area, where the PS1 protein is to be sprayed. The gold sheet is actually so thin after the treatment, that light is able to penetrate it, so they had to put it on a supportive layer of gold, thicker than the first, PS1-treated one.
The PS1 protein cannot attach itself alone to the gold. For doing that, the researchers applied a coating of thiols – chemical molecules that have a free end able to form strong bonds with the proteins.
The leaf device is now ready for electricity production. When you expose them to light, the PS1 complexes generate an electric current that can be harvested. In a living plant, those electrons would be used to reduce compounds as part of a chemical chain that produces new energy stores in the form of carbohydrates.
The sad part is that the current is very low, about 800 nanoamps per square centimeter. It isn’t economic at all, taking into account the device’s price versus the harvested current.
But research is on the way. Jennings says they’re investigating new methods to improve that current, and generate about 2 microamps (almost three times more), enough to power a small calculator. Also, the system is too fragile to light to be exposed directly to the Sun, which would burn the proteins.
Some may say this is not an important research, and it’s another worthless study made with a lot of money, but all great inventions must have a starting point, and if leaves can do it, I guess so can we, even more efficiently. So, again, like with other green discoveries, this is something to keep our eyes on. It could provide a maybe cheaper alternative to the current solar cells. Even Greenbaum, the PS1’s discoverer is impressed with his younger colleagues’ work: “This is very nice work by an outstanding group. The results represent an important research advance in bio-inspired solar energy conversion.”