This project aims to develop chemical techniques for fabricating porous nanoparticles (NPs) with a variety of compositions and predesigned sizes and shapes, some of which are not yet accessible by existing techniques. The approach will be based on templating hierarchical porous structures with controllable mesopore architectures and disassembly of such structures into their building blocks. Nanocasting techniques will be employed to create replicate structures and composite structures with a wide range of compositions. Physical properties of the NPs will be correlated with particle sizes and shapes. The porous NPs will be functionalized to modify their bulk and surface properties. New opportunities will arise to create extended 2D or 3D patterns and complex structures with novel architectures from the functional building blocks. A large number of applications have been suggested for NPs, and some of these would benefit from the additional porosity obtained by the proposed methods (mesoporous lasers, targeted drug-delivery systems, fluorescent tag hosts, NP catalysts with short diffusion paths, supercapacitors, hydrogen storage systems), new shapes with controllable aspect ratios and curvature (polymer reinforcement, magnetic carriers in magnetorheological fluids) and the ability to form composite particles (magnetic tags, high capacity electrodes). Because of the multidisciplinary nature of this project, students will become experts in a broad range of state-of-the-art synthetic and characterization techniques, involving concepts from chemistry, physics, materials science, and engineering, so that they are well prepared to tackle the complex challenges in advanced materials design. To reach an audience that may have only passing interest in science but may be attracted to the aesthetic aspects of materials chemistry, a poster exhibition showcasing the visually appealing nanostructures will be developed for display in local museums and on the web.
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Porous nano-objects with defined sizes and structures are particularly interesting, for example, as capsules for enzymes, a means of drug delivery, or building blocks for larger nanostructures. Producing tiny, three-dimensional objects in a targeted and controlled manner-and as simply and efficiently as possible-remains a challenge for scientists. In the proposed research, new processes will be developed for the production of nanoscopic cubes and other interesting shapes that are not usually accessible by conventional methods. Instead of building particles from smaller units, controlled disassembly of larger, lattice-like structures will be used. Many conventional methods for the production of nanoparticles suffer because the growing particles tend to clump together, making it difficult to achieve a uniform size. The shape of the particles can hardly be influenced at all. The alternate approach to be studied involves first building up a lattice structure in an ultrasmall mold and then disassembling it to get the desired shape. The molds used for the lattice are tiny plastic spheres, which assemble themselves like marbles in a box. Between the spheres in this structure, there are small, shaped spaces, which will be filled with precursors that convert into shaped nanoparticles with tiny pores when the spheres are burnt off by heating. By altering the mold, the sizes and shapes of the resulting, sponge-like particles can be controlled. The shaped, porous nanoparticles provide a starting point for complex nanostructures with potential applications in power storage, detection and pharmaceutics. Students participating in the project will acquire broad scientific and engineering skill necessary to design the complex materials critical for advancing America's technological competitiveness. To reach an audience that may have only passing interest in science but may be attracted to the aesthetic aspects of materials chemistry, a poster exhibition showcasing the visually appealing nanostructures will be developed for display in local museums and on the web.
