Novel Demonstrations of Optical Refrigeration in Enzymes and Polystyrene and TEM Imaging of Novel Fluoride Microstructures

Abstract

This work focuses on novel demonstrations of optical cooling in structures that have not beencooled via laser refrigeration previously. The primary study was focused on investigating the possibility of optical refrigeration being powerful enough to cool enzymes attached to the surface of the cooling crystals, with potential applications in biochemical techniques requiring thermocycling, such as the polymerase chain reaction. Another study focused on the potential development of radiation balanced whispering gallery mode lasers through use of cooling nanoparticles deposited on the surface is also presented. Finally, transmission electron microscopy work that helped to uncover novel microstructures in common rare earth- doped fluoride materials that would not have been discovered without use of the instrument. Chapter 1 presents an introduction to the concepts of optical refrigeration and the ther- mometry techniques used to track the temperatures of our optical refrigeration materials. The parameters that must be carefully balanced to attain optimal laser refrigeration are in- troduced and discussed in detail. The two primary methods of thermometry and the concepts that underlie them are also presented. Chapter 2 introduces the idea of optical refrigeration of enzymes by describing the tech- nique we hope it may eventually be applied to, that being the polymerase chain reaction. Data is presented showing the development of a synthetic technique for covalently attaching a test enzyme, horseradish peroxidase, to the surface of the cooling ytterbium-doped yttrium lithium fluoride crystals. It is shown that the enzymes remain functional while attached to the crystals and that the enzymatic reaction product is not generated by any source other than the bound enzymes. A data collection apparatus and method are designed in order to obtain comparable enzymatic reaction rate data across heating, cooling, and control con- ditions from a single confirmed cooling crystal coated with the enzymes, and experiments using this setup and method can repeatedly show reaction rate increase during heating trials, reaction rate decrease during cooling trials, and control trials landing in between them. This is the first demonstration of optical refrigeration of enzymes. Chapter 3 involves cooling experiments using polystyrene resonators coated with ytterbium- doped upconverting nanoparticles with the goal of creating a radiation balanced microlaser as well as provide an improved substrate for single molecule biophysics. Multiple thermom- etry methods are used to probe the temperatures reached at the surface of the microspheres and their surrounding environment. It is found that local cooling of the crystals at the sur- face of the crystals is possible, but overall cooling of the local environment is not achieved. However, the coated spheres demonstrate significantly reduced heating when compared to identical uncoated spheres of the same diameter. Chapter 4 largely departs from the subjects of the rest of this dissertation and moves to electron microscopy of novel structures synthesized within the Pauzauskie group. The two structures presented are of porous α phase sodium yttrium fluoride crystals and core-shell calcium fluoride crystals referred to as mandala structures. Data generated from multiple advanced techniques are presented, including elemental maps from energy-dispersive x-ray spectroscopy and three dimensional tomographic reconstructions. Hypotheses describing the possible reasons for growth of these unusual structures are presented and potential future applications for these crystals are discussed.