Heavy Cyanate Analogues as Precursors to Group III-V Semiconductor Nanoparticles

Materials capable of emitting light with a specific colour (or energy) have a variety of uses, predominantly in displays. Developing bespoke materials allows us to improve current applications, such as improving image resolution in displays, and access brand new technologies, such as biological imaging agents.
Semiconductor nanoparticles, known as quantum dots, are some of the smallest materials known that are capable of emitting light over a wide range of energies. Quantum dots are highly tuneable, emitting different energy light depending on their composition, size and surface character. Their miniscule size and customisable emissive properties has resulted in their extensive exploration and development.
Materials composed of cadmium, selenium and tellurium are most exploited in quantum dots, due in part to well-developed protocols for their preparation. Their reliable preparation, combined with attractive optical properties, lead to their commercialization in early quantum dot television displays. Yet despite significant progress, the highly toxic elements of which they are composed (cadmium and selenium) has proven a prohibitive factor in their wider adoption. The inherent toxicity of these elements largely precludes their use within biological applications. Moreover, growing legislative limitations on cadmium concentration in consumer goods has further reduced commercial interest.
Quantum dots composed of less toxic, more environmentally benign elements, such as gallium, indium, and phosphorus, are prominent alternatives to cadmium and selenium containing materials. Their contrastingly lower toxicity makes these materials enticing for use in consumer
and bioimaging applications.
A key challenge with this class of material is the highly reactive and dangerous chemicals required to make them. These chemicals ignite spontaneously in air, making them difficult to handle on a large scale. Furthermore, their high reactivity results in quantum dots of poorer optical quality, compared to cadmium and selenium materials. Our research looks to overcome these challenges by exploring a less reactive, more easily handled family of precursors.
Our research will investigate a family of emerging chemicals, known as heavy cyanate analogues, which may offer a more accessible and safer route to generate less toxic quantum dots. These chemicals have proven effective sources of elements such as phosphorus in
molecular research, but as of yet are unexplored in the preparation of quantum dots. We envision that these chemicals, some of which are considerably air and moisture tolerant, could be beneficial alternatives to current, more hazardous, precursors.
This work aims to investigate whether this new family of chemicals can be used to prepare quantum dots. This project falls within the EPSRC Manufacturing the Future research area. If successful, this work would represent an unprecedented application for this family of chemicals - taking fundamental research and applying it to larger, more valuable materials. With the easily scalable preparation known for these chemicals, they are attractive alternatives from both
a scientific and manufacturing perspective.
In summary, this research will explore heavy cyanate analogues as alternative precursors for low-toxicity quantum dots, with the goal of developing safer, industrially attractive preparations.

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.