Probing the internal environment of hollow metal oxide nanoparticles

Hollow nanoparticles are of great interest in fields such as catalysis, energy absorbing media, and additives for building materials. With these applications in mind, an understanding of the structural and mechanical properties of these hollow shells is essential.;Most of the research presented in this dissertation focuses on the Ag@CoO yolk-shell system, where silver nanoparticles are encapsulated in hollow cobalt oxide shells. New syntheses for silver nanoparticles as well as Ag@CoO yolk-shell structures are developed.;The silver nanoparticles were studied by x-ray diffraction in a diamond anvil cell up to quasi-hydrostatic pressures of 10 GPa, and a rhombohedral distortion of the crystal lattice not seen in the bulk was observed. A detailed mechanism of this distortion is proposed.;The Ag@CoO particles were similarly studied under pressure. Using the information from the bare silver particles, the pressure inside of the hollow spheres was determined The shells appear to shield the internal environment from the applied pressure up to the point where plastic deformation begins. By combining the information about the pressures inside and outside of these hollow shells, it was determined that the yield strengths of such materials are on the order of 500 MPa.;Ag@CoO particles were also studied at ambient pressure, using UV-Vis spectrometry. Although the results of this study are somewhat inconclusive at this time, it appears to be possible to determine what solvent is present inside of the hollow shells by monitoring the plasmon frequency of the encapsulated silver particles. In some cases, it may even be possible to monitor the diffusion of the solvent through the grain boundaries.;These two new methods of investigating the internal environment of hollow nanoparticles promise to provide valuable information about the properties of the shells necessary to effectively use these shells in the desired applications.