Mercouri Kanatzidis, a scientist at the U.S. Department of Energy's (DOE) Argonne National Laboratory, and Nan Ding, a chemist at Northwestern University, have discovered a little molecule that may make a big difference in the nuclear power debate by making nuclear plants safer.

The molecule features a bizarre mechanism in which it behaves like a Venus flytrap, closing selectively on radioactive ions.  That's a big deal as few molecules in the past have shown the potential to effectively and permanently isolate radioactive particles.

The researchers were exploring ways to trap radioactive cesium ions, a dangerous component of nuclear waste water.  Cesium radioactive isotopes typically have a long half life meaning that if they are accidentally released they decay slowly and pose a serious health risk.  One cesium isotope, Cesium-137, which has a half life of 30 years, has played a critical role in maintaining dangerous levels of radioactivity in the Chernobyl disaster zone.  Residents of the region have experienced higher cancer rates and incidences of other problems.

That's why it's so exciting to find a molecule that could potentially isolate those stray particles and allow them to be filtered out of local water supplies -- finding the metaphorical needle in a haystack.

Describes Professor Kanatzidis, "The name of the game in cleaning up nuclear waste is to concentrate the dangerous isotopes as efficiently as possible.  That's where this new material does its job."

The new material is a rigid frame composed of negatively charged metal sulfides.  Its interior has a pore that attracts positively charged ions.  Non-radioactive sodium ions are freely attracted inside the pore, and then interchanged with other sodium ions.  However, when radioactive cesium ions enter the pore, they get stuck.

The researchers discovered the reason behind this.  Sodium, like most positively charged ions, attracts a shell of water that helps to isolate it within the pore.  Cesium, a large ion, only weakly interacts with water, so it's relatively unprotected.  Sulfur atoms in the ring framework around the pore bind to the cesium, changing the shape of the pore, much like a Venus flytrap shutting on its prey.

Professor Kanatzidis elaborates, "Imagine the framework like a Venus flytrap.  When the plant jaws are open, you can drop a pebble in and the plant won't close—it knows it isn't food. When a fly enters, however, the plant's jaws snap shut."

He adds, "As far as we know, this Venus-flytrap process is unique.  It also works over a large range of acidities—an essential property for cleanup at different sites around the world, where pH can range considerably."

The research was published in the prestigious journal Nature Chemistry and could lead to discoveries of similar flytrap molecules that could be used to capture other radioactive ions.

Argonne National Laboratory is funded by the U.S. Department of Energy, but is privately managed by UChicago Argonne, LLC.  President Barack Obama has recently become a major advocate of the U.S. adopting nuclear power, pushing for more research grants and guaranteed loan funding for new plant construction.