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.
The second in a series of papers to be published by the photocatalytic activity indicator inks consortium is now available for download. It describes in detail the analysis method, that is a proposed ISO standard, for detecting the activity of a semiconductor photocatalyst on a range of surfaces, using a simple, reproducible technique.
Photocatalyst Activity Indicator Inks (Paii’s) are now featured on Wikipedia. The inks were pioneered by the Mills group over a number years, and development of newer, improved ‘smart inks’ for detecting the activity of photocatalytic surfaces is ongoing.
A simple, inexpensive method for the rapid testing of the photocatalytic activity of self-cleaning surfaces
A paper, published by the Mills group on November 14th, 2013, detailing a proposed ISO standard test for the testing of the activity of self-cleaning surfaces using a simple, inexpensive method, has been receiving considerable interest within the scientific community. The article, available via the link below, has been downloaded 667 times since its publication, with the most interest coming from the UK, US, India, China and Germany.
The article is available for download from:
Professor Mills and Dr Lawrie recently traveled to Seattle to engage with a company, Sensor Medical Technology. We met with members of the company, academia and patent lawyers in order to kick-start a new collaborative project to develop indicators for medical devices.
With the aid of travel funding awarded by the RSC, Dr Katherine Lawrie attended the world’s leading conference on optical sensors to present a poster on her work entitled ‘UV dosimetry for solar water disinfection (SODIS)’. The conference itself attracted 220 participants from 37 countries, bringing together engineers and scientists to discuss the recent progress and future trends in the design, fabrication, and application of optical sensing devices.
Wednesday March 19th was Green Impact “Platinum day” in the School of Chemistry and Chemical Engineering. After attaining a green impact gold award for our lab last year, all those in the school with gold awards came together to build on these awards and bring them beyond the localised effect of the lab, producing a series of events culminating in an “Environmental Communication Day with a Social Conscience”. During the day everyone in the school was invited to make their own smoothie (powered by a bicycle), participate in a treasure hunt and taste delights from around the world at a coffee morning which was contributed to by those of the many nationalities represented within the school. There were also a further two apple trees planted in the open quad area in the middle of the school, and the day ended with a quiz and environmental talks by Prof Martin Atkins and our very own Dr Katherine Lawrie. Katherine highlighted the work of the Mills group over the past few years which has gone some way to tackle environmental and humanitarian issues.
Open Access Paper – Extruded polymer films pigmented with a heterogeneous ion-pair based lumophore for O2 sensing
A novel approach to polymeric Ru(II)-diimine luminescent O2 sensors is described. The Ru(II)-diimine, tris (4,7-diphenyl-1,10-phenanthroline) ruthenium (II) dichloride ([Ru(dpp)3]2+), is first ion-paired to the surface of heterogeneous TiO2 particles, rendered negatively charged due to the alkali nature of the aqueous solution, to produce an O2 sensitive pigment with a strikingly high oxygen sensitivity (i.e. PO2 (S=1/2) = 0.002 atm, where PO2 (S=1/2) is defined as the amount of oxygen required to reduce the initial, oxygen free luminescence by 50%), and a rapid response to oxygen. The pigment is extruded in low density polyethylene (LDPE) to produce a thin (60 µm), flexible, O2 sensing plastic film, with an O2 sensitivity (PO2 (S=1/2) = 0.84 atm) comparable to the more traditional homogeneous lumophore ion-pair based O2 sensor ink films reported in the literature.
this is an open access article and can be downloaded free of charge from: http://pubs.rsc.org/en/Content/ArticleLanding/2013/AN/c3an01141k#!divAbstract
Three undergraduate students from Queen’s University of Belfast were granted summer studentships within the group, and worked on a variety of projects during their time here. Here’s what they have to say:
‘We spent the summer with the group assisting in research on photosensitive dyes. We mainly did work on the following:
– Testing photocatalytic indicator inks on a variety of active surfaces and testing prototype inks
– Modifying the formulation of inks to be used in marker pens, and producing pens featuring photocatalyst test inks. The pens provide a convenient way of applying ink to a photocatalytic surface to test its activity.
– Work with indicator dyes in development for the SODIs project. The project involves the use of solar energy to disinfect water. The inks can be used to show when the water has received enough UV light to be sterilised.
We really enjoyed the experience, and look forward to putting the skills we learnt into practice in our future studies’.
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 (http://www.youtube.com/watch?v=uhWog0X-C0E) shows such an ink being photobleached in air and then recovering its original colour. In the second movie (http://www.youtube.com/watch?v=EJhGTf0UEuM) 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.
During a recent trip to Prague to attend the SP4 meeting on semiconductor photochemistry we found we had run out of time and needed to produce a 3 min movie for an imminent pitch for funding our photocatalyst work through InkIntelligence. So, during the conference AM went out with Christopher O’Rourke and David Hazafy and filmed various parts, in the pouring rain, in different parts of Prague. This movie was filmed on an iPhone and the sound was recoded on a separate iPhone, in AM’s top pocket; Chris O’Rourke put it all together. Needless to say – we were all soaked at the end – but we did get through to the next round!