STIR 3 (IMAGE) Rice University Caption Rice University chemists who discovered that chemicals used in Billups-Birch reductions of carbon nanotubes react with the white PTFE stir bars, turning them black. They recommend using glass stir bars, like the one in the middle, for such reductions. Credit Brandon Martin/Rice University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.