Collaborative Research: Operando Three-dimensional Super-resolution Imaging of Catalytic Events in Porous Nanocatalysts

在化学测量与成像计划和化学系催化计划的支持下，佐治亚州立大学的宁芳教授和爱荷华州立大学的黄文宇教授正在开发一种三维超分辨率成像技术，以在单分子水平上了解纳米孔中的分子运动和反应。设计和合成了具有良好几何结构和可控复杂性的高度可调的核壳结构，并在光学成像系统下进行了可视化。所提出的显微镜的原位3D成像能力使它们成为与其他传统方法(如电子显微镜和原子力显微镜)互补的有价值的表征技术。两个团队还在设计单分子成像实验来研究多步骤催化反应，在多步骤催化反应中，两个或两个以上的化学转化由纳米工程多功能催化剂催化，以避免每一步产生的中间产物的分离、纯化和转移。这两个机构的研究生和本科生在构建催化纳米结构和开发在单分子水平上了解分子运输和催化的新仪器能力方面获得了宝贵的技能。亚特兰大和艾姆斯地区的高中生接触到成像、纳米科学和催化的概念，以加强高中的STEM教育。在这项工作中，定义明确的多相催化体系，通过胶体纳米粒子嵌入到排列好的通道的核壳介孔二氧化硅材料中，被开发出来。获得了纳米分辨率的单分子轨迹，以阐明孔大小、长度、取向和表面配体对分子传输和转化的影响。利用核壳多孔结构模型获得的关于纳米尺度约束输运的新的实验见解可以推广到指导用于分离和催化的多孔材料的发展。这项研究的长期目标是使用在平台催化系统上使用成像技术获得的知识来指导我们未来针对各种化学转化的催化剂设计。

With support from the Chemical Measurement and Imaging Program and the Catalysis Program in the Division of Chemistry, Professor Ning Fang of Georgia State University and Professor Wenyu Huang of Iowa State University are developing a three dimensional super-resolution imaging technique for understanding molecular movement and reactivity in nanopores at the single-molecule level. Highly tunable core-shell structures with well-defined geometry and manageable complexity are designed and synthesized, and then visualized under the optical imaging systems. The in situ 3D imaging capability of the proposed microscopes makes them valuable characterization techniques complementary to other conventional methods, such as electron microscopy and atomic force microscopy. Both teams are also designing single molecule imaging experiments to study multi-step catalytic reactions, in which two or more chemical transformations are catalyzed with a nanoscale-engineered multifunctional catalyst to avoid the need for separation, purification, and transfer of intermediates produced in each step. Graduate and undergraduate students in these two institutions acquire valuable skills in building catalytic nanostructures and in developing new instrumental capabilities to understand molecular transport and catalysis at the single-molecule level. High school students in the Atlanta and Ames area are exposed to the concepts of imaging, nanoscience, and catalysis to enhance STEM education in high schools. In this work well-defined heterogeneous catalytic systems, whereby colloidal nanoparticles are embedded within core-shell mesoporous silica materials of aligned channels, are developed. Single molecule trajectories with nanometer resolution are acquired to elucidate the effects of pore size, length, orientation, and surface ligands on molecular transport and conversion. New experimental insights on transport in nanoscale confinement acquired with the model core-shell porous structures can be generalized to guide the development of porous materials for separation and catalysis. The long-term objective for this research is to use the knowledge acquired using the imaging technique on the platform catalysis system to guide our future catalyst design for a wide range of chemical transformations.