The research interests of the Mills group are wide and varied including: dye and semiconductor photochemistry, redox catalysis (in particular, oxygen catalysis), solar energy conversion (in particular artificial photosynthesis) and colour and fluorescence based indicators and smart inks and plastic films.

An Intelligence Ink for Oxygen

The group has created a smart, oxygen sensitive ink, which is activated (photobleached) upon a short exposure to UVA light.  In the absence of oxygen the ink stays bleached, but in its presence it recovers its original colour at a rate which is proportional to the ambient level of oxygen.  The attached movie ( shows such an ink being photobleached in air and then recovering its original colour.  In the second movie ( a piece of tape has been attached on the ink to ensure the absence of the oxygen and to show that the indicator stays photobleached in such an environment. Currently, Lucie Nemcova is exploring exploring ways to alter the response time of this indicator from a few hundred seconds to days, by varying the encapslatiing medium.  Such indicators have potential in any application where the presence or absence of oxygen is essential, such as in modified atmosphere packaging.

S-K. Lee, A. Mills and A. Lepre. An Intelligence Ink For Oxygen, Chem. Commun., 1912-1913, 2004.