Matching Items (4)

Filtering by

Clear all filters

134902-Thumbnail Image.png

Bi-phase Synthesis of the Zirconium Metal-Organic Framework, UiO-66

Description

Metal-organic frameworks (MOFs) are a new set of porous materials comprised of metals or metal clusters bonded together in a coordination system by organic linkers. They are becoming popular for gas separations due to their abilities to be tailored toward

Metal-organic frameworks (MOFs) are a new set of porous materials comprised of metals or metal clusters bonded together in a coordination system by organic linkers. They are becoming popular for gas separations due to their abilities to be tailored toward specific applications. Zirconium MOFs in particular are known for their high stability under standard temperature and pressure due to the strength of the Zirconium-Oxygen coordination bond. However, the acid modulator needed to ensure long range order of the product also prevents complete linker deprotonation. This leads to a powder product that cannot easily be incorporated into continuous MOF membranes. This study therefore implemented a new bi-phase synthesis technique with a deprotonating agent to achieve intergrowth in UiO-66 membranes. Crystal intergrowth will allow for effective gas separations and future permeation testing. During experimentation, successful intergrown UiO-66 membranes were synthesized and characterized. The degree of intergrowth and crystal orientations varied with changing deprotonating agent concentration, modulator concentration, and ligand:modulator ratios. Further studies will focus on achieving the same results on porous substrates.

Contributors

Agent

Created

Date Created
2016-12

152390-Thumbnail Image.png

Synthesis and stability of ceramic-carbonate dual-phase membrane for carbon dioxide separation

Description

Of the potential technologies for pre-combustion capture, membranes offer the advantages of being temperature resistant, able to handle large flow rates, and having a relatively small footprint. A significant amount of research has centered on the use of polymeric and

Of the potential technologies for pre-combustion capture, membranes offer the advantages of being temperature resistant, able to handle large flow rates, and having a relatively small footprint. A significant amount of research has centered on the use of polymeric and microporous inorganic membranes to separate CO2. These membranes, however, have limitations at high temperature resulting in poor permeation performance. To address these limitations, the use of a dense dual-phase membrane has been studied. These membranes are composed of conductive solid and conductive liquid phases that have the ability to selectively permeate CO2 by forming carbonate ions that diffuse through the membrane at high temperature. The driving force for transport through the membrane is a CO2 partial pressure gradient. The membrane provides a theoretically infinite selectivity. To address stability of the ceramic-carbonate dual-phase membrane for CO2 capture at high temperature, the ceramic phase of the membrane was studied and replaced with materials previously shown to be stable in harsh conditions. The permeation properties and stability of La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF)-carbonate, La0.85Ce0.1Ga0.3Fe0.65Al0.05O3-δ (LCGFA)-carbonate, and Ce0.8Sm0.2O1.9 (SDC)-carbonate membranes were examined under a wide range of experimental conditions at high temperature. LSCF-carbonate membranes were shown to be unstable without the presence of O2 due to reaction of CO2 with the ceramic phase. In the presence of O2, however, the membranes showed stable permeation behavior for more than one month at 900oC. LCGFA-carbonate membranes showed great chemical and permeation stability in the presence of various conditions including exposure to CH4 and H2, however, the permeation performance was quite low when compared to membranes in the literature. Finally, SDC-carbonate membranes showed great chemical and permeation stability both in a CO2:N2 environment for more than two weeks at 900oC as well as more than one month of exposure to simulated syngas conditions at 700oC. Ceramic phase chemical stability increased in the order of LSCF < LCGFA < SDC while permeation performance increased in the order of LCGFA < LSCF < SDC.

