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

非技术描述：最近，预测路径已经发展到具有高比表面积和明确定义的纳米孔的材料，这些材料要么以周期性阵列排列，要么以单个纳米颗粒的形式存在。这些新型材料在催化、分离、环境净化、可控药物输送、电子学和传感器开发等方面具有吸引力。一些最有效的合成方法涉及到被称为胶束的表面活性剂聚集体，这些胶束通常是球形或圆柱形的，作为周期性材料或中空纳米球或纳米管中纳米尺度孔隙的模板。然而，不同类型的胶束模板化纳米多孔材料的路径是分开演化的，几乎没有协同作用。该项目旨在弥合以胶束为模板的周期性纳米结构和纳米颗粒之间的鸿沟，这样关于这些结构中每一种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。考虑的设计特征包括孔洞形状、孔洞直径和孔洞入口的大小。该项目主要集中在10到40纳米大小的孔，这些孔在生物分子的固定(例如在酶催化中)、大小分子的吸附和多相催化中非常重要。为了便于应用，并对纳米材料设计有了基本的了解，人们开发了方便的方法来合成这种长度的孔洞材料。技术细节：该项目专注于两类密切相关的胶束模板材料：有序(周期)介孔材料和单胶束模板纳米粒子(纳米球或纳米管)。最近有人提出了一种制备单胶束模板纳米粒子的预测途径，该途径包括在已知的条件下降低骨架前体与表面活性剂的比例，以获得有序的介孔材料。这一新的方法是理解这两种纳米材料形成的统一概念框架的开始，这两种纳米材料受合成早期阶段胶束对象的结构及其交联性的能力所支配。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分歧。这一目标是通过深入研究以Pluronic嵌段共聚表面活性剂为模板的大孔有序介孔材料的形成和结构剪裁以及相关的纳米球和纳米管来实现的。这些材料中相对较大的孔径(14-40 nm)为通过透射电子显微镜显示结构(包括纳米颗粒外壳上的孔隙率)提供了更好的机会，并且很容易通过气体吸附测孔仪和小角X射线散射来探测。激光光散射被用来深入了解合成不同阶段存在的胶束结构，这种知识与胶束模板多孔性材料的性质有关。阐明了周期性多孔材料或单个纳米颗粒的形成条件，并跟踪了单个颗粒合成过程中的结构发展。对纳米粒子外壳上开口大小的定制正在进行研究。发展了一种简便的、在室温下合成有序介孔材料和相关的单胶束模板粒子的方法。探索了在回旋状多孔网络上合成大孔二氧化硅的扩展。该项目旨在让博士后研究员、研究生和本科生参与该项目的研究。

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.