Pressure-induced Phase Transition and New Quantum Regimes in Low-dimensional Materials

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Description
High-pressure science has been advancing rapidly in the past several decades due to its potential to access bond engineering and lattice reconstruction. Thanks to the development of pressure devices and advanced in-situ probing technics, it is possible to probe structural

High-pressure science has been advancing rapidly in the past several decades due to its potential to access bond engineering and lattice reconstruction. Thanks to the development of pressure devices and advanced in-situ probing technics, it is possible to probe structural phase transitions as well as materials’ optical, electrical, and magnetic properties under extreme pressure, which will in turn help explain new emerging materials’ phases and phenomena. As one of the most popular high-pressure devices, the diamond anvil cell has been used to control the crystal structure and interatomic spacing of materials by applying high pressure while accessing their material properties in-situ. In this dissertation, advanced spectroscopy techniques combined with diamond anvil cells are used to help determine how emergent quantum materials behave under high pressure. A comprehensive summary is offered on the synthesis, characterization, and high-pressure studies of various low-dimensional material systems, such as 2D Ruddlesden-Popper hybrid lead bromide perovskites (CH3(CH2)3NH3)2(CH3NH3)nPbnBr3n+1, (n = 1 and n = 2); guanidinium based lead iodides (2D Gua2PbI4 and 1D GuaPbI3), in which researchers discovered extraordinary luminescent properties and extremely high quantum conversion efficiency; 2D Janus MoSSe and WSSe monolayers, in which the mirror symmetry is broken and an electrical field is built in due to different electronegativity of the top and bottom atom layers; and 2D tellurene, which possess a large potential application in optoelectronic devices and sensors. In combination with the density function theory simulations of such collaborators as Dr. Can Ataca (organic–inorganic halide perovskite), Dr. Arunima K. Singh (tellurene), and Dr. Houlong Zhuang (Janus), this study offers comprehensive and detailed insights into the fundamental physics and mechanics of how crystal structure and band structure evolve at high pressure, discovering new phases, understanding the phase transition mechanism, and determining optoelectronic device applications.
Date Created
2021
Agent

Genetic Engineering of Cyanobacteria to Improve Photosynthetic Yield

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Description
Increasing energy and environmental problems describe the need to develop renewable chemicals and fuels. Global research has been targeting using microbial systems on a commercial scale for synthesis of valuable compounds. The goal of this project was to refactor and

Increasing energy and environmental problems describe the need to develop renewable chemicals and fuels. Global research has been targeting using microbial systems on a commercial scale for synthesis of valuable compounds. The goal of this project was to refactor and overexpress b6-f complex proteins in cyanobacteria to improve photosynthesis under dynamic light conditions. Improvement in the photosynthetic system can directly relate to higher yields of valuable compounds such as carotenoids and higher yields of biomass which can be used as energy molecules. Four engineered strains of cyanobacteria were successfully constructed and overexpressed the corresponding four large subunits in the cytochrome b6-f complex. No significant changes were found in cell growth or pigment titer in the modified strains compared to the wild type. The growth assay will be performed at higher and/or dynamic light intensities including natural light conditions for further analysis.
Date Created
2020-05
Agent

Multiplexed Nucleic Acid Programmable Protein Arrays

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Description

Rationale: Cell-free protein microarrays display naturally-folded proteins based on just-in-time in situ synthesis, and have made important contributions to basic and translational research. However, the risk of spot-to-spot cross-talk from protein diffusion during expression has limited the feature density of

Rationale: Cell-free protein microarrays display naturally-folded proteins based on just-in-time in situ synthesis, and have made important contributions to basic and translational research. However, the risk of spot-to-spot cross-talk from protein diffusion during expression has limited the feature density of these arrays.

Methods: In this work, we developed the Multiplexed Nucleic Acid Programmable Protein Array (M-NAPPA), which significantly increases the number of displayed proteins by multiplexing as many as five different gene plasmids within a printed spot.

Results: Even when proteins of different sizes were displayed within the same feature, they were readily detected using protein-specific antibodies. Protein-protein interactions and serological antibody assays using human viral proteome microarrays demonstrated that comparable hits were detected by M-NAPPA and non-multiplexed NAPPA arrays. An ultra-high density proteome microarray displaying > 16k proteins on a single microscope slide was produced by combining M-NAPPA with a photolithography-based silicon nano-well platform. Finally, four new tuberculosis-related antigens in guinea pigs vaccinated with Bacillus Calmette-Guerin (BCG) were identified with M-NAPPA and validated with ELISA.

Conclusion: All data demonstrate that multiplexing features on a protein microarray offer a cost-effective fabrication approach and have the potential to facilitate high throughput translational research.

Date Created
2017-09-20
Agent