Property-Enhanced Porphyrins

In natural photosynthesis, the sun light is directly collected and conveyed to a pair of precisely organised porphyrins, the special pair, which undergoes charge separation. The liberated electron is then translated into chemical energy that is used to develop the living organism. In brief, photosynthesis consumes carbon dioxide and water to produce energy-rich molecules and delivers Oxygen as a by-product. While the efficiency of natural photosynthesis is questionable, its molecular building blocks are self-assembled, made from common non-toxic elements and its waste and by-products are environmentally favourable. In relation to our most pressing environmental challenges and ever-increasing energy consumption, photosynthesis thus represents the perfect solution.

However, the complexity of the molecular architecture involved in photosynthesis renders it difficult to reproduce artificially. Nevertheless, it is possible to mimic specific aspects of photosynthesis and researchers have concentrated their efforts in the development of carbon capture, bio-fuel production, water splitting and photovoltaic solar cells. Each of these approaches to artificial photosynthesis includes an antenna system to harvest the sun light. Alike in natural photosynthesis, the role of the antenna in these artificial systems can be played by a porphyrin.

Within femto- to picoseconds after absorbing the incoming sun light energy, the porphyrin undergoes specific mechanisms. Of particular interest to this project, we will investigate the following mechanisms: internal conversion, inter-system crossing and direct charge separation. Each of these relaxation pathways dictates the overall device's conversion efficiency. It is therefore crucial to understand the factors that can enhance these specific pathways to develop more efficient devices.

We propose use the latest laser technology to investigate these mechanisms that are ultrafast by nature. More precisely, we will systematically study the effect of atom substitution, ring bending, and ring expansion in series of unique single-porphyrins that differs from one-another by a single constituent. Similarly, to investigate the effect of host electronegativity, we will investigate porphyrin-embedded complexes (called cytochromes) that differs from one another by the nature of their ligand, and thus electrostatic environment.

The outcome of this project is to generate a list of physical characteristics that enhance either internal conversion, inter-system crossing or charge separation. With such list in hand we would then be able to design improved porphyrins for specific applications.

Fossil fuels has been driving the British national economy and international policies for the past century. Unfortunately, the environmental changes associated with the extensive consumption of fossil fuels have now become a threat to the international and national social and economic equilibrium as we know it today. Consequently, the adaptation of UK's industries to a more sustainable energy production will be the key factor for the country's competitiveness in the next decades. In the particular case of the UK, the EPSRC has been one of the major driver for this adaptation by investing in its Solar Technologies research area portfolio. Indeed, it is agreed that solar energy is the one sustainable energy source that, if harvested adequately, has the potential to respond to the ever-demanding energy needs of our society. This project, is directly aligned with EPSRC's effort in developing its Energy sector, and has the potential to impact the society at large.

Energy and environment are subjects that affect our daily lives. This project, because it aims at fostering the development of more efficient ways to generate renewable energy, will impact, in the mid- and long-term, all aspect of our lives, indiscriminately. If solar energy comes to liberate us from our oil dependences, as it is expected in the next decades, then this project would be an integral part of this transition.

Knowledge of a more efficient way to convert sunlight into chemical or electrical energy is a determinant step toward sustainable prosperity. An in-depth understanding and subsequent ability to control the relaxation pathways of photo-excited porphyrins will lead to the development of a cleaner energy production. This project thus comes right in time to foster technological innovations in renewable and sustainable energies.

The project's aims are also directly aligned with those of the Grantham Centre for Sustainable Futures; a joint project between the University of Sheffield and the Grantham Foundation. Through this collaboration, the output of the project will inform policy and the development of products for industrial application. Both of which will in turn affect the wider society by building fairer societies and preserve our natural resources for the future generations.

In economic terms, since the output of the project is to provide with a systematic approach in synthetizing porphyrins for specific applications, it will therefore participate in reducing the overall cost of research. For example, under better guidance, the research in the fields of Dye-Sensitized Solar Cell will be more effective. Consequently, this project will help maximizing the impact that governmental research funding has in a key investment area such as Solar Energy.

While in this section is only concerned with a summary of impacts, the pathways to achieve these impacts are detailed in the attached Pathway to Impact document.