Hope Bretscher

Undergraduate Student: Class of 2015
Major: Physics
Minor: Human Rights
Hometown: St. Louis, MO 
Awards: Dean's List, Student Marshall, Grainger Scholarship
Research: Condensed matter physics, defects in diamond
Research Advisors: David Awschalom (IME), Richard Axelbaum (WUSTL)

I began working in Professor Richard Axelbaum's lab in the Environmental, Electrical and Chemical Engineering Lab at Washington University in St. Louis the summer after my freshman year in college. In Professor Axelbaum's lab, the first summer, I studied the cathode side of lithium ion batteries. We made cathodes out of Li1.2Mn0.54Co0.13O2, which exhibits good electrochemical properties, like retaining capacity after many cycles, and high initial capacity of energy storage. However synthesizing the powder was a challenge, and we sought to improve the production method so that we could make denser particles, thereby delivering a higher density of energy within a battery. We experimented with using spray pyrolysis, in which solution is atomized then heated so that droplets react and the water evaporates, forming micron-sized hollow-shell particles with precise stoichiometry, and are subsequently annealed to complete the reaction. While spray pyrolysis is relatively repeatable, the particles produced are very porous and hollow. This means that when made into a battery, the energy density is relatively low. I assisted by preparing solutions for spray pyrolysis, using the Brunauer, Emmett and Teller (BET) device to measure the surface area, and experimented with using a flame (rather than a heated reaction chamber) to synthesize the powder and make denser particles with good electrochemical properties (that were consistent and good for making efficient, cost effective, and cycle-able batteries).

After my second year, I returned to the same lab and continued to research the lithium-ion powder. I continued many of the same duties as the previous summer, but was able to get more involved with experimental design. I helped to dope the solution with other chemicals to improve the electrochemical properties. Additionally, I designed and built a high-pressure nozzle system to try to synthesize powder more rapidly. I'm glad I got the chance to return to the lab, so that I got a deeper understanding of the research and more involved in the research process.

The fall of my third year, I began working in the Awschalom Lab in the IME. This lab researches the spin properties of nitrogen vacancy (NV) in diamond, a solid state system that has potential applications in quantum computing and nanoscale sensing. NV centers have long coherence time, on the order of milliseconds, and the spin state can be optically initialized and read out, meaning we can manipulate and measure through optical means. Additionally, NV centers are sensitive to electric and magnetic fields and temperature. I began helping by doing small projects, like writing labview or matlab programs and using solidworks to design some parts for a cryostat and logic tree. Later in the school year, I began to learn how to build a setup on an optical table. I then continued research over the summer through the UChicago REU. During this time, I built a confocal microscope to study the NV centers and began running simple characterization experiments to understand the properties of the diamonds we are analyzing. In the future, I will continue to improve the experimental setup, adding radio frequency capability and pulse timing, so that we can do other characterization experiments, like Rabbi, ESR, and Hahn Echo.