Optical Property, Charge Carrier Relaxation and Charge Transfer Properties in Chemically-Synthesized Layered TiS2 Nanodiscs with Controlled Lateral and Transverse Dimensions

非技术描述：这项研究项目研究了一类新的二维纳米材料的性质，即层状过渡金属二卤化物，其中通过控制纳米尺度的尺寸可以获得体相中没有观察到的独特的电子、光学和传输性质。由材料的光谱表征和计算机模拟专家组成的研究团队合作，以了解物理和化学结构的变化如何调整材料的性能。这一研究结果将对这些纳米材料的潜在光电子应用具有重要意义。该项目的首席研究员还与一家工业合作伙伴合作，为多个学科的本科生和研究生开发了一项仪器培训计划，重点是信号测量和处理。这一努力缩小了这些主题的当前课程与许多科学和工程学科所要求的仪器技能之间的差距。技术描述：该项目使用化学合成的二硫化钛纳米盘作为模型系统。在化学合成中，可以控制纳米盘的厚度，从几个原子层到十几个原子层变化，并且纳米盘的直径可以从几十到几百纳米变化，在两个垂直方向上提供显著的尺寸控制范围。利用这些纳米材料，我们的研究集中在以下几个方面：(I)了解纳米TiO2S的光学跃迁能和层间声子如何受纳米盘厚度和直径的变化以及载流子的光激发的影响；(Ii)了解载流子弛豫和电荷转移的速率和路径与尺寸变化和界面结构的关系。时间分辨泵浦探测光谱和电子显微镜是阐明其结构-性质关系的主要实验工具。利用密度泛函理论对不同维度的纳米盘的电子和振动结构进行了计算，提供了这种层状材料体系的结构相关材料性质的原子图。

Non-technical Description: This research project investigates the properties of a new class of 2-dimensional nanomaterials, i.e., layered transition metal dichalcogenides, where unique electronic, optical and transport properties not observed in the bulk phase can be harvested through the control of the dimensions in nanoscale. The research team, consisting of experts in the spectroscopic characterization and computer simulation of the materials, collaborates to gain an understanding on how the variations of the physical and chemical structures can tune the material properties. The outcome of this research will be valuable to the potential optoelectronic applications of these nanomaterials. The principal investigator of this project also develops, in collaboration with an industrial partner, a training program on instrumentation, focusing on signal measurement and processing, for both undergraduate and graduate students in multiple disciplines. This effort narrows the gap between current curriculum on such topics and the instrumentation skills required in many science and engineering disciplines.Technical Description: The project utilizes chemically synthesized titanium disulfide nanodiscs in solution as a model system. The nanodisc thickness can be controlled in chemical synthesis, varying from a few to more than ten atomic layers, and the nanodisc diameter can be varied from tens to hundreds of nanometers, providing a significant range of dimensional control in two perpendicular directions. Using these nanomaterials, the research focuses on the following specific tasks: (i) understanding how the optical transition energy and interlayer phonon of titanium disulfide nanodiscs are influenced by the variations of both the nanodisc thickness and diameter and by the photoexcitation of the charge carriers; and (ii) understanding the rates and pathways of the charge carrier relaxation and charge transfer correlated with the dimensional variation and the interfacial structure. Time-resolved pump-probe spectroscopy and electron microscopy are the main experimental tools to elucidate the structure-property relationship. The calculation of the electronic and vibrational structures of the nanodiscs of different dimensions, employing density functional theory, provides an atomistic picture of the structurally dependent material properties of this layered material system.