Contributors

Agent

Created

Date Created
2013

154445-Thumbnail Image.png

Microfluidic tools for protein crystallography

Description

X-ray crystallography is the most widely used method to determine the structure of proteins, providing an understanding of their functions in all aspects of life to advance applications in fields such as drug development and renewable energy. New techniques, namely

X-ray crystallography is the most widely used method to determine the structure of proteins, providing an understanding of their functions in all aspects of life to advance applications in fields such as drug development and renewable energy. New techniques, namely serial femtosecond crystallography (SFX), have unlocked the ability to unravel the structures of complex proteins with vital biological functions. A key step and major bottleneck of structure determination is protein crystallization, which is very arduous due to the complexity of proteins and their natural environments. Furthermore, crystal characteristics govern data quality, thus need to be optimized to attain the most accurate reconstruction of the protein structure. Crystal size is one such characteristic in which narrowed distributions with a small modal size can significantly reduce the amount of protein needed for SFX. A novel microfluidic sorting platform was developed to isolate viable ~200 nm – ~600 nm photosystem I (PSI) membrane protein crystals from ~200 nm – ~20 μm crystal samples using dielectrophoresis, as confirmed by fluorescence microscopy, second-order nonlinear imaging of chiral crystals (SONICC), and dynamic light scattering. The platform was scaled-up to rapidly provide 100s of microliters of sorted crystals necessary for SFX, in which similar crystal size distributions were attained. Transmission electron microscopy was used to view the PSI crystal lattice, which remained well-ordered postsorting, and SFX diffraction data was obtained, confirming a high-quality, viable crystal sample. Simulations indicated sorted samples provided accurate, complete SFX datasets with 3500-fold less protein than unsorted samples. Microfluidic devices were also developed for versatile, rapid protein crystallization screening using nanovolumes of sample. Concentration gradients of protein and precipitant were generated to crystallize PSI, phycocyanin, and lysozyme using modified counterdiffusion. Additionally, a passive mixer was created to generate unique solution concentrations within isolated nanowells to crystallize phycocyanin and lysozyme. Crystal imaging with brightfield microscopy, UV fluorescence, and SONICC coupled with numerical modeling allowed quantification of crystal growth conditions for efficient phase diagram development. The developed microfluidic tools demonstrated the capability of improving samples for protein crystallography, offering a foundation for continued development of platforms to aid protein structure determination.

Contributors

Agent

Created

Date Created
2016

157302-Thumbnail Image.png

Analyzing cellular properties with dielectrophoresis

Description

Dielectrophoresis (DEP) is a technique that influences the motion of polarizable particles in an electric field gradient. DEP can be combined with other effects that influence the motion of a particle in a microchannel, such as electrophoresis and electroosmosis.

Dielectrophoresis (DEP) is a technique that influences the motion of polarizable particles in an electric field gradient. DEP can be combined with other effects that influence the motion of a particle in a microchannel, such as electrophoresis and electroosmosis. Together, these three can be used to probe properties of an analyte, including charge, conductivity, and zeta potential. DEP shows promise as a high-resolution differentiation and separation method, with the ability to distinguish between subtly-different populations. This, combined with the fast (on the order of minutes) analysis times offered by the technique, lend it many of the features necessary to be used in rapid diagnostics and point-of-care devices.

Here, a mathematical model of dielectrophoretic data is presented to connect analyte properties with data features, including the intercept and slope, enabling DEP to be used in applications which require this information. The promise of DEP to distinguish between analytes with small differences is illustrated with antibiotic resistant bacteria. The DEP system is shown to differentiate between methicillin-resistant and susceptible Staphylococcus aureus. This differentiation was achieved both label free and with bacteria that had been fluorescently-labeled. Klebsiella pneumoniae carbapenemase-positive and negative Klebsiella pneumoniae were also distinguished, demonstrating the differentiation for a different mechanism of antibiotic resistance. Differences in dielectrophoretic behavior as displayed by S. aureus and K. pneumoniae were also shown by Staphylococcus epidermidis. These differences were exploited for a separation in space of gentamicin-resistant and -susceptible S. epidermidis. Besides establishing the ability of DEP to distinguish between populations with small biophysical differences, these studies illustrate the possibility for the use of DEP in applications such as rapid diagnostics.

Contributors

Agent

Created

Date Created
2019