Committee

Prof. Mark Losego – School of Materials Science and Engineering (advisor)

Prof. Juan-Pablo Correa-Baena– School of Materials Science and Engineering

Prof. Guoxiang (Emma) Hu – School of Materials Science and Engineering

Prof. Antonio Facchetti – School of Materials Science and Engineering

Prof. Marta Hatzell – George W. Woodruff School of Mechanical Engineering

Abstract

Vapor phase modification of polymers can be used to create hybrid organic-inorganic materials for a variety of technological applications. Vapor phase infiltration (VPI) statically exposes polymers to gaseous metal precursors that can adsorb, diffuse into and react with the polymer matrix. When conjugated polymers (CP) are exposed to the appropriate oxidizing precursors, the electrical conductivity and optical absorbance of the conjugated polymer can be modified. Vapor doping of conjugated polymers has drawn interest because of its solvent-free nature. However, the inorganic clusters infiltrated into the conjugated polymer during VPI have only been seen as scattering centers inhibiting electron mobility. In this thesis we will explore the possibility of using these inorganic clusters as catalyst centers and the conjugated polymer as a dye-sensitizing agent. To understand the hybrid material made and the possible application fields we will explore three fundamental questions. First, can CP-MOx dye-sensitized hybrid photocatalysts be made using VPI? A variety of analytical approaches will be used to explore the light-matter interactions and electronic structure of the hybrid material. In particular, the ability, or lack thereof, of the CP to become excited and donate that excited electron to the MOx is essential to any dye-sensitization process.

Second, how can nanostructured P3HT be used to achieve a higher performing photocatalyst? Its well know that nanostructuring of materials can create more effective catalysts through increased surface area and active sites. CPs like P3HT can be synthesized with functional various functional groups on either their end groups (the first and last monomer of a polymer) or their side chains. If carboxylic acids or aldehyde/ester groups are attached then a condensation or Grignard reaction, respectively, can be used to bind CPs to nanoparticles. The possibility of attaching CPs to nanoparticles and their resulting hybrid structure and catalytic capabilities will be explored to understand the possibility of nanostructuring VPI-made CP-MOx hybrid photocatalyst.

Finally, how can we modify the oxidation state of VOx to increase the catalytic rate? Differing VOx oxidation states exhibit differing electronic structures and catalytic capabilities. Various ALD processes have been developed to modify the oxidation state of the deposited material. Herein, we will explore the possibility of modifying the oxidation state of VPI infiltrated VOx and its effect on the catalytic rate of the hybrid material.

This thesis will explore the possibilities of using vapor phase infiltration as a new approach for making hybrid photocatalysts and how the electronic structure of the inorganic and organic materials interact in the hybrid material. Use of VPI to make hybrid photocatalysts opens up a new method for making dye-sensitized photocatalysts with nanosized MOx clusters concentrated towards the surface of the substrate. Knowledge of the electronic structure of the hybrid material will inform future hybrid material design and provide insight into the light-matter interactions of such hybrid materials.