Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor

Paul A. Charpentier

Abstract

Light absorbing inorganic nanoparticles in transparent plastics such as poly(ethylene-co-vinyl acetate) (EVA) are of enormous interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light. However, how to stabilize the QDs for long product life spans without "blinking" while enabling their easy integration into polymer systems is lacking. This work examines different approaches for loading mesoporous silica encapsulated QDs into EVA polymer films which can control plant growth in greenhouses or enhance PV panel efficiencies.

Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm sizes were synthesized using a modified facile approach based on the pyrolysis of single molecule precursor. To make both the bare and core-shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown onto the QDs through a modified reverse microemulsion technique. Silica encapsulated QDs were then melt-mixed with EVA pellets using a twin-screw extruder and pressed into thin films with controlled thickness. A novel supercritical carbondioxide (scCO2) processing method was also explored that utilizes scCO2 to disperse silica encapsulated core-shell quantum dots into EVA. The novel photo-stable light selective films show high visible light and decreased UV transmission. Also, silica layer showed improved infrared and thermal wavebands retention in the films. Beside polymer nanocomposites, a facile process has also been developed to covalently link QDs to TiO2 nanowires through a bifunctional organic linker that enhanced photoctalytic property and stability of nano TiO2.