Novel thermo-molecular effects at nanoscale interfaces: from nanoparticles to molecular motors

纳米材料为将热量转化为其他形式的能量提供了新的机会，因为它们可以承受比宏观系统大得多的温度梯度，从而产生更强的非平衡效应。这些非平衡效应可以利用在发电从废热，热电，与温度梯度相关的最重要的非平衡现象之一，这在能量转换中具有巨大的实际意义。我们最近报道了一种新的非平衡效应在水中，热分子极化，在温度梯度下的分子的热重定向导致相当大的静电场。这是一个新的概念，可以为设计和制造新的基于分子的能量转换器件提供基础。纳米材料为利用这种新效应提供了许多可能性，但同时也面临许多挑战，因为需要在非常小的尺度上管理散热。散热是一个非常普遍的问题，在许多不同的学科：生物学（分子发动机），物理学，化学，工程（表面的化学反应，微电子设备，冷凝蒸发过程）和医疗应用（“纳米加热器”热治疗）。蛋白质，特别是生物分子马达的能量耗散已经通过长期的进化过程得到优化。我们可以通过研究这种结构中的散热来吸取教训，因此，将它们用作制造纳米材料的新仿生方法的模板。实现这一目标需要开发适当的工具来量化纳米材料和生物分子中的热传递。在纳米材料特有的尺度上工作的一个优点是，可以在几度的温差下实现非常大的梯度。这些梯度足够强，可以在固体中引起局部相变，甚至破坏生物细胞，这是癌症治疗中正在利用的一个概念。我们已经表明，这种幅度的梯度可以在极性流体中引起强极化效应，其量级为操作液晶显示器所需的静电场。因此，纳米材料和热分子效应的结合为设计新的能量转换方法提供了一个令人兴奋的原理。不过，对这些小材料的研究并不是小事，因为它们很小且复杂，使它们成为实验探针的困难目标。实验方法测量纳米材料中热传输与尺寸和化学成分的依赖性的能力有限，限制了我们开发模型的能力，从而限制了我们设计可用于能量转换装置的材料的能力。事实上，我们对纳米尺度下控制热传输的机制的理解仍然很少，但有证据表明，它们的描述需要分子方法。尽管在过去的几年里，我们对纳米材料中热传输的理解取得了很大的进步，但在不久的将来，还有许多挑战需要解决。在最近的工作中，已经报道了新的和令人兴奋的非平衡效应，表明有空间探索新的原理，并可能利用它们来设计能量转换设备。在本项目中，我们将开发新的计算/理论方法来研究纳米材料和生物分子中的热传输。这种方法将使我们能够以前所未有的细节水平研究热流。这将使发展必要的突破所需的微观背景成为可能，以实现新的和变革性的能量转换技术中热分子效应的潜力。

Nanomaterials provide new opportunities for the conversion of heat into other forms of energy as they can sustain much larger temperature gradients than macroscopic systems, hence producing much stronger non equilibrium effects. These non equilibrium effects can be exploited in the generation of electricity from waste heat, thermoelectricity, one of the most important non equilibrium phenomena associated to temperature gradients, which has enormous practical implications in energy conversion. We have recently reported a novel non equilibrium effect in water, thermo-molecular polarization, where the thermal reorientation of the molecules under temperature gradients leads to sizeable electrostatic fields. This is a novel concept that can provide the basis to design and make new molecular-based devices for energy conversion. Nanomaterials offer many possibilities to exploit this novel effect, but at the same time many challenges, as it is necessary to manage heat dissipation at very small scales. Heat dissipation is a very generic problem, featuring in many different disciplines: biology (molecular motors), physics, chemistry, engineering (chemical reactions at surfaces, microelectronic devices, condensation-evaporation processes) and medical applications ('nanoheaters' for thermal therapy treatments). Energy dissipation in proteins and in particular biological molecular motors has been optimised through a long evolution process. There are lessons we can learn by investigating heat dissipation in such structures, and hence, use them as a template for new biomimetic approaches to make nanomaterials. Realising this objective requires developing appropriate tools to quantify heat transfer in nanoscale materials and biomolecules. One advantage of working at the scales characteristic of nanomaterials is that very large gradients can be achieved with temperature differences of a few degrees. These gradients are strong enough to cause local phase transformations in solids, and even destroy biological cells, a notion that is being exploited in cancer therapies. We have shown that gradients of this magnitude can induce strong polarization effects in polar fluids, of the order of the electrostatic fields needed to operate liquid crystal displays. Hence, the combination of nanomaterials and thermo-molecular effects offers an exciting principle to design novel energy conversion approaches. The investigation of these small materials is not trivial though, since they are small and intricate, making them a difficult target for experimental probes. The limited capability of experimental methods to measure the dependence of thermal transport with size and chemical composition in nanoscale materials limits our ability to develop models and hence design materials that can be exploited in energy conversion devices. Indeed, our understanding of the mechanisms controlling heat transport at the nanoscale is still scarce, but there is evidence that their description requires a molecular approach.In spite of the great advances over the past years in our understanding of heat transport in nanomaterials, there are many challenges to tackle in the near future. In recent work, new and exciting non-equilibrum effects have been reported, showing there is room to explore new principles and possibly exploit them to design energy conversion devices. In the present project we will develop new computational/theoretical approaches to investigate heat transport in nanoscale materials and biomolecules. This methodology will enable us to investigate heat flow at an unprecedented level of detail. This will make possible the development of the microscopic background needed to make the necessary breakthroughs to realise the potential of thermo-molecular effects in new and transformative energy conversion technologies.