Scientists used ultrashort pulses of light to take a closer look at photosynthesis in plants, and, in doing so, discovered that molecular vibrations can actually enhance the efficiency of photosynthesis.
The researchers believe that this will allow for people to manufacture better solar cells and energy storage systems.
Photosynthesis allows plants to get energy from the sun. By converting sunlight, water, and carbon dioxide, plants create food for themselves and emit oxygen for animals to breathe. Even though the process is vital for life on Earth, scientists still have a lot to learn about it.
For this study, researchers extracted the photosystem II reaction centers from the leaves of plants. Photosystem II is located in the chloroplasts of plant cells and is a group of proteins and pigments that provide the backbone of photosynthesis. It is also the only natural enzyme to split water into hydrogen and oxygen by using solar energy.
After extracting the photosystem II reaction centers, the researchers then initiated photosynthesis by using carefully timed sequences of ultrashort laser pulses. By taking snapshots of the process in real time, they were able to view the molecular vibrations that actually help enable separation, which is the process of removing electrons from atoms during the beginning of photosynthesis.
“This particular system is of great interest to people because the charge separation process happens extremely efficiently,” said lead author Jennifer Ogilvie. “In artificial materials, we have lots of great light absorbers and systems that can create charge separation, but it’s hard to maintain that separation long enough to extract it to do useful work. In the photosystem II reaction center, that problem is nicely solved.”
In the end, the scientists found that specific vibrational motions occur during charge separation.
“What we’ve found is that when the gaps in energy level are close to vibrational frequencies, you can have enhanced charge separation,” Ogilvie added. “It’s a bit like a bucket-brigade: how much water you transport down the line of people depends on each person getting the right timing and the right motion to maximize the throughput. Our experiments have told us about the important timing and motions that are used to separate charge in the photosystem II reaction center.”
The findings are published in the journal Nature Chemistry.