Plasmonic metamaterials: enabling new routes for localized surface chemistry.

超材料是由周期性的纳米或微米尺度的积木组成的人造结构，通常由层状导体、半导体和介质阻挡层组成。在金属超材料中，局域电子共振，即等离子体激元共振，集中在纳米结构附近。这些谐振是高度可调的，可用于各种应用，包括窄带滤光器、光伏元件和超灵敏分析设备。这项拟议的研究计划的长期目标是开发新的超材料，我们将利用这些材料进行空间控制的等离子体介导的化学反应，并与过渡金属二卤化物(TMDs)集成。首要目标在于了解等离子体激元模式在特定辐照条件下与其他分子或材料的基本相互作用。我们将开发具有特定形状和几何形状的新的2D元结构。具有线各向异性或手性各向异性的结构将被创建和优化，以在可见光和红外光谱范围内的线或圆偏振光下响应。我们将使用我们的纳米光子基础设施与加拿大光源的中红外光束线相结合，制造具有从可见光到红外范围的多个共振的等离子激元平台并对其进行表征。我们将使用这些结构来研究等离子体激元介导的反应。通过等离子体激发产生的热载流子，无论是电子还是空穴，将被用于研究重氮盐在金属表面的官能化或炔叠氮环加成等反应。热载流子的协同作用和可能的热效应将在温度控制的条件下和在激发光源的明显辐照下进行研究。利用等离子体介导的化学将在分形结构上进行多种化学图案化。这种结构展示了多个等离子体共振，每个等离子体共振都可以有选择地用特定的波长和偏振激发，从而能够对化学功能化进行精确的空间控制。我们将把TMD的激子特性与我们的元结构中的表面等离子体共振结合起来。我们预计，这种等离子体激子-激子杂化材料将表现出更好的光学和电导性能。利用尖端增强光谱，我们有望测量增强的发光和二次谐波的产生。手性等离子体结构与与激子波长匹配的共振相结合，应该会产生增强的圆偏振光发射。除了该计划提供的基本知识外，还将利用等离子体激元实现的新的杂交特性和空间控制的分子图案来构思性能和灵活性远远超过技术水平的下一代光子设备。

Metamaterials are artificial structures composed of periodical nano- or micro-scale building blocks generally composed of layered conductors, semiconductors and dielectric barriers. In metallic metamaterials, local electronic resonances, known as plasmon resonances, are localized in the vicinity of the nanostructures. These resonances are highly tunable and can be exploited for a variety of applications including narrow-band optical filters, photovoltaic elements, and ultrasensitive analytical devices. The long-term objective of this proposed research program is to develop new metamaterials that we will exploit for spatially controlled plasmon-mediated chemical reactions and integration with transition metal dichalcogenides (TMDs). The overarching goal lies in understanding the fundamental interactions of plasmon modes with other molecules or materials under specific irradiation conditions. We will develop new 2D metastructures with specific shapes and geometries. Structures with linear or chiral anisotropies will be created and optimized to respond under linearly or circularly polarized light in both the visible and the infrared spectral ranges. Plasmonic platforms with multiple resonances spanning from the visible to the infrared range will be made and characterized using our nanophotonic infrastructure in conjunction with the mid-infrared beamline at the Canadian light source. Plasmon-mediated reactions will be investigated using these structures. Hot carriers, either electrons or holes, generated through the excitation of plasmons will be used to investigate reactions such as functionalization of diazonium salts on metal surfaces or alkyne-azide cycloadditions. The synergistic role of the hot carriers and probable thermal effects will be investigated under temperature-controlled conditions and under distinct irradiance of the excitation light source. Multichemical patterning using plasmon-mediated chemistry will be conducted on fractal structures. Such structures exhibit multiple plasmon resonances that can each be selectively excited with specific wavelengths and polarizations,  thus enabling precise spatial control of chemical functionalization. We will combine the excitonic properties of TMDs with surface plasmon resonances from our metastructures. We anticipate that such hybrid plasmon-exciton materials will exhibit enhanced optical and conduction properties. Using tip-enhanced spectroscopy, we expect to measure enhanced luminescence and second harmonic generation. The combination of chiral plasmonic structures with resonances that match the excitonic wavelength should yield enhanced emission of circularly polarized light. In addition to the fundamental knowledge provided by this program, the new hybrid properties and spatially controlled molecular patterning enabled by plasmon will be exploited for the conception of the next generation of photonic devices with performance and flexibility well beyond the state of the art.