Metal-fungus hybrids make for more powerful catalysts

[Guest guest]

Metal-fungus hybrids make for more powerful catalysts

24 September 2008

New Scientist (subscription) - UK*

NewScientist.com news service

Colin Barras

http://technology.newscientist.com/article/dn14802-metalfungus-

hybrids-make-for-more-powerful-catalysts.html

It brings a new meaning to the phrase organic chemistry. Chemists

have discovered that fungi can naturally absorb microscopic metal

particles into their flesh in a way that could see metallic fungus

used as catalysts or disinfectants.

Industrial catalysts often rely on processes that happen on the

surface of metals, so tiny nanoparticles of catalyst with large

surface-area-to-volume ratios are particularly effective. But such

particles are only effective if they are prevented from clumping

together using a chemical solution, which makes it difficult to

separate the catalyst from the products of a reaction.

Now Eychmüller's team at the Dresden University of

Technology in Germany has discovered that fungi can assimilate and

stabilise nanoparticles as they grow. Because the nanoparticles are

immobilised on fungal filaments, they can be easily recovered later.

Metal mould

Eychmüller's team fed media containing gold, silver, platinum or

palladium nanoparticles to common fungi, including Penicillium.

After two months the researchers examined the fungi under a scanning

electron microscope and found that the growing filaments had become

coated in a crust of nanoparticles up to 200 nanometres thick. The

newly bling fungi seemed unaffected by their metallic coat. One

species could even cope with a coating of silver, known to be toxic

to microorganisms, and used as a disinfectant in some clothing.

" We've been surprised and impressed by [the fungi's] resilience, "

says Eychmüller.

Crucially, although the crust is much thicker than the individual

nanoparticles, which are 10 to 20 nanometres across, the

nanoparticles do not clump together to form larger particles. Since

their surfaces are unobstructed, they retain their powerful

catalytic properties.

Silver coating

As well as using metal-coated fungi as catalysts, those decorated

with silver could be used for their disinfectant properties, says

Eychmüller.

He thinks studying how fungi bind to the particles could also help

understand why some organisms are prone to accumulating heavy metal

pollutants. " There ought to be reasons why a specific

nanoparticle 'docks' to a specific fungus, " says Eychmüller. " So far

not too much is known about interactions on that level. "

Journal Reference: Angewandte Chemie International Edition, DOI:

10.1002/anie.200801802

Nanotechnology - Follow the emergence of a new technology in our

continuously updated special report.