Photo-Responsive Luminescent Lanthanide Complexes

Photo-switches are chemical compounds that can switch between two stable forms when light is shone onto the compound. A common example is a class of compounds called azobenzenes. They work similarly to a light switch on the wall, when the stimulus is applied this induces a change. In the case of a switch in your home the stimulus is your hand and the change is whether the light is switched on or off. Whereas with the photo-switch, the light is the stimulus and the output is, in the case of azobenzene molecules, a change in length of the compound. Photo-switches have functions in sensors, electronic devices, and in medical and biological applications. For example drug release could be stimulated by light or the mechanisms involved in responsive biological systems, such as ion channels, can be further understood. Using photo-switches within a more complicated system can lead to control over the forms of photo-switch present and thus their interactions with other compounds in the system.
Lanthanides are a group of elements which have unique properties. One property is long- lived luminescent (the ability to emit light), in comparison to the luminescence of biological species. Research has found that this luminescence can be controlled by the presence of other compounds (chromophores) which can either change the intensity of the luminescence or turn off the luminescence completely. This switchable property means that emission can be turned on or off depending on the nature and state of the interacting chromophore. This makes them exciting compounds for bio-imaging. Their optical properties also make them attractive compounds for optic-electronic devices, such as screens and displays.

The aim of this project is to engineer a system in which the azobenzene photo-switch influences the luminescence of the lanthanide. For this to work, energy transfer between the two species must occur. Energy transfer can either happen through space and is dependent on how close the two species are relative to each other (Forster Resonance Energy transfer) or directly though a bond attaching the two species together (Dexter Energy transfer). Understanding and determining the mechanism of energy transfer aids in the engineering of a switchable luminescent lanthanide complex. In addition, the type of azobenzene and lanthanide chosen need to be considered. Recently azobenzenes have been discovered that switch length when visible light is shone onto them, these are promising candidates as visible light is much less destructive to surrounding enviroments than UV-light. The lanthanide chosen must have good luminescent properties and in order to work well with the azobenzene it must be able to absorb/emit light in a similar range to the light that induces switching in the azobenzene.
Combining azobenzene photo-switches and lanthanide complexes is a new area in chemistry. Both separately are well researched, however there has only been a few examples when the two have been combined in a single system. Through synthesising a new photo-responsive lanthanide complex, in which the luminescence can be influenced by the length of the azobenzene leads to the possibility of many new and exciting discoveries. This project falls within the ESPRC physical sciences research area.

The primary impact of the OxICFM CDT will be the highly-trained world-class scientists that it delivers. This impact will encompass both the short term (during their doctoral studies), the medium term (subsequent employment) and ultimately the longer timescale defined by their future careers and consequent impact on science, engineering and policy in the UK.

The impact of OxICFM students during their doctoral studies will be measured by the culture change in graduate training that the Centre brings about - in working at the interface between inorganic synthesis and manufacturing, and fostering cross-sector industry/academia working practices. By embedding not only from larger companies, but also SMEs, we have developed a training regime that has broader relevance across the sector, and the potential for building bridges by fostering new collaborations spanning enormous diversity in scientific focus and scale. Moreover, at a broader level, OxICFM offers to play a unique role as a major focus (and advocate) for manufacturing engagement with academic inorganic synthetic science in the UK.

From a scientific perspective, OxICFM will be uniquely able to offer a broad training programme incorporating innovative and challenging collaborative projects spanning all aspects of fundamental and applied inorganic synthesis, both molecular and materials based (40+ faculty). These will address key challenges in areas such as energy provision/storage, catalysis, and resource provision/renewal necessary to enhance the capability and durability of UK plc in the medium term. To give some idea of perspective, the output from previous CDTs in Oxford's MPLS Division include two start-up companies and in excess of 30 patents.

It is not only in the industrial and scientific realms that students will have impact during their timeframe of their doctorate. Part of the training programme will be in public engagement: team-based challenges in resource development/training and outreach exercises/implementation will form part of the annual summer school. These in turn will constitute a key part of the impact derived from the CDT by its engagement with the public - both face-to-face and through electronic/web-based media. As the centre matures, our aspiration is that our students - from diverse backgrounds - will act as ambassadors for the programme and promote even higher levels of inclusion from all parts of society.

For our partners, and businesses both large and small in the manufacturing sector, it will be our students who are considered the ultimate output of the OxICFM CDT. Our programme has been shaped by the need of such companies (frequently expressed in preliminary discussions) to recruit doctoral graduates who can apply themselves to a broad spectrum of multi-disciplinary challenges in manufacturing-related synthesis. OxICFM's cohort-based training programme integrates significant industry-led training components and has been designed to deliver a much broader skill set than standard PhD schemes. The current lack of CDT training at the interface of inorganic chemistry and manufacturing (and the relevance of inorganic molecules/materials to numerous industrial sectors) heightens the need for - and the potential impact of - the OxICFM CDT. Our students will represent a tangible and valuable asset to meet the long-term skills demand for scientists to develop new materials and nanotechnology identified in the UK Government's 2013 Foresight report.

In the longer term, the broad and relevant training delivered by OxICFM, and the uniquely wide perspective of the manufacturing sector it will deliver, will allow our graduates to obtain (and thrive in) positions of significant responsibility in industry and in research facilities/institutes. Ultimately we believe that many will go on to be future research leaders, driving innovation and changing research culture, and thereby making a lasting contribution to the UK economy.