Optical probing and control of heat propagation at the nanoscale

适用于大多数纳米电子和光电子器件的最基本和最关键的问题之一是有效散热。加热也不利于新型太阳能电池材料的耐久性，包括聚合物和杂化卤化物钙钛矿薄膜。同时，热能的定向输送为热疗和其他基于局部热刺激的应用开辟了新的可能性。热管理和传输对于纳米颗粒和结构尤为关键，因为它们的体积很小，因此热容量对过热和与热有关的故障非常敏感。由于显而易见的原因，从宏观世界已知的流行的冷却方法不能直接应用于纳米级。因此，最近提出了许多不同的方法来实现热流/散热，并进行了实验测试。例如，已经证明，热可以通过准一维纳米结构非常有效地传播，例如金属纳米线和碳纳米管。然而，现有的解决方案不允许控制热流的效率。我们建议通过开发和优化纳米级温度探测的微观工具和设计允许(光学)控制热传输的新材料来解决纳米系统中的热量散失问题。我们的方法是基于嵌入在介电纳米晶体中的稀土离子的光控温度传感和冷却特性。在这里，我们利用众所周知的稀土离子多条光致发光谱线的随温度变化的强度比来测量局部温度。在扫描探针法中，稀土离子掺杂纳米晶将被用来记录空间分辨率低于50 nm的温度图。定向热传输将通过长度可达几十微米的金属纳米线来实现。局部光学冷却将使用声子辅助吸收，在第二种方案中，通过尖端的金属探头来实现。最后，我们将结合所开发的功能来演示通过纳米线介导的热传输来远程控制物质的释放。这种合作的附加价值是，它将两个团队聚集在一起，他们拥有解决纳米到微米级热传输领域的重要问题所需的互补专业知识。NCU团队在纳米线等离子激元和稀土离子的光物理以及材料制造和处理方面拥有深入的经验。另一方面，LMU团队在近场光学显微镜和光谱学以及其他扫描探针技术方面拥有强大的专业知识。本项目的结果将对纳米尺度加热和冷却方案的开发以及在纳米电子学、光电子学和热疗中的各自应用具有重要意义。

One of the most fundamental and critical issues that applies to the majority of nanoscale electronic and optoelectronic devices is the effective dissipation of heat. Heating is also detrimental to the durability of novel solar cell materials including polymer and hybrid halide perovskite thin films. At the same time, the targeted delivery of heat energy opens up promising new possibilities for thermotherapy and other applications based on local thermal stimuli. Thermal management and transport is particularly critical for nanoparticles and structures, which due to their small volume and hence heat capacity are extremely sensitive to overheating and heat-related failure. For obvious reasons, popular cooling methods known from the macroworld cannot be directly applied at the nanoscale. Therefore, a number of different approaches that enable heat flow/dissipation have been recently presented and experimentally tested. It has been shown, for instance, that heat can propagate very efficiently through quasi 1D nanostructures such as metallic nanowires and carbon nanotubes. Presented solutions, however, do not allow for the control of the efficiency of heat flow.We propose to address the issue of heat dissipation in nanosystems by developing and optimizing microscopic tools for nanoscale temperature probing and by designing new materials that allow to (optically) control heat transport. Our approach is based on the photo-controlled temperature sensing and cooling properties of rare-earth ions embedded in dielectric nanocrystals. Here, we exploit the well-known temperature dependent intensity ratios of the multiple photoluminescence emission lines of the rare-earth ions to measure local temperatures. In a scanning probe approach, rare-earth ion doped nanocrystals will be used to record temperature maps with sub 50 nm spatial resolution. Directional heat transport will be implemented by metallic nanowires reaching length scales up to several tens of micrometers. Local optical cooling will be achieved using phonon-assisted absorption and, in a second scheme, by a pointed metal probe. Finally, we will combine the developed functionalities to demonstrate the remote-controlled release of substances through nanowire-mediated heat transport. The added value of this collaboration is that it brings together two teams with the complementary expertise needed to address important questions in the field of thermal transport on the nanometer to micrometer scale. The NCU team has in depth experience in nanowire plasmonics and the photophysics of rare-earth ions together with material fabrication and handling. The LMU team, on the other hand, has strong expertise in near-field optical microscopy and spectroscopy as well as other scanning probe techniques. The results of the present project will be important for the development of both nanoscale heating and cooling schemes and respective applications in nanoelectronics, optoelectronics as well as thermotherapy.