Engineering purple bacterial photovoltaic complexes for device applications

该项目涉及首次尝试将一种为生物光合作用提供动力的蛋白质转化为一种可用于高效太阳能电池核心的材料。该项目推出之际，人们对替代技术越来越感兴趣，这些技术可以在不加剧环境变化的情况下为人类提供越来越多的能源。人类正面临一场能源危机。据估计，到21世纪中叶，我们的全球能源需求将翻一番，到2100年可能会增加两倍以上。由于众所周知的原因，增加化石燃料的燃烧将无法满足这一飙升的能源需求，尽管目前正在考虑的许多替代能源可能在短期内满足需求，但它们面临着能力有限、地理分布不均、对环境的不利影响以及政治/安全问题。全球唯一可自由使用的替代能源是太阳能。生物光合作用每年消耗大约250太瓦的太阳输出，使目前全球人口对16太瓦的能源需求相形见绌，但仍然只是地球上每年12万太瓦太阳能的一小部分。人类的大部分能源一直以各种方式依赖于光合作用的产物，但现在人们对利用这种免费且基本上无害的能源的清洁技术方法越来越感兴趣。随着硅基太阳能电池板的出现，光伏，即直接从光能中产生电流，已经成为公众熟悉的概念。然而，这项技术有其局限性，迫切需要开发更轻、更便宜、对稀有元素的依赖更少、在非最佳条件下更有效的替代光伏材料。很可能在未来，太阳能将通过各种技术获得，每一种技术都适合特定的条件。在过去十年中，人们对光伏蛋白质的兴趣迅速增长，其中一种方法是使用天然光伏蛋白质作为光伏材料。植物、藻类和细菌通过被称为反应中心的纳米级蛋白质来利用光能。这些蛋白质捕获光能并将其转化为有机体可以使用的形式，在关键事件中，光能被用来沿反应中心的长度移动电子，在一端留下正电荷，在另一端留下负电荷。就像电池或硅太阳能电池板的端子一样，这种电荷差异可以用作电源。已经知道，如果将反应中心小心地从植物或细菌上移走，并以特定的方式连接到电极上并照明，就可以产生电流。这项技术发展的下一个阶段是通过改变自然反应中心的结构和处理光能和电子的方式的各个方面，使其成为更有效的光伏材料。该项目是朝着这一方向迈出的第一步，寻求将反应中心从光合作用细菌转变为一种能产生更大光电流的材料，更适合在太阳能电池内运行，而不是在细菌内运行。以这种方式开发天然反应中心的吸引人的方面是，它们将收获的光能转化为电势差，效率接近100%，它们可以通过自然过程大量合成，并且它们具有自我组装和自我保护/修复的能力。这项研究的长期目标是开发用于收集太阳能的新材料，要么通过直接适应天然蛋白质，要么通过提供新的见解来激励新一代光伏材料。

This project is concerned with the first attempts to convert a protein that powers biological photosynthesis into a material that can be used at the heart of an efficient solar cell. The project comes at a time when there is growing interest in alternative technologies for providing mankind with increasing amounts of energy in ways that will not exacerbate environment change. Mankind is facing an energy crisis. It is estimated that our global energy demand will double by the middle of the 21st century, and could more than treble by 2100. For well-understood reasons increased burning of fossil fuels will not be able to meet this soaring energy demand, and although many of the alternative energy sources currently being considered may address need in the short term, they suffer from limited capacity, uneven geographical distribution, adverse environmental impact and political/security problems. The only source of alternative energy freely available across the whole planet is solar energy. Biological photosynthesis consumes around 250 terawatts of the sun's output annually, dwarfing the current 16 terawatt energy demand of the global population, but still only a tiny fraction of the 120,000 terawatts of solar energy incident on the Earth every year. Humans have always been reliant on the products of photosynthesis for the bulk of their energy, in a variety of ways, but there is now increasing interest in clean technological approaches to harvesting this free and largely benign source of energy. Photovoltaics, the direct generation of electric current from light energy, has become a familiar concept with the public through the advent of silicon-based solar panels. However this technology has its limitations, and there is a pressing need to develop alternative photovoltaic materials that are lighter, cheaper to produce, less reliant on rare elements, and are more efficient under non-optimal conditions. It is likely that in the future solar energy will be harvested through a wide range of technologies, each suited to particular conditions. One approach that has seen a rapid growth in interest over the last ten years is the use of natural photovoltaic proteins as a photovoltaic material. Plants, algae and bacteria exploit light energy through nanometer-sized proteins called reaction centres. These proteins capture light energy and convert it into a form that the organism can use, and in the key event light energy is used to move an electron along the length of the reaction centre, leaving a positive charge at one end and a negative charge at the other. Just as with the terminals of a battery, or a silicon solar panel, this difference in charge can be used as a source of power. It is already known that if reaction centres are carefully removed from a plant or bacterium, and attached in a particular way to an electrode and illuminated, an electric current can be generated. The next stage in the evolution of this technology is to adapt natural reaction centres as more effective photovoltaic materials by altering their structures and various aspects of how they deal with light energy and electrons. This project is a first step in this direction, seeking to convert the reaction centre from a photosynthetic bacterium into a material that will produce larger photocurrents and is better suited to operation inside a solar cell rather than inside a bacterium. The attractive aspect of exploiting natural reaction centres in this way is that they convert harvested light energy into an electrical potential difference with an efficiency that is close to 100 %, they can be synthesised in large quantities through natural processes, and they have capacity for self-assembly and self-protection/repair. The longer term goal of the research is to develop new materials for harvesting solar energy, either through direct adaptation of natural proteins, or by providing new insights that will inspire new generations of photovoltaic materials.