Professor Mills has a wide range of research interests. These interests include: dye and semiconductor photochemistry - in particular the use of semiconductors as photocatalysts in water and air purification and in selective organic oxidations; electrochemical sensor development for electroactive gases, such as hydrogen, oxygen, chlorine etc.; colourimetric and fluorimetric sensor development for gases of interest in clinical analysis (such as O2, CO2, NO and anaesthetic gases); design, synthesis, characterisation and mechanistic studies of new inorganic materials for catalysing redox reactions - including reactions involving hydrogen, oxygen and chlorine evolution; oxidative and reductive dissolution processes of inorganic materials, with a special interest in the dissolution of metal and metal oxide particles; novel biphasic catalytic and photocatalytic systems for organic oxidation reactions. Other research interests include fundamental studies of: (i) solvatochromism and (ii) biphasic catalytic systems for organic oxidation reactions using platinum group metal oxides as mediators. Current major research themes include: semiconductor photocatalysis for solar energy conversion (such as solar-driven water-splitting and CO2 fixation) and optical sensors and intelligent inks. Much of Professor Mills' research is directed at creating novel, innovative chemical systems of commercial worth.
Professor Mills' research group has current collaborative links with a number of industries including the following: Pilkington Glass (semiconductor photocatalysis), Johnson and Johnson Medical (optical gas sensors for clinical analysis), Johnson Matthey (semiconductor photocatalysis, photoelectrochemical cells and PGM catalysts in food packaging) Cryovac, SunChemical, Toppan, Multisorb, Ciba and Crown Holdings (optical sensors for food and drink packaging). To date, Professor Mills has published over 235 papers in international journals and 8 published patents. The technology in his patent on oxygen indicators (GB2002/003994) is currently under license to a major label manufactuer (UPM) has generated £400k todate and is the basis of UPM's Shelf Life Guard label. Professor Mills is on the editorial boards of the Journal of Photochemistry and Photobiology and the Journal of Fluorescence. The research group comprises currently: 7 postdoctoral research workers and 3 postgraduate students.