First author

The most prevalent form of uranium is its soluble uranyl dication: a radioactive contaminant that is notoriously difficult to extract from the environment because it is very unreactive. Polly Arnold and her co-author and husband, Jason Love, both based at the University of Edinburgh, UK, combined their different chemistry skills to produce a reactive uranium compound that defies long-held assumptions (see page 315). Arnold talks to Nature about how she and her co-workers proved the textbooks wrong.

Little is known about uranium's chemical properties. Why is that?

Textbooks are full of assumptions about uranium chemistry that have no direct proof. Compared with other metal atoms, uranium atoms are big and have many electrons, which makes it hard to describe their bonding using traditional chemical modelling programs. According to the textbooks, we shouldn't have been able to make this compound.

How were you able to make a reactive uranium compound?

The uranyl dication is made stable by its two uranium–oxygen double bonds. No one thought it was possible to make just one end of the compound chemically reactive. We used an organic molecule as a scaffold that was shaped in such a way that when the uranyl bound, it sat unsymmetrically. This made the dication less stable and allowed it to react with nearby organic groups in unexpected ways. We hope to put other molecules on the uranyl dication.

Were there safety issues with this work?

The uranyl dication is pretty safe. We only use depleted uranium, which is the residue left after uranium is processed to make fuel and gives off hardly any radioactivity.

Will this molecule be useful to clean up toxic waste?

Not directly, but we can use it to help us understand how uranium precipitates from groundwater, as well as how to make uranyl dications less mobile and contaminating. The compound will also be helpful for modelling the behaviour of plutonium ions in nuclear waste, because it is as reactive as plutonium but much less radioactive.

How did your husband come to be your co-author?

The funny thing is we've been trying to separate our careers since we met in the same lab 12 years ago, because we thought it would help us find dual jobs at one location. We've ended up with two very different skills that are quite complementary. It's turned out to be a very productive collaboration.