Collaborative Research: Directing molecular assemblies into covalently bonded 2D organic materials

新不伦瑞克罗格斯大学的Robert Bartynski和Sylvie Rangan教授以及纽瓦克罗格斯大学的Elena Galoppini教授得到了国家科学基金会化学部高分子、超分子和纳米化学(MSN)计划的支持，以开发在金属表面创建碳基二维材料的新方法。定制设计的分子构建块的有序阵列组装在单晶表面上，然后受到外部刺激，如热、光或高能电子，将相邻的分子连接在一起，形成扩展的二维片状材料。在暴露于外部刺激之前，通过明智地选择和放置化学构建块来控制片材的拓扑和功能。由此产生的薄片有望展示各种新的特性和现象，如新形式的磁性、几乎没有或几乎没有电阻的导电以及高效的光发射或吸收。该研究项目的成功为二维材料在纳米电子、传感器、太阳能电池、发光二极管和其他设备中的新应用开辟了道路，这些设备需要可加工性、可调性、高性能和传统材料无法获得的性能。在实施该项目的过程中，参与的学生在多学科的科学研究环境中接受了广泛的培训，并提供了在国家实验室与科学家互动的机会。来自代表不足的少数民族群体的本科生参与了该项目，并对高中生和教师进行了指导。该项目生成了一个用于表面合成二维(2D)材料的“工具箱”。探索了与表面合成相关的不同成键机制，并开发了创建表面反应等级的方法，以指导分子单元之间分子间C-C键的形成，从而创建新的2D有机体系。该工具箱涉及(A)开发具有战略位置的官能团的特殊设计的分子前体，(B)使用官能团之间的分子间和/或分子内相互作用，以及对织构金属的表面模板效应，以控制分子前体在单晶表面的组装。特别强调了通过脱氢(消除H2)、脱卤化(消除X2，X=Br、Cl、I)和脱氢氟化(消除HF)反应形成C-C键。通过包括扫描隧道显微镜在内的表面科学技术的综合组合来研究所产生的2D结构的性质，通过基于同步加速器的电子能谱、直接和反向光电发射以及从头计算理论方法的组合来研究电子性质。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智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Professors Robert Bartynski and Sylvie Rangan of Rutgers University New Brunswick and Professor Elena Galoppini of Rutgers University Newark are supported by the Macromolecular, Supramolecular and Nanochemistry (MSN) Program in the Division of Chemistry of the National Science Foundation to develop new methods for the creation of carbon-based two-dimensional materials on metal surfaces. Ordered arrays of custom designed molecular building blocks are assembled on single crystal surfaces then subjected to an external stimulus, such as heat, light, or energetic electrons, to link together neighboring molecules creating an extended two-dimensional sheet material. The topology and functionality of the sheet are controlled by judicious selection and placement of the chemical building blocks prior to exposure to the external stimulus. The resulting sheets hold the promise of displaying a wide variety of novel properties and phenomena such as new forms of magnetism, conduction of electricity with little or no resistance, and efficient emission or absorption of light. Success of this research project opens the way to new applications of two-dimensional materials in nano-electronics, sensors, solar cells, light-emitting diodes, and other devices that require processability, tunability, high performance, and properties that cannot be obtained with conventional materials. During the course of conducting the project, the students involved are broadly trained in a multidisciplinary science research environment and provided a chance to interact with scientists in national laboratories. Undergraduate students from under-represented minority groups are involved in the project and high school students and teachers are mentored. The project generates a "toolbox" for on-surface synthesis of two-dimensional (2D) materials. Different bonding mechanisms that are relevant to on-surface synthesis are explored and ways to create a hierarchy of surface reactions to direct the formation of intermolecular C-C bonds between molecular units to create new 2D organic systems are developed. The toolbox involves (a) the development of specially designed molecular precursors with functional groups placed at strategic positions, (b) the use of inter-molecular and/or intra-molecular interactions between functional groups, as well as surface templating effects on textured metals, to control the assembly of the molecular precursors on single crystal surfaces. A particular emphasis is placed on the formation of C-C bonds by dehydrogenation (elimination of H2), dehalogenation (elimination of X2, X = Br, Cl, I) and dehydrofluorination (elimination of HF) reactions. The nature of the resulting 2D structures are studied through an integrated combination of surface science techniques, including scanning tunneling microscopy, and the electronic properties are examined through a combination of synchrotron-based electron spectroscopies, direct and inverse photoemission as well as ab-initio theoretical methodsThis 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.