CAREER: Development of 2D Materials with High Optical Sensitivity and Efficient Charge Transport Through Local Chemical Modification

只有一个原子厚度的材料，被称为二维（2D）材料，具有与许多传统材料相媲美的光学和电子特性。这些二维材料的两个关键特性——吸收光的能力和移动电荷的能力——通常是相互竞争的物理特性，其中一个的增强会削弱另一个。这项研究活动旨在通过纳米尺度的局部表面化学控制来开发具有高光吸收率和高导电性的二维材料。该项目研究了新的化学途径来功能化2D材料，以及单片2D材料表面的光学活性区域如何与电子活性区域相互作用。这种功能对于广泛的应用至关重要，包括光电探测器，太阳能光伏发电和化学传感器。项目活动为研究生和本科生在电化学、表面科学、化学光谱学和纳米尺度输运现象的研究领域提供培训。此外，该研究还支持为代表性不足和经济条件较差的中学生提供互动实验室活动，以及通过开放教科书图书馆倡议和OAKTrust数字资源库开发开源图书章节。该研究项目探索了新的化学途径和技术，以提高石墨烯、二硫化钼和含硫族化物的碲化物原子薄片的光学灵敏度和响应时间。化学改变二维材料的表面，使其与电磁辐射强烈相互作用，而不破坏材料内部的电荷传输，目前是一个重大挑战。在这里，利用重氮盐通过多步电化学氧化和还原反应，探索具有光学活性有机染料和量子点的二维材料的化学功能化，以创建与可见光和红外光具有强相互作用的二维材料。此外，光学光刻和基于尖端的纳米光刻提供了将光活性区域与高导电性区域集成的途径，使得一个区域的光激发电荷态可以有效地耦合到相邻区域。合成工作得到了广泛的光学和电子测量技术的支持，包括纳米级红外显微镜，x射线光电子能谱，拉曼光谱和荧光显微镜，以及背门控晶体管测量，以研究局部化学成分对电荷激发和输运的影响。本研究中获得的基础知识可以应用于赋予各种2D材料独特的光学、热学和机械性能，而不会牺牲电荷传输性能。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Materials only a single atom thick, known as two-dimensional (2D) materials, possess optical and electronic properties that rival many traditional materials. Two key properties of these 2D materials - ability to absorb light and the ability to move charge - are often competing physical properties, where enhancement of one diminishes the other. This research activity seeks to develop 2D materials with both high optical absorptivity and high electrical conductivity through nanometer-scale control of local surface chemistry. The project investigates new chemical routes to functionalize 2D materials, and how optically active regions interact with electronically active regions on the surface of a single 2D sheet. Such functionality is critical for a wide range of applications, including photodetectors, solar photovoltaics, and chemical sensors. The project activities provide training to graduate and undergraduate students in the research areas of electrochemistry, surface science, chemical spectroscopy, and nanoscale transport phenomena. Additionally, the research supports interactive laboratory activities for underrepresented and economically disadvantaged secondary school students, as well development of open source book chapters through the Open Textbook Library Initiative and the OAKTrust Digital Repository.This research project explores new chemical pathways and techniques to improve both optical sensitivity and response time on atomically thin sheets of graphene, molybdenum disulfide, and telluride containing chalcogenides. Chemically altering the surface of 2D materials to interact strongly with electromagnetic radiation without disrupting charge transport within the material is currently a significant challenge. Here, chemical functionalization of 2D materials with optically active organic dyes and quantum dots is explored via multi-step electrochemical oxidation and reduction reactions utilizing diazonium salts to create 2D materials possessing strong interaction with visible and infrared light. Further, optical lithography and tip-based nanolithography provide routes to integrate optically active regions with regions of high electrical conductivity, such that charge states optically excited in one region can efficiently couple to adjacent regions. The synthesis efforts are complimented by a wide range of optical and electronic measurement techniques, including nanoscale infrared microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, and fluorescence microscopy in concert with back-gated transistor measurements to investigate the effect of local chemical composition on charge excitation and transport. The fundamental knowledge gained in this study can be applied to impart unique optical, thermal, and mechanical properties to a wide range of 2D materials without sacrificing charge transport performance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.