Supercritical Carbon Dioxide Makes Decaffeinated Coffee and Precisely Sized Nanoparticles

More nanoparticle research promises improved photovoltaics


Chemists at Idaho National Laboratory and Idaho State University in a textbook case of serendipity came upon a method that not only allows for making precisely sized nanoparticles but also makes it possible for lower temperatures to be used in their production, saving on energy costs.

The team hit upon the idea of using "supercritical" carbon dioxide to streamline the reaction. Supercritical fluids are a bit like a mix between a gas and a liquid. They can diffuse through solids, for example, but also dissolve substances like a liquid does. Supercritical carbon dioxide has been used for years to decaffeinate coffee.

When Fox, Pak and Rodriguez introduced supercritical carbon dioxide into their reaction vessel, the only immediately noticeable result was a thick yellow goop.

"We thought it was a failed experiment," Fox says.

But when the chemists looked more closely, they discovered the goop was full of very small, incredibly uniform semiconducting nanoparticles. The same reaction, roughly, that industry uses to transform raw materials into semiconducting nanoparticles had taken place — but it generated a better, less variable product.

The new reaction could proceed at a much lower temperature — 65 degrees Celsius rather than 300 — it also promised to save a great deal of money and energy.

The Next Big Future  has a pretty thorough look at the research and its possible impact and you can also take a look at the video below:

Of course, it’s another development in nanoparticles that has everyone clamoring about enabling solar cells to be more effective. In this case, they are supposed to help solar cells become ten times more effective in gathering the sun’s energy.

I don’t want to burst anyone’s balloon but I don’t think the big obstacle to much improved nano-enabled solar cells is due to not getting uniformed and cheaply produced nanoparticles. The issues for nanotech in photovoltaics remain manufacturing and reliability, not really cheaper and more uniform nanoparticles.

While I don’t want to diminish this research, maybe we should stop jumping to “ten times” conclusions about this stuff.

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IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.