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Synthesis, Characterization and Pore Structure Analysis of Mesoporous Materials

  • Author(s): Saldarriaga Lopez, Laura Carolina
  • Advisor(s): Tolbert, Sarah H
  • et al.
Abstract

Self-assembly provides a route to make mesoporous structures that have accessible internal surface area. These types of materials show promise for use in opto-electronic devices as well as for energy storage devices. In this work we synthesize a range of mesoporous thin films from molecular and nanocrystal precursors. We characterize these films' porous structure and surface area using ellipsometric-porosimetry.

This work is divided into three parts; the first section focuses on synthesizing and characterizing mesoporous semiconducting films. Two approaches are utilized, one in which germanium Zintl clusters co-assemble with a charged surfactant via electrostatic attractions to produce an ordered organic/inorganic composite that can later be converted into a porous network by surfactant removal. The other method uses pre-formed cadmiun selenide nanocrystals that coassemble with diblock copolymer micelles to produce a porous film with large accessible surface areas. Both of these nanostructured semiconductors are electrically interconnected, making them suitable for a range of applications.

In the second part of this work we focus on studying the pore structure of four different porous metal-oxide films. Mn3O4: FeMn2O3, ITO, and ITO coated with V2O5. All of these systems use nanocrystal/diblock copolymer assembly methods described above to produce a 3-D porous network with large accessible surface areas. Mn3O4, FeMn2O3 are redox active materials that were synthesized for their redox capacities. ITO nanocrystals coated with V2O5 are also redox active due to the vanadia coating. In all 3 systems the porous architectures exhibit high surface areas, providing ample redox active sites, and an interconnected open porosity, facilitating solvent/ion diffusion to those sites. In the case of ITO coated with vanadia we investigated the effect of vanadia coating thickness on surface accessibility.

In the final section we examine ways to measure surface area of thin films using ellipsometric-porosimetry combined with two different solvents: isopentane and methanol. We studied the advantages and disadvantages of each solvent in determining the surface area of the film.

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