In this case, the team used a modified virus as a kind of biological scaffold that can assemble the nanoscale components needed to split a water molecule into hydrogen and oxygen atoms.
Splitting water is one way to solve the basic problem of solar energy: It’s only available when the sun shines. By using sunlight to make hydrogen from water, the hydrogen can then be stored and used at any time to generate electricity using a fuel cell, or to make liquid fuels (or be used directly) for cars and trucks.
Other researchers have made systems that use electricity, to split water molecules or tried to use the photosynthetic parts of plants directly for harnessing sunlight, but these materials can have structural stability issues. Belcher’s new biologically based system skips the intermediate steps and uses sunlight to power the reaction directly.
Belcher, who is the Germeshausen Professor of Materials Science and Engineering and Biological Engineering at MIT, decided that instead of borrowing plants’ components, she would borrow their methods. In plant cells, natural pigments are used to absorb sunlight, while catalysts then promote the water-splitting reaction. That’s the process Belcher and her team decided to imitate.
Belcher and her team engineered a common, harmless bacterial virus called M13 and encapsulated it in a microgel matrix so that it would attract and bind with molecules of a catalyst and a biological pigment. The viruses became wire-like devices that could very efficiently split the oxygen from water molecules.

The viruses simply act as a kind of scaffolding, causing the pigments and catalysts to line up with the right kind of spacing to trigger the water-splitting reaction. The role of the pigments is “to act as an antenna to capture the light,” Belcher explains, “and then transfer the energy down the length of the virus, like a wire.”

Using the virus to make the system assemble itself improves the efficiency of the oxygen production fourfold, doctoral student Yoon Sung Nam says. The researchers hope to find a similar biologically based system to perform the other half of the process, the production of hydrogen.
—– David L. Chandler, MMIT News Office

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