Plasmon-exciton nanostructures based on 2D semiconductor nanocrystals for near-infrared photonics

在这个项目中，我们将开发在近红外(NIR)区域活跃的新型等离子体激子-激子混合纳米结构。作为制备这些复合结构的材料平台，我们选择了铜硫化物(Cu2-xA，其中x=0-1，A=S，Se或Te)二维(2D)纳米晶。我们的选择依赖于Cu2-xA的多晶性，它显示出一系列不同的化学计量比适应不同的晶相，以及通过阳离子交换对这些纳米晶体进行化学转化的可行性。该项目将结合以下两个主要部分：1)开发尺寸和晶体结构可控的半导体Cu2-xA二维纳米材料的胶体合成，并通过阳离子交换反应将其化学转化为半导体二维金属硫化物，如CDA、PBA、HGA和Ag2A，包括它们的异质结构；2)制备平面层状组装形式的复合荧光等离子体材料，并利用先进的光学光谱技术研究层间的相互作用。本项目所针对的2D材料的成分和结构操纵程度将远远超过现有的最先进的直接湿化学合成方法以及化学气相沉积或剥离方法。对其结构和组成的控制是精确设计其光电性能的关键。从实用角度看，具有高吸收系数和高发光量子产率的半导体纳米晶与具有强等离激元共振的纳米粒子的结合有望提高光电子器件的效率。这样的概念对于近红外区域非常重要，在那里很难实现高效率。一方面，缺乏合成具有近红外活性的铜、铅、汞和银硫化物二维纳米材料的合成方案，另一方面，几乎还没有研究近红外区等离子体和激子结构之间的相互作用，这促使我们追求这些目标。该项目的工作计划分配给一名博士生研究人员，由两名学生助理支持。这项工作不仅将对胶体2D半导体纳米材料的化学基础及其合成方法产生影响，还将提供一系列具有明确应用潜力的各种材料。由此得到的材料和结构具有可调的光物理性质，在太阳能电池、发光太阳能聚光器、发光二极管和光探测器中将是非常有前途的候选材料。

In this project we will develop novel hybrid plasmonic‒excitonic nanostructures active in the near-infrared (NIR) region. As a material platform for the fabrication of these composite structures we choose copper chalcogenide (Cu2‒xA, where x = 0–1 and A = S, Se or Te) two dimensional (2D) nanocrystals. Our selection relies on polymorphism of Cu2‒xA which exhibits a range of different stoichiometries adapting various crystal phases and a feasibility of chemical transformations of these nanocrystals via cation exchange.The project will combine the following two main parts: 1) development of a direct colloidal synthesis of semiconductor Cu2‒xA 2D nanomaterials with well controlled dimensions and crystal structure and their chemical transformations via cation exchange reactions into semiconductor 2D metal chalcogenides, such as CdA, PbA, HgA, and Ag2A, including their hetero-structures; 2) fabrication of composite fluorescent‒plasmonic materials in the form of planar layered assemblies and investigation of interactions between the layers using advanced optical spectroscopy techniques. Degrees of compositional and structural manipulation of the 2D materials targeted in this project will go far beyond the existing state-of-the-art methods for their direct wet chemical synthesis as well as chemical vapor deposition or exfoliation. Control of their structure and composition is a key to the precise engineering of their optoelectronic properties. From practical point of view, the combination of semiconductor nanocrystals with high absorption coefficients and high photoluminescence quantum yields and nanoparticles with a strong plasmon resonance is promising for the improvement of the efficiency of optoelectronic devices. Such a concept is of great importance for the NIR region, where a high efficiency is difficult to achieve. The lack of synthetic protocols for the synthesis of NIR-active copper, lead, mercury, and silver chalcogenide 2D nanomaterials on one hand, and practically not investigated yet interactions between plasmonic and excitonic structures in the NIR region on the other, motivate us to pursue these goals. The work plan of the project is assigned to a doctoral researcher supported by two student assistants.This work is expected to have impact not only on the fundamentals of chemistry of colloidal 2D semiconductor nanomaterials and their synthetic methodology, but also to provide a range of various materials with a well-defined application potential. The resulting materials and structures with tunable photophysical properties will be very promising candidates for applications in solar cells, luminescent solar concentrators, LEDs, and photodetectors.