Doctor of Philosophy
Chemical and Biochemical Engineering
Charpentier, Paul A.
One method to increase the productivity of greenhouse agriculture is to increase the amount of photosynthetically available light within. This was accomplished through the use of nanocomposite greenhouse film comprised of light downshifting zinc oxide quantum dots and ethylene vinyl acetate copolymer. As this material will be used on a commodity scale, two different approaches – a large batch process and continuous plug flow reactor – were designed for mass production of zinc oxide. A design of experiment was performed to determine which synthesis parameters contribute more strongly to the quantum dot’s growth. This was done for a small-scale batch synthesis and a continuous plug flow reactor. In both cases, temperature was determined to be the most important factor, with total reagent concentration being the second most important factor. The growth parameters for the plug flow reactor were tested for their effect on the quantum yield of the nanomaterial; in this case, the ratio between the hydroxide base and zinc ions was the most important factor. Furthermore, the effects of capping agents on the growth was also analyzed and it was determined that siloxane and polymer capping agents were found to give the most luminescent quantum dots. Different siloxane agents, with differing functional group side chains, were successfully attached to zinc oxide nanomaterial and these were melt mixed into nanocomposites with ethylene vinyl acetate copolymer to ascertain their effects on the composite’s material properties. It was found that vinyltrimethoxysiloxane was the capping agent which gave the greatest increase in material properties at a loading of 1 percent. This composite was also found to be resistant to UV induced weathering and possessed a greater thermal stability. The composite was also shown to increase the hydrophobicity and decrease the thermicity for greenhouse films. Lastly, the light downshifting ability was measured and shown to increase the growth rate of photosynthetic green algae by 4.7 percent. This material shows excellent promise for use a greenhouse film – it has a higher tensile strength, resistance to degradation, more hydrophobic, insulates better, and increases available light.
Summary for Lay Audience
The objective of this research project was to produce transparent film nanocomposites for greenhouses that contain tiny zinc oxide crystals within. These crystals absorb UV light and reemit it as blue light, thus increasing the quantity of light available within the greenhouse for the plants to use to grow. The optimal methods to produce the zinc oxide was studied and two methods for large-scale production were devised – a large batch process and a continuous reactor. Lastly modifications were made to the zinc oxide crystals to enhance several properties of the composites including strength, stability, insulation and wettability. These novel films should increase the productivity of greenhouses they are installed in.
Hiscott, David V., "Light downshifting zinc oxide-ethylene vinyl acetate nanocomposite greenhouse films" (2020). Electronic Thesis and Dissertation Repository. 6981.
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