Metal-Sensitive Functionalization and Self-Assembly of Bimetallic Nanocrystals

化学系的大分子、超分子和纳米化学项目支持格鲁吉亚理工学院的董琴教授和她的小组开发称为纳米晶体的微小晶体。 它们的纳米晶体含有两种金属，其化学功能和纳米晶体内的空间位置被精确控制。 金属纳米晶体在催化能量转换、环境保护和有机合成方面发挥着至关重要的作用。尽管取得了一些成功，但通过在空间上将反应物限制在催化位点同时原位检测最终产物和中间产物来真实的实时监测催化反应仍然是一个艰巨的挑战。研究小组通过开发纳米晶体来解决这一挑战，其中一种金属可以作为催化剂，而另一种金属可以报告“化学指纹”（与反应相关的信号）。在这项研究中开发的概念，材料和方法可以在与固态化学，催化，传感和光子学相关的广泛应用中找到用途。该小组招募妇女和少数民族学生以及社区学院和少数民族机构的学生进行暑期研究。 这项工作是与称为东南纳米技术基础设施走廊的国家纳米技术协调基础设施合作进行的。在这项由大分子，超分子和纳米化学（MSN）计划支持的研究中，秦教授的团队开发了新的设计原理和方法，通过金属选择性表面功能化和自组装，从Ag@M（M：Pt，Pd和Rh）核框架纳米立方体制备一类新型的双功能纳米反应器。具体地，在两端带有异氰化物基团的分子用于选择性地结合到核-框架纳米立方体的边缘上的M原子，充当“夹子”以使两个纳米立方体面对面以产生二聚体。两个纳米立方体之间的差距区域自然呈现出良好控制的纳米反应器，其中侧面可以用反应物正交官能化，而未被异氰化物配位的M原子将充当催化剂。由于两个Ag纳米立方体之间的强等离子体耦合仅由几纳米的间隙分开，纳米反应器提供了一种独特的能力，通过原位Sers监测各种类型的重要催化反应。模型反应包括硝基芳烃的氢化，用于生产化学上不利的产物，如羟胺和偶氮化合物，以及肉桂醛的键选择性氢化，这是生产香料、农用化学品和药物化合物的关键催化反应。该研究不仅能够实时表征多相催化反应，还有助于合理设计新的或改进的催化剂材料。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。

The Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division supports Professor Dong Qin and her group at the Georgia Institute of Technology to develop tiny crystals called bimetallic nanocrystals. Their bimetallic nanocrystals contain two metals whose chemical function and spatial position within the nanocrystals are precisely controlled. Metal nanocrystals play a vital role in enabling catalysis for energy conversion, environmental protection, and organic synthesis. Despite some success, it remains a daunting challenge to monitor the catalytic reactions in real time by spatially confining the reactants to the catalytic sites while detecting the final and intermediate products in situ. The research team addresses this challenge by developing bimetallic nanocrystals in which one of the metals can serve as a catalyst while the other can report the ‘chemical fingerprint’ (signals associated with the reaction). The concepts, materials, and methods developed during this research may find use in a broad range of applications related to solid-state chemistry, catalysis, sensing, and photonics. This team recruits women and minority students as well as those from community colleges and minority institutions for summer research. This effort is carried out in collaboration with the National Nanotechnology Coordinated Infrastructure called the Southeastern Nanotechnology Infrastructure Corridor. In this research supported by the Macromolecular, Supramolecular and Nanochemistry (MSN) Program, Professor Qin’s team develops new design principles and methods to fabricate a novel class of bifunctional nanoreactors from Ag@M (M: Pt, Pd, and Rh) core-frame nanocubes via metal-selective surface functionalization and self-assembly. Specifically, molecules bearing isocyanide groups at the two ends are used to selectively bind to the M atoms on the edges of the core-frame nanocubes, serving as “clips” to bring two nanocubes face to face for the generation of a dimer. The gap region between the two nanocubes naturally presents a well-controlled nanoreactor, in which the side faces can be orthogonally functionalized with the reactants while the M atoms not coordinated by isocyanide will serve as the catalyst. Due to a strong plasmonic coupling between the two Ag nanocubes separated by a gap of only a few nanometers, the nanoreactor offers a unique capability to monitor various types of important catalytic reactions by in situ SERS. The model reactions include the hydrogenation of nitroaromatics for the production of thermodynamically unfavorable products such as hydroxylamine and azo compounds, as well as the bond-selective hydrogenation of cinnamaldehyde, a catalytic reaction pivotal to the production of fragrance, agrochemical, and pharmaceutical compounds. This research not only enables real-time characterization of heterogeneous catalytic reactions but also sheds light on the rational design of new or improved catalyst materials.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.