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Joshua Choi
Applied & Engineering Physics
I am interested in developing next-generation photovoltaic devices using lead chalcogenide nanocrystals as building blocks. These nanocrystals offer exciting opportunities for designing efficient and inexpensive solar cells using their unique properties, such as large absorption cross section, tunable energy levels, solution processability and possibly efficient generation of multiexcitons. Understanding and controlling the properties of the interface become crucial for the device performance, as the separation of photogenerated electron-hole pairs -- a crucial step in energy conversion -- must occur across these interfaces. Moreover, as many of the unique properties of the nanocrystals only emerge when the nanocrystal size is ultra-small (a few nanometers), the high surface-to-volume ratio of nanocrystals makes the properties of interfaces and surfaces all the more important. |
Faculty Advisor:
Tobias Hanrath |
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TEM image of lead chalcogenide nanocrystals
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Henry Kostalik
Chemistry and Chemical Biology
I am interested in developing fuel cell membranes that posses both chemical stability and mechanical strength, in addition to being highly conductive. Within a fuel cell, the membrane serves as the ion-conducting interface between the anode and cathode. As a result, the membrane is a central, and often performance-limiting, component of the fuel cell. Our synthetic approach is to prepare diblock copolymers with functionalized hydrophilic blocks and hydrophobic support blocks. Block copolymers have been shown to microphase separate and it is our expectation that this will lead to fuel cell membranes with interconnected ion-conducting nanochannels resulting in unabated ion conduction through the materials. |
Faculty Advisor:
Geoffrey W. Coates |
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TEM micrograph of a microphase separated block copolymer
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Kendra Letchworth-Weaver
Physics
My research involves the study of electrochemical effects at solid-liquid interfaces directly from first principles physics. I am currently modifying joint density functional theory (JDFT) software developed by the Arias group to include effects such as Debye screening in dielectric fluids. These modifications will allow us to model at the nanometer scale the electron density and other physical properties of systems during chemical reactions as a function of the applied electrochemical potential. Since this information is extremely difficult to determine from experiment, it can ultimately be used to aid in the fundamental understanding of electrochemical phenomena which will, in turn, aid in the design of new electrocatalysts for numerous industrial and consumer applications. We will study transition states in catalytic reactions at cathodes in fuel cells, lithium ion battery anodes, and photocatalysis reactions in novel solar-cell and direct solar-to-hydrogen technologies. |
Faculty Advisor:
Tomás Arias |
 
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Oxygen-terminated Chromium (Cr2O3) surface in a dielectric fluid, modeled using JDFT. The results indicate that while the dielectric solvent has little effect on the bonding of a chlorine atom (left), the solvent prevents a hydrogen atom (right) from bonding, even though an O-H bond will readily form in vacuum.
(Figure by S. Petrosyan) |
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Sudhir Prabhu
Chemical and Biomolecular Engineering
I am interested in using enveloped viruses to spatially control the content of solid-supported lipid bilayers (SLBs) to create patterned surfaces that can interface biological and inorganic materials at the nanoscale. SLBs are formed from thermodynamically unstable 100nm unilamellar vesicles. Upon contact with treated glass surfaces, these vesicles rupture and then self assemble into 4-nm-thick lipid bilayers. Since controlling the content of viral membranes is straightforward, viruses can be used to deliver desired lipids/proteins to SLBs that are engineered to interact with specific materials such as metals and nanoparticles. Additionally, since membrane fusion of many viruses is triggered by acidic environments, by tightly controlling the local pH of SLB-virus mixtures I will be able to pattern desired components into specific areas of an SLB. This technology will be useful in creating novel interfaces between inorganic and biological surfaces for biosensing applications. |
Faculty Advisor:
Susan Daniel |
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Artist’s rendering of a solid-supported lipid bilayer (SLB).
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Daniel Shai
Applied and Engineering Physics
am using an experimental technique to study electron energy and momentum distribution on surfaces. This technique lends itself to the study of laterally-confined materials, including high-temperature superconductors. We can control the properties of these materials by evaporating atoms and molecules onto their surface, or even by growing unstable surfaces and interfaces that would never exist outside of a lab. The electron energy and momentum studies can be used in conjunction with other surface-sensitive techniques that give information about the electron distribution in real space. Together, these techniques make a powerful tool for understanding the properties of surfaces and interfaces. |
Faculty Advisor:
Kyle M. Shen |
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Electronic properties of high-temperature superconducting materials. (Top) Momentum distribution of electrons near the Fermi energy. (Bottom) Ratio of unoccupied states (within a finite energy window) to occupied states in real space.
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Jonathan Shaw
Electrical and Computer Engineering
I am interested in controlling electron capture, removal and retention in a metal complex or organic molecule embedded in a dielectric-metal nanocrystal/molecule-based memory device. Due to their self-assembling nature, high density coverage, and naturally existing multiple redox states, these molecule-based devices will allow precise step charging, which can potentially offer a solution to the difficulties in scaling nonvolatile memory devices. The large diversity of potential molecules will also allow us to expand our scope to investigate biomolecules for sensing and proteomics. The complex structure of our devices will require a good understanding of the molecular/dielectric interface and its affect on electron transfer. |
Faculty Advisor:
Edwin C. Kan |
