Sunday, 17 January 2010

Powered By Titanium Leaves


Leaves absorb lots of sunlight, and then use the energy from that light to turn water and carbon dioxide into sugars. That’s photosynthesis.

So when scientists were looking for efficient ways use sunlight to split water and generate hydrogen for power, they turned to the intricate architecture of leaves. Rather than create a solar cell with some of the attributes of a leaf they decided to turn a real leaf into an artificial one...

The work, reported by New Scientist, comes out of Shanghai Jiao Tong University in China, led by Fan Tong Xian. Fan and his colleagues dipped a couple of different leaves (Anemone vitifolia was one of them) into dilute hydrochloric acid, and replaced the magnesium in the leaf with titanium.

Magnesium is a key part of chlorophyll, one of the raw ingredients needed from photosynthesis. You’ll remember chlorophyll from the green slug story

The leaves were then dried and cooked, getting rid of pretty much everything that wasn’t originally chlorophyll. This left a titanium oxide network plus a few tougher parts of the leaf. Titanium oxide just happens to be the material used in solar cells to make them more efficient.

The resulting ‘structure’ had lens-like cells on its surface to capture light, as well as the veins that not only move water and sugar through the living plant but also serve to direct light deeper into the leaf. This artificial leaf even had the tiny stacks within plant cells called thylakoids (just few nanometres thick) that increase the surface area for chlorophyll to absorb light.

These leafy creations were then dipped in an alcohol solution and flooded with light. Turns out they were twice as good at absorbing that light as a standard form of titanium oxide called P25.

It's early days for this project, but clearly the plant world still has plenty to teach us.

Image: leaf of Chrysophyllum cainito – what an amazing design!

1 comment:

Andrew said...

Wow that's really interesting!