Design of Novel Large-Pore Nanoporous Materials through Understanding of Micelle Templating Process

非技术描述：最近，预测途径已经发展到具有高表面积和定义良好的纳米级孔隙的材料，要么排列在周期性阵列中，要么存在于单个纳米颗粒中。这些新材料在催化、分离、环境清理、控制药物输送、电子和传感器开发方面具有吸引力。一些最强大的合成方法涉及表面活性剂聚集体，称为胶束，通常呈球形或圆柱形，作为周期性材料或空心纳米球或纳米管中纳米级孔的模板。然而，不同类型胶束模板纳米多孔材料的制备途径是各自独立的，协同作用不大。该项目旨在弥合胶束模板周期性纳米结构和纳米颗粒之间的鸿沟，这样关于这些结构的知识就可以很容易地用于理解其他已知结构和设计新结构。所考虑的设计特征包括孔隙形状、孔径和气孔入口的大小。该项目主要关注10至40纳米的孔隙，这些孔隙在生物分子的固定化（例如酶催化）、大分子和小分子的吸附以及多相催化中非常重要。为了促进纳米材料的应用，并获得纳米材料设计的基本见解，开发了具有这种长度尺度孔隙的材料的方便方法。技术细节：该项目专注于两个密切相关的胶束模板材料家族：有序（周期性）介孔材料和单胶束模板纳米颗粒（纳米球或纳米管）。最近提出了一种单胶束模板纳米颗粒的预测途径，该途径涉及在已知条件下降低框架前驱体与表面活性剂的比例，以提供有序的介孔材料。这种新方法是理解这两种纳米材料形成的统一概念框架的开始，这些纳米材料是由合成早期阶段发生的胶束物体的结构和它们的交联能力所控制的。目前的项目旨在弥合有序介孔材料和单胶束模板纳米颗粒之间的鸿沟。通过深入研究大孔有序介孔材料的形成和结构裁剪，以及相关的纳米球和纳米管，通过Pluronic嵌段共聚物表面活性剂模板化来实现这一目标。这些材料中相对较大的孔隙尺寸（14-40 nm）为透射电子显微镜的结构可视化（包括纳米颗粒外壳上的孔隙度）提供了更好的机会，并且易于通过气体吸附孔隙度测定和小角度x射线散射进行探测。激光散射被用于深入了解胶束结构在合成的不同阶段，这些知识与胶束模板多孔材料的性质相关联。阐明了周期多孔材料或单个纳米颗粒形成的条件，并跟踪了单个颗粒合成过程中的结构发展。目前正在研究如何调整纳米颗粒外壳上的开口尺寸。开发了方便的室温合成有序介孔材料和相关的单胶束模板颗粒。对大孔二氧化硅在螺旋孔网络上的合成进行了拓展。该项目旨在让博士后、研究生和本科生参与项目研究。

NON-TECHNICAL DESCRIPTION: Recently, predictive pathways have been developed to materials with high surface areas and well-defined nanoscale pores, either arranged in periodic arrays or existing in individual nanoparticles. These novel materials are attractive in catalysis, separations, environmental cleanup, controlled drug delivery, electronics and development of sensors. Some of the most powerful synthetic approaches involve surfactant aggregates known as micelles, which are usually spherical or cylindrical in shape, as templates for nanoscale pores in periodic materials or in hollow nanospheres or nanotubes. However, the pathways to different kinds of micelle-templated nano-porous materials evolved separately with little synergy. The project is intended to bridge the divide between the micelle-templated periodic nanostructures and the nanoparticles, so that the knowledge about each of these structures can readily be used to understand other known structures and design new ones. The design features considered include the pore shape, pore diameter and size of the entrances to pores. The project is primarily focused on pores of size from 10 to 40 nanometers, which are important in immobilization of biomolecules (for instance in enzymatic catalysis), adsorption of large and small molecules, and heterogeneous catalysis. Convenient methods for the synthesis of materials with pores at this length scale are developed to facilitate their applications and gain fundamental insight into nanoscale materials design.TECHNICAL DETAILS: The project is focused on two families of closely related micelle-templated materials: ordered (periodic) mesoporous materials and single-micelle-templated nanoparticles (nanospheres or nanotubes). A predictive pathway to single-micelle-templated nanoparticles was recently proposed which involves the lowering of the ratio of the framework precursor to surfactant under conditions known to afford ordered mesoporous materials. This new approach is the beginning of a unified conceptual framework for understanding of the formation of these two kinds of nanomaterials governed by the structure of micellar objects occurring at early stages of the synthesis and their ability to cross-link. The current project is intended to bridge the divide between the ordered mesoporous materials and single-micelle-templated nanoparticles. The objective is being achieved through an in-depth study of the formation and structural tailoring of large-pore ordered mesoporous materials, as well as the related nanospheres and nanotubes, templated by Pluronic block copolymer surfactants. The relatively large size of pores (14-40 nm) in these materials provides enhanced opportunities for the structure visualization (including the porosity on the shells of nanoparticles) by transmission electron microscopy, and is readily probed by gas adsorption porosimetry and small-angle X-ray scattering. Laser light scattering is being used to gain profound insight into micellar structures present at different stages of the synthesis and this knowledge is being correlated with the properties of the micelle-templated porous materials. The conditions for the formation of either periodic porous materials or individual nanoparticles are elucidated and the structural development in the synthesis of the individual particles is followed. The tailoring of the size of openings on the shells of the nanoparticles is being investigated. Convenient, room-temperature syntheses of ordered mesoporous materials and related single-micelle-templated particles are developed. The extension of the synthesis of large-pore silicas on gyroidal porous networks is pursued. The project is designed to involve a postdoctoral fellow, graduate students and undergraduate students in the project's research.