Nanoscale Temperature Manipulation Based On Photothermal Properties Of Plasmonic Particles

Driven by the external light wave, free electrons at the surface of metallic particles oscillate collectively and form the well-known localized surface plasmon resonance (LSPR). The LSPR can strongly interact with incident light and efficiently turns it into thermal energy, which makes the particle perfect nanoscale heat source. The highly localized, flexible, efficient heat source has shown great potential in applications such as cancer therapy, chemical catalysis, thermal imaging, thermal modulation, optical absorber. Also a serious of delicate physical or chemical processes induced by the nanoscale heat source has raised much research interests. Manipulating these processes needs a way of controlling the temperature distribution with high spatial precision.In the thesis, we explore a way of nanoscale temperature manipulation, which based on the photothermal properties of plasmonic assembly. We study light absorption properties as well as the subsequent heat transfer process of the plasmonic trimer systems. We show that, temperature changes can be both localized and controllably directed within the plasmonic assembly by rotating the incident light polarization direction. Our work mainly includes two parts:The first part, we study the optical properties of plasmonic assemblies. It is started by the simplest configuration, i.e. a plasmonic dimer. It is found that the absorption intensity of gap mode is very sensitive to polarization direction. Based on the photothermal properties of the gap mode, we continue to investigate the absorption properties of a plasmonic trimer. Calculations show that a large absorption contrast among the particles can be achieved, and the contrast can be controlled by rotating incident light polarization direction, which provides a way to allocate heat into the three particles with a high contrast in amount.The second part, we study the heat transfer process of the plasmonic trimer after light absorption. It is found that a large temperature contrast among the particles can be achieved although the gap distance between the neighboring two particles is merely several nanometers. Finally, photothermal property dependence on the particle radius and interparticle gap is also investigated, which reveals that the combination of absorption contrast and interparticle thermallization contributes to the nanoscale temperature difference among the particles.The ability of nanoscale selective heating provides a possible way of remotely manipulating the nanoscale thermally induced physical or chemical processes with unprecedented spatial precision.