CAREER:Two-Dimensional Materials with Addressable Surfaces

非技术概述：二维（2D）材料是晶体材料，只有单层或几层原子厚。这种材料最近在纳米（光）电子学，催化，传感和能源生产的新技术的发展中受到了广泛的关注。该NSF CAREER项目由材料研究部的固态和材料化学项目支持，整合了以设计和合成新的二维材料系列为中心的研究和教育活动，并促进了对其表面功能化和物理性能之间关系的理解。实现2D材料的巨大变革性承诺取决于开发有效的方法来控制表面化学，从而改变薄层的固有物理特性和材料化学。这仍然是大多数已知2D材料的主要挑战。它们在化学上不起反应。为了克服这一障碍，该项目开发了一系列基于簇合物的金属硫属化物2D材料。单个簇的表面可以更容易地改性，同时保持无机层的内部结构完整。总体目标是开发化学策略，通过连接不同的分子来改变这些2D材料的外部，然后研究这些修饰如何改变这些层的光学和电子特性。该项目通过提供一条创建具有可调物理，化学和表面特性的多功能2D材料的途径，促进了对2D材料的科学理解和潜在技术应用。这种2D材料从未被合成过，它们新颖的基于簇的结构产生了独特的物理性质。研究工作与教育和宣传活动相结合，旨在增加历史上代表性不足的群体在STEM中的参与，并加强科学工作队伍。该项目由材料研究部的固体与材料化学项目支持，将以新型二维材料的设计与合成为中心的研究与教育活动相结合，进一步理解材料的表面功能化与物理性能之间的关系。所提出的材料是由共价连接的金属硫族化物簇，取代不稳定的卤素原子。这些2D材料是从块状层状货车德瓦尔斯簇固体、Re 6Se 8 Cl 2和Mo 6S 3Br 6剥离的。该研究测试了这些2D材料的光学和电子性质受到表面配体性质的强烈影响的假设。PI和他的学生开发了取代反应，用一系列具有编程特征（电荷，配体场强，偶极）的配体对2D材料的表面进行功能化，并测量功能化前后的光学性质和表面电子状态。将材料集成到模型电子器件中，以探测配体取代对电子性质的影响。2D材料领域发展的一个关键因素是控制其性能的能力。在这种情况下，表面功能化策略的发展具有极大的科学和技术兴趣，作为创建具有可调物理，化学和表面特性的多功能2D材料的途径。目前的方法受到严重限制，因为它们产生非常低的表面覆盖率，它们产生大量的缺陷和/或它们依赖于弱的非共价相互作用。这项研究克服了这些障碍，使2D材料的共价官能化具有高覆盖率，同时保留无机框架的内部结构。（初中，高中，本科和研究生）追求STEM职业，以及扩大在STEM历史上代表性不足的群体的参与，并加强本科化学课程。从历史上代表性不足的群体招收学生的重点主要有四种方法：（1）对来自纽约市的中央哈莱姆和布朗克斯的初中和高中学生进行外联活动;（2）招募本科生到PI的实验室工作，以获得早期研究经验;（3）招募和指导研究生进行化学和材料科学相结合的多学科研究;（4）将研究纳入化学本科课程。该奖项反映了NSF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。

Non-Technical Summary:Two-dimensional (2D) materials are crystalline materials which are only a single layer or a few layers of atoms thick. Such materials have recently received widespread attention for the development of novel technologies in nano(opto)electronics, catalysis, sensing, and energy production. This NSF CAREER project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, integrates research and educational activities centered on the design and synthesis of a new family of 2D materials, and advances the understanding of the relation between their surface functionalization and physical properties. Realizing the great transformative promises of 2D materials hinges on the development of effective methods to control the surface chemistry and thereby change the intrinsic physical properties and materials chemistry of the thin layers. This remains a major challenge for most known 2D materials. They are chemically non-reactive. To overcome this hurdle, the project develops a series of cluster-based metal chalcogenide 2D materials. The surfaces of the individual clusters can be modified more easily while leaving the internal structure of the inorganic layer intact. The overall goal is to develop chemical strategies to change the outside of these 2D materials by attaching different molecules, and then study how these modifications alter the optical and electronic properties of the layers. This project advances the scientific understanding and potential technological applications of 2D materials by providing a path towards creating multifunctional 2D materials with tunable physical, chemical and surface properties. Such 2D materials have never been synthesized and their novel cluster-based structures produces unique physical properties. The research effort is integrated with educational and outreach activities aimed at increasing the participation of historically underrepresented groups in STEM, and strengthening the scientific workforce. A coordinated effort spans high school and middle school outreach, interdisciplinary research training for undergraduate and graduate scientists, and curriculum development.Technical Summary:This NSF CAREER project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, integrates research and educational activities centered on the design and synthesis of a new family of 2D materials, and furthers the understanding of the relation between their surface functionalization and physical properties. The proposed materials are composed of covalently-linked metal chalcogenide clusters capped by substitutionally labile halogen atoms. These 2D materials are exfoliated from bulk layered van der Waals cluster solids, Re6Se8Cl2 and Mo6S3Br6. The research tests the hypothesis that the optical and electronic properties of these 2D materials are strongly influenced by the nature of the ligands on the surface. The PI and his students develop substitution reactions to functionalize the surface of the 2D materials with a series of ligands with programmed characteristics (charge, ligand field strength, dipole), and measure the resulting optical properties and surface electronic states, before and after functionalization. The materials are integrated into model electrical devices to probe the effect of ligand substitution on the electronic properties. A critical factor for the development of the field of 2D materials is the ability to control their properties. In this context, the development of surface functionalization strategies is of great scientific and technological interest as a path towards creating multifunctional 2D materials with tunable physical, chemical and surface properties. Current methods are severely limited because they yield very low surface coverage, they generate a vast number of defects and/or they rely on weak non-covalent interactions. This research overcomes these hurdles and enable the covalent functionalization of 2D materials with high coverage rates while preserving the internal structure of the inorganic framework.The educational component of this NSF CAREER project aims to inspire students (middle school, high school, undergraduate, and graduate) to pursue careers in STEM, as well as broaden the participation of historically underrepresented groups in STEM and enhance the undergraduate chemistry curriculum. The focus on recruiting students form historically underrepresented groups prevails in four approaches: (1) Outreach activities to middle-school and high-school students from Central Harlem and the Bronx in New York City; (2) Recruit undergraduate students to work in the PI's laboratory for early research experiences; (3) Recruit and mentor graduate students in multidisciplinary research combining chemistry and materials science; (4) Integrate the research into the Chemistry undergraduate curriculum.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.